Suppression of damaging effects of <i>Callosobruchus maculatus</i> (F.) (Coleoptera: Chrysomelidae) by plant powders

Abstract

Powders prepared from plant species available in Nigeria are reported to possess ovicidal, larvicidal, pesticidal, antifeedant and repellent properties against various insect pests and are regarded as environmentally compatible pesticides. This study evaluated the action of Azadirachta indica A. Juss, Hyptis suaveolens Poit. Piper guineense Thonn. & Schum andCymbopogon citratus Gaern against the damaging effects of Callosobruchus maculatus (F.) in stored cowpea. The experiment was carried out at temperature of 30 ± 1 o C and relative humidity of 72 ± 3%. The plant powders were compared at the rate of 2.5 g per 50 g cowpea seeds including the untreated control. The experiment was laid out in a completely randomized design with three replications. The results showed that all the botanicals gave protection to the stored cowpea seeds and significantly (p<0.05) reduced mean adult emergence and seed weight loss (3.75-4.06%) caused by C. maculatus when compared with the untreated control (6.07%). The number of emerged adults from untreated seeds progressively increased with time of exposure compared to the treated seeds. The increasing order of effectiveness of the botanicals in terms of their insecticidal activities against C. maculatus was P. guineense, C. citratus, H. suaveolens, and A. indica. The study, therefore, shows that the botanicals could serve as protectants against C. maculatus in stored cowpea seeds.

A survey of the damage caused by the Callosobruchusmaculatus (F.) on different legume seeds sold in Njikoka Local Government Area, Anambra State, Nigeria

“…The findings of this study has shown that C. maculatus (F.) is a major pest of stored legumes on sale in markets in the study area. The observation is in agreement with Yusuf et al (2019) who noted that the storage of cowpea seeds over long periods is threatened by bean beetle infestation. In this study, the damage levels were greatest on V. unguiculata (var.…”

“…Callosobruchus maculatus (F.) (Coleoptera: Bruchidae), also known as the cowpea weevil is a major pest of stored seeds of cowpea, pigeon pea and the African yam bean in tropics and subtropics (Yusuf et al, 2019;Ofuya and Lale, 2001 is a field-to-store pest and ranked as the principal postharvest pest of cowpea in the tropics because its attack starts in the field if the legumes are left unharvested especially cowpea. This soon spreads to the store after harvesting and storage (Caswel, 1981).…”