NEARLY THREE quarters of Scottish fields have exceeded the recommended treatment threshold, as the wheat bulb fly threat grows, according to survey results.

In total, 71% of fields assessed exceeded the treatment threshold of 2.5 million eggs/ha, according to the latest Scottish Agricultural College (SAC) Crop Protection Report.

In one example, a new Scottish record of 29.6 million eggs/ha was found in a field following potatoes in East Lothian.

For growers sowing wheat in October, the treatment threshold is reduced to 1.25 million eggs/ha. The survey found 86% of later sown fields exceeded this suggested level.

The SAC advises growers who plan to sow wheat after potatoes or vegetables to sample soils for wheat bulb fly eggs, as there is still time to do so, providing soil has not been cultivated.

Where there is a risk of bulb fly damage, the SAC recommends three control options, but warned that with the record egg numbers this year, no single treatment may be sufficient.

  • Treat seed with Evict (tefluthrin)
  • Apply soil drench of chlorpyrifos at egg hatch
  • Apply a ‘deadheart‘ treatment of dimethoate when ‘deadhearts‘ first appear

Growers should contact their local SAC Agricultural Adviser for further guidance or to arrange for soil samples to be taken.