Growers warned to be vigilant for wheat bulb fly

UK - January 20, 2009

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% 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.

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

“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/m². However, a lower threshold of 100-250 eggs/m² is appropriate for wheat crops drilled from November onwards, spring wheat and barley and also those earlier sown crops still at the single shoot stage when egg hatch gets underway.”

Where crops are assessed as high risk Dow AgroSciences recommends Dursban WG at 1kg/ha in 200 to 1,000 litres of water. If necessary Dursban WG can be applied to frosty ground but should not be tank mixed and an interval of at least 14 days is required between applications of Dursban WG and Atlantis.

To choose the right time for application growers are advised to use Dow AgroSciences Pestwatch service, run in conjunction with ADAS.