Coccinellid Beetles on Sugar Beet in Eastern England, 1961–75

SUMMARY The times of flight and the annual fluctuations in the numbers of coccinellid beetles on sugar beet crops in eastern England from 1961 to 1975 were determined using yellow, cylindrical sticky traps and by examining plants in plots which had not been treated with insecticide. Adalia bipunctata (L.) was the coccinellid most often trapped and it formed 33 per cent of the total catch. Propylea 14‐punctata (L.) formed 25 per cent of the total catch. Coccinella septempunctata L. was less often caught, forming only nine per cent of the total catch on traps, and it was uncommon on sugar beet except when the plants were heavily infested with Aphis fabae Scop, in August. The ‘plagues’ of C. septempunctata occasionally recorded on the East Anglian coast occurred only in years when aphids had been common on cereal crops. Although coccinellids are one of the causes of the rapid decline of aphid populations on sugar beet in August, no evidence was found that they play an important part in controlling the spread of yellowing viruses. However, they may prevent a crop from becoming heavily infested with aphids which are potential vectors in the spring and they may destroy aphids overwintering on virus‐infected weeds and other sources of infection.