Pollen beetle migration is active across all of the UK according to weather stations monitored by the Bayer Pollen Beetle Predictor. Conditions remain moderate for most of the UK, except some parts of the East of England (Woodbridge, Halsted, Ely) which are experiencing good conditions for pollen beetle.
The extent of the migration is low throughout the UK, with the highest migration (26%) north of the M25 (Harlow and Welwyn Garden City) and to the west of Watford in the Chiltern region (Amersham).
While many crops had a slow start to spring growth, oilseed rape has started to catch up and is close to flowering in many regions. Mark Hemmant, Technical Manager at Agrovista comments: “In the East, crops at threshold for pollen beetle are few and far between. Crops which were sown early are beginning to flower, so it is highly unlikely these will require a treatment for pollen beetle this season.
“For those with backwards crops, affected by pigeon damage or the Beast from the East, there is no substitute for walking the crop, but careful monitoring of the Bayer Pollen Beetle Predictor will help determine when is best to measure beetle numbers and compare against threshold levels.”
Despite the imminent flowering of oilseed rape, which will take the crop beyond the susceptible period for pollen beetle damage, Rothamsted Researcher Dr Sam Cook warns that the next few weeks will be a critical period to monitor for migration events.
She says: “If the warm temperatures predicted do indeed occur, temperatures will be high enough to cause large scale migration events, as well as perfect conditions for feeding activity. This could be a problem if crops are still in the green-yellow bud stage, so careful monitoring of the pollen beetle predictor tool is vital in the coming weeks until the crop is flowering. And remember insecticides should only be used if thresholds are exceeded.”
Revised thresholds for winter and spring oilseed rape are: (Source: HGCA Information Sheet 18/Spring 2013 ‘Monitoring and control of pollen beetle in oilseed rape’)
|Plant population per m2||Pollen beetle per plant|
Growers and agronomists should continue to check the prediction tool to monitor for new migrations and the extent of that migration. This will help determine when is the best time to monitor crops in order to assess the mean number of beetles per plant for comparison against threshold levels.
If insecticides are required, the extra timing flexibility of Biscaya (thiacloprid) could be useful, suggests Neil Thompson, marketing manager for the Bayer product. “Where crops are uneven, Biscaya’s label allows for treatment where some very early flowering has begun, which could help protect crops at different growth stages.”