INCIDENCE AND IMPACT OF CHILO PARTELLUS SWINHOE (LEPIDOPTERA: CRAMBIDAE), THE CEREAL STEM BORER AND ITS NATURAL ENEMIES ON MAIZE (ZEA MAYS L.) IN SHIRE VALLEY AGRICULTURAL DEVELOPMENT DIVISION IN MALAŴI

Abstract

The incidence and impact of Chilo partellus and its natural enemies was assessed in maize plants applied with 0kgN/ha, 60kgN/ha and 120kgN/ha in the dry season of 2004 and 2005 under irrigation at Masenjere and Kasinthula in Malaŵi. The impact was assessed by excluding C. partellus and natural enemies with the insecticides, carbofuran and dimethoate, respectively. The plant nitrogen was significantly low in plots with 0kgN/ha than in 60kgN/ha and 120kgN/ha, which were not significantly different. C. partellus infestation and damage significantly increased in 60kgN/ha and was followed by 120kgN/ha. C. partellus egg parasitism by Trichogramma spp. and larval parasitism by C. flavipes were not significantly different in the nitrogen treatments. Trichogrammaspp. parasitism efficiency was however significantly high in 120kgN/ha. The impact of C. partellus on maize was 29% mean grain yield loss at Masenjere and 82 % at Kasinthula. The yield loss was higher in 0kgN/ha than in 60kgN/ha and 120kgN/ha despite there being more borers and damage in the 60kgN/ha. Yield loss was lower at Masenjere where egg parasitism was higher than at Kasinthula. The effect of sorghum and pearl millet grown on borders of maize plots and effect of intercropping maize with desmodium on stemborer incidence and parasitism in maize was assessed. C. partellus infestation significantly increased in maize with sorghum border. Maize bordered with pearl millet had significantly lower stemborer infestation than mono-cropped maize. Maize with a desmodium intercrop had significantly lower stemborers than monocrop at Kasinthula. At Masenjere it was the opposite. C. partellus egg and larval parasitism by Trichogramma spp. and C. flavipes were not affected by border crops and desmodium intercrop. Maize yield did not significantly differ with border crop type. Desmodium intercrop also did not significantly affect yield.