This weeks Pestwatch report indicates that egg-hatch for Wheat Bulb fly is increasing in Cambridgeshire and Suffolk and last week saw the first egg hatch in Yorkshire. The start of plant invasion by Wheat Bulb Fly larvae was detected in Cambridgeshire, with larvae at the first instar stage.
Starting in January, results of the weekly soil sampling are issued by Dow AgroSciences and ADAS as Pestwatch reports. These provide weekly data on egg hatch and plant invasion and offer advice on the timely application of the soil insecticide Dursban WG. Weekly information can be accessed at www.dowagro.com/uk/cereal/pest/htm. With the cold winter and frequency of snow cover, it is likely that PestWatch will be extended by a few more weeks this spring.
Data published week-commencing the 22nd February indicates that egg-hatch was between 7% and 13.5% on organic soils in Cambridgeshire, with up to 3.5% plant invasion. Egg-hatch in Suffolk on mineral soils was 9% and last week egg hatch started in Yorkshire and was at 6.7%.
Sarah Hurry of Dow AgroSciences explains that the higher numbers of Wheat Bulb fly eggs found in autumn 2009 means that growers should remain vigilant and be ready to treat vulnerable fields with Dursban WG (chlorpyrifos). "With the late season there will be a great deal of spraying to be done in a very short time. Once the weather warms up egg hatch will progress rapidly and the season could be rushed. An application of Dursban WG made now will last well into April to cover even this delayed and prolonged egg hatch. So it will pay to take any opportunity to treat fields at risk now before the spring spray rush starts."
"Dursban is an effective soil insecticide and should be applied at egg hatch at 1 kg/ha in 200-1000 litres of water. It has a long residual life in the soil of 6-8 weeks under normal conditions, meaning that most larvae will be controlled as they hatch over the longer period of time predicted this year. Optimum conditions for activity occur when soil temperatures are above 5 °C."
For further information, please contact Sarah Hurry, Dow AgroSciences on the Dow Technical Hotline on 0800 689 8899.
Dursban WG (75% w/w chlorpyrifos formulated as a Water Dispersible Granule) is recommended for the control of Wheat Bulb fly as well as Leatherjackets, Frit fly and Wheat Blossom Midge. For Wheat Bulb fly, two applications at dose rates of 1 kg/ha maybe applied. It is packed in a 1 kg pack.
