Warning for Growers over Blossom Midge Numbers

Article excerpt

It's likely to be a bad year for Wheat Blossom midge, according to preliminary Pestwatch information collected jointly by ADAS and Dow AgroSciences.

Analysis of last year's harvest samples revealed that more than 50% of grain suffered attack from Wheat Blossom midge larvae. Such a high level of damage indicates a significantly increased risk this season, experts warn.

As ADAS' Jon Oakley explains, "The numbers of overwintered larvae are now so high that serious damage is likely to occur whenever suitable hatching conditions coincide with ear emergence.

"Assume that each damaged grain was caused by just one larvae. With 40 grain sites per ear and 500-600 ears per square metre, we could be looking at between 100 and 120 million larvae per hectare in the worst- affected regions.

"Economic threshold levels for treatment are just one million per hectare," he points out.

Soil temperatures rising above 13C during late May, combined with sufficient rainfall to wet the top 10mm of soil promote Wheat Blossom midge development. In June, temperatures must stay above 15C just before dusk.

Mr Oakley stresses that advice, issued in previous years, to use wind speed as another indicative factor may no longer be relevant. "Numbers in many areas are now so high that this is probably now no longer a critical factor, except for flights between fields."

ADAS and Dow AgroSciences are working together on the Pestwatch system, which collates data from soil sampling of cocoons to produce a likely pattern of hatching and emergence. …