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Pre-Harvest Weed Control and Desiccant Timing Maximum Residue Limits for 2015 (PCN Summer 2015) JUL 2 2015 | Consumers and Producers | Pulse Crop News

This article appeared in the Summer 2015 issue of Pulse Crop News.

Another growing season is upon us, and the pulse industry in Canada, including Alberta Pulse Growers (APG) and Pulse Canada, collaborated to bring you the latest information on maximum residue limits (MRLs). It is important to inform growers on any desiccant/harvest management tools that may cause marketing restrictions. Here is an update on product information on the 2015-16 season.

Desiccants and harvest management tools are used by growers all over the world to help facilitate efficient and timely harvest in crops with uneven maturity. The desiccation process rapidly destroys plant cell membranes to allow lush green plant (crop and weed) material to dry quickly prior to harvest. Because desiccants are not systemic, there is a risk that if harvest is delayed, treated plants may regrow from lateral buds protected from the initial application. Herbicides registered for desiccation prior to the harvest of pulse crops in Western Canada include: Diquat (Reglone), saflufenacil (HEAT), flumioxazin (Valtera), carfentrazone (Aim, CleanStart), and glufosinate (Good Harvest).

While glyphosate is registered for preharvest use for pulse crops, its primary purpose is control of perennial weeds. Drydown is slowest with glyphosate, especially under poor natural drying conditions, but death of plants is complete – virtually eliminating regrowth of the treated plants. Application of desiccants or harvest aids occurs late in the growing season. Proper application of harvest aids or desiccant products can ensure that growers avoid problems marketing their harvested crops, by not exceeding MRLs set by regulatory agencies in Canada and importing countries.

While the Canadian pulse industry continues to work to reduce risk for growers in marketing their pulse crops, each herbicide must be addressed individually and not all desiccants may have MRLs established in certain markets and for certain crops. Growers must be aware of international regulations that might limit their marketing options. This year, guidance from the pulse industry around those regulations includes faba beans. Producers may desiccate faba beans with Reglone (diquat) or they may also use glyphosate. Various glyphosate products can be used according to the Minor Use Registration, but check the 2015 Alberta Crop Protection Guide for application instructions.

How to reduce your risks

As per guidance in previous years, in order to reduce risks associated with exceeding MRLs and maximize options for marketing crops, growers should do the following to keep product residues at trace levels or levels well below accepted maximums:

  • Do not exceed the pesticide’s application rate according to the label.
  • Time the application according to the pesticide label. Early application of desiccants or glyphosate greatly increases the risk of higher herbicide residue.
  • Consult with your exporter/processor about the use of harvest management aids as they pertain to international markets.
  • Consult the below Pulse Canada chart indicating market considerations and regulatory status of specific pesticides for certain key markets.

The 2015 Alberta Crop Protection Guide (commonly referred to as the Blue Book) has the most up-to-date information for crop protection and includes information regarding harvest aids and desiccants. Hard copies may be purchased from the Alberta Agriculture and Forestry website or accessed free of charge in electronic format at$Department/deptdocs.nsf/all/agdex32.

Chart information provided by Pulse Canada. The charts in this article are not recommendations for the use of any one desiccant/harvest management tool over another.