Monitoring reveals orange wheat blossom midge hotspots

UK - June 10, 2009

The latest Pestwatch report from Dow AgroSciences show hotspots for OWBM activity could occur in areas not covered by the survey as adults have been reported flying as far a field as Kent, the Midlands, Cornwall and Yorkshire. Counts show average pupation across the country is 4.2% with the highest, at 12.2%, detected in Yorkshire.

Technical expert David Roberts says: “OWBM emergence could coincide with the susceptible crop stage so growers should be monitoring their own fields. Priority should always be given to milling or seed crops.

“Pheromone traps provide the earliest warning of midge activity. If the number of midges caught is at a threshold of 30 or more, wheat ears should be assessed by fieldwalking in the evenings. Yellow sticky traps can be used to help a visual inspection.

Thresholds within the crop remain the same as last year: 1 midge per 3 ears of feed wheat, or 1 midge per 6 ears of milling/seed crops. If the upper threshold of 120 is met or exceeded in pheromone traps, the risk is high and to save time there is no need to carry out an in-field inspection. The highest risk is on the three nights after numbers caught in pheromone traps increases.

“Where a risk assessment shows midge threatens a crop, Dursban WG which contains chlorpyrifos, offers the widest window of application. Chlorpyrifos is the only product available that controls adults, eggs and hatching larvae. Pyrethroids will kill adult midges but not eggs laid the day before.”

To reduce adverse effects on beneficial insects, Dow AgroSciences recommend growers should consider leaving a 12 metre strip around field margins.