Abstract
Post-harvest losses caused by Callosobruchus maculatus is a major constraint to cowpea production and the improper use of synthetic insecticides by most farmers have resulted in environmental, health hazards, and development of insecticide resistance in insects. This study evaluates the efficacy of solar heat treatment using double-layered black polypropylene sheets in suppressing the development of the cowpea bruchid eggs and the effect of the heat absorbed on the germination potential of cowpea seeds. Five pairs of 2 – 3-day old adult C. maculatus were allowed to oviposit for ten days on 50 g cowpea seeds in a glass jar in the laboratory before exposure to 24, 48, 72 and 96 h solar heat treatment regimes. Infested cowpea seeds but not exposed to solarization was set along with the treatments while uninfested cowpea seeds was also set along and used as part of the germinability test. The experiment was laid out in a completely randomized design and treatments were replicated four times. The results showed that there were no significant differences among the number of eggs laid by adult C. maculatus on the cowpea seeds before solar heat treatment. Solar heat treatment of the cowpea seed at 24 h achieved 100% egg mortality of C. maculatus thus preventing adult emergence. The effect of solarization on seed viability showed that there were no significant differences between the infested cowpea seeds exposed to different solar radiation regimes when compared to uninfested cowpea seeds – range; 74% – 99% germination. The results showed that 24 h solar heat exposure of cowpea seeds in double-layered black polypropylene sheets could be the thermal death point of C. maculatus eggs on the seeds in the study area.
Highlights
IntroductionThe cowpea weevil, Callosobruchus maculatus (Fab.) is the major cause of post-harvest losses to cowpea
Cowpea Vigna unguiculata (L.) Walpers is an important legume in many developing countries (Adam and Baidoo 2008) which serves as a major food and animal feedIn storage, the cowpea weevil, Callosobruchus maculatus (Fab.) is the major cause of post-harvest losses to cowpea
This is in consonance with earlier reports by Lale and Ajayi (2001) and Lale and Vidal (2003) who studied the effect of solarization on egg mortality and progeny emergence of C. maculatus and showed that; solar heat treatment of cowpea seeds can adequately control infestation by cowpea seed bruchids
Summary
The cowpea weevil, Callosobruchus maculatus (Fab.) is the major cause of post-harvest losses to cowpea. It begins its infestation from the field and into storage (Peter and Sule 2019a). The use of chemical insecticides and fumigants are the major control measures adopted by majority of farming households in Nigeria and other developing nations. While these chemical control measures are largely effective, their improper use has attendant effects such as environmental pollution, human health problems, and development of insecticide resistance in insects (Okrikata and Oruonye 2013). Due to the low scale production practices and high poverty levels of most farmers in sub-Saharan Africa and other countries in the tropics, they opt to rely on indigenous traditional control measures to preserve their stored agricultural produce and products (Medugu et al 2020)
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