Progressive Crop Consultant - July / August 2022

July / August 2022 How to Manage Plant-Parasitic Nematodes in Almond New Water Quality Regulations Will Change How Vegetables Are Grown on the Central Coast Leveraging the Soil Microbiome with Plant Growth Promoting Rhizobacteria

September 28th - 29th

See pages 22-23

Volume 7: Issue 4 Photo courtesy of R. Ehsani

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PUBLISHER: Jason Scott Email: jason@jcsmarketinginc.com EDITOR: Marni Katz ASSOCIATE EDITOR: Cecilia Parsons Email: article@jcsmarketinginc.com PRODUCTION: design@jcsmarketinginc.com Phone: 559.352.4456 Fax: 559.472.3113 Web: www.progressivecrop.com

IN THIS ISSUE

4

How to Manage PlantParasitic Nematodes in Almond

CONTRIBUTING WRITERS & INDUSTRY SUPPORT

10

New Water Quality Regulations Will Change How Vegetables Are Grown on the Central Coast

16

Leveraging the Soil Microbiome with Plant Growth Promoting Rhizobacteria

24

Winter Cover Crops in Annual Rotations

28

How Crops Can Help Crop Advisors Through Systemic Acquired Resistance

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36

Michael Cahn UCCE Irrigation and Water Resources Farm Advisor, Monterey, Santa Cruz and San Benito Counties

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Bradley S. Higbee Amber Vinchesi-Vahl Research Entomologist, Field R&D Manager, Trécé, UCCE Vegetable Crops Advisor, Colusa, Sutter Inc. and Yuba Counties Catherine Keske Andreas Westphal IoT4Ag Site Director, Department of Agricultural Economist, Nematology, UC UC Merced Riverside JW Lemons Eryn Wingate CCA, CPAg CCA, Tri-Tech Ag Products, Inc. Sarah Light UCCE Agronomy Advisor, Sutter, Yuba and Colusa Counties

UC COOPERATIVE EXTENSION ADVISORY BOARD Surendra Dara

Steven Koike Tri-Cal Diagnostics

Kevin Day

UCCE Integrated Pest Management Advisor, Stanislaus County

Director, North Willamette Research and Extension Center

UC Merced Research Center Aims to Improve Yields, Production Efficiency through Internet of Things

Richard Smith UCCE Vegetable Crop Production and Weed Science Farm Advisor, Monterey, Santa Cruz and San Benito Counties

UCCE Pomology Farm Advisor, Tulare and Kings Counties Elizabeth Fichtner UCCE Farm Advisor, Kings and Tulare Counties

Jhalendra Rijal

Mohammad Yaghmour

UCCE Area Orchard Systems Advisor, Kern County

Katherine Jarvis-Shean UCCE Orchard Systems Advisor, Sacramento, Solano and Yolo Counties

The Impact of Pistachio Sanitation on Navel Orangeworm Damage and Egg Trap Counts

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The articles, research, industry updates, company profiles, and advertisements in this publication are the professional opinions of writers and advertisers. Progressive Crop Consultant does not assume any responsibility for the opinions given in the publication.

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HOW TO MANAGE PLANT-PARASITIC NEMATODES IN ALMOND SUCCESSFUL STRATEGIES WILL INCLUDE A COMBINATION OF RESISTANT ROOTSTOCKS, PREPLANT TREATMENTS AND POST-PLANT MANAGEMENT.

By ANDREAS WESTPHAL | Department of Nematology, UC Riverside

Figure 1. Almond grafted onto Krymsk 86 in a field under presence of root-knot nematodes. Photo at right shows a compromised tree on a root-knot nematode infected root system (all photos by A. Westphal.)

This article is the first in a series highlighting industry-funded research through the Almond Board of California.

T

he expansion of almond in many different regions of California exposes the crop to diverse field environments. This includes conditions of soil texture, microclimates, weather patterns and soil pathogen load. Frequently almond follows itself or other perennial crops that leave behind assemblies of diverse species of plant-parasitic nematodes. Walnut and grape may harbor nematode species that can also be damaging to almond.

Some production issues can be averted by rootstock choice, but currently there is no commercial rootstock available that combats all possible nematode infestations.

Different combinations of root-knot nematodes (Meloidogyne spp.), root lesion nematodes (Pratylenchus vulnus), ring nematodes (Mesocriconema xenoplax) and other species are common in almond orchard soils. Preplant soil fumigation with 1,3-D containing materials formulated as Telone is fre4

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quently used to reduce soil infestations What Can Be Done Long-Term? of plant-parasitic nematodes. EnvironOne promising strategy to deal with mental and human health concerns nematode problems in orchards is the have led to restrictions of this method. use of pathogen-resistant and tolerant Township caps limit the annual amount rootstocks. Conceptually, a rootstock of material that is permitted to be that does endure nematode infection applied to soils. Currently proposed and reproduction with minimal damchanges to the application patterns of age will be ideal for avoiding negative Telone potentially make treatments nematode impacts. Despite this temptmore expensive and some of the protoing solution, several caveats include: cols may encumber efficacy. Alternative, (1) Rootstock choice is a once-in-a-life cost-effective soil preplant treatments time decision; the decision is final for are urgently needed. the life of the orchard; (2) Frequently multiple species of plant-parasitic nemIn a current Almond Board of Califoratodes exist in a given field; resistance nia-funded project, new materials and to one nematode species likely does nematode management strategies are not protect from infection by anothdeveloped and adopted for commercial er; (3) Rootstocks with resistance to a use. Alternative preplant treatment certain nematode species may not be options may not have as high efficaavailable; and (4) Other environmental cy levels as a properly administered parameters may weigh in heavier on Telone fumigation. As a result, future the rootstock choice than response nematode management strategies likely to plant-parasitic nematodes. will comprise a management system of preplant soil treatments coupled with postplant strategies.

Continued on Page 6 July / August 2022

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Figure 2. Root system of a tree suffering from severe root-knot nematode infection (right) and close-up of galled root (left). Each of the root-knots harbors multiple females of the nematode. The plant response leads to this excessive tissue.

Continued from Page 4 In contrast to these challenges, once sustainable resistance is identified, the utility is truly enticing. As an example, the resistance to southern root-knot nematodes of peach rootstock ‘Nemaguard’ has protected stone fruit and almond orchards for over 60 years. This

root-knot nematode resistance has been hugely successful, but Nemaguard is vulnerable to root lesion and ring nematodes. Also, some of the horticultural characteristics of Nemaguard are not fully satisfactory. Novel rootstocks with similar resistance but devoid of some of those weaknesses have entered the market, but the “robust” rootstock

that can cope with just any soilborne malady still needs to be discovered.

Additional challenges of relying entirely on host plant resistance for nematode management are illustrated by the recent discovery of peach root-knot nematodes in California. This nematode overcomes all root-knot nematode

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resistances currently used in rootstocks for almond production in California.

Such virulence then requires using other means for nematode suppression.

The same is true because of the susceptibility to root lesion nematode and ring nematode in most currently used rootstocks. Preplant soil treatment is frequently indicated for a prospective field for almond production.

Is Damage Being Caused

by Nematodes?

The first step to the cure needs to be diagnosis. While aboveground symptoms of other diseases may be easier spotted and are in instances more specific, soilborne pathogens and pests are somewhat secluded. The symptoms of some of microscopic causal agents become visible. For example, the “conks” that develop on tree bases after infection with the bacterium Agrobacterium tumefaciens are fairly diagnostic.

In nematode diseases, the field diagnosis is much more challenging. General symptoms that warrant further diagnosis include excessive wilting during high ET despite sufficient soil moisture, lack of tree vigor and uneven growth throughout the orchard. Frequently, these symptoms are confounded by other soil differences. For example, one area of the field may be especially sandy, rightfully being identified as prone to water stress. While this can lead to some of the general stress symptoms, the severity of growth suppression can be increased by the presence of plant-parasitic nematodes that are favored by this soil texture composition.

In this example, the observed damage resembles the summation of the abiotic and biotic stresses. Root-knot nematodes and ring nematodes are species that do show preference for sandy soils.

If these species are introduced in a field with variable soil texture composition, they are likely to strive to large, damaging population densities in the sandier areas of the field compared to those of heavy ground. When diagnosing field problems, this complex interplay of factors needs to be considered.

In the example of a field diagnosis case near Chico, Calif., several of these soil

parameters interfered with one another. In this high-wind area, Krymsk 86, known for favorable anchoring abilities and tolerance to severe wind events, was chosen. The rootstock sensitivity and susceptibility to root-knot nematodes had been discounted as a risk factor because these nematode species are rarely observed in this part of California. Limited problems were observed until the second-leaf of the orchard. At that time in one area of the field, typical

Continued on Page 8

Figure 3. Healthy tree without rootknot nematode infection of the same planting.

THE BEST WAY TO MANAGE PATHOGENS BEFORE THEY BECOME AN ISSUE.

TriClor is chloropicrin based and can be used as a standalone or as a complement to Telone® depending on your orchard redevelopment needs. When targeting soil borne disease and nematodes, TriClor and Telone® can be applied in a single pass. This reduces application costs, promotes early root development, and improves soil health. For more information about TriClor and Telone or to schedule an application contact TriCal, Inc.

669-327-5076

www.TriCal.com Authorized distributor for Telone® *TriClor and Telone are federally Restricted Use Pesticides.

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Figure 4. Drip irrigation system placed on top of the soil.

The tubing at one-foot spacing has an emitter at every one foot, wetting the soil uniformly to deliver treatment suspensions of potentially nematicidal compounds.

Continued from Page 7 nematode symptoms of stunted uneven growth were observed. When excavating the poor-looking trees, severe nematode-induced galling was detected (Figures 1, 2, 3, see pages 4,6,7).

Examining the field conditions, it was determined that the nematode damage foremost occurred in a slightly sandier area of the field. Anecdotal evidence provided that the field tends to flood on the side of the field where the nematode damage was. This alone will not cause the nematode damage, but principally flood water can bring in pathogens and pests, especially when it transports a lot of soil. Plant-parasitic nematodes are not omnipresent. These microscopic worms rely on passive transport via soil and plant material. In this particular example, the introduction may have been many years ago because for nematodes to build up and distribute by field operations throughout a land area takes extended time periods.

Tackling the Successful Establishment of a Vigorous Almond Orchard

Currently, preplant soil treatments are critical for the successful establishment of a vigorous almond orchard. While the tedious search for rootstocks with resistance to multiple soil-borne maladies is an ongoing effort of a collaborative team of UC and the USDA-ARS, 8

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Figure 5. Experimental spray blade assembly. Stainless steel tubing is tack-welded to the back side of the horizontal blades allowing, for material dispensing while the implement is pulled through the upper soil.

it is a lengthy process, and at the time provides no comprehensive solution for every field situation. The search for novel chemistries that are more environmentally benign, have highest levels of efficacy and are economically competitive has been ongoing and produced some candidates that warrant orchard testing. In addition to the material expense, application methods and protocols need to be refined to take advantage of the efficacy under economically viable scenarios.

In designing preplant treatment protocols, the novel chemistries of limited fumigation capacity need to be delivered to the site of action, preferably five feet deep with water as a carrier.

Initial studies have relied on a drip irrigation set-up that allows dispensing drench water of six-acre inch total to every square foot of the soil surface (Figure 4). While some true non-fumigants should be safe to apply to the soil surface, others need to be at least slightly incorporated during application to avoid evolution of volatile organic compounds, or soils need to be covered by plastic tarp. A so-called “spray blade” accomplishes an incorporation with limited gassing-off of the chemical. Horizontal sweeps are pulled a few inches below the soil surface while dispensing material via a tube system attached to the sweeps (Figure 5). Drench water could then be applied more easily via overhead irrigation July / August 2022

systems. These methods are currently investigated.

Once an orchard is established, nematode management tools that are crop-safe and of limited crop residue risk are highly desirable to provide opportunities to mitigate remedial or resurging nematode issues. Materials in this testing program are fulfilling these needs, and their rates and application patterns are further investigated. Tested techniques include directed dispensing over the rootzones of the plant or injection via the drip or microsprinkler irrigation system (chemigation). The principal efficacies of the materials allow this type of exploitation. These studies of combinatory management strategies are currently conducted in young orchards at the research center.

In summary, there are multiple aspects that need to be evaluated to improve on the abilities to manage plant-parasitic nematodes. The Kearney Agricultural Research and Extension Center, provides the facilities and opportunities to investigate these key aspects. This project expands to surrounding counties and relies on the UC ANR continuum involving local farm advisors. The final goal is the implementation of effective and economically acceptable strategies.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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New Water Quality Regulations Will Change How Vegetables Are Grown on the Central Coast

By RICHARD SMITH | UCCE Vegetable Crop Production and Weed Science Farm Advisor, Monterey, Santa Cruz and San Benito Counties and MICHAEL CAHN | UCCE Irrigation and Water Resources Farm Advisor, Monterey, Santa Cruz and San Benito Counties

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he area covered by the Central Coast Regional Water Quality Control Board (CCRWQCB) extends along the coast from Santa Barbara to southern Santa Clara counties. It has governmental authority to enforce state water quality regulations within its jurisdiction. Since 2004, the regulations have consisted of a series of conditional waivers and early enforcement efforts focused on educating growers on practices to improve nutrient use efficiency.

Complying with the limits/targets set

by Ag Order 4.0 will be challenging for growers (all photos courtesy R. Smith.)

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In 2014, the conditional waiver expanded to include reporting of total applied nitrogen (N) for growers who produce crops that potentially have a high risk for nitrate leaching, such as vegetables and berries. Conditional waivers for agricultural discharges needed to be renewed every five years. In April 2021, the CCRWQCB approved Ag Order 4.0, which does not have an end date and includes additional regulations to protect water quality, such as riparian buffer areas and expansion of regulations that limit pesticide discharges to waterways. Ag Order 4.0 also includes requirements for reporting loading of N to the groundwater, and for the first time, includes limits on levels of N loading in agricultural production fields.

Nitrogen loading will be estimated by reporting the applied (A) minus the removed (R) nitrogen to fields during

July / August 2022

a calendar year. This calculation, also known as the ‘A minus R’ metric, is subdivided into smaller components.

The A value is the sum of N in fertilizer (Afertilizer), N in irrigation water (Airrigation), N supplied by compost (Acompost) and, in organic production, N mineralized from organic fertilizer (Aorganic fertilizer). The R value is the sum of N removed in the harvested portion of the crop (R harvest), N scavenged during the winter fallow period by cover crops or immobilized by high-carbon compost (Rscavenge), N removed by denitrification bioreactors (Rtreated), N sequestered in woody plant biomass (Rsequestered) and other unspecified forms of N removal from fields (Rother).

Reporting of N loading for Ag Order 4.0 includes three pathways to compliance, but pathway No. 1 is most likely to be used by most ranches unless they have wells that have very high concentrations of nitrate (> 40 ppm NO3-N) in the irrigation water (for more information on the pathways to compliance, go to the Ag Order 4.0 section of the CCRWQCB website: waterboards.ca.gov/centralcoast/water_issues/programs/ilp/regulatory_information.html ).

To comply with the regulations, the A minus R metric cannot exceed targets or limits shown in Table 1. The A minus R metric is calculated over the growing

Table 1. A-R regulatory schedule

season on a land-acre basis. If two or more crops are grown on the same physical acre, each crop contributes to the value for the year. Dates in the third column in Table 1 are for growers reporting directly to the CCRWQCB. However, the last column shows compliance dates for growers participating in a third-party program, which has compliance dates delayed by one year.

In addition, the third-party limits are replaced by targets. This is significant because limits are enforced by regulatory action and targets are enforced by education on improved practices to achieve compliance. The third-party organization set up to work with growers is Central Coast Water Quality Preservation, Inc. (CCWQP).

Regulatory

A-R

Compliance Date

Status

lbs N/ac/year

Target 500 Target 400 Limit 300 Limit 200 Limit 150 Limit 100 Limit 50 * All regulatory actions are targets

Compliance Date* Third Party

2023 2025 2027 2031 2036 2041 2051

2024 2026 2028 ---------

The following sections discuss the calculations for estimating the applied (A) and removed (R) nitrogen for complying with Ag Order 4.0.

The “A” Side of the Equation

Afertilizer is the amount of N from fertilizer added to grow a crop. The actual units of N in lbs/acre are used in this calculation.

Airrigation is the amount of N contained in the irrigation water that is taken up by the crop. For most vegetable and berry crops grown on the central coast, the volume of water that must be accounted for in this calculation is equivalent to volume needed for crop evapotranspiration (ETc). For crops where less water is applied than ET, the volume of applied water can be used in the calculation. To calculate Airrigation, use the equation: Airrigation = water volume (inches) × nitrate-N concentration of water (ppm N) × 0.227 The factor 0.227 converts the units inches × ppm N to lbs N/acre.

For example, if a lettuce crop uses 7.3 inches for ET and is irrigated with

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Continued from Page 11 water that has a 37 ppm NO3-N concentration, the Airrigation would be 7.3 inches x 37 ppm N x 0.227 = 61 lbs N/acre.

Acompost is the amount of N provided by compost. Given that the amount of N mineralized from compost depends on the carbon to nitrogen (C:N) ratio, not all the N in compost becomes available.

This fact is recognized in the Ag Order as follows: For compost with a C:N ratio of <11, the amount of N in the compost is multiplied by 0.10, and for composts with a C:N ratio of >11, the amount of N in the compost is multiplied by 0.05.

Measuring soil nitrates to account for residual soil nitrate N is a key practice to help comply with Ag Order 4.0.

Only the estimated amount of N mineralized from compost is added to the A side of the equation. These discount factors were an important change made by the Regional Board staff to reflect the actual quantity of N from compost

that would be contributed to the crop and to avoid disincentivizing the use of compost, a key soil health practice.

Aorganic is the amount of N that is mineralized from organic fertilizers during the season. The amount of N mineralized also depends upon the C:N ratio of the material, and the CCRWQCB is using the regression curve in a recent paper published by Lazicki et al (2020) to determine the amount of N mineralized.

For instance, a material like 4-4-2 has a C:N ratio of 7.3 (29% C/4% N) and has a discount factor of 0.39 (Table MRP-3 in Attachment B of Ag Order 4.0). This means that if 100 units of N are applied as 4-4-2, the amount mineralized from this material and that is attributed to the A side of the equation is 39 lbs/acre (100 lbs x 0.39). This discount factor acknowledges the fact that not all N in organic fertilizer mineralizes during the cropping season and was also an important adjustment to Ag Order 4.0.

The “R” Side of the Equation

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Rharvest is the amount of N removed from the field in the harvested product. The amount of N removed is calculated by a removal coefficient composed of the percent moisture multiplied by the percent N of the harvested product.

This coefficient is then multiplied by the net pounds of product harvested from a field to determine lbs N/acre removed.

Over the past two years, N removal coefficients for many vegetable commodities grown on the Central Coast have been developed.

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An example of how crop N removal is calculated for romaine lettuce: Solids content of the crop = 5.69% (0.0569) Nitrogen content of the crop = 3.15% (0.0315) Crop N removal coefficient = 0.0569 x 0.0315 = 0.00178 If the net weight of a romaine crop was 30,000 lbs/acre, then total N removal in

Continued on Page 14 12

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porating high carbon amendments, such as almond hulls and green waste, to lower the concentration of nitrate in the topsoil in the fall before winter rains occur. Growers already apply compost (typical C:N ratio of 10 to 12) but could substitute high-carbon amendments (C:N ratio of >30) which can quickly facilitate its use. Currently, high-carbon amendments have been granted a credit of 30 lbs N/acre in Ag Order 4.0. However, once the research on this practice is completed, this practice may be warranted greater credits on the R side of the equation.

Rtreat is the quantity of N removed from tile drainage and irrigation runoff by denitrification bioreactors or constructed wetlands. This practice is more likely to be used in the areas with perched water tables where high nitrate tile drain water impacts the surrounding sloughs and creeks. Highly managed denitrification bioreactors can remove as much as 100 ppm N from drainage water over a two-day period.

Bioreactors must be designed and sized for the volume of discharge anticipated during the growing season.

Rsequestered is the quantity of N that is captured in the woody plant tissue of perennial crops, such as vineyard and orchards, and is not relevant to the vegetable industry.

Use of cover crops is incentivized in Ag Order 4.0.

Continued from Page 12 the crop is 54 lbs/acre (0.00178 x 30,000 = 54).

It is important to note that N removed by this crop is modest in relation to the amount of N that is often applied. For instance, average lettuce application rates are 175 lbs/acre. It is evident that growers face some major challenges in complying with the application limits as the limits ratchet down over the next several years.

Rscavenge is the amount of N captured by cover crops or immobilized by high-carbon compost during the winter fallow period. The CCRWQCB agreed to credit non-legume winter cover crops that meet the following criteria: 1) are grown for ≥ 90 days during the winter fallow period; 2) accumulate more than 4,500 lbs/acre of dry biomass; and 3) have a C:N ratio of ≥ 20 when incorporated. Non-legume cover crops routinely contain 100 to 150+ lbs N/acre and represent a significant credit in the A minus R metric. As a result, cover crop use may be incentivized, but there are economic constrains to their use on the central coast where land rents are high and multiple rotations of high-value crops such as vegetables are required to remain economically competitive.

However, growers may find some creative ways to include cover crops in their production systems to gain the credit (and soil quality benefits) that they provide.

High-carbon amendments were also included in the Rscavcategory. This practice is still being researched to fully enge understand how much N can be immobilized by incor-

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Rother is the quantity of N removed from the field in other unspecified ways. One form of N removal not addressed in Ag Order 4.0 is the gaseous loss of N by denitrification from soil.

Studies of denitrification losses have measured losses that range from 2 to 37 lbs N/acre/crop. Comprehensive studies are needed to better understand the denitrification N losses from vegetable production fields on the central coast.

Practices to Move Towards Compliance

Complying with the limits/targets set by Ag Order 4.0 will be challenging for growers. Growing two to three vegetable crops per year creates pressure to become more efficient at managing nutrients as the limits/targets on N applications ratchet down in the next few years. In scenarios that we have run, the A minus R limit of 300 lbs N/acre/year will become very challenging for growers to comply with in typical double-cropped vegetable systems.

Key practices that will provide the most improvements in N use efficiency include: 1) measuring residual soil nitrate and adjusting fertilizer applications accordingly; 2) accounting for the nitrate in irrigation water as part of the N budget; and 3) improving irrigation efficiency to help maintain residual soil nitrate in the active rootzone of crops.

Growers that are preparing for Ag Order 4.0 regulations are beginning to experiment with these practices and become familiar with their use. Some farming operations are quite far along on the learning curve. They are training their staff to adjust fertilizer rates based on soil nitrate quick test values and are accounting for N contributions from irrigation water.

Other growers are experimenting with irrigation management to use water more carefully during crop establishment to avoid unnecessary leaching of soil nitrate. Unfortunately, increasing effort in nutrient and irrigation management adds more challenges to the already challenging job of producing crops of good quality and yields and staying afloat during these stressful times of high input costs. Fortunately, there is still time to begin experimenting and implementing best practices for nutrient and irrigation management. The good news is that a number of crop consultants are familiarizing themselves with these practices and can assist growers that are interested in their use.

In addition to the three key practices mentioned above, other technologies are available that may be able to provide additional efficiencies for applied and removed nitrogen. Nitrogen fertilizer technologies, such as controlled release materials and nitrification inhibitors, may be able to better control the availability of N in the soil to match crop uptake. As mentioned earlier, creative ways of incorporating cover crops into vegetable rotations will provide a key practice for capturing N that might otherwise be leached and make it available for the next vegetable crop while gaining a valuable credit on the R side of the equation.

To help growers better manage both nutrients and water, we developed CropManage, an online decision support tool that estimates water and nitrogen needs of many of central coast crops. The online software can be used on a field-by-field basis to estimate how much fertilizer N would be appropriate to apply at different stages of development. The nitrogen recommendations can account for available soil nitrate as well as nitrate available in irrigation water. The software also automates calculations for estimating irrigation sets using CIMIS reference evapotranspiration data and models of crop coefficients. The algorithms used in

CropManage are based on UC research and many field trials. Each year, we offer trainings on using the decision support tool as well as provide online documentation to help users get started using CropManage. CropManage is free to use and can be accessed at cropmanage.ucanr.edu.

how vegetables are grown on the Central Coast in the coming years. There is a window of opportunity to experiment on how to address limits that will be applied to the use of N fertilizers. Now is the time to make the decisions needed to address this new reality.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

In summary, the finalization of Ag Order 4.0 will have a significant impact on

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Well-known PGPRs belong to the genera Bacillus and Pseudomonas.

Species in these genera occur naturally in agricultural soils, but growers can inoculate crops with specific strains isolated for their beneficial effects and compatibility with host plants (photo courtesy USDA.)

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LEVERAGING THE SOIL MICROBIOME WITH PLANT GROWTH PROMOTING RHIZOBACTERIA

By ERYN WINGATE | CCA, Tri-Tech Ag Products, Inc.

icrobiology critically influences soil quality and has uncovered many types of organisms that can increase crop production potential. Pathogenic organisms yield, offset fertilizer requirements and aid in pest control. can destroy an entire crop while beneficials produce Growers can navigate the biological amendment market and organic matter, cycle nutrients, suppress pathogens and enpromote beneficial soil organisms by understanding founhance plant growth. High fertilizer prices, regulatory pressure, dational microbiology concepts and some of the ways the pesticide resistance and environmental concerns drive inmicrobiome improves soil and plant health. creased interest in the soil microbiome’s potential to support agricultural production. Research over the past few decades Soil Microbiology Foundations Soils contain vast numbers of bacteria, archaea, fungi and protists. One teaspoon of soil contains about one hundred Advertorial million to one billion bacteria, which adds up to roughly the weight of two cows per acre[5,6]. Microbial cells range in Calculating Calcium Requirement To Leach Salts size from less than one micron, or 4/100,000ths of an inch, When using a soil test to determine how much to 100 microns[5,6]. About 50,000 bacterial cells can fit in a calcium to apply to leach salts, it is best to use the single layer on a dime. Bacterial cell shapes include spherical, rod and spiral, while the most notable soil fungi form Saturated Paste Extract numbers, usually reported in filamentous hyphae[1]. Microbes fill every trophic niche with meq/l. Most standard salinity leaching calculations autotrophs, providing the ecosystem foundation by fixing are based on these soluble numbers. The three carbon, and various types of heterotrophs grazing, predating, cations: Ca, Mg and Na make up virtually all the and decomposing other microorganisms and plant or animal positive ions that aid soil colloid aggregation. Bicartissue. Together, the organisms in the soil microbiome facilibonate, HCO3- is an anion that has influence, because tate plant growth and support the aboveground ecosystem by it can take out some of the free solution Ca to form cycling carbon, water and essential nutrients. precipitated lime. To account for this impact, use the Adjusted SAR. Plant Growth Promoting Rhizobacteria If a Mid-West style test is used on an alkaline soil Beneficial soil microorganisms include a diverse range of bacteria: archaea, fungi and protozoa. These broad groups where you only get Ammonium Acetate values, the of organisms carry out specific functions that directly reported value for “free” Ca can be artificially high benefit plants by facilitating nutrient uptake or suppressing because the Ammonium Acetate blows apart the pests and pathogens. Microbial activity also benefits plants lime. All plant available nutrients are not only the indirectly by developing organic matter and improving soil ones in solution. Plant roots create a mild acid which quality. While the entire microbial ecosystem supports plant can make many of the soil bound nutrients available. growth, Plant Growth Promoting Rhizobacteria (PGPRs) Check with your certified crop advisor for more offer specific advantages for agriculture. information.

Source: Blake Sanden, UCCE Irrigation/Soils Advisor PGPRs inhabit the rhizosphere, the layer of soil one to two Ask for it by name millimeters thick directly surrounding plant roots[5]. The Blue Mountain Minerals rhizosphere attracts soil organisms with root exudates high Naturally the Best! in nutrients and carbon. Bacterial populations thrive in the For more information 209-533-0127x112

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rhizosphere, reaching populations 10 to 100 times higher than in the bulk soil, further away from plant roots[2]. Most rhizobacteria have neutral impact on crop growth, and only 2% to 5% benefit crops in ways significant enough to earn classification as PGPRs[5]. Wellknown PGPRs belong to the genera Bacillus and Pseudomonas. Species in these genera occur naturally in agricultural soils, but growers can inoculate crops with specific strains isolated for their beneficial effects and compatibility with host plants. PGPRs promote crop growth through many direct and indirect mechanisms, including but not limited to: • Plant hormone production • N2 fixation • Nutrient mineralization •

Siderophore production

• Induced Systemic Resistance

• Antibiotic production

environmental conditions[2,3,5].

•

Chitinase production

•

Competitive inhibition of pathogens

Other types of nitrogen-fixing bacteria form symbiotic relationships with nonleguminous crops. Actinomycetes colonize certain trees and woody plants.

Trees inoculated with actinomycetes are sometimes used in land reclamation projects to stabilize degraded soil and revive fertility[3]. Maize, rice, wheat, sugarcane and other grasses can host several types of endophytic diazotrophic bacteria. In addition to nitrogen fixation, these bacteria also improve root shape and enhance fine root hair growth, increasing nutrient and water absorption into the plant.

Endophytic diazotrophs, including Azotobacter, Azospirillum, Acetobacter, Azoarcus and others are commonly used in agricultural crops in Mexico, Brazil and other tropical regions[3].

Atmospheric N2 Fixation

Farmers have relied on nitrogen-fixing bacteria for thousands of years to maintain soil fertility. Widely known crops include soybeans, peanuts and other legumes, but some grasses and woody plants also form symbiotic relationships with nitrogen-fixing microbes.

Legumes host six different groups of bacteria in the family Rhizobiaceae.

Rhizobia colonize plant roots, forming nodules where they fix atmospheric nitrogen to support their own growth while feeding the plant. Well-nodulated hosts can derive most of their N requirement from rhizobia, but efficacy depends on several factors, including bacterial population density, compatibility between bacteria and host, use of N fertilizer, soil quality and other

Continued on Page 18

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requires enzymatic degradation by phytase to release the P into a plant-available form. Roots produce insufficient phytase quantities to meet their growth requirements, so plants often depend on several types of Phosphorus Solubilizing Bacteria (PSB) to meet their demand[5].

Compost, mulch, liquid organic fertilizers and other organic soil amendments that add energy rich carbon substrates, while reducing tillage can preserve the microbial communities after establishment (photo courtesy Rex Dufour, NCAT.)

Continued from Page 17

Phosphorus Availability

Plant-available phosphorus often limits crop yield, even in soils where total P content is high. P fertilizer applied to alkaline or calcareous soils precipitates into unavailable forms quickly, representing significant financial loss. Similarly, the investment in manure and compost cannot be recovered until microbial populations mineralize the organic P, N and other nutrients. Phytate, the predominant form of organic P,

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Pseudomonas, Bacillus, Raoultella, Enterobacter and other PGPRs increase P availability and uptake by producing phytase, solubilizing mineral P through soil acidification, or by complexing ionic P to prevent precipitation. Root colonization by multiple PSBs simultaneously can significantly increase P concentrations in plant tissue. For example, rice inoculated with both Gluconacetobacter and Burkholderia had higher P concentrations than when inoculated with each individually[5]. Inoculating with PSBs and managing fields in ways that promote beneficial microbial growth can improve the crop’s P uptake efficiency, reducing reliance on frequent fertilizer applications.

Iron Availability

Iron availability also commonly limits crop growth in alkaline soils. Above pH 6.5, iron precipitates out of solution by binding with oxides, hydroxides and oxyhydroxides. Some plants acidify the soil, surrounding their roots to solubilize and absorb iron, while others rely on organic chelating agents to deliver the micronutrient. Microorganisms such as Pseudomonas fluorescens aid in iron uptake by releasing siderophores, carbon compounds that bind with iron, keeping it in bioavailable form at neutral to alkaline pH. Many grasses and other plants acquire iron by producing their own phytosiderophores, but some species can recognize and absorb siderophores produced by beneficial bacteria and fungi[5].

When crops continue exhibiting iron deficiency symptoms even after fertilization, inoculation with siderophore-producing microorganisms may help alleviate the problem.

Compatibility between every crop variety and siderophore producer is unknown, but beneficial inoculant providers may be able to help determine whether your crop has the potential to absorb the type of siderophore produced by their proprietary strain.

Pathogen Suppression and Induced Systemic Resistance

Promoting beneficial microbial growth can help prevent crop damage from plant pests and pathogens. PGPRs suppress deleterious organisms in several ways, including competitive inhibition, antibiotic production and by triggering plant defense pathways. PGPRs can suppress pathogenic population growth by outcompeting their opponents for access to nutrients, carbon substrates, space for growth, or other resources[2,3,4,5]. PGPRs employ many competitive adaptations to sequester nutrients and starve out pathogens. While siderophore production is widely known for its positive influence on iron nutrition, bacterial iron chelation also

Continued on Page 20 18

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Continued from Page 18 plays an important role in suppressing plant pathogens via competitive inhibition. Siderophores help beneficials outcompete pathogenic organisms by preventing their opponents from accessing iron. Different microorganisms recognize and absorb specific types of siderophores, and population growth often depends on each species’ iron sequestration capability. Beneficials that produce unique siderophores can sequester enough iron to induce deficiency in pathogens, preventing infection in host plants[2,5].

PGPRs also suppress soilborne disease by producing antibiotics, enzymes and secondary metabolites that kill or damage target organisms. Although specific modes of action are not yet fully understood, researchers have documented several mechanisms targeting the electron transport chain, enzymes, cell walls and zoospores. Pseudomonas chlororaphis and P. fluorescens produce the antibiotic, pyrrolnitrin, along with several secondary metabolites to control the fungal pathogen Sclerotinia sclerotiorum in canola and Rhizoctonia solani in cotton[2,5]. Some of the same antibiotics and metabolites that control pathogenic fungi also offer nematocidal effects. For example, pyrrolnitrin suppresses C. elegans while chitinase reduces infestation by Meloidogyne incognita, a root knot nematode that infects tomatoes and other crops[5].

Beneficial microorganisms can also aid in crop protection by strengthening the plant’s immune system response to pest and disease pressure. Pseudomonas, Serratia, Bacillus and other PGPRs can help prevent crop damage by triggering Induced Systemic Resistance (ISR), whereby plants initiate defense strategies in response to microbial signaling. Several bacterial compounds and cellular structures can act as signals, alerting the plant to potential threats from disease organisms. In response to microbial signaling, plants protect themselves by building thicker cell walls, fast closures on stomata and other structural defenses[2,5].

Promoting Beneficial Microbial Growth

Ongoing soil microbiology research will continue revealing the mechanisms driving beneficial microbial activity. While many questions remain unanswered, growers can experiment with strategies likely to elicit plant growth promoting microbial interactions.

Compost, mulch, liquid organic fertilizers and other organic soil amendments add energy rich carbon substrates, while reducing tillage can preserve the microbial communities after establishment. Live microbial inoculants have the potential to improve yield and decrease chemical applications, but efficacy depends on many biological and environmental factors. Choose strains compatible with the crop and apply inoculants when soil conditions favor establishment. Managing the soil microbiome may require trial and error but understanding foundational microbiology concepts and experimenting with new management practices will help growers unlock the soil’s microbial potential.

References 1) Becker, W. M., Hardin, J., Berton, G., & Kleinsmith, L. (2012). The World of the cell (Eighth Edition). Benjamin Cummings.

2) Beneduzi, A., Ambrosini, A., & Passaglia, L. M. P. (2012).

Plant growth-promoting rhizobacteria (PGPR): Their potential as antagonists and biocontrol agents. Genetics and Molecular Biology, 35(4 suppl 1), 1044–1051. https://doi. org/10.1590/s1415-47572012000600020 3) Successful soil biological management with beneficial microorganisms. Plant Production and Protection Division: Soil biological management with beneficial microorganisms. (n.d.). Retrieved June 3, 2022, from https://www.fao.org/ agriculture/crops/thematic-sitemap/theme/spi/soil-biodiversity/case-studies/soil-biological-management-with-beneficial-microorganisms/en/ 4) Sylvia, D. M., Fuhrmann, J. J., Hartel, P. G., & Zuberer, D. A. (2005). Principles and applications of Soil Microbiology (Second Edition). ELSEVIER.

WRCCA SEEKS NOMINATIONS FOR CCA OF THE YEAR

By MARNI KATZ | Editor

W

estern Region CCA is now accepting nominations for its annual CCA of the Year award. The Western Region Certified Crop Adviser of the Year Award recognizes a WRCCA who has shown dedicated and exceptional performance as an agronomist and leads others to promote agricultural practices that benefit the farmers and environment in the Western Region. The winner will be announced at the annual Crop Consultant Conference in Visalia on Sept. 28.

“The Western Region CCA of the year recognizes the best of the best of our membership and that membership covers California, Arizona and Hawaii so we’ve got a wide pool of folks to choose from, about 1,400 certified crop professionals and agronomists in the region,” said WRCCA Board Chair Karl Wyant.

“We are looking for that top 1% who is setting the standard for their region, and providing that quality crop advising experience and information.”

Nominations are due by the last Friday in July. Guidelines, nomination form, and a rubric for selecting an eligible certified professional agronomist are available on the WRCCA website at wrcca.org/cca-of-the-year.

5) Van, E. J. D., Trevors, J. T., Rosado, A. S., & Nannipieri, P. (2019). Modern Soil Microbiology (Third Edition). CRC Press.

6) Washington State University. WSU Tree Fruit | Washington State University. (n.d.). Retrieved May 30, 2022, from http://treefruit.wsu.edu/orchard-management/soils-nutrition/soil-biota/

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc. com

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September 28th - 29th IN VISALIA OFFERS TWO DAYS OF ACTIVITY FOR CCAS AND PCAS

P

rogressive Crop Consultant “We are excited to again work with Magazine’s two-day Crop ConsulWestern Region CCA to bring this tant Conference will return to the popular event for crop consultants in Visalia Convention Center on Sept. 28 the Western United States to the Valley, and 29 offering for the first time two and expect another sell out event,” said concurrent sessions of seminars to sigJCS Marketing Publisher and CEO nificantly increase continuing education Jason Scott. “We are also happy to be opportunities for PCAs, growers and expanding our education platforms Certified Crop Advisers. to include two full days of CEU talks geared specifically for PCAs and CCAs.” The Crop Consultant Conference has become a premier event held in the San More than 10 hours of DPR CEUs and Joaquin Valley each September for Pest 13 hours of CCA CEUs, plus additional Control Advisors and Certified Crop credits for CDFA FREP and Arizona Advisers. Co-hosted by JCS Marketing, DPR are currently pending. Attendthe publisher of Progressive Crop Conees will also have access to exclusive sultant Magazine, and Western Region online CEU opportunities. In addition, Certified Crop Advisers Association, vendors will be available to discuss the the event brings industry experts and latest techniques, products and techsuppliers, researchers and crop consulnologies for this sophisticated audience. tants together for two days of education, During the industry lunches, Western networking and entertainment.

Region CCA Association will present 22

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its annual CCA of the Year Award and honorariums and scholarships to deserving winners.

Topics for the two days of seminars include: seminars on managing pests and diseases in high value specialty crops, fertilizer and irrigation management strategies in a limited supply situation, soil health, new technology, and tips for improved application and efficiency.

Several laws and regulation topics will also be discussed.

Registration is required and early-bird fees for the two-day event are $175, or less than $15 per CE unit. Take advantage of early bird pre-registration at progressivecrop.com/conference.

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WINTER COVER CROPS IN ANNUAL ROTATIONS

By SARAH LIGHT | UCCE Agronomy Advisor, Sutter, Yuba and Colusa Counties

By AMBER VINCHESI-VAHL | UCCE Vegetable Crops Advisor, Colusa, Sutter and Yuba Counties

Figure 1. Closeup of vetch.

W

e conducted a three-year trial evaluating winter cover crops in annual rotations in the Sacramento Valley. The field was certified organic and had been in wheat the year before the project, and then was planted to tomato followed by rice. Replicated plots of purple vetch (Figure 1) were planted at two rates in December 2018.

Treatment 1 (T1) was planted at 70 lb seed/A and Treatment 2 (T2) at 140 lb seed/A. The second year, the rates were reduced to 35 lb seed/A and 70 lb seed/A, and the cover crop was planted in November 2019. A fallow control was included in each replication in each year.

We had three replications of each treatment in a randomized complete block design. Cover crop termination began in mid-April 2019 and late March 2020.

The very heavy winter and spring rains in 2019 also meant termination was delayed by 3 weeks in year one (originally scheduled for mid-March 2019.)

The ground was worked heavily in fall 2018 and required moisture to protect the integrity of the beds so that beds would not collapse when the cover crop was drill seeded. However, once it began raining, the rain continued heavily for weeks. Thus, planting was delayed to the end of December 2018 as the field needed to be dried down before the planter could 24

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Table 1. Average percent cover for both years.

Figure 2. Top: 2019 average percent cover by plot; Bottom: 2020 average percent cover by plot.

enter the field. Driving on a field when the soil is wet will destroy soil structure and lead to soil compaction. Another good practice is to plant cover crops after July / August 2022

summer groundwork is completed but before the first rain in the fall. The seeds will sit in the ground and germinate after first rainfall. Minimizing tillage when

possible will maintain soil structure and may allow for more flexibility in fall cover crop planting because beds will be firm enough to plant even in dry conditions.

Unfortunately, the cover crop was planted at twice the intended rate in 2018 due to an error with the planter.

The first time that equipment is used to plant a cover crop, consider calibrating machinery and doing a test run to accommodate cover crop seed size. The manual can provide a starting point for settings but only calibration with both sides of the planter will ensure a consistent and accurate planting rate.

For all results, values denoted by different letters indicate significant differences between treatments.

Percent Cover

In mid-March 2019 and late March 2020, five one-square-meter areas of each plot were randomly evaluated for percent cover. Data included percent of

Table 2. Breakdown of percent nitrogen, total nitrogen per acre, percent carbon and total carbon per acre for different kinds of biomass (weeds, wheat, vetch) in treatment 1 (low seeding rate) and treatment 2 (high seeding rate) in 2019.

total weeds, bare soil, volunteer wheat (in 2019 only) and vetch within the quadrat. In 2019 and 2020, both rates of the vetch cover crop had significantly lower weed cover and bare soil compared to the fallow control (Figure 2, see page 24). There were no significant differences in wheat cover between treatments in 2019 (Table 1, see page 24). Maintaining soil coverage throughout the year is an important practice

for improving soil health and provides multiple benefits, such as reducing erosion, reducing soil evaporation, maintaining moderate soil temperature and reducing soil surface compaction.

Biomass

Biomass was removed from each plot in three random one-square-meter areas

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Table 3. Breakdown of percent nitrogen, total nitrogen per acre, percent carbon and total carbon per acre for different kinds of biomass (weeds, vetch) in control, T1 (low seeding rate) and T2 (high seeding rate) in 2020.

Figure 3. Average pounds per acre of total carbon and nitrogen from biomass by treatment in March 2019 compared to biomass sampled a month later in April 2019 (field rate is equal to T1 (low seeding rate)).

Continued from Page 25 on the same day percent cover was evaluated in 2019. These samples were dried and then sent to the lab for analysis. One sample from each plot was separated into weeds, wheat and vetch, and those samples were run separately. Wet soil conditions delayed cover crop termination, and in mid-April 2019, biomass samples were collected again from a portion of the field that remained, which was planted in the T1 (low) rate. In 2020, biomass samples were collected and analyzed using the same procedures as 2019, except that no wheat was collected from separated samples, only vetch and weeds. Samples were collected the same week as cover crop termination.

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In 2019, vetch contributed more carbon (C) and nitrogen (N) at the higher planting rate. Although the volunteer wheat and weeds contributed carbon and nitrogen, vetch is higher in percent N and contributes more nitrogen per pound of biomass. Table 2 (see page 25)

provides the breakdown from one plot of each rate as an example. Volunteer wheat was sampled when still green, so nitrogen had not moved into the seed.

Wheat will not fix nitrogen; however, wheat can mine residual soil N from depth. The warm weeks between when we first collected biomass and when the grower was actually able to terminate the cover crop led to a significant increase in biomass. The comparison of the T1 samples collected on Marth 18, 2019 to the field rate (same planting rate) samples collected a month later on April 16, 2019 indicated that the cover crop total N increased by almost a factor of four (69 lb N/A compared to 271 lb N/A) in the last month of growth (Fig. 3). Similarly, total C increased by a factor of five (from 721 lb C/A to 3,651 lb C/A) (Figure 3). For reference, on March 18, control plots averaged 910 lb C/A and 80 lb N/A and T2 averaged 981 lb C/A and 97 lb N/A. Figure 4 demonstrates the difference in vetch growth between March 18 and April 11, 2019.

In 2020, the higher rate of vetch contained more nitrogen in lbs/A (135) than the lower rate of vetch (97), and both treatments were significantly higher than the control plots (62), which only contained weeds. Both treatments also contained more carbon in lbs/A (T1: 1,299, T2: 1,562) than the control plots (902), though were not significantly different from each other. Again, vetch contributes more nitrogen per pound biomass because it is higher in percent N. Table 3 provides the breakdown from one plot of each treatment.

Figure 4. Photo comparison between vetch cover crop growth on March 18, 2019 (L) and April 11, 2019 (R).

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there was a difference in residue cover between the two seeding rates in year one, the main difference between the two seeding rates was regarding total nitrogen. Total N with the higher seeding rate was significantly higher both years, while total C was only higher in year two. Both treatment rates provided the benefit of out-competing weeds and reducing bare soil. When selecting a seeding rate, growers can make decisions on cost per unit N in cover crop residue regarding additional seed costs based on the ability to apply other nitrogen sources and overall budget.

Cover crop termination can be a big challenge in years like 2018 where rain and warm temperatures increased the vetch biomass four-fold, especially for the higher seeding rate.

Figure 5. Residue cover.

Figure 6. Percent residue cover in 2019 and 2020. Values denoted by different letters indicate significant differences between treatments. There were differences between treatments in 2020.

Residue Cover

Residue cover can improve water infiltration and reduce loss of topsoil to erosion among other things (Figure 5). On May 16th, 2019 and March 23rd, 2020, tape was placed in a transect of each plot and we counted the presence or absence of residue on the soil surface at six-inch intervals. Total points with residue were converted to a percent. In 2019, T1 (low) had significantly less residue cover than T2 (high) or Control plots. In 2020, there were no significant differences between treatments (Figure 6).

Crop Yields

We hand-harvested 15-foot sections of processing tomatoes from the middle bed of each plot in August 2019. To-

In this trial, we found that cover crops were able to out-compete weeds, improve soil health, maintain soil coverage and add nitrogen to the system. Our grower collaborator also noticed better soil aggregation and water infiltration in the treated plots as well. Although there were weather-related project challenges, cover crops can be incorporated into rotations in the region relatively easily and can add value in the short and long term. If it is possible to plant early in the fall, weather related challenges at planting will be reduced. If possible, termination timing can increase the total nitrogen in a cover crop as legume growth (like vetch) rapidly increases as the days get longer and the temperature increases. However, there are other factors around maintaining soil moisture and cash crop planting date that need to be considered. Managing cover crops may be different from year to year in our diverse California growing conditions.

matoes were sorted for red, green and culled fruit and evaluated for quality (Brix, hue and pH). Control plots yielded an average of 37 tons per acre, T1 averaged 44 tons/acre and T2 resulted in the numerically highest average yield at 47 tons/acre. There were no statistically significant differences in yield This project was part of a three-year or quality. However, a variety trial was Healthy Soils Demonstration Projplanted in two of the plots, which may ect funded by the California Climate have affected the results. This field was Investments program and the California also organic and suffered some yield Department of Food and Agriculture and loss from a johnsongrass infestation. would not have been possible without our The 2020 organic rice yield for the grower collaborator. field averaged 66 sacs dry and we were unable to collect yield data by plot. In addition, rice blast infected the field late in the season and reduced yield.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com Conclusions Is a higher seeding rate worth it? While July / August 2022

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How Crops Can Help Crop Advisors Through Systemic Acquired Resistance

By JW LEMONS | CCA, CPAg

C

CAs and PCAs around the world face plant diseases and pests. We all struggle with similar hurdles and roadblocks. I am referring to regulations on what we can spray and how we can apply chemistries to combat the diseases and pests that attack our crops. The public has become more cautious with what goes on their food. Some of this is warranted and some is a result of miscommunication and misunderstanding. Regardless, we as crop consultants and growers face changes and challenges.

I ask myself continuously what tools, new or old, do I have to prevent crop yield loss and quality loss. I discover new technology every month and try to study the mode of action and the positives as well as the negatives. Old reliable chemistry may no longer be an option. For example, fumigation has taken a very different path.

States have removed or discontinued labels and many pests and diseases have developed resistance against certain chemistry.

I picked the subject of plants and their immunity and/or built-in resistance because it exists, and we can use it as a tool. I have read numerous articles as have many of you on Systemic Acquired Resistance (SAR) in plants. Scientists can talk and debate for years on end about which genes are triggered and what triggers the plant to defend itself. As a crop consultant, I try and understand all the effects and turn it into a simpler communication. I base this on research findings and the results of continuing trials. When a positive response is triggered, and labels are approved, I can then present alternatives to consultants and growers.

This is a brief overview on natural 28

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A potato leaf previously treated with a systemic acquired resistance (SAR) activator is inoculated with potato virus Y by USDA virologist Pete Thomas (photo by Peggy Greb, courtesy USDA.)

Systemic response after pathogen infection. A systemic signal (probably NHP-related) leads to an accumulation of SAR proteins such as SA, Pip and NHP in systemic leaves. This is called primed state. When another pathogen now infects this leaf the immune system can react much faster. This is then called systemic acquired resistance (SAR).

resistance in plants; if the reader wants more detail, I point them toward the many great scientists and research work discovered over the past century. You can read and absorb this at your own pace.

What is Systemic Acquired Resistance?

Some of the science is explained by

knowing that a plant’s natural resistance is regulated by two fundamental mechanisms: the “nonhost” and the “genefor-gene” resistance, respectively. The latter is relevant when a certain cultivar resistant (R) gene product recognizes an a-virulence gene product in the attacking pathogen. This can trigger biochemical reactions that halt the pathogen around the site of attempted invasion.

For nearly a century, plant scientists have known that when a plant survives a disease, it often is more resistant to subsequent infections. It’s as if the plant’s immune system has become stronger.

Plants may benefit by some temporary immunity after a challenge triggers

Continued on Page 30

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Continued from Page 29 a defense reaction. There can be a hypersensitive response (HR). This process, mediated by accumulation of endogenous salicylic acid (SA), is called systemic acquired resistance (SAR).

This SAR can provide some limited resistance against unrelated pathogens, such as viruses, bacteria and fungi, for a relatively long-lasting period. SAR may be more potently activated in plants pretreated with chemical inducers, most of which appear to act as functional analogues of SA. I could go on about this covering genes, pathogenesis related proteins (PR), exogenous inducers (both synthetic chemicals and natural products), and we could discuss signal transduction between the inducer and the PR proteins.

I will simply bring to your attention that plants do have a natural immune system. We can enhance this resistance with materials that are available for us from many manufactures. Crop consul-

tants can introduce the ability to induce a systemic resistance in the current year’s crop by triggering a chemical response within the plant, providing a powerful tool for growers. All of us strive for the best integrated pest management (IPM) we can design. Now, inducing resistance can be integrated into the crop protection program and may reduce conventional pesticide use.

logical control of plant disease.

Plant Defense Products

Complete articles have been written on single products that can trigger a plant’s defensive system. There are too many to cover in a short article. I will try to point out a few so people can look further into this type of technology. I will start with elicitors. An elicitor can be defined as a chemical or biochemical compound that is introduced in small concentrations to a living system to promote the biosynthesis of the target bioactive compound.

Various biotic or abiotic factors induce systemic resistance in plants that is phenotypically like pathogen-induced systemic acquired resistance (SAR). Some of the biotic or abiotic determinants induce systemic resistance in plants “Elicitors are the low-molecular-weight through salicylic acid (SA) dependent compounds which trigger plant imSAR pathway, while others require jasmune response by activating signal monic acid (JA) or ethylene. Host plant cascade. Elicitors are classified into two remains in induced condition for a types (i.e., pathogen derived elicitors or period, and upon challenge inoculation, exogenous elicitors) and plant derived resistance responses are accelerated and elicitors (endogenous elicitor). Most enhanced. Induced systemic resistance of the exogenous elicitors of the plant (ISR) is effective under field conditions defense responses are nonspecific and and offers a natural mechanism for bio- differ widely in their chemical nature, including protein, oligosaccharides, glycoprotein and lipids. Inducible defense responses can be triggered, not only upon the encounter of the plant tissue by pathogen, but also upon the elicitor treatment. Therefore, elicitors are now extensively used to study the molecular mechanism of defense responses,” – (Suzuki, 1999) Progress and continued research have continued not only on preharvest plants, but also on postharvest fruits and vegetables. The definitions of elicitors change with each publication you read. Scientists attempt to breed plants and use biotechnology to induce accumulation of secondary metabolites to help trigger defensive responses. Biotic elicitors, such as fungal homogenates, chitosan, jasmonates, jasmonic acid and methyl jasmonate, are both used to stimulate secondary metabolite production. Examples of these are nicotine alkaloids or phenylpropanoids in plant cells. Fungal and bacterial extracellular metabolites are produced when an infection damages cells. Reproducing these fungal elicitors and treating a

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®

plant with them has been studied.

As consultants, we accept that disease control is largely based on the use of fungicides, bactericides and insecticides (chemical compounds toxic to plant invaders, causative agents or vectors of plant diseases.) Many of these chemicals or the degradation of these chemicals have been shown to have hazardous effects on the environment and human health. As good consultants and stewards of the land, we must continue the search for new, harmless means of disease control. By using natural phenomenon of induced resistance to protect plants from disease, we can achieve sustainable goals.

There are many common commercial products currently used. I recommend you talk extensively with your biological and chemical providers and request a breakdown of current successful products that are designed to induce the crop’s immune system. With multiple countries scrambling to introduce or reintroduce synthetics, various acids, bioactives, sugars, inorganic salts and much more, you need to look into this alternative for your IPM program.

We have barely touched the surface of inducing plant defenses. Elicitors can be one of the greatest tools we have. Once again elicitors are compounds, which activate chemical defense in plants.

Various biosynthetic pathways are activated in treated plants depending on the compound used. In review, some of the commonly tested chemical elicitors are salicylic acid, methyl salicylate, benzothiadiazole, benzoic acid, chitosan and so forth, which affect production of phenolic compounds and activation of various defense-related enzymes in plants. Their introduction into agricultural practice could minimize the scope of chemical control, thus contributing to the development of sustainable agriculture.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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31

UC Merced Research Center Aims to Improve Yields, Production Efficiency through Internet of Things

By CATHERINE KESKE | IoT4Ag Site Director, Agricultural Economist, UC Merced

Figure 1: Mobile robot from UC Merced Computer Science Engineering Professor Stefano Carpin’s lab.

U

C Merced is one of four universities co-leading an ambitious project to create a system of Internet of Things (IoT) precision agriculture technologies to improve food, energy and water security for decades to come.

The UC Merced project is part of the Internet of Things for Precision Agriculture (https://iot4ag.us/) Engineering Research Center (ERC), funded through a prestigious National Science Foundation program. ERCs are designed to produce systems of commercially available products to address societal grand challenges like food security. In addition to facilitating cutting-edge research, ERCs like IoT4Ag offer workforce development, education and

32

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outreach programs.

What is IoT?

IoT systems can be programmed to connect, collect and share data without direct human-to-computer interaction.

In the ag tech space, plant-specific information can be communicated to growers in real time through hand-held devices like phones or tablets. A system of interconnected precision agriculture devices is projected to provide cost savings for growers because nutrients and water are applied where and when they’re most needed.

Experiments are being conducted in a vineyard where the navigation software that autonomously moves the robot through preassigned GPS waypoints is being tested. Figure 1 (see page 32)

July / August 2022

shows a mobile robot from UC Merced Computer Science Engineering Professor Stefano Carpin’s lab. The two yellow boxes mounted on the red and yellow posts are GPS receivers. The computer is controlled by the laptop mounted on the back. Note that in this case, the robot does not have the soil moisture sensor.

Figure 2 shows a mobile robot from Carpin’s lab equipped with a system to measure soil moisture. The sensor is placed at the bottom of the linear actuator visible between the two wheels.

When the robot reaches an assigned GPS waypoint, it stops, lowers the actuator and sticks the soil moisture probe in the soil. The data is read and stored in a data logger (to log when and where the sample was taken and the value.)

Then the robot lifts the sensor and

moves to the next waypoint. The photo was taken in an experimental vineyard located in central California.

Sensors, robots, computers and other technologies can be deployed to detect plant stress. Figure 3 (see page 34) shows an unmanned aerial vehicle collecting a hyperspectral aerial image in a pistachio orchard. The aerial hyperspectral image along with the data from the newly developed water stress sensor and an algorithm can predict water stress for the entire orchard. '

Figure 2: This mobile robot from Carpin’s lab is equipped with a system to measure soil moisture (photo courtesy UC Merced Robotics Lab.)

Testing IoT Technology on Tree Crops

Almonds, pistachios and pomegranates are among the first crops in the Central California test bed located near the UC Merced campus. The test bed will eventually expand to include row crops, such as corn, already being evaluated at the Purdue University test site.

Technology developed through IoT4Ag will be made commercially available over the project’s 10-year period. By 2030, it’s anticipated that IoT systems will be deployed across four states, including California.

Reza Ehsani, UC-Merced Professor of Mechanical Engineering, recently developed a new low-cost, wireless sensor that can monitor water content and sap flow in tree trunks. This sensor can be used to predict tree water stress. The sensor was used to collect data during the entire growing season in a pistachio orchard (Figure 4, see page 35) In addition to researching sensors and robotics, IoT4Ag investigators are advancing sensor fusion, data imaging, communication networks and battery recharge stations for unmanned aircraft.

Technology advancement for all these components is necessary to deploy fleets at large agricultural scales.

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Grower Adoption: Opportunities and Challenges

Growers face several tradeoffs between cost and information when deciding whether to adopt IoT technology. Nearly every decision that growers make comes down to whether the technology

Continued on Page 34

Contact us for ways to add Pacific Gro results to your program.

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33

ent and water deficiencies. Growers can make specific management decisions on the spot. Intervention at critical points in plant development can save plants and increase yield. But does the technology pay for itself? Implementing the IoT4Ag system in a cost-effective way is essential.

Figure 3: This photo shows an unmanned aerial vehicle collecting a hyperspectral aerial image in a pistachio orchard (photo courtesy Reza Ehsani, UC Merced.)

Continued from Page 33 pays for itself by increasing yield and reducing costs. Most growers appreciate additional information, but what do they do with it? Is this additional informational information worth the added expense?

IoT4Ag is striving to develop reliable,

cutting-edge technology and to make systems cost-effective at every step of implementation. Expenses may include sensors and robotics that collect and transmit data as well as licenses and subscription fees to support infrastructure. Infrastructure includes data storage, internet and hand-held devices.

We’re developing systems and technologies to rapidly alert growers about nutri-

In addition to conducting cost analysis, my colleagues and I are evaluating the benefits from data collected through digital platforms. Think of the hidden benefits of a “free” platform like Facebook that facilitates communication between many users who voluntarily offer personal information. Eventually, IoT technologies may become less expensive and available to others because a few individuals are willing to share their yield and nutrient information.

Industry may be able to offer products or subscriptions at a reduced cost to growers. Analogously, some technologies like high-speed internet become widely available in rural areas because a few subscribers’ demands are willing and able to pay for the internet service.

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Is providing information through a digital platform worth the loss in privacy? I think it depends how that information is used. Research shows that three or four years of field data can really help growers manage their crops. But what happens to that data over the span of years?

Where does that information go? What are the implications of this? It’s important to understand the lifecycle of the data being collected.

We are also conducting focus group research and interviewing California growers to gain firsthand perspectives on data privacy and security and other barriers to adopting precision ag and IoT technology. Growers in the few published studies have included row crop growers rather than those of tree crops. Results from my barrier to adoption study are expected in late summer or early fall.

There is still opportunity for interested growers to participate in the barrier to adoption focus groups. Interested growers can contact me directly at ckeske@ucmerced.edu.

Figure 4: A prototype of a newly developed low-cost sensor for monitoring water stress in trees (photo courtesy Reza Ehsani, UC Merced.

Comments about this article? We want to hear from you. Feel free to email us at article@ jcsmarketinginc.com

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July / August 2022

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35

The Impact of Pistachio Sanitation on Navel Orangeworm Damage and Egg Trap Counts

By BRADLEY S. HIGBEE | Research Entomologist, Field R&D Manager, Trécé, Inc.

Ground mummy sampling.

S

160 acres and was assigned a treatment, omone and almond meal-baited sticky anitation has been shown to be “Full sanitation” or “No sanitation”, for traps in equal numbers to the egg traps. beneficial in reducing navel orangethe duration of the trial. Full sanitaThese data are not reported here but will worm (NOW) populations and tion consisted of shaking and poling be addressed in a future article. damage in pistachio orchards; however, (2005-10 only) the trees, sweeping and the impact is not as great as has been All plots received the same NOW inblowing the berms and then shredding demonstrated in almond. This is likely secticide applications within each year, or disking twice. In the “No sanitation” and these typically consisted of two due to the inability to destroy mummies plots, shaking and poling or shaking “hullsplit’ applications in August prior that are on the ground. The standard the trees were performed in 2006-08 to the first harvest shake (typically early shaking and poling efforts can reduce (Table 1, see page 38); otherwise, there to mid-September.) Harvest samples mummies in the trees as well as in were no sanitation efforts until weeds of about 1000 nuts (3 to 500 nuts from almonds. But due to the smaller, harder were mowed in late April/early May. three adjacent trees) were taken from Sanitation assessments were conducted nature of pistachio mummies, the typeach egg trap location just prior to both in two-tree-by-four-tree areas (two adical mower/shredder equipment is not the first and second harvest shakes for a jacent rows with a total of eight trees.) able to pulverize the pistachio mumtotal of about 8000 nuts from each plot.

All mummies from the ground and in mies as well as almond mummies. Egg NOW damage was pooled for the two the tree were collected and counted septraps have been a standard monitoring harvest sample dates and the overall arately and the total divided by eight to tool in nut crops for decades. In this mean for each treatment is shown in obtain the mummies per tree.

For each study, looking at the impact of pistaTable 1. plot, four areas were sampled in each chio sanitation on harvest damage, we quadrant for a total of sixteen sample looked at number of mummies in the areas. All mummies were dissected in tree and on the ground after sanitation Sanitation the lab for presence of NOW (results Table 1 lists the mean number of mumwas performed and the impact on the not reported here.) mies on the ground and in the trees for number of eggs on egg traps. plots receiving partial or no sanitation There were four egg traps in each (No San) and plots receiving full saniquadrant of each plot. Egg traps were Methods tation (Full), along with NOW damage loaded with commercial almond meal In 2005, three replicate treatment plots (no oil added) which was replaced every levels. The NOW damage reduction were established in pistachio orchards in the full sanitation treatment ranged two weeks. Traps were checked and egg that were planted in 1973 and located counts recorded each week. The design in western Kern County. Each plot was Continued on Page 38 of this experiment also included pher-

Drive row and berms prior to sanitation activities (all photos courtesy B. Higbee.)

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Drive row after mowing for weeds in No san plot.

Our IPM solution doesn’t take days off.

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L

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F

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Ground Mummies

Tree Mummies

Mean/tree Partial Trtmnt

Yr

No San

None

2005

Shake/Pole

2006

Shake/Pole Shake only

% NOW Dmg mean %

Mean/tree

* sig diff

Full

No San

Full San

No San

Full

Difference

249

25

13.41

0.01

2.4

1.73

0.67*

27.9

829

147

0.06

0.01

0.25

0.07

0.18*

72.0

2007

601

142

0

0.01

5.1

3.5

1.6*

31.4

2008

932

335

52.66

0.22

1.43

0.86

0.57*

39.9

None

2009

1731

537

149.0

0.1

1.67

1.54

0.13

7.8

None

2010

729

459

8.8

0.23

0.44

0.25

0.19*

43.2

None

2011

763

239

54.7

3.4

0.42

0.11

0.31*

73.5

None

2012

344

170

123.6

1

3.66

2.80

0.86*

23.5

None

2013

519

450

100.5

0.625

2.8

2.6

0.2

7.1

None

2014

1132

297

168.7

12.3

2

1.8

0.2

10.0

None

2015

1875

426

147.9

9.7

2.85

2.7

0.15

5.3

882

293

74.5

2.5

2.1%

1.6%

0.17%

23.8%

Mean

% Reduction

Table 1: The number of mummies per tree on the ground and in the trees from plots where sanitation was performed (Full) compared to plots with partial or no sanitation (No San). Percent NOW damage calculated from experimental field samples taken at harvest and processed by hand. Statistically significant damage differences are indicated by an asterisk.

Mummies on berm that escaped blowing and sweeping.

Continued from Page 36 from 5% to 73.5% with an average of 23.8%. The greatest benefit was in years of relatively high NOW damage, such as 2005, 2007 and 2012. There were some years in which the damage reduction was 10% or less (2009, 2013, 2014 and 2015), but in 7 out of the 11 years of the study, NOW damage was reduced by 23.5% or more. Over the duration of this study, the mean damage reduction was 23.8% with the Full averaging 1.6% and the No San averaging 2.1%. It is important to notice that even though there was an overall reduction of nearly 70% in the number of “Ground Mummies” in the Full treatment (882 in No San vs 293 in Full), there were still a significant number of mummies on the ground. Tree mummies were reduced 38

Progressive Crop Consultant

to 2.5/tree on average, and considering that a proportion of these mummies contained blank nuts not suitable for NOW development, this should be an acceptable level and on par with almond recommendations for trees.

Egg Trapping

Figures 1 to 3 are representative graphs of egg trap dynamics for the purpose of characterizing the response of trap counts to different mummy loads in pistachio orchards. Figures 1, 2 and 3 show weekly egg trap counts in Full and No San treatments for 2013, 2014 and 2015. In 2013, there was a very large difference in tree mummies between the treatments, while ground mummy counts were slightly higher in the No San treatment.

July / August 2022

The difference in tree and ground mummies was numerically high in 2014 and 2015 (Table 1). First flight egg trap counts for 2013 show a peak of nearly 800 eggs/trap/week in the Full plots while the No San plots peaked at about 100 eggs/trap/week, and this peak occurred about two to three weeks later than the large peak in the Full treatment. In 2014, there were large differences in both ground and tree mummies between the treatments, and two first flight peaks occurred.

The first peak occurred simultaneously in the two treatments, with the Full at about 160 eggs/trap/week and the No San at about 25 eggs/trap/week. The difference in second peak magnitude between treatments was much less pronounced, with the peak in the Full plots at about 90 eggs/trap/week and the No San at about 65 eggs/trap/week with a delay of about one week. Also in 2014, the second flight peak was more pronounced and the No San peak was greater than the Full peak (60 eggs/trap/ week vs 25eggs/trap/week), displaying a reversal in the trend from the first flight.

In 2015, peak counts and differences between treatments were much lower (20 eggs/trap/week), but the trend from 2014 was repeated; higher counts in the Full treatment for the first peak with higher counts in the No San treatment in subsequent peaks.

Conclusions

The reduction in both tree and ground mummies was substantial in the Full plots, an average of over 96% reduction for tree mummies and nearly 67% for ground mummies. This resulted in lower damage in the “full” plots each of the 11 years in this study. However, due to the pattern of nut susceptibility to NOW attack and regardless of the relative abundance or pressure from NOW populations, NOW damage was 2% or less in six of the 11 years (Table 1). The average percent reduction in NOW damage in those years was 0.26%. In the five years that NOW damage was above 2%, the average reduction was 0.7%, but in the two highest years of damage, 2007 and 2012, the reduction was 1.6% and 0.86%, respectively. The results from 2007 are particularly interesting; NOW damage was highest and the difference between treatments the greatest (5.1% vs 3.5%), and shaking and

After second pass with shredder.

poling was performed in both the Full and No San treatments, resulting in virtually no tree mummies in either treatment.

However, there were 601 and 142 ground mummies/tree in the No San and Full treatments, respectively, suggesting that ground mummies are an important source of host material for NOW reproduction. This also suggests that if ground mummies could be reduced further, perhaps to an equivalent level commonly found in well sanitized almond orchards (five to ten mummies/tree), NOW damage could be reduced to an even greater extent.

Figure 1: Egg trap counts for traps in fully sanitized (Full) plots and plots receiving no sanitation efforts (No San) in 2013.

1050 NOW degree-days from biofix occurred on June 5, 2100 degree-days on July 20 and 3150 degree-days on September 1.

A few things that are clear from Figures 1 to 3: 1. Based on parallel trapping data with sex pheromone traps (not presented here), attractiveness of almond meal-baited egg traps to NOW females appears to diminish after midJune (the end of the first flight) and does not have a good correlation to relative NOW population densities.

2. Since NOW damage was around 2% in each of these years and egg trap counts were vastly different, there seems to be absolutely no correlation between relative NOW populations as represented by egg traps and NOW damage at harvest.

3. The fully sanitized plots had much higher first-flight egg trap counts than the plots that had no sanitation efforts.

4. The much greater difference between tree mummies (14 to 160 times more in No san plots) relative to ground mummies (1.2 to 4 times more in No san plots) suggests that egg traps have much less competition in fully sanitized orchards, resulting in much higher egg counts than would occur under the same conditions in an orchard that is not sanitized with the same NOW abundance.

Based on this study, sanitation as practiced is likely worthwhile, but it will have the most impact in years of high NOW damage. Egg traps, while still very good at establishing a biofix in pistachio orchards (not necessarily true in almonds), may not be a good relative indicator of population abundance between orchards unless the number of tree mummies is similar. If improvements in ground mummy destruction equipment are realized and prove to be practical, sanitation would likely have a much greater and more consistent impact and NOW management in pistachio would be vastly improved.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

Figure 2: Egg trap counts for traps in fully sanitized (Full) plots and plots receiving no sanitation efforts (No San) in 2014. 1050 NOW degree-days from biofix occurred on June 1, 2100 dd on July 14 and 3150 dd on August 24.

Figure 3: Egg trap counts for traps in fully sanitized (Full) plots and plots receiving no sanitation efforts (No San) in 2015.

1050 NOW degree-days from biofix occurred on June 10, 2100 dd on July 21 and 3150 dd on September 1.

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39

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