28 March 1997

Pollen beetles early in rape

POLLEN beetles are easy to find in rape crops this spring, prompting calls for care with control measures.

Warm weather has brought the earliest colonisation by the pest for over 10 years.

However, forward crops have also developed rapidly and will soon be beyond the at-risk green/yellow bud stage, says ADASs Guildford-based crop consultant, Nick Cooper. For such crops the normal 15 beetles a plant threshold stands.

However, less advanced crops may linger at the susceptible stage longer, particularly if conditions remain cooler. Use a threshold down to five beetles a plant for crops now at the early bud stage, he advises.

If spring rape is at the green bud stage as late winter crops start flowering the pests activity will be extended still further.

The early spring could also advance seed weevil attack, which normally occurs as the first pods set, adds Rob King, insecticide manager for Cyanamid.

He warns against trying to control both pests with one spray.

Only in spring rape, where bud and flowering stages are much closer, could both be hit with one spray. "If that is done, the seed weevil rate of 200ml/ha of Fastac must be used and not the pollen beetle rate of 100ml/ha."