15 March 2002

Gout fly on rampage

EARLY autumn cereal drillers are reaping an unwelcome reward, as severe gout fly damage threatens yield loss, even in well-tillered crops.

"Its the worst Ive ever seen," says Albert Bull who farms 120ha (300 acres) near Marlborough, Wilts. "We have severe damage in wheat and barley sown from Sept 10-20. Most of the main shoots are affected."

Signs are that min-tilled crops, possibly less visible to the fly in the autumn, are less affected, notes Farmer Focus writer Jim Bullock. "And the damage is definitely worse in low lying fields.

"Anything sown after Sept 20 is almost free of the problem," notes Shropshire independent consultant Tony Howell who is particularly concerned at the threat posed to later sowings and spring cereals by the pests second generation.

"Last year we saw the heads of wheat and barley attacked. The most significant thing in terms of yield loss this season will be gout fly."

Advice that well-tillered crops can afford to take a certain amount of damage is misplaced, he believes. "We need urgent answers on how to control this pest."

Richard Overthrow of the Arable Research Centres says Secur (imidacloprid) seed dressing and autumn insecticides seem to offer little control. "Like blossom midge its very tricky to hit the right spray timing for gout fly, and there is no indication that anything really controls it."

Damage effectively transforms September-sown crops into October-drilled ones, so reducing yield potential, he explains. Timely nitrogen to boost survival of remaining tillers is advocated. "But we wont really know how well crops have compensated until harvest."

&#8226 With increasing levels of wheat bulb fly larvae being found and recent spraying windows at a premium, ADAS advises that any remaining control strategy should be based on dimethoate.

Suggested thresholds for treatment range from 10% shoot attack at single shoot stage to 20% at main shoot plus two tillers. &#42