Entomopathogenic Fungal Infection and Nymph Production in Bird Cherry-Oat Aphid, Rhopalosiphum padi

Aphids are key pests in agricultural ecosystems. The bird cherry-oat aphid, Rhopalosiphum padi, causes significant damage in cereal crops. Entomopathogenic fungi like Beauveria and Metarhizium are infective to aphid species. We examined in the laboratory the effect of applications of suspensions of conidia of one strain each of Beauveria cf. bassiana and Metarhizium brunneum upon parthenogenesis (asexual nymph production) in winged females of R. padi on wheat leaves. Females were showered once with aqueous suspensions of Beauveria and Metarhizium conidia. For Metarhizium (at 5x10⁷ conidia/ml), after 48 hours, nymph numbers/female were reduced 54% (averages of 15.8 vs. 7.28 nymphs/female in untreated and treated insects, respectively);  after 120 h, nymph numbers were reduced 59% (averages of 23.8 vs. 9.85 nymphs/female in untreated and treated insects, respectively). Metarhizium killed nearly 100% of adult winged females after 120 hours. Similarly, single applications of Beauveria conidia (at 8x10⁷ conidia/ml) resulted in up to 62% reduction in nymph production after 96 hours and high initial alate mortality.  Applications of entomopathogenic fungi should be further evaluated as management tools in R. padi and other aphids as well.