Low wheat bulb fly pressure trend continues

Friday, 20 September 2019

The low wheat bulb fly pressure trend looks set to continue in 2019, according to early results from the AHDB autumn survey of this cereal pest.

Conducted by ADAS, the survey uses soil samples from 30 fields, split equally across sites located in the East and North of England that are prone to attack, to calculate the number of eggs per square metre.

The results can indicate whether treated seed could potentially reduce the risk of unacceptable crop losses.

According to the initial results, a seed treatment would potentially be beneficial for late-sown winter crops* at just two of the 12 sites.

Both of these ‘moderate-risk’ sites were located in North Yorkshire, with egg populations slightly above the 100/m2 threshold. The other ten sites were categorised as ‘low risk’.

*Seed treatment thresholds

Chemical control is limited to seed treatments, with thresholds as follows:

  • Early-sown winter wheat crops (before November) are unlikely to benefit from seed treatment, as they have more time to tiller and are better able to withstand attack. Egg populations greater than 250/m2 are considered likely to result in a negative economic impact on yield. However, seed treatments lack persistence to protect such crops.
  • For late-sown winter wheat crops (November to December), consider seed treatments where populations exceed 100 eggs/m2
  • For late-winter/spring-sown crops (January to March), consider seed treatments irrespective of the population size (unless no eggs are present)

Access survey results and threshold information via the dedicated AHDB web page: ahdb.org.uk/wbf