For England the first weekend of April was warmer than forecast with southerly winds taking temperatures up to the mid teens in many parts of the country. This is just what is needed for pollen beetle migration and as a result Bayer Pollen Beetle Predictor is showing that much of the country has progressed to 10-20% migration while the northern home counties and southwest have reached 20-30% migration. Scotland however had a far cooler week with temperatures hardly touching 10C so the map there is showing just 4-13%migration.
Currently the Bayer Pollen Beetle Predictor new migration map is showing moderate migration conditions in England and no migration possible in Scotland and the Borders. The BBC Weather outlook for the coming week is changeable. Westerly winds are forecast to take over from the southerly winds of last week taking temperatures down to around 10C again below normal for the time of year with April showers.
While pollen beetle can now be found easily in oilseedrape crops, numbers are well below threshold and reports back from volunteers in the AHDB funded project (Validation of an IPM strategy for pollen beetle)led by Rothamsted Researchs Dr Sam Cook show that crops generally are almost past the damage susceptible stage.
The projects protocol requires volunteers to start trapping on 1st March and continue until the crop is at BBCH 61early flowering when approximately 10% of flowers on the main raceme are open across three quarters of the crop. This marks the end of the damage susceptible period. Of the projects 19 trapping sites this spring, two Bury St Edmundsand York have already reached this cut off point.
In last weeks bulletin Dr Cook predicted that Spring2016 was shaping up to be one where crops could mostly make it past the damage susceptible stage before pollen beetle were seen in significant numbers. Cropand migration development over the last week combined with the weather outlook for the week ahead add further confidence to this prediction.
To access Bayer Pollen Beetle Predictor click on: http://www.bayercropscience.co.uk/tools-and-services/agronomy-online-tools-and-services/pollen-beetle-predictor/