Insecticidal activity of isolated Purpureocillium lilacinum PL1 against whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) on cassava plantations in southern Viet Nam

Abstract

Background: Whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is a plant-damaging insect in tropical and subtropical regions that causes agricultural damage worldwide, including in Viet Nam. The abuse of pesticides derived from chemicals has resulted in the evolution of insect-resistant strains, polluting the environment and threatening human health. Using entomopathogenic fungi (EPF) for biological control is an alternative strategy in integrated pest management. Hence, an attempt was conducted to isolate, characterize and evaluate the efficacy of EPF, Purpureocillium lilacinum against whitefly B. tabaci under laboratory and field conditions. Results: Purpureocillium lilacinum PL1 (PL1) was isolated from the whitefly B. tabaci cadavers and subsequently identified using morphological study and internal transcribed spacer sequencing. Purpureocillium lilacinum PL1 had effectively grown and sporulated at temperatures ranging from 25 to 35 °C and throughout a broad pH range, which is particularly advantageous against the harsh tropical monsoon climate. Bioassay study indicated that 1 × 107 conidia/ml of P. lilacinum PL1 had a high lethality against the whitefly B. tabaci nymphs in vitro with efficiency was 88.24% after 7 days of treatment. The median lethal concentration (LC50) of P. lilacinum PL1 to B. tabaci after 7 days of treatment was 1.24 × 105 conidia/ml. In field conditions, 1 × 107 conidia/ml of P. lilacinum PL1 lowered the population of B. tabaci nymphs with efficacy was 78.86% after 2 batches, 7 days after treatments. Conclusion: The findings indicated that P. lilacinum PL1 was effective in the biological control of B. tabaci nymphs, which could be a potential alternative to chemical pesticides for pest management.