22 May 1998

Flying insect look-alikes

SEVERAL small insects are currently flying which can be confused with wheat orange blossom midge, according to ADAS entomologist Jon Oakley.

That said the first two triggers needed for a repeat of the 1993 OBM outbreak which cut some yields by a third have already occurred.

Bladder pod midge in oilseed rape and another fly which feeds on fusarium in the bottom of cereal crops are among those which could be mistaken for OBM, says Mr Oakley. "They are inherently difficult to tell apart."

IACR-Brooms Barn reported finding OBM in sugar beet crops several weeks ago. Aprils soakings provided the soil moisture needed to stimulate over-wintering OBM larvae, and the recent sudden rise in temperature speeded the life cycle into adults, explains Mr Oakley.

The larvae can survive in the soil for 14 years, he notes. "It is hanging on in some hot spots in river valleys in the south west."

Weather is key

Much depends on the weather, he explains. "The flies have to be in the ear to do damage and they need warm settled weather in the evening to lay their eggs. If you can find one or more flies on three ears during the later stages of ear emergence you should act."

For specific treatment of OBM chlorpyrifos (as in Dursban) insecticide is the correct choice, says Mr Oakley. But pyrethroid sprays against aphids give some control of low infestations, he notes. &#42