The insecticidal potential of neorautanenia mitis (a.ritch) against prostephanus truncates (horn) in stored maize

A dissertation submitted in partial fulfillment of the requirements for the degree of master of science in crop science

This study was carried out to evaluate the insecticidal potential of Neorautanenia milis to the Larger Grain Borers Prostephanus truncatus (Hom) (Coleoptera: Bostrychidae) and its mammalian toxicity. Laboratory studies were conducted to asses the efficacy and the basic mode of action of N. milis on P. truncatus. Further studies were conducted to asses the toxicity of N. milis on mammals using rats (Mastomys natalensis). The efficacy was assessed at six rates (0, 1, 2, 5, 7 and 10% w/w N. milis in 50g of maize grains) with 5 replications. The repellency was evaluated in the choice bioassay at five rates (1,5, 10, 15 and 20% w/w N. milis in 50g of maize grains) in 5 replications. The contact mode of action was evaluated using Student’s t or t-test. Anti-oviposition was evaluated in non choice bioassay system at six rates (0, 1, 2, 5, 7 and 10% w/w N. milis in 50g of maize grains) in 3 replications. Actelic super dust at a rate of 0.05g in 1kg of maize was also used for comparison. Mammalian toxicity was evaluated by exposing rats to six rates (0, 5, 12.5,25, 50 and 75% w/w N. milis in Broiler mash) in 6 replications. The lethal dose (LD5q) was determined by the graphical method of Miller and Tainter. Split-plot arrangement in a Complete Randomized Design (CRD) was used while Two-way ANOVA was used in the analysis of data. The results showed that N. milis powder and liquid extracts were statistically significant (p<0.05) in reducing the number of damaged grains. Repellency and ant-oviposition are presumed to be the key mode of action of N. mitis. The study indicated that the plant tuber is toxic to rats, therefore care should be exercised during the preparation and handling of the food stuff treated with N. mitis.

The Prime Minister’s Office, Regional Administration and Local Government through Nkasi District Council