WHEAT CROPS in eastern England are at particular risk from wheat bulb fly and growers need to be vigilant as egg hatch is about to begin, experts have warned.

Sampling from traditionally higher risk fields (e.g. crops following sugar beet, potatoes or vining peas) last autumn found that around half of crops in eastern counties are at “high risk” from bulb fly attack, with egg counts of over 250/m2, according to ADAS’s David Green.

Some 18% of fields in eastern areas were found to be at “very high risk” with counts of over 500 eggs/m2, he added. But the risk is generally lower further north, where nearly half (42%) of fields are classed as ‘moderate risk’.

Crop growth stage will have an important effect on risk of damage, he said.

“In terms of development, crops have gone from being very forward to relatively normal, or slightly backward in some cases and could need careful managing this season.

“Those that were drilled late and have not yet tillered well will be at most risk [from bulb fly attack]. Early sown, well tillered crops can cope better with higher bulb fly populations.”

The results from the 2005 survey are similar to 2004, added Dow AgroSciences; David Roberts.

Some agronomists are already reporting signs of early damage and growers need to assess the risk for each field and spray if necessary, he said.

He suggests using Dursban WG (chlorpyrifos) at 1kg/ha in 200-1,000 litres of water.

More information on the wheat bulb fly survey can be found at www.hgca.com