Conducted by ADAS, the survey involves taking soil samples in September from 30 fields prone to WBF attack (split equally across sites located in the East and North of England) and calculating the number of WBF eggs per 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 (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 (322 eggs/m2).
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 per square meter has been relatively low in the last few years. With a complete absence of post-drilling control options, this is good news for farmers.”
Survey results, the report and threshold information can be accessed via the dedicated AHDB web page: ahdb.org.uk/knowledge-library/wheat-bulb-fly
AHDB is also asking people to guide investment in pest monitoring services over the next five years by completing a short survey. The survey, which closes on 30 November 2018, can be accessed via cereals.ahdb.org.uk/pestsurvey