OILSEED RAPE growers have been told to keep a close eye on crops after the first signs of cabbage stem flea beetle larval invasion have been seen.

Signs of the larval activity were spotted in young oilseed rape crops in Lincolnshire trial plots last weekend (Oct 9-10), according to BASF.

“The larvae have been seen on crops that emerged at the beginning of September, and are now at the 3 to 4 leaf stage,” said the company‘s insecticides product manager, David Marris.

“There are pin-prick like marks on the leaf stalk, and when cut open very tiny larvae can be seen inside. If unchecked, the larvae can inflict a lot of damage.”

He also warned growers that larvae damage can increase the chances of infection from diseases such as phoma.

He urged growers to monitor crops closely for larval activity and recommended treating with a foliar spray such as Contest (alphacypermethrin).

“Current autumn recommendations are to treat crops where a threshold of 50% of petioles have been damaged, or where an average 5 larvae per plant are observed,” added BASF Technical Adviser, John Young.