Abstract: Chilo partellus is an important stem borer pest in East Africa. To manage it’s infestation, the parasitoid, Cotesia flavipes Cameron was introduced in Kenya and post release surveys showed that parasitism was steadily rising. However, due to lack of quantitative data on the parasitoid’s impact, there are doubts on whether this parasitoid is an important mortality factor in stem borer management. This experiment was thus undertaken at the Kenyan coast to estimate the impact of C. flavipes on stem borers and maize yield. Using insecticide exclusion method, maize subplots were subjected to three treatments: treatment A (sprayed with Bulldock), treatment B (sprayed with Dimethoate) and treatment C (controls). Percentage infestation and parasitism were estimated at three maize growth stages. At the end of the experiment, maize was harvested, dried and weighed. Chilo spp dominated the stem borer community followed by S. calamistis. Stem borer infestation levels varied among treatments (F2,87=6.92; p<0.05) and low infestation was recorded in treatment A compared to B and C. Infestation levels also varied with maize growth stages (F2,87=11.07; p<0.001 ). The main parasitoid species recovered were Cotesia flavipes and Cotesia sesamiae (Cameron). Parasitism in treatments A, B and C were 16.2±7.4, 20.9±4.9 and 20.7±6.9% respectively with no significant difference among treatments ( =3.56; p>0.05). Parasitism varied significantly among maize growth stages ( =21.6; p<0.05). Maize yield did not vary among treatments A (20.8±2.1), B (24.1±2.0) and C (20.5±1.6) (F2,27 =1.148; p>0.05) showing that the rise in parasitoid action has not translated into significant maize yield increase.
Keywords: Moist lowland tropics, Chilo partellus, Cotesia flavipes, impact, parasitism, insecticide exclusion method, maize yield.
Title: IMPACT OF PARASITOIDS ON LEPIDOPTERAN STEM BORER INFESTATION LEVELS AND MAIZE YIELD AT THE KENYAN COAST
Author: Esther Adhiambo Abonyo, George Otieno Ongámo, Catherine Wanjiru Lukhoba, Gideon Nzioka Nyamasyo, Gerphas Ogola Okuku, Midingoyi Soul-Kifouly, Hippolyte Affognon, Bruno P. Le Ru
International Journal of Life Sciences Research
ISSN 2348-313X (Print), ISSN 2348-3148 (online)
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