APHID NUMBERS are building in cereal and sugar beet crops due to mild winter and spring conditions, a leading expert has warned.

“The good news is that the aphid‘s natural enemies have also benefited, and could be a significant factor in controlling infestations this year,” said ADAS consultant, Jon Oakley.

“Provided that numbers do not increase to infest over half the (wheat) tillers before flowering, it is safe to let the situation develop and see if the various natural enemies do the job for you.”

A reduced rate aphicide, to tip the balance in favour of the natural enemies, could be used if this threshold is exceeded, he advised.

Grain aphids feed on leaves and ears of wheat, barley and oats in spring and summer.

Infestation before flowering can reduce grain number, while later attacks reduce grain size, although not quality.

Thousands of aphids have been caught in water traps, according to Alan Dewar from Broom‘s Barn sugar beet research station.

But very few of these are the vectors of virus yellows – M persicae and M euphorbiae, he noted.

“We have been finding some in crops, but nothing above threshold levels.”

Home-Grown Cereals Authority Topic Sheet No 45 – Summer pest control on wheat – gives information on controlling wheat blossom midge as well as aphids.