Development of four strains of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) on barley, corn (maize), rice, and wheat

Abstract

Differences in development of four strains of Sitophilus oryzae (L.) (LS-2, Minnesota, Savannah, and Tanzania-90) on diets of hulled barley, yellow corn (maize), brown rice, and soft red winter wheat at 28°C and 55–60 r.h., were analyzed in terms of total progeny production, average time (days) to adult emergence, and rate of emergence with an analysis of variance. Significant main effects of strain and diet were obtained. Across all strains, progeny production was highest on barley and lowest on corn. All measured growth parameters indicated that corn was the least suitable diet of the tested cereals for this species. The Savannah strain of S. oryzae produced significantly more progeny and had shorter development times than the other strains. The strain from Tanzania produced smaller numbers of progeny, had significantly longer development times, and a significantly slower rate of emergence on wheat compared to that of the other strains. The Tanzania strain does not have the major amylase isozyme present in this species and has less than 50% of the total amylase activity found in the other three strains. It is postulated that the strong Tanzania × wheat interaction is caused by combination of naturally-occurring amylase inhibitors in ingested wheat with digestive amylase in this weevil strain and a subsequent decreased efficiency in food utilization.