Midge monitoring advised as crops approach ear emergence

GROWERS are urged to use pheromone traps to provide advanced warning of orange wheat blossom midge risk as wheat crops approach ear emergence (GS 53-59).

Although crops may grow through the vulnerable ear emergence phase in days, treatments should be applied as soon as thresholds are reached where conditions favour midge emergence and flight.

Pheromone traps provided a helpful early warning during the risk period, which usually runs from late May to mid-June, said David Ellerton, technical director with agronomists Procam.

“Finding 30 or more male midges per day in traps indicates risk to crops in the following week when females can be expected to be laying eggs. This is the cue to start checking crops at dusk for female midges, to assess whether or not treatment is needed.”

Treatment thresholds are one midge per three ears in susceptible feed crops and one midge per six ears in milling and seed crops. Biscaya (thiacloprid) or Dursban (chlorpyrifos) give better results than pyrethroids, said Dr Ellerton.

This was confirmed in an ADAS trial at High Mowthorpe last year where the three options were assessed on the basis of larvae remaining per ten ears after treatments. Compared with the untreated control with 62 larvae, chlorpyrifos controlled them down to three, Biscaya had 11 and lambda-cyhalothrin left 35.

“Being able to treat the whole field is an important consideration too, particularly for quality seed and milling crops,” said Dr Ellerton. “Biscaya is the only product that can be used to tackle midge across the whole field.”

For chlorpyrifos, environmental protection advice is not to spray summer applications within 12m of the edge of the growing crop. And for the pyrethroid lambda-cyhalothrin there is a restriction not to spray cereals after 1 April within 6m of the edge of the crop.

HGCA guidelines should be followed to avoid unnecessary spraying, said Dr Ellerton. “If midge numbers don’t reach thresholds or crops have passed the vulnerable stage by the time midges become active; don’t spray.”