Different cereal grains affect demographic traits and digestive enzyme activity of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

Abstract

The lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) is one of the primary pests of stored grains in many areas of the world. Demographic performance of R. dominica can be altered by nutritional quality of host grains on which it was reared. We raised R. dominica on six different cereal crops (barley, maize, rice, rye, sorghum and wheat), to test the impacts of the insect nutrition on population growth and digestive enzyme activity. The experiments were done at 28 ± 1 °C, relative humidity of 60 ± 5% and a photoperiod of 14:10 h (L:D). The developmental time of R. dominica fed on maize was prolonged as compared with other diets. Survival rate of immature stages was the highest on wheat and rye, and lowest on maize. The highest values of adult longevity, fecundity, and egg fertility were on wheat, and lowest values were on maize. The intrinsic rate of increase (r) and finite rate of increase (λ) were the highest when R. dominica was reared on wheat and rye, and lowest when it was fed on maize, rice and sorghum. The highest amylolytic activity of adults was on maize, whereas the lowest activity was on barley and sorghum. Moreover, proteolytic activity of adults was the highest on sorghum and lowest on rye. Our findings indicated that maize, rice and sorghum were unsuitable hosts for feeding, development and population increase of R. dominica. The results of this study will be useful to introduce unsuitable diets for developing transgenic grains against R. dominica.