Physicochemical, in vitro, and in vivo compatibilities of fungicides and mycoinsecticides used in maize crops

• Compatibility of entomopathogenic fungi (EPF) isolates with fungicides was tested. • Fungicides inhibited growth, conidia, and viability of purified isolates of EPF. • Commercial formulation procedure mitigates the negative effects of some fungicides on fungal development. • No EPF extrusion in Dalbulus maidis cadavers exposed to binary mixtures was observed. • Half-life of active ingredients in maize leaves depended on fungicide formulation. Given the operational advantages and temporal coincidence of diseases and pests, tank mixtures of fungicides with mycoinsecticides are commonly verified in cornfields practices in Brazil. Thus, we examined the compatibility of Beauveria bassiana isolates IBCB66 and Simbi BB15 and Cordyceps javanica isolate Esalq-1296, which are used in the management of corn leafhopper ( Dalbulus maidis ), with synthetic fungicides used in maize crops in Brazil. All tested fungicides completely inhibited colony-forming units (CFUs), growth, conidiogenesis, and conidial viability of the isolates. However, the formulated mycoinsecticides reduced the negative effects of some fungicides, with FlyControl® ( B. bassiana isolate Simbi BB15) showing the least sensitivity to propiconazole + difenoconazole-, bixafem + prothioconazole + trifloxystrobin- and trifloxystrobin + tebuconazole-based fungicides. An increased in exposure time from 1.5 to 3 h generally increases fungicide toxicity to entomopathogens. However, binary mixtures of these products showed little change in pH and electrical conductivity (EC), but some mixtures exhibited phase separation after 10 min stirring. In vivo bioassays with D. maidis adults showed increased mortality in some mixtures, yet no cadavers displayed fungal extrusion, potentially compromising their secondary cycles of epizootic at cornfields. Additionally, UHPLC/MS/MS analyses indicated that the degradation kinetics ( k ) of the same active ingredient varied significantly among fungicide formulations, with high differences in the half-life times (DT 50 ) of tested fungicides. Consequently, in light of persistence of these synthetic fungicides and behavioral aspects of D. maidis , mycoinsecticides should be applied in isolation preferebly before fungicides in the phytosanitary management of maize crops.