Prepare to monitor oilseed rape for pollen beetle

Oilseed rape growers should get ready to monitor crops for pollen beetle with pest migration generally expected to get going in the next fortnight.

Based on the current long-range weather forecast, Rothamsted Research scientist Sam Cook says she generally expects pollen beetle migration to start between 10 and 15 March, with daytime temperatures currently peaking around 5C.

Pollen beetles need sustained temperatures of 10-15C to break hibernation but migration has made an early start in some parts of East Anglia.

See also: Champion sprayer’s tips for tackling weeds and disease

Bayer’s Pollen Beetle predictor is now live for growers and agronomists to forecast the start, peaks and progress of pollen beetle migration into crops this season.

The free web tool serves as an early warning and reminder to get out in the field and check crops for the pest, with the aim of cutting down monitoring time and avoiding unnecessary spraying.

Screenshot of Bayer's pollen beetle map

Red markers on Bayer’s pollen beetle predictor tool indicate migration in parts of East Anglia has commenced already.

Dr Cook says growers and agronomists should check the tool’s “migration start” map every two to three days to get an indication of initial pest pressure.

Once a grower’s local monitoring site is coloured yellow, which means pollen beetle migration is expected to start within the next few days, she says growers can switch focus to the “new migration” map.

“This tells you when it’s time to get into crops and assess average numbers against threshold. It helps to focus monitoring effort to when it’s most needed and facilitate practical use of thresholds,” explains Dr Cook.

The interactive maps can be used on desktop computers or mobile devices, with users able to move and zoom around the map to find the pollen beetle pressure in their local area.

Go to the “tools and services” section of Bayer’s website, click on “agronomy online tools and services” and choose “Pollen beetle predictor”.

Pollen beetle spray thresholds

The AHDB’s pollen beetle thresholds are listed below.

 Less than 30 plants/sq m  The threshold is 25 pollen beetles per plant
 30-50 plants/sq m  The threshold is 18 pollen beetles per plant
 50-70 plants/sq m  The threshold is 11 pollen beetles per plant
 More than 70 plants/sq m  The threshold is seven pollen beetles per plant

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