INFLUENCE OF PANICLE COMPACTNESS AND HOST-PLANT RESISTANCE IN SEQUENTIAL PLANTINGS ON POPULATION INCREASE OF PANICLE-FEEDING INSECTS IN SORGHUM-BICOLOR (L) MOENCH

The effects of panicle compactness and host plant resistance on the ra te of population increase of sorghum midge (Contarinia sorghicola Coq. ), head bugs (Calocoris angustatus Leth.) and head caterpillar (Helico verpa armigera Hb.) in large concentric plots over three sequential so wings during the 1985-86 rainy seasons were studied. Early-planted cro ps suffered less damage than the late-planted crops. H. armigera damag e was negligible in genotypes with loose panicles. Calocoris angustatu s population increase was lower in genotypes with loose panicles. Pani cle compactness did not affect the damage caused by C. sorghicola and Campylomma spp. Host plant resistance had a marked effect on the rate of population increase across sowing dates in the case of sorghum midg e and head bugs. Thus, cultivars with resistance to insects and/or wit h loose panicles can help to reduce the losses caused by panicle-feedi ng insects in sorghum.