Inhibition of the spoilage yeast Pichia occidentalis in a wheat germ diet for mass rearing of Drosophila suzukii

A wheat germ diet was initiated for the mass rearing of Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) and subsequent production of its parasitoid Trichopria drosophilae Perkins (Hymenoptera: Diapriidae). However, the main problem of the diet was the microbial contamination affecting the batches of good pupae production. Therefore, the concentration of four antimicrobials was optimized through the Taguchi orthogonal array for the inhibition of microbial contamination, identified as Pichia occidentalis (Kurtzman et al.) Kurtzman et al. The optimized Taguchi‐selected‐antimicrobials concentrations were 1.33 g l−1 of potassium sorbate, 1.33 g l−1 of propyl paraben, 1.33 g l−1 of sodium propionate, and 0.16 g l−1 of triclosan. When the antimicrobials were added to the diet, colony‐forming units of P. occidentalis were inhibited by two orders of magnitude. Such inhibition means that the D. suzukii females produced 61.1 and 79.3% more pupae and adults, respectively, than the diet with no antimicrobials. These results increase the potential of the wheat germ diet as an artificial diet for mass rearing of D. suzukii and T. drosophilae.