9 January 1998

Extra flea beetle sprays not cost effective

Extra flea beetle sprays not cost effective

FLAX flea beetle is best controlled using Vitavax RS (carboxin + gamma-HCH + thiram) insecticide seed treatment, followed by one follow-up spray if needed.

Extra sprays are not cost-effective, says ADAS entomologist Jon Oakley. And although drilling date can influence susceptibility, it should not be used as a control measure.

"Last year the flea beetles came late, and April-sown crops were attacked," he recalls. "In contrast, March-sown crops escaped. But the threat varies with conditions, so drilling date should not be used as a control measure." Rolling seed-beds seems to reduce damage underground, by making it harder for beetles to find the seed, he adds.

ADAS trials last year compared different seed treatments. They showed Vitavax RS gave higher plant populations and less cotyledon damage than Hydraguard (gamma-HCH + thiram).

If beetles are still evident in the crop two weeks after emergence and damage to cotyledons can be found consider using a single follow-up spray, Mr Oakley advises. Six years of ADAS trials have confirmed that there is no economic return from following a seed treatment with two sprays. "If a follow-up spray is required, a pyrethroid is the best choice if it is cold. In warmer conditions, above 10C, gammacol will work better." &#42

FLEA BEETLES

&#8226 Vitavax RS best seed treatment.

&#8226 Rolling reduces damage.

&#8226 Only use follow up spray if beetles and damage seen two weeks after emergence.

&#8226 Pyrethroid best follow up.