Title: Check your options before spraying grain crops for weeds
[Country News Mon 18 Oct, 2010, p24] -- There are three reasons to apply non-selective herbicides late in the season: just prior to harvest to manage late season weeds; to prevent weeds setting seed; or, for pre-harvest desiccation of the crop to accelerate or even up ripening to assist with harvest. It is essential to check if these practices are acceptable to buyers, as in some situations markets have extremely low or even zero tolerance to some pesticide and herbicide residues.
With increasing annual ryegrass pressure in many cropping areas of Australia, growers are assessing their options for incrop spray topping. Similarly, decisions are also being made about which products to use for crop desiccation.
Some formulations of glyphosate and diquat may be applied by air pre-harvest.
Do not apply treatments where drift onto sensitive crops and pastures is likely to occur.
Paraquat is not registered for aerial application.
Given the late timing of these applications, there is an increased risk that such uses may result in detectable residues in harvested crops, potentially leading to breaches of MRL5, or impacting on grain germination and seed quality.
In-crop spray topping with paraquat or glyphosate in pulse crops and pastures is an effective strategy for controlling ryegrass.
It should be used as a tool with other integrated weed management techniques such as cutting crops for hay, breakcrops and green and brown manuring.
Timing of application and rates of product are crucial to maintaining crop yield while reducing ryegrass seeds.
Late season herbicide use in canola Diquat is the only registered option for late season use in canola.
No herbicide products are currently registered for underthe-cutter-bar spraying during windrowing or swathing operations of canola.
Grain handlers and marketers regularly conduct surveillance on grain receivals for residues.
The National Residue Survey conducts ongoing surveillance of grain.
It is essential that growers seek advice from their grain buyers before using late applications of herbicides.
This is especially important for seed that is intended for sprouting.