Abstract:

Beauveria bassiana (Balsamo) Vuillemin is one of the entomopathogenic fungi used against broad host insects and plant pathogens. Fungicides have side effects on entomopathogenic fungi. In vitro assay was performed to examine the compatibility of B. bassiana with eight commonly used fungicides (Azoxystrobin 75 g/l+Metalaxyl-m 37.5 g/l+ Fludioxonil 12.5 g/l FS, Boscalid 25%+ Pyraclostrobin 12% WG, Copper Hydroxide 361.1 g/l SC, Azoxystrobin 250 g/l SC, Triticonazole 80 g/l + Pyraclostrobin 40 g/l FS, Fludioxonil 12.5 g/l + Metalaxyl 10 g/l SC, Captan 50% WP, Tebuconazole 250 g/l EC) using contact application technique. Fungicides at various concentrations (Recommend Dose-RD, half of the Recommend Dose-0.5 x RD and twice the Recommend Dose-2 x RD) were mixed in Potato Dextrose Agar (PDA) media post-autoclaving. Approximately 25 ml of the mixture was poured into a Petri dish (90 mm) and allowed to cool. Mycelium disc (5 mm in diameter) was taken from 14-days-old B. bassiana grown on PDA using a sterile cork borer and placed in the center of each Petri dish containing fungicide + PDA. PDA plates without fungicide were used as a control. Petri dishes were incubated in the dark at 25±1 °C for 14 days. In vitro experiments were carried out with three replicates depending on a completely randomized plots design. In the study, the compatible fungicide with B. bassiana ET 10 isolate was found to be Copper Hydroxide at 0.5 x RD concentration. Azoxystrobin and Copper Hydroxide were compatible with Bb 18 isolate. Only two (Azoxystrobin + Metalaxyl-m + Fludioxonil and Tebuconazole) of the eight fungicides completely inhibited the mycelial growth of ET 10 isolate and were found harmful. Azoxystrobin + Metalaxyl-m + Fludioxonil completely inhibited the growth of Bb 18 isolate and was not found compatible. This study clearly shows that fungicides have the potential to inhibit the mycelial growth of entomopathogenic fungi under in vitro conditions. However, these results need to be further verified in vitro under both greenhouse and open-field conditions.

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