With the first case of glyphosate-resistant Italian ryegrass occurring in Ireland earlier this year, it is more important than ever to ensure that a full kill of grass weeds is achieved when using a glyphosate product.

Steve showed the Irish Farmers Journal a trial at the Agrii Italian ryegrass trial site, which used different glyphosate products, rates and different water rates to see what is the most effective against Italian ryegrass.

The trial plots consisted of a crop of winter wheat that was badly infested with Italian ryegrass. It was sprayed off in late May before the Italian ryegrass set seed.

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One area was also mowed and the regrowth was sprayed off.

This produced a similar kill level to the crop that was not mowed before being sprayed and seemed to have no beneficial effect. Roundup Powermax was applied at two different rates, 1kg/ha (720g/ha glyphosate) and 2kg/ha (1440g/ha glyphosate) in 200l/ha of water.

It was very clear that the plot with the lower rate of the product still had green leaves visible, and plants were not completely dead as they were in the plot with the higher rate.

A water volume of 100l/ha was also trialled with 1kg/ha of Roundup Powermax.

This provided better control than the 200l/ha treatment, but Steve warned that there can be other issues with using a lower water volume.

These plots were sprayed with a handheld plot trial sprayer at walking speed.

In a field with a normal sprayer, higher forward speeds, gusts of wind and higher boom heights, can lead to poor leaf coverage, therefore reducing efficacy and the potential for weeds to survive and become resistant increases.