Integrated management of bean Bruchid,Acantlloscelides Obtectus say (Coleoptera: Bruchidae), on stored beans in Eastern Kenya

Abstract

A survey was carried out on stored beans in three districts (Meru central, Meru north and Tharaka) in eastern Kenya to identify the bruchid species responsible for the bean damage and the existing management options currently used against the pest by farmers in the study area. The study established that, Acanthoscelides obtectus Say was the dominant pest species of stored beans and farmers still rely on mainly chemical pesticides in its control in eastern Kenya but damage as experienced by farmers was still high. Farmers have not adopted several bruchid control options that have been developed and recommended by researchers. It was also confirmed by this study that farmers could easily adopt the current technologies from their fellow farmers than from agricultural extension officers. Experiments were carried out using six bean varieties to determ ine the possibi Iity of pest resistance to A. obtectus damage under storage conditions by artificial infestation. All the bean varieties tested were damaged but did not show any significant difference in terms of ovipositor (F=0.287 df 5,30 P<0.05), F 1 progeny adult emergence (F=0.78 df 5,105 P<0.005) and seed damage (F= 1.08 df 5,105 P<0.05) in all the six bean varieties studied. It can be inferred that all the bean varieties were equally susceptible to A. obtectus damage under ambient storage conditions (mean temperature of 21.5° C and 65-80% relative humidity) hence varietal resistance is not a viable control option against A. obtectus in the area. The traditional grass thatched stores showed a lower adult emergence and seed damage of26.6% and 2.5% compared to pantry stores, which had 48.0% and 4.6% respectively, hence provide ideal storage structures that would prolong the safety of bean seeds from A. obtectus damage than pantry stores commonly used by farmers in eastern Kenya. The effect of neem (Azadirachta indica A. Juss) seed oil (NSO), indigenous seed protectants (bean debris and ground pea powder) and actellic super dust (pirimphos methyl + on Mwitemania (GLP 92) bean variety was assessed under storage conditions. Neem seed oil (NSO) was significantly effective and was similar to actellic super dust (pirimphos methyl + permithrin) in reducing A. obtectus F 1 progeny adult emergence and seed damage in comparison to bean debris, ground pea powder and the untreated control. Neem seed oil can therefore substitute actellic super dust (pirimphos methyl + permithrin), the recommended pesticide, in the management of bean bruchid (A. obtectus) under storage conditions. An integrated pest management (IPM) strategy that