The many advantages of pre-harvest glyphosate
Leaving glyphosate application until mid-September will miss some of the shoots that did not emerge after the harvest.
A sizeable proportion of growers use pre-harvest glyphosate as a harvest aid.
The benefits of applying pre-harvest glyphosate to uniform, weed-free, standing wheat crops is questionable, but barley seems to benefit even if weed-free.
Most of the grain should be at or below 30% moisture content in order to avoid a yield penalty. And pre-harvest glyphosate also has cross- compliance implications. Crops intended for seed should not be treated.
Is my crop 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, actively growing and accessible to the spray.
At least five or six hours of drying after application is essential for satisfactory results with all glyphosate products containing tallowamine surfactant formulations.
&A number of adjuvants are available which will improve the spreading and deposition of the glyphosate and also generally improve rain fastness.
Options include Addup, Arma, Frigate. The rate of adjuvant is related to water volume, for example, one litre of Arma per 1,000 litres of spray volume.
* Most winter oilseed rape crops were at or fast approaching the correct stage for pre-harvest burn-off with glyphosate last week.
Glyphosate should be applied to winter oilseed rape when at least two-thirds of the seeds are turning from green to brown in the middle of the main stem. Harvest takes place two to three weeks later.
However, it is hard to find independent research clearly supporting one method of oilseed rape harvesting over another, as regards minimising seed losses.
The most important thing now is to correctly assess the crops for a suitable pre-harvest treatment as there may not be enough time left between treatment and harvest.
Pod sealants are chemicals used to reduce pod shatter. These are applied pre-harvest, but results have been variable. Variety, site aspect, disease and weed status, and availability of machinery will all need to be taken into account before choosing a suitable method.
Swathing should be carried out when the middle pods are turning brown. Harvest takes place two to three weeks later, depending on weather.
Diquat should be applied when all the seeds in the bottom third of the plant are brown-black, seeds in the middle pods are reddish- brown, and more than 50% of the seeds in the upper pods are green. Harvest takes place about 10 days later.
