Activity of natural occurring entomopathogenic fungi on nymphal and adult stage ofPhilaenus spumarius

Abstract

ABSTRACTThe spittlebugPhilaenus spumarius(Hemiptera: Aphrophoridae) is the predominant vector ofXylella fastidiosa(Xanthomonadales: Xanthomonadaceae) in Apulia and Europe. Current control strategies of the insect vector rely on mechanical management of nymphal stages and insecticide application against adult populations. Entomopathogenic fungi (EPF) are biological control agents naturally attacking spittlebugs and may effectively reduce population levels of host species. Different experimental trials in controlled conditions have been performed to i) identify naturally occurring EPF onP. spumariusin Northwestern Italy, and ii) evaluate the potential for biocontrol of the isolated strains on both nymphal and adult stages of the spittlebug. Four EPF species were isolated from deadP. spumariuscadavers collected in semi-field conditions:Beauveria bassiana, Conidiobolus coronatus, Fusarium equisetiandLecanicillium aphanocladii. All the fungal isolates showed entomopathogenic potential against nymphal stages ofP. spumarius(≈ 45 % mortality), except forF. equiseti, in preliminary trials. No induced mortality was observed on the adult stage.Lecanicillium aphanocladiiwas the most promising fungus and its pathogenicity against spittlebug nymphs was further tested in different formulations (conidia vs blastospores) and with natural adjuvants. Blastospore formulation was the most effective in killing nymphal instars and reducing the emergence rate ofP. spumariusadults, reaching mortality levels (90%) similar to those of the commercial product Naturalis®, while no or adverse effect of natural adjuvants was recorded. The encouraging results of this study pave the way for testing EPF isolates againstP. spumariusin field conditions and find new environmentally friendly control strategies against insect vectors ofX. fastidiosa.