Effect of moringa (Moringa oleifera) leaf powder, neem (Azadirachta indica) leaf powder, and camphor on weevil (Callosobruchus maculatus F.) in stored cowpea (Vigna unguiculata (L.) Walp) seeds

Abstract

Cowpea (Vigna unguiculata (L.) Walp.), one of the most important leguminous crops, is widely cultivated throughout the tropics, especially in the savanna regions of the world. However, its seed is attacked by several insect pests both in the field and in storage, especially the cowpea weevil. To control weevils, most farmers have adopted the use of chemical insecticides, but these insecticides come with health and environmental problems, and as a result, there is advocacy for the use of bio-pesticides in the form of tree botanicals. This study was conducted to assess the effects of neem leaf powder (NLP), moringa leaf powder (MLP), and camphor against the cowpea weevils (Callosobruchus maculatus) in a completely randomized design. Six treatments were used and allocated as T1 (control), T2 (4g of camphor), T3 (25g of NLP only), T4 (25g of MLP only) T5 (50g of NLP only) and T6 (50g of MLP). The treatments were replicated three times. The parameters studied were the numbers of damaged and undamaged seeds, the numbers of dead and live weevils, and the taste of cowpea seeds. The treatments effectively protected the cowpea seeds during the storage period of eight weeks. The preservation of cowpea seeds given by camphor was significantly different from the other treatments. However, there was no significant difference (p >0.05) between the neem and moringa leaf powders treatments. The use of moringa and neem leaf powders might be adopted by cowpea farmers in sub-Saharan Africa as alternative, cheap, and available sources of biopesticides to use as chemical insecticides. If cowpea seeds are to be stored for consumption purposes, moringa leaf powder should be used since most respondents preferred the taste of cowpea seeds treated with moringa. Additionally, the storage duration of eight weeks was too short for the experiment, so further studies can be carried out for an extended period of more than eight weeks.