This year has been one of the lowest-risk years for wheat bulb fly since monitoring began, according to the final results from the AHDB autumn survey of the pest.
Conducted by ADAS, the survey involves taking soil samples in September from 30 fields prone to wheat bulb fly attack (split equally across sites located in the East and North of England) and calculating the number of eggs on each square metre.
Egg counts at seven of these sites (two in the east and five in the north) exceeded the 100/m² seed treatment threshold, which applies to late-sown (November to December) winter wheat crops.
Early sown crops (sown before November) are unlikely to benefit from seed treatment, as such treatment lacks sufficient persistence to protect crops.
Where egg counts are greater than 250/m², economic losses should be anticipated. In 2018, only one site had more than 250 eggs/m² – a potato site in Cambridgeshire where 322 eggs/m² was recorded.
For late-winter/spring sown crops (January to March), seed treatments should be considered, if eggs are present.
Charlotte Rowley, who manages pest research at AHDB, said: “Wheat bulb fly has been monitored since 1984.
The number of fields with more than 250 eggs/m² has been relatively low in the last few years. With a complete absence of post-drilling control options, this is good news for farmers.
Full survey results, the report and threshold information can be accessed via the dedicated AHDB web page.
AHDB is also asking growers to guide investment in pest monitoring services over the next five years by completing a short survey.
The survey, which closes on November 30, 2018, can be accessed via cereals.ahdb.org.uk/pestsurvey.
Wheat bulb fly risk has been charted since 1984. For crops sown in September to October, egg populations greater than 250/m² are considered likely to result in a negative economic impact on yield.
