Field populations ofMythimna separataand its parasitoid, Cotesia rujicrus, were sampled from maize over two successive seasons. Populations ofM. separatalarvae (up to 1.5 larvae per plant) were detected in February of both years. Larvae were heavily parasitised byC. ruficrus, which caused mortality of up to 98070.C. ruficruscocoon masses were hyperparasitised byEupteromalusspp. from March onwards, but this occurred too late to affect primary parasitism ofM. separata. Early collection ofC. ruficrusadults adjacent to the crop suggested parasitism of host generations preceding that on the maize.M. separatalarvae occurred mostly on mature cobs and did not affect fertilisation or cause significant seed damage.
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