Cover Story

Major Pests and Control Programs for the MD Turfgrass Industry in 2023

Lawn Turf, Part 2: Lawn Care

By Dr. Kevin Mathias

A phone survey was conducted in the fall of 2023 to determine the key turfgrass pests within the turfgrass industry. The survey asked turfgrass professionals what their major pest problems were within the areas of insect, weed, and disease problems and what type of control programs were used. The following article covers the major pest problems and control actions taken by lawn care businesses in Maryland. Also, the survey looked at pest control options in Montgomery County, Maryland due to more restrictive legislation regarding pesticide choices.

Lawn Turf

The major lawn turf consisted of a tall fescue/ Kentucky bluegrass mixture while turfgrasses such as zoysiagrass and the fine fescues were minor turfgrasses in lawn turf.

Major Pest Problems

Weed Pests

Weeds were considered the predominant pest of lawn turf and far outweighed insect and disease related issues. Also, more ‘call back’ type service was required with regards to weed related issues. The major grass weeds mentioned were Japanese stiltgrass and crabgrass followed by rough bluegrass and common bermudagrass.

The major broadleaf weeds were white clover, oxalis, and wild violets followed by ground ivy, spurge, and smartweed. Although not a broadleaf weed, nutsedge was considered a major weed pest.

Figure 1. Grass weeds mentioned as major weed pests in Maryland lawns.

Figure 2. Japanese stiltgrass is considered a highly invasive summer annual grass in Maryland lawns

Figure 3. The predominant lawn weeds found on Maryland lawns in 2023

Grass Weed Control

Weed control programs for summer annual grasses consisted of cultural and chemical control options. Herbicide options centered on the use of preemergence herbicides with Barricade (prodiamine) and Dimension (dithiopyr) listed as the products of choice. Since Japanese stiltgrass is the major summer annual grassy weed which germinates earlier than crabgrass two applications of a preemergence herbicide are often required. The first application is done in late fall with a second application in the spring. For crabgrass control and other summer annual weeds Dimension or Barricade provided acceptable control.

Weed control for rough bluegrass and bermudagrass require more custom type applications. Bermudagrass competitiveness was reduced with Acclaim (fenoxaprop) or Acclaim and Turflon (triclopyr) applications. Also, non-selective Round-up (glyphosate) applications followed by reseeding was performed in limited situations. For rough bluegrass the only herbicide of choice was a Round-up application followed by reseeding. [Editor’s Note: Since this survey, Velocity PM has been labelled for rough bluegrass suppression on home lawns.]

Broadleaf Weed Control

For broadleaf weed control the phenoxy based herbicides were the product of choice consisting of 2,4-D, mecoprop, and dicamba in two- and three-way combinations. For more difficult to control weeds such as wild violets, triclopyr was often used in combination with 2,4-D or by itself.

Nutsedge control herbicides listed included the following: Dismiss (sulfentrazone), Sedgehammer (halosufuron), and Solitare (sulfentrazone and quinclorac).

Insect Pests

Insects were not a major pest problem on Maryland lawns based on the 2023 survey. Though white grubs were listed as a pest problem, their damage to Maryland lawns was minor and spotty. The fall armyworm outbreak in 2021 was of some concern to lawn care operators even into the 2023 growing season.

Control action for white grubs varied with regards to a preventative versus a rescue type application or on an as needed basis. If a preventative approach was used, then two criteria were often used to determine if an insecticide was applied. The criteria were: 1) was there a history of grub damage and or 2) the customer would have to sign up for that specific treatment.

Acelepryn (chlorantraniprole) was the insecticide of choice for preventative control while Dylox (trichlorfon) was used for rescue type applications. White grub control insecticide applications varied from as low as 5% to over 50% of lawn care customers.

Disease Pests

Due to favorable conditions such as moisture and temperature, disease development occurs regularly in Maryland lawn turf. Since the majority of lawn turf consists of tall fescue or tall fescue- Kentucky bluegrass mixture the major diseases reported were brown patch and red thread followed by Pythium, dollar spot, and gray leaf spot.

Figure 4. Major diseases reported to occur on lawn turf.

The fungicides listed by lawn care operators often consisted of combination products containing two fungicides with different modes of action. For example, the fungicide Armada consists of Bayleton (triadimefon) and Compass (trifloxystrobin). Both of these fungicides have different modes of action and also increase the overall efficacy and spectrum of disease control. Fungicide applications were generally done on an “as-needed basis”.

Montgomery County Lawn Care Pest Control Options

In 2015 Montgomery County, MD passed legislation that would restrict pesticide options for pest control in lawn turf. The legislation requires any pesticide applied to lawn turf meet OMRI (Organic Materials Review Institute) certification or carry an EPA Exemption 25(b) label.

Implementation of the law was to initially begin in 2016 on county owned property and to private lawns by 2018. However, court challenges to this new legislation pushed the timeline of implementation back to 2019-2022 time period. For example, the city of Rockville did not enforce this new law until 2022.

Weed Pests

The common weeds included plants such as crabgrass, Japanese stiltgrass, bermudagrass, clover, oxalis, and nutsedge and mirrored what was mentioned earlier except that there were less control options available. Also, the majority of pesticides that meet the new Montgomery County requirements were for weed control purposes. The following herbicide products used were as follows; Fiesta, corn gluten meal, A.D.I.O.S, and Homeplate.

The herbicide Fiesta was most often used for selective broadleaf weed control in lawn turf. Multiple applications (2-4) were required to get acceptable control. The active ingredient in Fiesta is a chelated form of iron known as FeHEDTA. Aso the herbicide A.D.I.O.S. is a salt-based product containing several different salts such as sodium chloride and potassium chloride and has labeling for broadleaf weed control in turf but can also be quite injurious under certain environmental conditions. The non-selective herbicide, Homeplate, consists of the fatty acids caprylic and capric acid. All three of these herbicides lack systemic type activity and require repeat applications.

Figure 5. The major type of herbicides used in lawn turf in Montgomery County MD in 2023.

The preemergence herbicides that contain corn gluten meal contain proteins that interfere with root growth during weed seed germination of small seeded grassy and perennial weeds. It is also a source of nitrogen (10% by weight).

With regards to insect control, only white grubs were considered a key pest with only the insecticide containing Bt galleriae (grubGONE) used for control in Montgomery County, MD. Often diseases such as brown patch and others were mentioned but were not treated.

Due to restrictive measures in Montgomery County on selecting pesticides, a number of lawn care operators would prefer to emphasize primary cultural practices such as higher mowing heights, irrigation practices, and proper fertility programs to combat and reduce pest activity. If pest damage did occur, then overseeding or reseeding of a lawn was performed instead of applying a pesticide. One such lawn care business who often had noticeable weed encroachment during the summer months, such as nutsedge and Japanese stiltgrass, had reduced visual turf quality during this time period. However, they would then implement a fertility and aerification program followed by overseeding in early fall. By late fall the turfgrass stand masked the presence of any weed issues and consisted mostly of a green and uniform stand of tall fescue (Figures 6 & 7). Other lawn care operators also stated that instead of applying a OMRI listed pesticide they would rather offer an overseeding program that would result in an increase in turf quality.

Figure 6. Japanese stiltgrass encroachment in a tall fescue stand. Summer of 2023.

Figure 7. A uniform stand of a tall fescue lawn after overseeding (late Oct. 2023).

Summary

Weeds are considered the major pest problem in lawn turf in Maryland. Japanese stiltgrass was the most invasive annual grass problem followed by crabgrass. Preemergence herbicides such as Barricade and Dimension were the preferred herbicide to control these weeds.

The major broadleaf weed was white clover. Several more difficult to control weeds were wild violet and oxalis. The auxin-based herbicides such as 2,4-D, MCPP, and dicamba were used individually or in combination with each other. However, for the more difficult to control weeds triclopyr by itself or combined with an auxin-based herbicide was used. If nutsedge was present then Dismiss, Sedgehammer, or Solitare was applied to reduce the nutsedge population.

Insect pests were minor with white grubs considered a key insect pest. Acelepryn was the preferred insecticide for controlling white grubs preventatively while Dylox was used as a rescue type treatment.

The weather in the Mid-Atlantic region favors a number of diseases throughout the growing season. Brown patch and red thread were the two major diseases mentioned as key pests on lawn turf. Disease control using a fungicide was mainly done on a “as needed basis” and would normally consist of a fungicide combination that would combine different modes of action.

Due to restrictions in pesticide choices in Montgomery County, MD lawn care operators would rely more heavily on primary cultural practices such as mowing, fertility, and irrigation to reduce pest problems. If turfgrass loss did occur then reseeding or overseeding programs were performed rather than relying on OMRI based products for pest control. However, the major OMRI based pesticide that was applied was FIESTA and was used multiple times to reduce broadleaf weeds in lawn turf.