Sustainableagricultureincreasinglyreliesonbiologicalcontrolagentsasalternativestosyntheticpesticides(Baleetal.2008).Entomopathogenicnematodes(EPNs)arewidelyusedtocontrolsoil-dwellinginsectpests.However,manybeespeciesalsonestanddevelopinsoil,raisingconcernsaboutunintendedexposure.EPNsaretypicallyappliedfromspringtoautumn,overlappingwithperiodswheresoil-dwellinginsectsareeitherinhibernationornesting.However,potentialrisksfromEPNssuchasSteinernemaspp.andHeterorhabditisspp.remainpoorlystudied(Cappaetal.2022,Dutkaetal.2015).Here,wetesttheeffectsoftwocommercialEPNspeciesonthehibernationsuccessofbufftailedbumblebee(Bombusterrestris)gynes(i.e.,futurequeens).