Orange blossom midge threatens wheat

1 June 2001



Orange blossom midge threatens wheat

By Andrew Swallow

ORANGE blossom midge could devastate wheat yields and quality this year if warm, wet weather coincides with ear emergence, warn specialists.

“This year could be close to where we were in 1993-94,” says Dow Agrosciences agronomist Colin Bowers.

Then, yield losses were as high as 40% and many milling samples were spoilt by the pest whose larvae feed on the developing wheat kernel.

Mr Bowers said that all areas in central and southern England should be considered at risk.

ADAS entomologist David Green echoed these concerns. “Last year damage was quite bad, having built up for the past few years.

“Growers should be alert,” he warned.

Second and subsequent wheats are most at risk, as adults emerge into the host crop, but given favourable weather midges will fly into first wheats too.

Growers are advised to check crops from ear emergence until flowering in still conditions.

Control threshold for milling and seed crops is one midge in every six ears inspected. For feed wheat a threshold of one in three is adequate.

Chlorpyrifos (as in Dursban) is the only approved control chemical.

Pyrethroids give partial control, but the timing for grain aphid applications is too late for blossom midge control, says Mr Bowers.

Recommended rate for Dursban on the midge is 1 litre/ha, costing about 10/ha (4/acre). It can be tank-mixed with an ear-spray fungicide, he adds.

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