The ability of the predatory mite Amblyseius swirskii Athias-Henriot to feed on some species of crop fungi was investigated to determine the effect of plant fungi on mite development and reproduction. Larval and nymphal survival, developmental duration, total oviposition, and female longevity of the mite were compared among different dietary regimes: cucurbit powdery mildew on pumpkin leaf, Pinus thunbergii pollen, Ephestia kuehniella eggs, pumpkin leaf, mycelia of sooty mold, mycelia and conidia of sooty mold, Potato sucrose agar medium, and distilled water. Mites completed development and laid eggs only on cucurbit powdery mildew, P. thunbergii pollen, and E. kuehniella eggs. Mites fed mildew took 1.5 days longer to complete their development than those on the other two diets, and adults oviposited significantly fewer eggs than those fed E. kuehniella eggs, but similar numbers as those fed P. thunbergii pollen. These results demonstrated the possibility that the plant fungus cucurbit powdery mildew facilitates mite colonization and reproduction on crops.