BIOPESTICIDES: ALTERNATIVES FOR MANAGEMENT OF CALLOSOBRUCHUS MACULATUS

Abstract

ABSTRACT Among insect pests of stored legumes, Callosobruchus maculatus is ranked as the most important with seed loss as high as 60-100% having been reported. Chemical control using synthetic insecticides is usually advocated. These chemicals can have undesirable side effects including human and animal health concerns, development of insecticide resistance andenvironmental contamination. Biopesticides, especially the use of semiochemicals, botanical extracts and microbial pesticides provide a sustainable and innovative alternative to the sole use of synthetic insecticides. The components of the sex pheromone for C. maculatus have been identified as 3-methyleneheptanoic acid, (Z)-3-methyl-3-heptenoic acid, (E)-3-methyl-3- heptenoic acid, (Z)-3-methyl-2-heptenoic acid and (E)-3-methyl-2-heptenoic acid, nonanedioic acid and 2,6-dimethyl-1, 8-octanedioic acid. The use of semiochemicals and pheromones in particular can allow for better monitoring of C. maculatus in warehouses and other grain storage facilities. In small scale situations, use of pheromones for mass trapping of C. maculatus may be feasible and should be advocated under such circumstances. The use of semiochemicals forenhancement of the effectiveness of biological control agents of C. maculatus has been explored. Preliminary research indicates that it may be possible to use semiochemicals to manipulate the behavior and increase the efficacy of natural enemies of storage pests including C. maculatus. Various plants and their extracts have been investigated for use in management of all stages of C. maculatus. Several of these have repellent, antifeedant, contact toxicity and/or oviposition deterrent properties. Essential oils derived from various plant parts are particularly effective as fumigants due in large measure to their volatile nature. Use of botanical extracts is particularly appealing for resource poor farmers from developing countries as both the plant materials, as well as most of the techniques used for extraction of the active components are readily available to them. Biological control using microbial agents is another viable strategy for management of C. maculatus. A number of entomopathogenic fungi in particular have been isolated, tested and their efficacy against the cowpea seed beetle demonstrated. Culture and formulation preparation of these fungi and other microbial agents can also be done at the farm level. The combination of several biopesticidal options offers sustainable and ecologically appropriate alternatives to the sole use of synthetic insecticides for management of C. maculatus and these are explored in the current chapter.