Time for action on wheat bulb fly
Egg-hatch for Wheat Bulb fly is now fully underway in Cambridgeshire and Suffolk, with some plant invasion taking place.
Data from weekly soil sampling indicates 19-47.4% egg-hatch on organic soils in Cambridgeshire, with up to 10.9% tiller invasion. Egg-hatch in Suffolk on mineral soils was measured at 55.7%.
Weekly sampling results have been issued by Dow AgroSciences and ADAS as Pestwatch reports since January. These provide weekly data on egg-hatch and plant invasion and offer advice on the timely application of the soil insecticide Dursban WG.
Higher numbers of wheat bulb fly eggs found in autumn 2009 means priority should be given to treat vulnerable fields as soon as conditions allow, according to agronomists and spray manufacturers.
Sarah Hurry, of Dow AgroSciences, said the late start to the season meant there would be a great deal of spraying to be done in a very short time. “South of the Humber sprays should be applied as soon as possible,” she added.
An application of Dursban WG or Equity now should last well into April to cover the delayed and prolonged egg-hatch. Ms Hurry said: “If necessary Dursban can be applied to frosty ground but should not be tank-mixed in this situation.”
Dursban should be applied at egg-hatch at 1kg/ha per 200-1000l of water. It will remain effective in the soil for 6-8 weeks under normal conditions, controlling most larvae as they hatch over this year’s longer time period.
Optimum conditions for activity occur when soil temperatures are above 5 °C.