The IPM Decisions Platform shows pollen beetle migration into crop is likely.
A red warning status is being seen for pollen beetle migration at some ADAS sites, according to the IPM Decisions platform.
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The alert indicates that the air temperature may be higher than the threshold at which pollen beetles migrate, putting crops at growth stage 51-59 at risk of damage.
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At ADAS聮 Terrington and Boxworth sites (GS 53), the IPM Decisions Decision Support System estimated a high risk of pollen beetle migration into crops by Thursday (March 30).
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Dr Eleanor Dearlove, ADAS IPM consultant says: 聯Currently the rainy weather is not ideal for beetle migration despite the temperatures, but there is a potential risk of damage if conditions improve and crops are at the susceptible green/yellow bud stage.
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聯Of course, potential migration into the crop is only half the story as beetle numbers need to be sufficiently high to justify an insecticide treatment. Oilseed rape has a strong capacity to tolerate pollen beetles as it tends to produce excess flowers which can be lost to the beetles without affecting crop yield.聰
Threshold
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By assessing plant populations, growers can get an indication of the pollen beetle threshold for their crop.
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Dr Dearlove says: 聯Ideally, measure the plant population at several positions in the field. Count the number of plants within a square foot and multiply by 11 to give the numbers/sq.m, or for crops in wide rows about 50cm apart, count plants in one-foot length of row and multiply by six.聰
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The pollen beetle thresholds (see table below) depend on the plant population which is a reliable indicator of the number of flowers produced.
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聯With this information it is then possible to predict the number of flowers which can be lost to pollen beetle before any impact on yield will be apparent.聰
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Plant population (number/sq.m) | Pollen beetle threshold (number per plant) |
Less than 30 | 25 |
30-50 | 18 |
50-70 | 11 |
More than 70 | 7 |
Source: AHDB
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聯Monitoring data and experience suggest that beetle numbers rarely exceed 10 per plant so a quick calculation of plant populations will give you a good indication of the likely risk of pollen beetle damage. It is also important to remember that pollen beetle resistance to pyrethroid insecticides is now widespread throughout the UK, so it is vital to minimise the use of these insecticides.
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"Next week, we are forecast cooler weather and the risk of migration will decrease."
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Growers can register for free for IPM Decisions and add their farm to get a risk estimation by visiting: platform.ipmdecisions.net
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BASIS CPD points are available for users.
Actions
- Register for the IPM Decisions platform to get predictions on pollen beetle migration for your area.
- Check plant populations and growth stages to assess the risk from pollen beetle.
- Remember pollen beetles rarely reach threshold levels in the UK.
- Do not spray crops once they are in flower.
Source: ADAS
