Characterization of an entomopathogenic fungi, Aspergillus sp. R55 as a biocontrol agent against invasive rugose spiraling whitefly infesting oil palm in India

Background Rugose spiraling whitefly (RSW), a native Central America species, was first reported in India during 2016. Since then, the observed rapid geographical distribution and consistent incidence over the years gave the insect, a key pest status on oil palm. Being an alien pest and oil palm being a perennial crop, a microbial entomopathogenic fungi (EPF) can only tackle the pest in ecofriendly and sustainable manner. In view of this, the present study was conducted to isolate EPF against RSW in soils of oil palm plantations using a custom developed insect baiting using soil solution technique. Results The present study led to isolation of a potential Aspergillus sp. R55. The isolate, R55, is highly virulent against adult and nymphal stages of RSW with LT 50 of 1.5 and 2.04 days at 10 6 conidia/ml, respectively. However, egg stage showed no mortality even at the highest concentration tested (10 8 conidia/ml). A two-year multilocational field evaluation of R55 in three plantations showed an average pest reduction of 61.98 and 94.44%, by 10 and 15 days after treatment, respectively. Moreover, the R55 isolate conidia showed thermal stability and survival up to 50 °C after 1 h of exposure. Safety studies of the isolate on oil palm pollinating weevil showed no negative impact on weevil emergence when inflorescence was treated. Conclusion The biosafety attributes to oil palm pollinating weevil and field virulence of R55 designate the isolate as a potential biocontrol agent against RSW infesting oil palm. However, by being an Aspergillus sp. further environmental safety studies are under progress.