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 × 108 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.
Twenty isolates each of Beauveria bassiana and Metarhizium anisopliae were tested against the second instar larvae of Plutella xylostella through laboratory bioassay using larval dip method at the concentration of 1×10 7 conidia/ml. Higher larval mortality of 88.85% and 81.44%, were observed with NBAIR Ma-4 and NBAIR Ma-35 isolates of M. anisopliae and 77.36% with NBAIR-Bb-5a isolate of B. bassiana. Further studies on dose and time mortality with four isolates indicated lowest LC 50 value of 2.6×10 4 conidia/ml and LT 50 of 86.6 hours with NBAIR Ma-35 isolate. These isolates have to be further tested against P. xylostella in infested fields of cabbage and cauliflower.
Surveys were conducted during 2017 and 2018 in the citrus orchards of Punjab, India to record the incidence of different insect pests and their natural enemies. During October-December, Entomopathogenic Fungus (EPF), Aschersonia aleyrodis was found to infect nymphs and pupae of citrus whitefly, Dialeurodes citri on the lower leaf surface of Kinnow from the orchards of Hoshiarpur, Ludhiana, Mansa and Fazilka districts.The fungus was isolated from the infected nymphs and pupae and morphological studies were conducted to confirm the identity of the entomopathogenic fungus. Aschersonia aleyrodis was reported for the first time on D. citri under Punjab conditions and this EPF also confirmed by amplification and sequencing of beta tubulin gene showed 99.40 per cent identity in NCBI, GenBank. Hence further studies on the host range, interaction with other insect pests and parasitoids, survival and longevity should be conducted to explore the potential of this fungus as microbial biocontrol agent for citrus whitefly.
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