Suppression of bacterial contamination of artificial diet for the west indian sweetpotato weevil, euscepes postfasciatus (Coleoptera: Curculionidae), by adding hydrochloric acid to the diet

Abstract

The pH of the articial diet used for insect rearing generally affects the bacterial contamination of the diet. We examined the effect of adding hydrochloric acid (HCl) to the articial diet of Euscepes postfasciatus on bacterial contamination of the diet. First, we reared the species using diets prepared with various HCl concentrations to determine the concentration that does not adversely affect the survival and development of E. postfasciatus. The use of HCl at a lower concentration than 0.12% does not remarkably affect insects. Next, we compared bacterial contamination among the following four groups. Insect eggs were inoculated with three of these groups: 0.072% HCl diet, 0.036% HCl diet, and diet without HCl added (positive control). In the fourth group, HCl was not added to the diet, and the eggs were not inoculated (negative control). The contamination rate in the 0.036% diet was not signicantly lower than in the positive control, whereas the rate in the 0.072% diet was lower than in the positive control but not signicantly higher than in the negative control. We concluded that adding HCl to the articial diet of E. postfasciatus was quite effective for preventing bacterial contamination of the diet.