Abstract

In this study we investigated the effects of different cryomazine concentrations and host type on the biology of the southern cowpea weevil Callosobruchus maculatus F. (Coleoptera: Bruchidae). Our results showed that increasing cryomazine concentration led to the increase in the average incubation period of eggs and low hatching rate, reaching the highest average of egg incubation period 13.25 days for insects reared on a mung beans treated with cryomazine concentration of 3 and 5%. The lowest average for incubation period reached 9.25 days when insects reared on cowpea treated with 1% concentration of cryomazine. Insect reared on peas treated with 5% cryomazine concentration had a lower average percentage of hatching eggs, 1.25% in comparison with the control (67.25%). The maximum average rate of eggs hatching reached 55% of insects reared on mung beans treated with 1% cryomazine concentration compared with the control (75%). High cryomazine concentration reduced the percentage of pupation and adult emergence; the average percentage reached 19.83 and 27.08%, compared with the control 87.33 and 88.5% respectively. Thus, increasing cryomazine concentration not only led to the increase in the average duration of larvae and pupae of insects bred to all nutritional hosts except peas where the insect was unable to complete its life cycle but also led to reduction in the percentage of pupation and adult emergence.

Key words: Adult emergence, egg hatchability, insect growth regulating (IGR), incubation period, Trigard.