Studies on the biology and control of groundnut borer Caryedon serratus (Olivier) (Coleoptera: Bruchidae)

Abstract

The groundnut borer, Caryedon serratus is a serious pest of stored groundnuts, Arachis hypogaea in some parts of the world. It causes heavy ii losses in stored groundnuts in Western Kordofan state especially El Nohoud area. In this study the survey covered fields and stores. The survey revealed that, C. serratus was absent in the fields during October. While it was present in stores and infestation become severe with time. This study revealed that the mean of loss in weight reduced from 100 gm in May 2005 to 38.85 gm in February 2006. The pest consumes all inner contents of infested seeds. Adults escape from excessive heat by burrowing among nuts. Adult female usually lays eggs singly on shelled or unshelled groundnuts. The eggs are small, semi-ovid in shape and yellowish in colour during the first day, and turns to whitish after hatching. Translucent shriveled eggs indicate unfertilized or dead embryo. Larvae of C. serratus were creamy whitish in colour. They were observed to bore and inter into groundnut seeds and feed on it soon after hatching. The pupal cocoons, made by the full grown larvae. Cocoons usually were formed on the surface of the seeds or inside the seed. The cocoon was ovate in shape. The empty cocoon was paper like. The average number of eggs laid by 10 females per day was 63.8 eggs under room condition when the pest reared on shelled groundnut. The oviposition period and post oviposition period was 6.1 and 2.3 days respectively. The longevity of male and female was 8.5 and 9.5 days respectively. The incubation period, larval period, pupal period and generation period of C. serratus were 6, 25.5, 12 and 45 respectively. The iii percentage of egg hatchability, t he percentage of the larvae which reached the pupal stages, the percentage of pupae matured to the adult stage and the total percentage of survival in all stages were 82%, 88%, 94% and 68 respectively. In this study the life tables data analysis revealed that the net rate of reproduction (RO), weight generation time (T) the innate capacity for numerical increase (rm) and the doubling generation time (DT) were 8.057, 48.48, 0.0142 and 48.59 respectively. All botanicals used in this experiment as neem leaf ethanolic extract at dose 5, 2.5 and 1.5ml/50gm, neem seed kernel powder at dose 5, 3 and 1gm/50gm and neem oil at dose 5, 2.5, and 1.5ml/50gm exhibited very good ovicidal effect against C. serratus and caused mortality between 78.8% to 100%. Also all botanicals at all doses showed strongly larvicidal effect against C. serratus and caused mortality between 95% to 100%. When C. serratus was fumigated by kafor oil 100% mortality of .adults was recorded within 24 hours at dose 10ml/28.3cm2