Trapping, identification and rearing of edible palm weevils in Kenya and Uganda

Abstract

Palm weevils, Rhynchophorus spp. (Coleoptera: Curculionidae) double as devastating invasive pests of palms, and delicacies in many communities. This study evaluated ethyl acetate and 3-methyl-octan-4-ol for trapping palm weevils from coconut, oil and raffia palms in Kenya and Uganda; taking into account the distance of traps on oil palm from a forest or raffia palm. Eggs from the weevils from different locations were incubated and their larvae reared on sugarcane under laboratory conditions. All the 285 weevils collected were identified by morphological and molecular techniques as Rhynchophorus phoenicis, and the catch was female-biased. 3-methyl-octan-4-ol attracted more weevils than ethyl acetate. More weevils were caught at ~100 m away from the forest than within 15 m outside the forest; and on raffia palm than oil palm irrespective of distance apart. Eggs took ~4 d to develop and 95-100% of pupae developed into adults, irrespective of the collection site. Larval and pupal developmental periods for weevils from Uganda were longer than those of Kenya, resulting in egg-adult development of ~6 months and ~4 months, respectively. The sex ratio of laboratory produced males and females was similar. These results can guide in designing an integrated R. phoenicis management system with a dual benefit of protecting palms from weevil attack and utilising the weevils to improve human nutrition.