Early spring watch for Pollen Beetle activity

Pollen Beetle have been reported active on early-flowering hedgerow plants, which could mean an early risk of attack on oilseed rape this season.

Mild winter weather and highly advanced oilseed rape crops mean Pollen Beetle could attack early this year; Pollen Beetle are already reported to be actively feeding on early flowering primrose and other wild flowers.

Growers should be ready to treat with Hallmark Zeon if recognised economic thresholds are reached when oilseed rape crops are at the green to yellow bud stage, according to Syngenta Technical Manager, Michael Tait. "Growers must take extra care to avoid damage with any thin or backward crops from pest thresholds as low as five beetles per plant," he advises, "although the majority of strong crops will tolerate pest levels up to the threshold of 15 beetles per plant," he adds.

Mr Tait also points out that following identification of pyrethroid resistance among an isolated colony of Pollen Beetle on one field in Kent last year, growers should remain vigilant for reinvasion and pest presence after treatment, particularly if the beetle attacks are protracted this year.

"Our monitoring identified that in all but one of the 21 populations tested, the Pollen Beetles would be controlled by a pyrethroid insecticide. The resistance identified would reduce the efficacy of all pyrethroid insecticides. Monitoring by independent agronomists and other pesticide manufacturers revealed no additional incidence of resistance," reports Mr Tait.

At less than £5/ha Hallmark Zeon remains a cost effective control option, when alternative treatments could cost four or five times as much. "However, we would advocate that should a follow up treatment be required to counter Pollen Beetle reinvasion, growers switch to an alternative mode of action to minimise the risk of pyrethroid resistance developing over the next few seasons," he adds.

Picture: Growers must be ready to treat Pollen Beetle if economic thresholds as low as five beetles per plant are reached.