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CLOSE MONITORING REQUIRED FOR WHEAT BLOSSOM MIDGE
Date added: 23/05/08 |
Growers should spray for wheat blossom midge only when and if thresholds are reached and the crop is at the susceptible stage, says ProCam Group Technical Director, Dr. David Ellerton.
Although there are large numbers of midge pupae in the soils, they only cause economic damage if their emergence from the soil and their subsequent flight coincides with wheat at ear emergence (GS 53-59), he explains.
The weather conditions also need to be appropriate with calm still weather allowing insect flight.
Wheat growers should monitor wheat blossom midge populations and should put out traps in high risk fields one week before the first ears emerge.
“Only if thresholds are reached should spraying even be considered. Adult midges can be counted in the early evening when conditions are still. Thresholds are 1 midge per 6 ears for milling and seed wheat and 1 midge per 3 ears for feed wheat.
“When using traps the threshold is 20 adult midges in traps over 2-3 days for milling wheat and 30 adults for feed wheat in the same time period.”
Action is needed quickly after thresholds are reached as the spray window for the control of wheat blossom midge is very short.
“Of the recommended insecticide treatments, Dursban (chlorpyrifos) gives the most persistence, followed by Biscaya (thiacloprid). Pyrethroids have been used to control blossom midge but you have to be spot-on with timing in order to be effective.”
Wheat Blossom Midges can affect both yield and quality, but tend to be sporadic in nature. Yields can be reduced by up to 30-50% and damaged seed may fail to germinate. Affected seed is also more likely to be susceptible to diseases such as Fusarium. Quality criteria such as specific weight and Hagbergs can be reduced.
“If the soil is too dry, larvae won’t emerge. So in May when the larvae may emerge, the top 10mm of soil needs to be moist and the temperatures above 13°C. Adults only fly to the wheat ears to lay eggs when the air temperature is above 15°C and the wind speed less than 10 km/hour. Most crucial is the growth stage of wheat. Crops need to be between GS 53-55 when adults are flying,” Dr. Ellerton says.
PRM191
23rd May 2008
For further information please contact Dr. David Ellerton, ProCam Ltd., Royston, Herts. Telephone: 01763 261592
Issued by Philip Hainey, Proterra Ltd., Stamford, Lincs. Telephone: 01780 756299
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