With plenty of migration still to come and OSR crops now in the green to yellow bud stage the threat of pollen beetle hangs in the balance.
Last week, temperatures cooled to the low teens centigrade making conditions generally unsuitable for migration. The 'percent migration' map is showing that most of England still has 60 to 85 percent of this season's migration still to come. A handful of home countries met stations are showing migration half complete, but this is the exception. In Scotland and the borders migration has hardly started and there is 90% still to come.
With crops now generally in the green to yellow bud stage everything depends on the weather from here on. It was a chilly weekend with temperatures below 10C, but we would need a further fortnight of this to keep migration contained until crops are flowering in earnest. On the other hand, a couple of springlike days of 15C is all that's needed to trigger significant migration into crops.
This is precisely the kind of situation Bayer Pollen Beetle Predictor was designed to help manage. Keep a close watch on the new migration map over the coming fortnight and monitor crops as soon as indicated. If numbers exceed threshold, crop growth stage will be a key consideration in treatment decision-making.
Pollen beetle control is necessary up to the point when the crop starts to flower in earnest i.e. when more than 20% of buds on the main shoot are flowering on more than three quarters of the crop (GS62). Product labels restrict use of Plenum (pymetrozine) and Rumo (indoxacarb) to before first flowers open (GS60) but Biscaya (thiacloprid) can be used up to the end of the damage susceptible period.