Four local parasitoids of spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), were collected in Mexico in 2013–2015. To increase insectary production of the fly for mass rearing of its parasitoids, a wheat germ diet that uses low‐cost ingredients was optimized through the orthogonal array L9 (34, i.e., four controllable factors with three levels each) (Taguchi method). The resulting optimized diet consisted of 12 ml ethyl alcohol, 36 g maize flour, 45 g table sugar, and 42 g brewer's yeast. Confirmation tests indicated that this diet produced 33.9, 87.0, and 78.6% more larvae, pupae, and adults, respectively, than the old version (non‐optimized wheat germ recipe) but there were no statistical differences in sex ratio, hind tibia length of females, and developmental time from egg to adult. Additionally, the optimized diet had a similar performance in most of the evaluated parameters (same as in the confirmation tests) compared to banana, the current host of the D. suzukii colony. These results indicate that an improved wheat germ diet is available to rear this fly, which will facilitate the rearing of its local parasitoids.