INFLUENCE OF TEMPERATURES ON THE SUPPRESSION OF CALLOSOBRUCHUS CHINENSIS L. BY DINARMUS BASALIS (HYMENOPTERA: PTEROMALIDAE)

Abstract

The pulse beetle, Callosobruchus chinensis (L.) (Coleoptera: Bruchidae) is a serious pest that develops within the stored chick pea seed and widely distributed in the world. Synthetic insecticides and fumigants are common management tactics against pulse beetle, even though they have caused serious drawbacks. As an alternative chemical method, the use of biocontrol agents like parasitoid has been successfully used against C. chinensis. This pest is parasitized by pteromalid cosmopolitan ectoparasitoid Dinarmus basalis Rondani (Hymenoptera: Pteromalidae) in their larval-pupal stages. Efficacy of this parasitoid was investigated in the laboratory considering number of parasitoid progeny, host, dead host, dead parasitoid, percent parasitism and percent suppression at different temperatures and different parasitoid densities. All tests were consequently changed with the temperature and parasitoid density. The number of emerged parasitoid progeny (39.2) and dead parasitoid were minimum (2.2) at 20°C temperature while maximum (73.8 and 7.2) at 30°C temperature with 6 pairs of parasitoid. The mean number of host emergence and dead host (0.6) were decreased at 30°C temperature but increased (12.6 and 6.0) at 20°C. D. basalis showed higher parasitism (99.2%) and suppression (99.12%) of C. chinensis populations at 30°C whereas lower at lower densities and temperatures except 35°C temperature. Therefore, temperature and parasitoid density have the acute potential effects for allowing D. basalis to suppress populations of the pest, C. chinensis.