Callosobruchus Maculatus - Humans and Callosobruchus Maculatus

Humans and Callosobruchus Maculatus

C. maculatus is medically harmless to humans. There are no documented ill effects from inadvertently eating one of them, directly or through an infested bean. However, these beetles still limit production of beans.

A single larva of C. maculatus can diminish the weight of a cowpea by 3%, and multiple larvae will infest one cowpea in most storage infestations. Other legumes are not as weighty as the cowpea and will lose more of their percentage body mass due to one larva. Additionally, even slight damage can destroy a seed’s viability for the next planting season.

Due to the prevalence of this agricultural pest, many have been researching control options. In many developing countries where this beetle often causes the most damage to small scale farmers, people use the crushed leaves of ''Cassia ocidentalis mixed with the beans to deter C. maculatus. Many Cassia species are used as a deterrent as the genus is abundant in the tropics and is mildly effective at driving away C. maculatus. While the powdered form of the leaves is more effective against other pests than against C. maculatus, a warm water extract or the seed oil of Cassia is much more effective than the powdered leaves could ever be. The seed oil will not stop the adults from laying eggs, but it will increase the mortality of the eggs and of the first instar of the larvae. The warm water extract will deter the C. maculatus adults from laying the eggs at all. A combination of the two would likely be the most effective.

Other plant based controls include neem oil, nishinda, eucalyptus, and bankalmi. All of which kill.

Another option for control is biocontrol. D. basalis is effective at controlling the C. maculatus population in black gram in laboratory setting. Within a few generations there is no emergence of C. maculatus and no more emergence of D. basalis either, as they have killed all the available hosts. Anisopteromalus calandrae and Uscana mukerjii are also candidates for biocontrol. Both are effective at reducing the number of C. maculatus alive and emerging within a few generations.

Freezing the whole storage area will also control C. maculatus. Between 6–24 hours at -18°C will kill all adults and implanted larvae. If the cooling is slow, then a longer time might be required for all pests to die as they will instead acclimatize to the cold. It is not as elegant of a method, and it is not viable in developing countries where farmers might not have the access to enough electricity or the funds to sustain a cold room constantly.