Pollen beetle monitoring as part of an HGCA project indicates that crop shave now generally passed the damage susceptible phase and thresholds have not been breached.
The HGCA project Validation of an IPM strategy for pollen beetle being led by ADAS Dr Steve Ellis and Rothamsted Researchs Dr Sam Cook, involves volunteers monitoring crops and trapping pollen beetles with yellow sticky traps during spring migration. Dr Sam Cook says this years migration has been slow,due to relatively cool conditions, and this has allowed crops to reach the end of the damage susceptible phase before numbers have built up.
Volunteers have been recording the average number of beetles per plant by sampling ten plants along a transect of 30 metres from the headland towards the centre of the crop. Across the 10 locations monitored this year, peak number shave ranged from 1.4 to 14.7 during the damage susceptible phase and the mean across all sites was 8.8 beetles per plant.
Although thresholds have not been breached, we came close to them at three of the 10 sites in what has certainly been a low pressure season. For example,in the crop near Welwyn Garden City numbers reached 10.8 per plant versus a threshold of 11 for a crop with 50 to 70 plants per square metre. This reinforces the value of using Bayer pollen beetle predictor to see when you need to be out monitoring fields.
Todays percent migration map shows a wide-ranging picture. In England migration ranges from 19% complete in Norfolk/Suffolk to 86% in Surrey/Sussex andScotland it ranges from 19% complete at Huntly to 52% at Perth. Across the country as a whole migration is typically 50% complete which is low for this stage of the season.
Next year will be the final year of trapping for the HGCA project and DrCook is calling for volunteers. In 2016 well be looking for volunteers inScotland, West Yorkshire, Wales and the South West which are areas still to be covered by the project. However, volunteers anywhere will be very welcome and will add validity to this work which aims to save growers time and money by minimising the time needed for effective pest monitoring and helping to prevent unnecessary sprays.
Access pollenbeetle predictor at: www.bayercropscience.co.uk/pollenbeetlepredictor