Sugar Edition: October 2012
BRAZILIAN ‘ZERO TOLERANCE’ APPROACH TO WEED CONTROL by Jonty Ross (Technical Manager, Farmers Agri-Care)
The weed control practices in the Brazilian cane industry were analysed on a recent visit in August 2012. I was fortunate enough to join members of the Arysta LifeSciences team that visited mills and growers in the South Central region of the industry, which spans some 7.7 million hectares. The first fundamental difference between the two countries’ agronomic practices is that 70% of the Brazilian crop is not burnt, and is mechanically harvested. Both burning and manual harvesting will be outlawed by the end of 2014. The change to harvesting practices has had the following effects: •
A weed species shift has occurred, from a predominantly grass spectrum to a broadleaf spectrum. Many of the new broadleaf weeds are tough vines and creepers that cause mechanical complications with the harvesters; Trash blankets of up to 20cm deep are experienced on mechanically-harvested fields.
These factors have necessitated a ‘zero tolerance’ approach to weed control, where sub-standard weed management is not acceptable. The final choice of herbicide programme is determined by two key factors: 1. Weed species present on the specific land, as well as the degree of infestation; 2. Plant cane, wet or dry ratoon (seasonal variations similar to our winter and summer approach). A notable difference in their programme choice is a reluctance to apply herbicide over the cane foliage. Contact with the crop is minimised, and as such, knockdown active ingredients such as MCPA and paraquat are not even available for purchase. Strict pre-emergence applications are the norm: • • • •
To keep weed pressure levels down, And to minimise crop injury, Application is done straight after cutting, with GPS-guided spray rigs to avoid waiting for the cane rows to emerge to act as indicators for drivers, In severe pressure situations in plant cane, Pre-Plant Incorporated (PPI) applications are done, again to reduce weed pressure and prevent “fire-fighting” situations later.
The back-bone of their approach is therefore driven by herbicides with long residual activities, applied pre-emergence. Any treatments that are applied over the crop canopy will usually be single active ingredients at reduced rates, to extend residual activity. Interestingly, there are fewer herbicides registered in Brazil than in SA, although the active ingredients are similar. Examples of familiar brands that are used in their industry are: • • • • •
Dinamic: Velpar K3: Merlin: Authority: Lava:
used for long term weed control, especially where Morning Glory exists general weed control used for long term dry season grass control used for pre-emergence Cyperus rotundus control general weed control in wet ratoons and plant cane
used for Digitaria and Panicum maximum control in wet ratoons
FIG 1: Good weed control in Brazil, featuring: 1.) A ‘zero tolerance’ approach to weeds, 2.) Strict pre-mergence application timing, 2.) Minimal chemical contact with the crop
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“THE MERLIN CONCEPT” Integrating the Cost of Weed Control Merlin’s unique ability to withstand dry conditions has seen it become the benchmark weed control treatment for dry winter conditions. With the good early rains this year, results from Merlin treatments have been good. What sets Merlin apart is its ability to be applied under dry conditions. Growers use Merlin from the beginning of the cutting season in autumn, and continue right through winter regardless of dry periods, within reason. With rainfall, the Merlin will be activated. Taking this unique technical attribute further, Merlin offers an effective new approach to the cost of weed control. Known as the ‘Merlin concept’, this principle integrates the entire cost of weed control, from the start of cutting through to canopy closure. This integrated approach covers: 1. The cost of application: The exceptional length of control relieves burden on spray equipment once the weed pressure really starts in spring. 2. The cost of chemicals: Merlin mixes provide the lowest cost per week of chemical weed control available. It’s as simple as that! In ideal conditions, Merlin eliminates the need and cost of a second pre-canopy application. 3. The cost of labour: The cost of hand-weeding is rising far quicker than the cost of herbicides. •
This means the cost and efficacy of hand-weeding should be continually compared with the chemical alternative.
If the initial Merlin treatment does need a follow-up before canopy, there are many herbicide programmes that are cheaper per hectare and per week than hand-weeding.
• Generally, if more than 3 labour units are needed to hand-weed, rather use a chemical treatment. The ‘Merlin concept’ therefore reaches into other cost centres that have traditionally been treated separately from the cost of herbicides: •
It provides the grower with a tool to put together an integrated weed control solution,
Giving cost-effective weed management from cutting to canopy,
And reducing hand-weeding to below 4 labour units per hectare.
FIG 2: Merlin + Velpar: Season-long weed control, from cutting to canopy
fields last season. It allowed me to significantly reduce my labour units per hectare pre-canopy….”
Due to the effectiveness sprayed over trash, Dinamic H-100 has the ability to be applied earlier to fields than most wet season products, thus reducing the reliance on knockdown products (eg: paraquat).
Effectively lowering labour costs The 2011/2012 season saw the first commercial sales of Dinamic H-100. Excellent results were achieved on fields that were cut from September 2012 onwards, where Dinamic H-100 was applied within 2 weeks of cutting. The strong preemergence activity of this product was evident long into the summer months, this especially the case with difficult to control weeds such as Morning Glory (Ipomoea purpurea). This strong activity saw powerful root uptake of the product after rainfall events initiating renewed root uptake and death of the weeds. The long residual action continually reduces the weed populations emerging throughout the summer months significantly, allowing in many cases, significant reductions in labour units going through lands pre-canopy. Zumi Robert, farming in Upper Glendale, commented: “I applied Dinamic H-100 to my ratoon
FIG 3: Dinamic H-100: Morning Glory emerged through a thick trash blanket, showing symptoms of Dinamic root uptake
ADJUVANTS – PRODUCTS TO IMPROVE EFFICACY by Dr Brian de Villiers (Villa Crop Protection)
One of the latest adjuvant trends in South Africa is to market multi-purpose products. These adjuvants are supposed to fulfil multiple functions, some combinations being spreading/buffering; sticking/spreading or even ammonium sulphate/buffering/spreading adjuvants. While Villa understands the reason for developing these products, we question whether it is always possible to build in the full complement of two or even more
than two components. For example, do not expect a buffer/spreader adjuvant to have full buffering and/or full spreading properties. One or both of these properties may be limited. The ammonium sulphate adjuvants are a good example of this. Villa has recently tested a product that contains ammonium sulphate, buffer, humectant and surfactant (spreader) in trials, compared to Velocity-Dry that only contains
technical grade ammonium sulphate. The two most important requirements of ammonium sulphate adjuvants are (1) that they overcome glyphosate antagonistic salts in the carrier water and (2) provide a pH environment that is ideal for glyphosate absorption. The Velocity-Dry delivered on its label claims in that it fulfilled both of the abovementioned requirements. Unfortunately the other product did not have enough ammonium sulphate in the formulation to overcome all antagonistic salts because some ammonium sulphate was removed from the formulation to make place for the other components. Furthermore, it provided a spray solution pH that was way too low for glyphosate and did not spread very well.
We are not implying that all multi-purpose adjuvants are poor. On the contrary, there are very good multi-purpose adjuvants on the South African market. However, be very careful in just assuming that all products have a full complement of each component. At Villa, we try our best to keep the adjuvants as simple as possible as we know that they will add value to herbicide and pesticide sprays. This is the principle that we have followed with Velocity-Dry, Velocity-Glifo and Summit Super. We believe this method of developing adjuvants will ensure effective control of weeds and pests. Please contact your Farmers Agri-Care agent for advice on adjuvant choice.
SUGARCANE RUST GAINS MOMENTUM IN CANE by Jonty Ross (Technical Manager, Farmers Agri-Care)
The incidence of Brown Rust (Puccina melanocephala) in the South African cane industry has been documented as far back as 1941 (Bailey, 1979), and has led to the discarding of previously high yielding varieties. The practice of ploughing out susceptible varieties to combat this disease continues to this day. Brown Rust tends to infect young cane (2 â€“ 6 months old), and is favoured by cool nights and warm days, thus a major infection period is between September and November annually. Temperatures above 300C limit the spread and development of Brown Rust and as such, mid- to late summer infections are uncommon. Recently, a new species of rust was identified in the Swaziland and Umfolozi areas during 2009, and reappeared again in the 2011 season in Pongola, Umfolozi, Zululand North and Midlands North areas (The Link, Jan 2012). This species, Puccinia sparganiodes, has only recently been named African Rust (previously Ash Rust) and has been observed on N25, N31, N41 and N46 varieties, varying in age from 3 â€“ 10 months. Climatically, it appears as if African Rust favours cool, moist conditions, although not much more is known about this disease. Of major concern to the industry, however, is the threat of Orange Rust (Puccina kuehnii). The presence of Orange Rust has been confirmed in Gabon and the DRC, and was responsible for placing the Australian industry in dire straits in 2000. Of all the rust species found in cane, this species is the most aggressive and
attacks mature crops (> 6 months). It tends to favour warm, humid conditions. As such, the conditions for Orange Rust development are totally opposite to that of Brown Rust. What is also of great concern is that the cultivars that may or may not be susceptible to this disease are also unknown, the threat lying in the fact that those varieties that have been planted in order to minimise Brown Rust, may be susceptible to Orange Rust.
FIG 4: Visual differences in leaf lesions caused by (A) Brown Rust, (B) African Rust, and (C) Orange Rust
contains 750 g/kg isoxaflutole (isoxazole)
Reg. No. L6618, Act 36 (1947), CAUTION
contains 450 g/ℓ glyphosate (glycine)
Reg. No. L7166, Act 36 (1947), CAUTION
contains 700 g/kg amicarbazone (triazolinone)
Reg. No. L8692, Act 36 (1947), CAUTION
plus 750 g/kg hexazinone (triazine)
Reg. No. L7996, Act 36 (1947), HARMFUL
contains 500 g/ℓ ammonium sulphate
Reg. No. L 7768, Act 36 (1947), CAUTION
contains 1000 g/kg ammonium sulphate
Reg. No. L 8330, Act 36, (1947), CAUTION
contains 929 g/ℓ nitrogen solution/non-ionic surfactant
Reg. No. L8539, Act 36 (1947), CAUTION