Flea beetle populations are at an all time high this season and growers are warned that fledgling oilseed rape crops will be under heavy threat from the pest.

While the neonicotinoid insecticde seed treatment ban was bad news for growers earlier this year, the suggested spread of pyrethroid resistance from Germany could compound the issue.

On top of that, this spring and summer have provided perfect breeding conditions for cabbage stem flea beetle to the point where populations are believed to be higher than ever.

“I’ve had growers reporting large numbers of flea beetle being seen in trailers when harvesting their oilseed rape, which is an indication of the high pest pressure the new crop will face,” reports Syngenta’s Simon Roberts.

Read also: Crisis looms for flea beetle control

“If there was any doubt over the potential threat of flea beetle attacks without the protection of seed treatments this season, keep an eye on volunteer plants now emerging in stubbles.

“The wet and warm soil surface has seen a rapid flush of seedlings and a feeding frenzy for flea beetle,” he adds.

High populations of the pest are already hammering emerging brassica volunteers in stubbles, so the threat to emerging crops in the next few weeks is judged to be very high.

The leaf damage caused by flea beetle can occur incredibly quickly and be extremely destructive. If conditions remain hot and dry after emergence, with any check in crop growth, the damaged small plants can quickly shrivel and die.

Growers are being urged to plan control now and consider trapping beetles to test for pyrethroid resistance. Rothamsted Research is conducting a testing programme to assess the level of the problem.