Tandem use of endophytic entomopathogenic fungi and the generalist predator Chrysoperla carnea for reduced-risk aphid management

Abstract: The melon aphid Aphis gossypii is one of the most economically important crop pests that can be presently managed at greenhouse conditions with different commercial
mycoinsecticides. Recent studies also highlight the systemic efficacy of entomopathogenic
endophytic ascomycetes targeting aphids through the plant, therefore preventing possible risks related to the contact between the fungal inoculum and beneficial insects, whereas the
compatibility of such strategy with natural enemies has not yet been explored. In this study, we evaluated the biocontrol potential of two endophytic entomopathogenic ascomycetes (EA)
strains against A. gossypii in melon crops under greenhouse conditions. Based on their known endophytic behaviour, Metarhizium brunneum EAMa 01/58-Su and Beauveria bassiana EABb 01/33-Su strains were applied as a foliar spray and seed dressing respectively. Furthermore, the compatibility of these EA applications with the predator Chrysoperla carnea was assessed in a greenhouse in Córdoba (Spain), both in summer and in autumn. It is noteworthy that, in summer, foliar spraying with M. brunneum resulted in 35.0 % aphid mortality and a 20.4 % reduction in total per capita nymph production (TCNP) on sprayed colonised leaves. In contrast, leaves not sprayed with the fungal suspension but endophytically colonized caused 70.0 % aphid mortality and a 12.6 % reduction in TCNP, which demonstrates the systemic potential of this fungus. Compatibility between C. carnea and M. brunneum was also demonstrated, with a significant increase in prey consumption on endophytically-colonized leaves as compared with the controls. Seed dressing with B. bassiana led to 55.0 % aphid mortality and a 19.2 % reduction in TCNP but had no significant effect on C. carnea predation. The same trends were observed in autumn, although colder temperatures reduced aphid mortality. Our results highlight the potential of fungus-predator biocontrol strategies within an aphid Integrated Pest Management programme under greenhouse conditions.