The possibility of using Indian mustard, Brassica juncea, as a trap crop for the diamondback moth, Plutella xylostella, in South Africa

Abstract

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) was first reported as a pest in South Africa in the early 1900s. The cost of pesticides and the increasing resistance of P. xylostella to chemical control makes it necessary to explore alternative control methods. We investigated the crop preferences of P. xylostella to determine the possibility of using Indian mustard as a trap crop. Infestation levels of P. xylostella were tested on five different plants in the laboratory and the field: cabbage, Brassica oleracea var. capitata L.; cauliflower, Brassica oleracea var. botrytis L.; broccoli, Brassica oleracea var. italica L.; Chinese cabbage, Brassica pekinensis (Lour.) and Indian mustard, Brassica juncea (L.) Czern. Laboratory experiments indicated that females preferred to oviposit on Indian mustard. Field trials, however, indicated a higher larval infestation on broccoli, cauliflower and cabbage. Larval survival in the laboratory was lower on Indian mustard than on other crops, which may explain the low numbers found on Indian mustard in the field. Other possibilities for this discrepancy are discussed. Results indicated that Indian mustard has potential as a trap crop for P. xylostella in South Africa.