Results of the HGCA’s wheat bulb fly survey show that 2011 infestation levels are well below the highs of last autumn.
A total of 41 fields considered ‘at risk’ of infestation were sampled for the survey, conducted on behalf of HGCA by ADAS, with additional support from Syngenta.
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%) of the sampled fields, which compares favourably with levels of 55% and 28% for 2010 and 2009 respectively. This year’s high risk fields followed vining peas and potatoes.
In northern England, there were no fields in the very high risk category, but three (20%) deemed high risk. However, average counts for northern England remained similar to 2010 at 161/m2. High risk sites in the North followed potatoes.
“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,” commented Steve Ellis, ADAS entomologist.
Overall, 20% of the 41 fields sampled had egg populations greater than the high-risk 250/m2 threshold, compared to the long-term average of 23%.
“Even though this year’s results are lower than last season, growers should still consider the risk in their region carefully when deciding what action to take,” said Caroline Nicholls, HGCA Research Manager.
“Late-autumn sown crops in high-risk areas will require the most attention, but even moderate risk areas should be carefully managed as the pest threshold is much lower for crops sown from November onwards. Anyone concerned about this pest should view the survey in full on the HGCA website and also HGCA Topic Sheet 99, where there is useful information on control options,” she added.
All cereals, except oats, can be attacked by wheat bulb fly and the pest is most common in the eastern counties, the east Midlands and north east England. Eggs are laid in late summer, and the sites chosen by females for egg-laying vary from year to year.
Bare soil following fallows, set-aside, early harvested crops or root crops are favoured egg-laying sites. Larvae hatch between January and March and invade shoots, which eventually die back to show ‘deadheart’ symptoms of damage, potentially causing yield losses of up to 4 t/ha.
For more information on the survey results and the management of wheat bulb fly visit www.hgca.com.
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