Assessment of the potential of Beauveria bassiana and diatomaceous earth as alter-natives to chemical insecticides for the con-trol of Rhyzopertha dominica(F.) (Coleopte-ra: Bostrychidae) on wheat

Abstract

The wheat crop is the most important strategic crops in Egypt, because of its economic importance, directly related to the human diet in Egypt, the aim of this study is to find an environmental safe means to protect wheat from stored grain pests. Laboratory bioassays were conducted to assess the insecticidal efficacy of the two formulations of entomopathogenic fungus, Beauveria bassiana (BotaniGard and Biosect), and two formulations of diatomaceous earth (DE) (Insecolo and Foodgrade), used alone or in combination, against the lesser grain borer, Rhyzopertha dominicaadults on wheat grains. The results showed that, Dose and time dependent mortality was observed for all tested powders.Fungal formulations in DE provided better protection against the lesser grain borer by giving significantly better kill compared to control.The results showed a significant decrease in the number of emerged adults due to LC50 of tested powders-treated eggs. While, at LC95, for all tested powders adults emergence was completely suppressed. All tested mixtures were able to prevent adult emergence completely, except the mixtures that consist of the LC25 of both tested materials. Residual activity of all materials and their mixtures gradually decrease with in-creasing storage periods up to 12 weeksfor all treatments. No deleterious effect on the germination and the water ab¬sorption of wheat grains treated with the tested powders and their mixtures was noticed. The most promising fungus, Biosect was selected for in depth study. The results showed no side effects on the biochemical properties (total proteins, total carbohydrates, fat, starch, crude fiber, ash content and metabolic energy)of wheat grain after treatment with Biosect at the initial time and after storage. Biosect powder did not affect the baking quality of bread which was scored "good" for all acceptability parameters at initial and after 12 weeks storage. No adverse effect in the biochemical parameters of liver (albumin, ALT, AST, total cholesterol and total proteins) and kidney (creatinine and urea) functions of the albino rats, with prolongation of the period post treatment when compared with those of the control group.