Could host adaptation and host alternation be suitable alternatives for safer control of the cowpea beetle Callosobruchus maculatus during storage?

Abstract: In Tunisia, the cowpea weevil Callosobruchus maculatus is the major pest of stored chickpea Cicer arietinum. Its control is mainly based on the use of synthetic fumigants. This work aims to investigate the possibility of using host adaptation and host alternation as safer alternatives for the postharvest control of C. maculatus. For that, three hosts namely chickpea (Amdoun 1 and Beja 1 varieties), Lentils Lens culinaris (Ncir variety) and cowpea Vigna unguiculata (variety Black eye) were used. The cowpea seeds were provided from Algeria since this primary host is not cultivated in Tunisia. The host adaptation test consists in a survey on the development of a C. maculatus strain selected on chickpea, to determine the level of its acceptability and suitability on the three hosts during six generations and its evolution over time and successive generations in terms of pest fertility and host infestation levels. In addition, the effects of alternation of the three hosts on the pest fecundity and hosts weight loss were studied after six generations. A no-choice test was carried out in a completely randomized design, factorial scheme, with all hosts combinations and three replications. Results showed that host adaptation could limit C. maculatus population on lentils and cowpea compared to chickpea for storage periods not exceeding three months. Indeed, after one month of storage, infestation levels reached 69.33%, 50.66% for chickpea (Amdoun 1 and Beja 1 varieties respectively) toward 2.15% and 16.32% for lentils and cowpea. Regarding alternation of hosts’ trials, results showed significant reduction in C. maculatus fecundity within hosts’ combinations. Moreover, significant decreases in weight loss were observed.