Phytochemical Composition, Larvicidal Activity of Cocos Nucifera Extracts on Busseola Fusca Fuller and Its Effects on Growth And Yield of Maize

Abstract

Maize forms the staple food for most Kenyans. Although, current trends show Busseola fusca as the major pest causing a decline of about 400,000 tonnes of maize in Kenya. Most farmers use synthetic insecticides to control Busseola fusca, however, chemicals have residual effects in crop products, are expensive and harmful to the environment. Plant extracts are biodegradable and safe for human use but limited extracts that have been identified. There is a need to identify more plant extracts to control insect pests. Cocos nucifera is known to have antimicrobial and the phytochemical compounds of this plant may have larvicidal effects on Busseola fusca which may improve maize yield. However, its phytochemical composition and larvicidal activity on Busseola fusca has not been determined. This study aimed to investigate the phytochemical composition, larvicidal activity of Cocos nucifera extracts on Busseola fusca and its effects on growth and yield of maize. The experiment was carried out in a greenhouse at Maseno University. It was laid in a Completely Randomised Design, consisting of three replicates. The treatments consisted of coconut leaf, root and husk extracts at: 75%, 50%, 25%, 0% (negative control) and Karate (Lambda-cyhalothrin). Three holes of a depth of 2.5cm each were made in each pot. Two Pannar 15 maize seed variety were sown per hole in 20 litre plastic pots. The pots were filled with acrisol soils having a pH of 4.5-5.5. Cowdung organic manure, Diammonium phosphate and Calcium Ammoniun Nitrate were used to improve soil fertility. The seedlings were thinned to 3 plants per pot. Busseola fusca obtained from the International Center for Insect Physiology and Ecology in Nairobi, were released to 20 days old plants. The treatments were applied weekly and observations were made at 15 day interval. The data collected was subjected to analysis of variance and means separated at p≤ 0.05. The results showed the presence of tannins, saponins, steroids, terpenoids, flavonoids and glycosides. Alkaloids were absent in all the extracts. Coconut leaf extract at 75% concentration significantly increased the mean number of dead Busseola fusca, reduced leaf damage, reduced dead hearts and reduced the number of borer holes, while increasing chlorophyll content and increasing maize yield in grams. The mortality of stem borer, chlorophyll content and yield increased, as the number of dead hearts and borer holes reduced at the early stages of maize growth with increased exposure to the extract. The mortality of stem borer may be attributed to the phytochemicals present in the coconut extracts which have insecticidal, anti- feeding and larvicidal effects on insect pests. This in turn reduced leaf damage, dead hearts and borer holes hence increased maize yields. In conclusion, coconut extracts have potent larvicidal effects against Busseola fusca due to the phytochemicals present in the extract. Coconut leaf extract at 75% is recommended as the most effective biopesticides against Busseola fusca in order to improve the maize yields by farmers. Further research on the mode of action of the phytochemicals present in Cocos nucifera extracts against Busseola fusca is recommended.