Comparative Studies on Insect Pests of Cocoa Beans
in Farm and Town Storage Sites and Insecticide Tolerance in the Major Pest, Corcyra cephalonica (Stainton)
O.O. ODEYEMI, AO. ADEYERA and M.O. ASHAMO.
ABSTRACT: A survey was conducted to study the insect pests of dried cocoa beans in farm and town storage sites in Ondo State, South West, Nigeria. Also a glass-vial bioassay was used in estimating tolerance to insecticide in adult Corcyra cephalonica (Stainton), the major moth pest found in the storage sites. Laboratory reared C.
cephalonica were compared with first filial generation of the moths collected from farm and town storage sites in which control with insecticides has been inadequate.
Investigations revealed that hygiene practices and storage of cocoa beans improved in the town storage sites than in the farm sites. There were significant differences (P<O.005, Ll-test) in insect populations at both sites. C. cephalonica was prominent at the storage sites. Ahasverus advena (Walts) was present in the farm sites but absent in the town sites thereby indicating high moisture content in the cocoa beans at the farm level. Mouldiness in cocoa beans was moderate at the farm and town sites in the dry season while there was an increase in the wet season. Significant differences (P<0.05) in resistance among adult C. cephalonica were found among town, farm and laboratory reared groups using the insecticide, pirimiphosmethyl, Adult moths from the laboratory culture were least tolerant while those from town storage sites were the most tolerant species.