Be ready to monitor orange blossom midges and spray them,but only if fully justified.

That’s the advice to susceptible wheat variety growers as a new product is approved to tackle the pest.After promising to be a non-event after the long dry spell, field invasion has become possible after widespread heavy rain.

About 10mm will encourage soillarvae to pupate and develop into adults, though how fastthat happens is temperature-driven, says ADAS‘s Jon Oakley.”I think most parts of the country have had that by now and I expect to see midges flying from next weekend.”

Crops are vulnerable to attack by larvae from their eggs only from ear emergence to flowering and this season, with many well advanced, some southern ones may escape damage, says Mr Oakley.

“It’s unprecedented for them to be this early.”

Soissons, in particular, generally misses the midge because of its earliness, notes CropWatch agronomist Nick Brown.”Most crops are 14 days early, so it’s possible they are less likely to be hit.”

Midge flights

But ear emergence in the midlands and north is likely to coincide with midge flights, Mr Oakley believes.

ProCam’s David Ellerton is concerned should flowering be delayed once ears are out. “Crops could be a long while at risk, but growers should only spray when really necessary.”That makes assessing the threat, preferably by using traps, all the more important. “More people should be using them.”

Mr Brown, who considers there are too many insurance treatments, agrees.”Last year by careful use of pheromone traps coupled with a low risk year I only treated three fields for midge.”

Beneficial insects can take up to 18 months to recover after applications of chlorpyriphos (as in Dursban), he points out. “And with Hallmark you have to hit the adults before they lay eggs.”

Since 10 May growers seeking another, albeit dearer, option have access to Biscaya (thiacloprid).

Granted label approval for reducing midge damage, it is the best choice for growers seeking least impact on beneficial insects, having no field margin buffer restrictions, says Bayer CropSciences‘ Bill Lankford. “You can spray the whole field.”