22 November 1996

More aphid worry

COTTON melon aphid, Aphis gossypii, is adding to grower worries about insecticide resistance aphids (Arable, Nov 8).

The type is normally unknown in UK field crops, but has been detected in several samples collected from potato crops grown on farms in Lincs, Cambs and Sussex.

Normally seen in outdoor crops in the southern states of the USA and southern Europe, this black aphid is a common problem in UK glasshouse chrysanthemums. It carries a second type of resistance, so the target protein can cope with chemical attack.

"Almost certainly this aphid has come from glasshouses, but we have no idea of the extent of its spread outdoors. But it is yet another resistant aphid complication facing farmers," says Rothamsteds Alan Devonshire. &#42