1 November 1996

Bulb fly levels at record high

RECORD numbers of wheat bulb fly eggs have been recorded in Scotland this autumn, says SAC. And in England, ADAS forecasts the worst levels for a decade.

Insecticide dressings should be used on late-drilled wheats, and all crops at risk will need careful monitoring in the spring.

"I have never seen such high levels," says SACs Rod McKinlay. Two tests have detected 24.5m of eggs a hectare (2450/sq m), almost 10 times the threshold level. In East Lothian, 83% of samples are above threshold, in Fife, 75% and in Angus, 36%.

Growers yet to drill wheat in fields at risk should apply insecticide seed dressings (fonophos or chlorfenvinphos), he advises. "Most damage in our area comes after potatoes, though it can also occur after oilseed rape and set-aside."

More egg-hatch and deadheart sprays will be needed early next year, he adds. "Growers will have to pay particular attention to SAC and ADAS forecasts."

ADAS predictions, based on rainfall and soil temperature, show the highest risk for 10 years. Early field tests back that up – 38% of soil samples after potatoes and vining peas in Yorks have been above threshold. And samples from set-aside fields indicate higher egg counts than last year.

ADAS also recommends seed dressings. Soil sampling can be used to predict later insecticide treatments, especially useful in crops drilled recently after potatoes, peas or set-aside without an insecticide dressing. Cost is £70 a field.n