Comparative effects of Plutella xylostella (L.) (Lepidoptera: Plutellidae) and Crocidolomia pavonana (F.) (Lepidoptera: Crambidae) on cabbage yield in Tanzania

In a series of open field experiments, we studied the effects of two lepidopteran pests ( Plutella xylostella and Crocidolomia pavonana ) at equal population density on cabbage yield. Completely randomised plots were assigned to four treatments, replicated four times. Treatments were P . xylostella only, C . pavonana only, or P . xylostella and C . pavonana at 1:1 ratio at different phenological stages of cabbages and a control (without any caterpillars). The growth stages and applied densities were pre-heading, cupping and heading, with densities of 2, 4 and 6 larvae/plant, compared with control. The effects of the two species differed significantly in terms of both yield (P