Be vigilant against wheat bulb fly threat

WHEAT bulb fly egg hatch has begun at three sampling sites monitored by Dow AgroSciences Pestwatch in Cambridgeshire.

Egg hatch has been recorded at Linton, Holme Fen and Great Chesterford. While egg numbers have been low, percentage hatch has been high – up to 56 per cent on the sandy loam soils at Linton. Egg hatch has not been recorded yet on the Cambridgeshire fens at Manea, nor at the East Yorkshire site being monitored.

Dow AgroSciences technical expert David Roberts says growers need to be vigilant and undertake an accurate risk assessment to assess the right time to treat winter wheat.

“In any late drilled, struggling, backward or particularly thin crops it may be worth considering an application of Dursban WG (chlorpyrifos) at the first available opportunity as tiller survival will be very important in these crops.

“Late drilled crops of winter wheat following sugar beet could be particularly at risk.

“Treatment is usually justified where egg numbers exceed a threshold of 250/sq.m. However, a lower threshold of 100-250 eggs/sq.m is appropriate for wheat crops drilled from

November onwards, spring wheat and barley and earlier sown crops still at the single shoot stage when egg hatch gets under way.”

Dursban WG can be applied to frosty ground, but should not be tank mixed. An interval of at least 14 days is required between applications of Dursban WG and Atlantis (iodosulfuron+ mesosulfuron).