The latest results available from HGCA show wheat bulb fly infestation levels are way below autumn 2010, when highs were recorded. The wheat bulb fly survey, which was conducted by ADAS and HGCA, sampled a total of 41 fields considered ‘at risk’ of infestation and revealed that infestation levels had fallen since last year. image expired

In eastern England, average egg numbers were 179 per square metre compared with 309/m2 in 2010. High, or very high egg populations were found in five (19 per cent) of the sampled fields, whereas last year levels of 55 per cent and 28 per cent for 2010 and 2009 respectively. This year’s high risk fields followed vining peas and potatoes. Although overall averages remained high for egg populations, with 20 per cent of the 41 fields sampled showing populations greater than the high-risk 250/m2, infestation was down on the long-term average of 23 per cent.

In Northern England, while no fields were in the very high risk category, three (20 per cent of fields tested) were deemed high risk; average counts for northern England remained similar to 2010 at 161/m2, mostly following potatoes.

ADAS entomologist Steve Ellis said the reason for the drop-off was not immediately apparent, "There is no simple answer why we have seen a decrease in egg populations this year, but numbers are thought to be linked to pre-harvest rainfall, and the dry conditions experienced, particularly in the East, may have had an effect."

HGCA is still advising growers to be aware of the risks, particularly as crops sown in late autumn are more susceptible to pests. The HGCA website has more information on the survey as well as advice for dealing with wheat bulb fly, which can attack any cereal except oats.   

The fly mostly affects Eastern regions; bare soil following fallows, set-aside, early harvested crops or root crops are favoured by females for egg-laying in the summer months. Larvae hatch between January and March and invade shoots. He shoots die back, showing ‘deadheart’ symptoms. Wheat fly activity can cause losses of up to 4 t/ha.