Wheat and spring barley crops in susceptible fields (see below) are at high risk of damage from wheat bulb fly, according to latest reports.

In Scotland, 82% of soil samples processed by the Scottish Agricultural College exceeded the treatment threshold of 2.5million eggs/ha for early-sown wheat and 91% exceeded the 1.25million eggs/ha for wheat sown from October onwards.

Meanwhile, in England results of this year’s Home Grown Cereals Authority-funded survey of 31 ‘potentially high risk’ fields found that 41% of those in the east were classed as high or very high risk, slightly below the 50% last year.

In northern England, overall egg counts were down, with only occasional fields coming in as ‘moderate’ risk, said ADAS’s David Green.

“The weather this year was hot and dry initially, which does not favour egg laying, but wetter conditions in August delayed harvesting and a lot of wheat ears had fungal infections, which could potentially act as a food source,” he said.

Given the high risk, growers who are planning on sowing wheat in fields following sugar beet or potatoes should consider using a seed treatment, he advised.

What are susceptible fields?
• Farms with a history of wheat bulb fly problems
• Sowing wheat after potatoes, field vegetables, fallow set-aside, or any field where there has been bare soil since July

What can I do?
• Get soil tested
• Consider a seed treatment (e.g. Evict – tefluthrin)
• Apply chlorpyrifos soil drench at egg hatch
• Apply a dimethoate spray when deadheart symptoms appear in the crop (last resort)

Results of the latest HGCA wheat bulb fly survey will appear on www.hgca.com shortly.