Late SEASON Herbicide Use Fact Sheet

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LATe SEASON HerBICIDE use fact sheet

SEPTEMBER 2010

Stewardship for late season application of herbicides in winter crops

The responsibility to avoid herbicide residues in delivered cereal, pulse and oilseed grains sits squarely with grain growers and their advisers.

KEY POINTS ■ Correct usage: Product labels must be followed and withholding periods adhered to for all herbicides. Off-label use without a permit is not allowed photo : E mm a l e ona r d and can result in grain being unsaleable. ■ Residues: Late herbicide applications to crops increase the risk of detectable herbicide residues in harvested grain, potentially leading to breaches of maximum residue limits (MRLs). MRLs vary according to Diquat is the only herbicide registered for pre-harvest weed control in barley. herbicide, crop and market and these need to be understood. Table 1 Registration for late season herbicide use varies by crop ■ Registration: Diquat, including type – always check product labels before application. See Table 2 for Reglone®, is the only registered additional details. herbicide for pre-harvest weed control barley. However, Paraquat Diquat Glyphosate growers must be aware that some maltsters have certain Wheat ×   restrictions on the late season use of herbicides. Consult with Barley ×  × buyers before use. ■ Food Safety: Growers and Canola ×  × their advisers need to be aware of the implications of their Chickpeas    herbicide applications and the role they play in ensuring food Lentils    health safety and in protecting the grain industry. Faba beans    ■ Be responsible: Stewardship must be taken seriously by all Field peas    sections of the grain value chain. Note: = registered for late season in-crop use; × = not registered for use

The application of herbicides late in the season to prevent weeds setting seed or Late season herbicide use to desiccate crops must be carried out with caution and in line with herbicide There are three reasons to apply ■ in-crop spray topping of annual label recommendations. It is essential to non-selective herbicides late in the ryegrass to prevent seed set; and check if these practices are acceptable season: to buyers, as in some situations markets ■ for pre-harvest desiccation of the have extremely low or even zero tolerance ■ just prior to harvest to manage late crop to accelerate or even up to some pesticide and herbicide residues. season weeds; ripening to assist with harvest.

With increasing annual ryegrass in cereals are diquat in barley, and pressure in many cropping areas of registered glyphosate products on Australia, growers are assessing their wheat with a seven-day withholding options for in-crop spray topping. period. While diquat has some activity Similarly, decisions are also being made on ryegrass, it is more suited to crop about which products to use for crop desiccation. desiccation. Due to food safety concerns related photo : EMM A L E ONA R D Some formulations of glyphosate and to chemical residues in food grains, diquat may be applied by air pre- the Malting Barley Industry Barley harvest. DO NOT apply treatments Technical Committee (MBIBTC) has where drift onto sensitive crops and opposed the late season use of pastures is likely to occur. Paraquat is herbicides in malting barley crops. not registered for aerial application. Major purchasers of Australian malting barley have strongly indicated they do Given the late timing of these not want malting barley treated with applications, there is an increased risk late season herbicides. Even though that such uses may result in detectable diquat is registered for use on malting residues in harvested crops, potentially barley varieties, different maltsters have leading to breaches of MRLs, or different policies on the acceptability impacting on grain germination and of diquat. Growers are encouraged to seed quality. check with their barley buyer prior to In-crop spray topping with paraquat applying diquat to their malting barley or glyphosate in pulse crops and crop. pastures is an effective strategy for controlling ryegrass. It should be used Late season herbicide as a tool with other integrated weed use in canola management (IWM) techniques such as cutting crops for hay, breakcrops Diquat is the only registered option Late season application of herbicides must and green and brown manuring. Timing for late season use in canola. No be done with consideration of the withholding of application and rates of product are herbicide products are currently period and approval of grain buyers. Some crucial to maintaining crop yield while registered for under-the-cutter-bar markets have tolerances lower than the reducing ryegrass seeds. spraying during windrowing or swathing maximum residue limit (MRL) harvest weed operations of canola. control in barley. Pulse spray topping for late season applications in barley GRDC funded trials in the 1990s is diquat. Paraquat and glyphosate on in-crop spray topping peas, The herbicide are not registered for late season lupins, chickpeas, vetch and beans application in barley in Australia and the established that an application of malting barley industry has concerns glyphosate and paraquat was most facts over the potential use of these products effective at ryegrass flowering and when Tables 1 and 2 provide details on and their residual effect on grain. applied at registered rates. However, at registered product options for late ryegrass milk stage, paraquat was much season weed control (including spray Canola: Diquat is registered for use in more effective than glyphosate. Applied topping/crop topping) and desiccation canola. at registered rates it achieved 64 to 97 in a variety of broadacre crops. per cent control, whereas glyphosate at Pulses: Glyphosate, diquat and registered rates ranged from 14 to 74 The table also highlights where paraquat are registered for late season per cent. certain products are not registered for uses in many pulse crops (Table 2). particular uses. In these cases, the use Pulse registrations and witholding The yield of most pulse crops is not of such products may be illegal, and periods vary between product labels. reduced if crop topping is delayed until may result in growers and their advisers seeds in the top pods are 75 per cent exposed to the risk that their grain of their full size. However, given the goal contains residues at above the of in-crop spray topping is to achieve relevant MRL. effective ryegrass control, growers need ® to strike a balance between optimal Spray.Seed (paraquat/diquat) is not Warning timing for ARG control (which is often registered for late season application earlier) and yield loss. Of all legumes, early in a cereal or pulse crop and should Grain handlers and marketers maturing peas are most suited to in-crop not be used under any circumstances regularly conduct surveillance on spray topping. Chickpeas, due to their including in-crop spray topping, pre- grain receivals for residues. The long flowering and pod period, are the harvest canola dessication or under- National Residue Survey conducts least suitable. the-cutter-bar spraying during swathing ongoing surveillance of grain. or windrowing canola. These uses are illegal. It is essential that growers seek Late season herbicide advice from their grain buyers before use in cereals Wheat: Glyphosate and diquat are using late applications of herbicides. registered for use. The only herbicides which can be used This is especially important for seed in Australia for late season applications Barley: The only product registered that is intended for sprouting. PAGE 3

Table 2 Product registrationS for late season weed control and desiccation VARY by crop type – always check product labels (NOTE: Paraquat/diquat products, for example, Spray.Seed® are not registered for late season weed control or desiccation). Crop Paraquat (for example, GRAMOXONE®) Diquat (for example, REGLONE®) Glyphosate (for example, Roundup PowerMax®)

Pre-harvest weed control (all Paraquat is not registered for: Not all glyphosate formulations are registered for this use ■ in-crop spray topping; states) ■ pre-harvest crop desiccation; Spray as soon as the crop is Apply to mature crop from late dough stage (28 per cent ■ pre-harvest weed controls. mature and ready for harvesting. moisture) onwards. The higher rate will be required when crops Under wet spring conditions crops are heavy and leaf shading effects may occur. DO NOT USE PARAQUAT PRODUCTS FOR can periodically become infested Wheat THESE USE PATTERNS with weeds which seriously DO NOT use on crops intended for seed or sprouting. interfere with harvest operations. These use patterns are unregistered. Diquat will control these weeds Where wheat is grown in rotation with any herbicide tolerant allowing for efficient harvest. crop, management should be consistent with implementation of any management plan for herbicide tolerant crops. Withholding period (WHP): NOT required when used as directed. WHP: DO NOT harvest within 7 days of application.

Winter cereals – pre-harvest weed control (all states) Paraquat is not registered for: Glyphosate is not registered for: ■ in-crop spray topping; Spray as soon as the crop is ■ in-crop spray topping; mature and ready for harvesting. ■ pre-harvest crop desiccation; Under wet spring conditions crops ■ pre-harvest crop desiccation; ■ pre-harvest weed control can periodically become infested ■ pre-harvest weed control Barley with weeds which seriously DO NOT USE PARAQUAT PRODUCTS FOR interfere with harvest operations. DO NOT USE GLYPHOSATE PRODUCTS FOR THESE USE THESE USE PATTERNS Diquat will control these weeds PATTERNS allowing for efficient harvest. These use patterns are unregistered. These use patterns are unregistered. WHP: NOT required when used as directed. Paraquat is not registered for: Pre-harvest crop desiccation Glyphosate is not registered for: ■ in-crop spray topping; (all states) ■ in-crop spray topping; ■ pre-harvest crop desiccation; ■ pre-harvest crop desiccation; ■ Spray when 70 per cent of the under-the-cutter-bar spraying during ■ swathing or windrowing activities; pods are yellow and the seeds under-the-cutter-bar spraying during swathing or windrowing activities; ■ pre-harvest weed control; are browny or bluish and pliable. Canola Canola ripens unevenly and is ■ pre-harvest weed control; ■ spraying over the top of swaths or prone to pod shatter and seed loss. ■ spraying over the top of swaths or windrows windrows Direct harvest four to seven days after spraying. DO NOT USE PARAQUAT PRODUCTS FOR DO NOT USE GLYPHOSATE PRODUCTS FOR THESE USE PATTERNS THESE USE PATTERNS WHP: DO NOT harvest for at least 4 days after application. These use patterns are unregistered. These use patterns are unregistered. Pre-harvest crop desiccation Spray topping to reduce seed set – annual (all states) Pre-harvest application to reduce viable seed set of weeds ryegrass (NSW, Vic, SA, WA, ACT only) – annual ryegrass Dry beans/Dry peas/Pigeon Chickpeas/Faba beans/Field peas/Lentils/ peas/Lentils/Chickpeas/Faba Field peas/Faba beans Lupins/Vetch Use lower rate if ryegrass is flowering and higher rate Spray the crop when the ryegrass is at the beans/Lupins/Soybeans/ if ryegrass is at milky dough stage (refer to label for Mungbeans optimum stage, that is when the last ryegrass Spray as soon as the crop has specific timings). Chickpeas seed heads at the bottom of the plant have reached full maturity. Helps WHP: DO NOT harvest within 7 days after application. Faba beans emerged and the majority are at or just past overcome slow and uneven ripening Field peas flowering (with anthers present or glumes and weed problems at harvest. Pre-harvest application to desiccate a crop as a harvest open) but before haying off is evident – Lentils WHP: NOT required for dry beans, aid and weed control – annual weeds usually October to November. dry peas, mungbeans when used Pigeon peas+ as directed. Adzuki beans*/Chickpeas*/Cowpeas*/Faba beans*/Field Lupins@ Use of the higher rate in these crops is usually peas*/Lentils*/Mungbeans*/Soybean* more reliable and gives a greater reduction in (Refer to label for specific timings) Vetch# Lentils/Chickpeas/Faba beans Adzuki beans^ seed set. DO NOT harvest for 2 days after WHP: DO NOT harvest within 7 days of application. Cowpeas^ application. Mungbeans~ Reduction in crop yield may occur especially Pre-harvest application as harvest aid and weed control – if the crop is less advanced relative to the Soybeans~ Pigeon peas, Soybeans annual weeds ryegrass; that is if crops have a majority of DO NOT harvest for 4 days after green immature pods. The higher rate may application. Chickpeas* also increase any yield reduction. In practice (Refer to label for specific timings) crop losses in excess of 25 per cent may occur. WHP: DO NOT harvest within 7 days of application. *Application to crops intended for seed production or for WHP: DO NOT harvest for 7 days after sprouting may reduce germination percentage to commercially application. unacceptable levels.

Note: # Paraquat only / ^ Roundup PowerMAX® only / + Diquat only / ~ Roundup PowerMAX® and diquat only / @ Paraquat products and diquat only PAGE 4

Frequently asked questions

If I can’t effectively control ryegrass ■ Using a weed seed collection cart What is an MRL? in cereals – particularly barley – by in- behind the harvester. Growers The MRL for a product in a certain crop crop spray topping, what are the other may need to investigate the use of is calculated on the registered maximum options? contractors or hire of machinery for label application rate, so it is important this exercise. ■ Windrowing barley to control ryegrass that spray equipment is carefully calibrated has been partially successful with up ■ Well managed burning of concentrated to ensure the product is applied at the to 60 per cent ryegrass control when windrows containing seed. appropriate rate and use pattern. Keeping carried out when the barley is at firm an accurate spray diary and adhering to ■ dough stage (kernel no longer splitting Growing a pulse or canola crop the recommended application timings and when pinched, but leaving an indent). following year to provide further spray intervals as per label is crucial. However, windrowing usually results in options. Can I obtain a minor use permit some yield loss against the standing If existing registered products are for these products for late season crop due to pick up inefficiency. not suitable and other unregistered herbicide use? products are, why is registration not ■ Herbicides of alternative modes of forthcoming? No. Registration requires full approval by action should be considered as part of the APVMA through the normal registration IWM strategies, particularly the use of The industry is conducting research as process for label use. herbicides incorporated by sowing (IBS). to whether other products are suitable for late season herbicide use in cereals What are responsibilities from ■ Baling the crop is a means to recover and oilseeds ensuring weed efficacy agronomists in providing advice on some of the costs, particularly when and crop safety, and grain quality is safe late season herbicide use? demand for hay is high. from herbicide residues. The agronomist providing advice ■ Spray fallowing of areas with the assumes full liability for any advice given. heaviest infestation is another option.

Useful resources:

■ Information about MRLs and permitted use can be found at: www.pestgenie.com.au and www.apvma.gov.au ■ Syngenta Product Advice Line 1800 067 108 ■ Bayer Customer Service 1800 636 001 ■ Nufarm Customer Service 1800 639 899 ■ Dow AgroSciences Customer Service 1800 700 096 ■ Spraywise www.spraywisedecisions.com.au ■ Syngenta’s Agri-CAST Spray Window Forecasting Tool www.syngenta.com.au ■ Vendor declarations www.graintrade.org.au/contracts

Disclaimer Any recommendations, suggestions or opinions contained in this publication or arising by reason of any person using or relying on the information in this do not necessarily represent the policy or views of the Grains Research and publication. Development Corporation. No person should act on the basis of the contents of CAUTION: RESEARCH ON UNREGISTERED PESTICIDE USE this publication without first obtaining specific, independent professional advice. Any research with unregistered pesticides or of unregistered products reported The Corporation and contributors to this Fact Sheet may identify products by in this document does not constitute a recommendation for that particular use by proprietary or trade names to help readers identify particular types of products. the authors or the authors’ organisations. We do not endorse or recommend the products of any manufacturer referred to. Other products may perform as well as or better than those specifically referred All pesticide applications must accord with the currently registered label for that to. The GRDC will not be liable for any loss, damage, cost or expense incurred particular pesticide, crop, pest and region. www.coretext.com.au

Acknowledgements: The Late Season Herbicide Use Working Group; Bill Long, Ag Consulting Co.; Peter Arkle and Jason Sabeeney, Syngenta; Chris Preston, University of Adelaide; Mick Faulkner, Agrilink Agricultural Consultants; Peter Hooper, Allan Mayfield Consulting; Mark Slatter and Andrew Wells, Nufarm; James Eyres, ConsultAg. prod u ced b y