Pollen Beetle Control
Pollen beetle control:pyrethroid efficacy check advised
The spring 2011 HGCA information sheet on controlling pollen beetle and combating insecticide resistance in oilseed rape contains important updates to agronomic advice.
Results collected by the Insecticide Resistance Action Committee (IRAC) indicate that only 37% of samples in 2010 were susceptible to pyrethroids compared to 54% in 2009 and 85% in 2008. In 2009 and 2010 resistant insects were also found in the Midlands, northern England and Scotland.
The information sheet warns that continued use of pyrethroids for control of pollen beetle will cause resistance to intensify and spread even further. In light of these risks the UK Insecticide Resistance Action Group (IRAG-UK) has developed advice based on reducing use of pyrethroids and on exploiting other insecticide groups.
Bayer’s Dr Bill Lankford expects that in parts of the country where pyrethroid resistance has not yet been established, growers needing to control pollen beetle this year will understandably, for cost reasons, still want to try using a pyrethroid spray first.
“If you do this it’s essential to check efficacy 24 hours after application,” he advises. “If above threshold numbers of beetles have survived the pyrethroid spray you will need to treat again with an alternative such as the neonicotinoid Biscaya (thiacloprid) as soon as possible.
“Last year we received calls from growers seeking advice five to seven days after a pyrethroid had failed to knockdown populations. By this stage the resistant beetles will have done their damage to developing buds and it’s too late to take remedial action.”
In the south and east of England where resistance is now well-established Biscaya has become the treatment of choice Dr Lankford claims. “Growers have found it to be the most effective at preventing pollen beetle damage. This reflects trials experience in Germany where only 10% of populations are susceptible to pyrethroids and Biscaya has delivered yield benefits of 0.6 t/ha under high pollen beetle pressure.”
The spring 2011 HGCA pollen beetle information sheet can be downloaded at www.hgca.com/publications
