Effect of endophytic isolates of Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metchnikoff) Sorokin on Plutella xylostella (L.) (Lepidoptera: Plutellidae) in cabbage

Background The diamondback moth ( Plutella xylostella L.) (Lepidoptera: Plutellidae) is one of the major pests in cabbage which causes severe loss to the cruciferous crops. Entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae have been established as endophytes in cabbage plants by seed treatment/root inoculation/foliar application methods in glasshouse conditions. Main body A glasshouse experiment was conducted to study the effect of endophytic isolates of B. bassiana (NBAIR Bb-5a and NBAIR Bb-45) and M. anisopliae (NBAIR Ma-4 and NBAIR Ma-35) on P. xylostella in cabbage using detached leaf bioassay method. The isolates were applied through seed treatment/root inoculation/foliar application at the concentration of 1 × 10 8 spores/ml and evaluated at 15, 30, 45, and 60 days after treatment (DAT) in 2017 and 2018. These isolates were colonized in cabbage leaf tissues from 15 to 60 DAT. All 4 isolates showed different mortality percentages during 15–30 DAT, and no mortality was observed after 45 and 60 DAT in different inoculation methods during both years. Among the application methods tested, foliar application method gave the highest mortality of 70–80% at 15 DAT and 12–58% at 30 DAT mortality of 2nd instar larvae of P. xylostella in cabbage. Among the isolates tested, NBAIR Ma-35 showed the highest mortality (35–79%) in all the 3 inoculation methods tested. Conclusion Endophytic isolates of B. bassiana and M. anisopliae suppressed the population of P. xylostella on cabbage leaves in three inoculation methods tested. Among all the methods tested, foliar application method showed highest mortality. These promising isolates have to be further tested under field conditions for management of P. xylostella in cabbage.