CABBAGE STEM flea beetle could still be a problem in oilseed rape, despite many forward crops this autumn, growers have been warned.

Smaller backward crops or those affected by slug damage are likely to be at greatest risk and growers should check crops now for signs of beetle larvae, said BASF’s insecticide product manager, David Marris.

Larvae burrow into the petioles and later move into the stem and feed under the growing point, he explained. “Direct feeding damage can result in yield reduction and the harm to the petiole can increase the chances of infection from Phoma.”

ADAS’s David Green said that flea beetle numbers were high in parts of the West and East Midlands and Yorkshire. But in many areas further east, the risk is lower, he said.

Crops should be checked for signs of larvae or leaf scarring and treated with a pyrethroid when they reach the threshold of five larvae per plant, he added.

Mr Marris suggests using Contest (alphacypermethrin) to control the beetle at adult and larval stages.

For the latest field reports from agronomists around the country, see FWi’s Crop Watch.