Efficacy of selected plant powders on bean weevil (acanthoscelides obtectus) management in common beans

Abstract

The common bean Phaseolus vulgaris an important source of plant protein in many parts of the world, Uganda inclusive. Among the major food crops, it has one of the highest levels of variations in seed characteristics (shape, size, and colour), growth habit, maturity and adaptation. In rural areas of Uganda, the losses caused by storage insect pests in stored bean grain is one of the major problems faced by smallholder farmers. The major pest of stored bean is the bean weevil (Acanthoscelides obtectus) which can lead to a total loss if left uncontrolled. To overcome these losses encountered, this laboratory study investigates the efficacy of the selected plant powders on bean weevil (Acanthoscelides obtectus) in common beans. The plant powders used included; Neem (Azadirachta indica), garlic (Allium sativum) and actellic dust was used as a positive control plus that without any powder treatment (negative control) onto NABE 16 bean variety under storage for 15 weeks. The experiment was arranged in completely randomized design in three replications and data collected include; Insect mortality, adult emergency, damage, weight loss and percentage germination the of stored bean grains. Data collected were subjected to analysis of variance (ANOVA) procedure using GenStat 15th edition and mean comparisons were conducted using Bonferroni test at 5% level of significance. The results from this study revealed that there were significant differences between plant powder treatments and the synthetic treatment over the control throughout the storage period of the experiment. Among the plant powders used, neem powder was found to be more effective than garlic powder in the parameters measured (mortality, adult emergency, grain damage, weight loss and germination). The increase of weevil mortality and adult emergency was directly proportional with the increase in duration of storage. However, the plant powders had no negative effect on percentage germination when compared to the synthetic insecticide. It was also observed that the actellic dust which is a synthetic insecticide revealed superiority over neem powder treatment though their results were more comparable with duration of storage. It can therefore be concluded that, the insecticidal plant powders such as neem powder can be used to protect stored bean grains against weevil damage hence contributing to food security and hunger alleviation. Keywords; Neem, Garlic, Storage insect pests, Plant powders, Synthetic insecticide, Acanthoscelides obtectus