Applying pre-harvest glyphosate to a crop will give the most effective long-term control of scutch, thistles, potatoes, etc.
Best results are achieved when the weeds are actively growing in moist soils.
Leaving glyphosate application until mid-September will miss some shoots that did not emerge after the harvest.
A sizeable proportion of growers also use pre-harvest glyphosate as a harvest aide. The benefits of applying pre-harvest glyphosate to uniform, weed-free, standing wheat crops is questionable, while barley seems to benefit even if weed-free. However, most of the grain should be at or below 30% moisture content to avoid a yield penalty.
Applying pre-harvest glyphosate also has implications regarding cross-compliance, because these fields should have a green cover (sown crop or natural regeneration) established within six weeks of application.
Crops intended for seed, and certain premium markets (consult your merchant), should not be treated.
How do you know if your crop is ready for glyphosate? From 14 days before the normal harvest date, collect 20 grains from the centre of several ears.
Press your thumbnail firmly into the grain, and if the indentation holds on all the grains, the crop is ready for spraying.
Target weeds must be green, growing, and accessible to the spray.
At least five to six hours of drying after application is essential for satisfactory results with all glyphosate products containing tallow amine surfactant formulation.
A number of adjuvants are available which will improve the spreading and deposition of the glyphosate, reduce the effects of hard water, and also generally improve rain fastness, where not already included in the formulation.
Assess your water quality and select an additive carefully. Options include X-Change, which is good for hard water areas; and Validate; Frigate; etc.
The rate of adjuvant is related to water volume and pH of the water. Check your water pH and add a product like X-Change at a rate of between 0.1%-0.25% depending on the water pH.
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