Potential of the fungus Beauveria bassiana to control the coconut mite Aceria guerreronis (Acari: Eriophyidae)

Abstract

The coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae), is the main pest of coconut plantations in Brazil. Chemical control with acaricides is widely used to control this pest. Faced with the various social, economic, and environmental problems caused by acaricide overuse, there is a need for environmentally viable alternatives for controlling this pest, such as entomopathogenic fungi. Therefore, this study aimed to estimate the lethality of the fungus Beauveria bassiana (Bals.) Vuill. (Hypocreales: Cordycipitaceae) to A. guerreronis and to evaluate the selectivity of neem oil, mineral oil, and lime sulfur on in vitro mycelial growth of the fungus. These oils and the lime sulfur are alternative pesticides used in the control of coconut pests, however their side effects on B. bassiana are yet to be determined. Six increasing concentrations of the fungus were sprayed in arenas with A. guerreronis to estimate the lethal concentrations (LC). Subsequently, the neem and mineral oils, and lime sulfur were pipetted in Petri dishes to determine their selectivity to the fungus. The estimated mean lethal concentration (LC₅₀) of B. bassiana was 1.31×10⁵ conidia/mL while the LC₈₀ was 2.04×10⁶ conidia/mL. The mineral oil was considered selective for B. bassiana while the lime sulfur is not compatible with this fungus. In conclusion, B. bassiana has the potential to control A. guerreronis as well as the mineral oil can be used in the management of coconut pests without significantly impairing micelial growth of the fungus, and possibly not affecting its efficiency in the control of the pest mite.