Lime sulfur to control citrus flat mite and its interactions with the entomopathogenic fungus Lecanicillium muscarium

ABSTRACT

Lime sulfur is one of the few products indicated to control Brevipalpus yothersi in Brazilian organic citrus orchards. Other strategies, such as the use of entomopathogenic fungi should be evaluated, and Lecanicillium muscarium is one of the basic choices for pest management. Knowledge of the interactions between lime sulfur and this entomopathogen is critical for developing control strategies. With this goal, it was conducted the toxicological characterization of lime sulfur to B. yothersi and the compatibility evaluation with L. muscarium. Finally, the effects of L. muscarium and lime sulfur mixtures on B. yothersi control were evaluated. Product evaluation for B. yothersi was done through direct and residual contact bioassay, and different concentrations of lime sulfur mixed in potato dextrose agar culture medium were used to evaluate compatibility with L. muscarium. Lime sulfur was effective against adults of B. yothersi and caused eggs unviability of up to 71.0%, at a dose of 80 L per 2,000 L of H₂O. The lethal concentration (LC₅₀ and LC₉₉) of lime sulfur estimated for mite adults were 246.62 and 858.5 μg of sulfur per mL of H₂O (ppm a.i.). Lime sulfur concentrations of 180 to 560 ppm a.i. showed promise for use in combination with L. muscarium. However, concentrations of 1,000 and 5,600 ppm significantly reduced colony size and the number of spores/colony. The mixture of 100 and 180 ppm a.i. of lime sulfur with L. muscarium (10⁸ conidia·mL^–1) was not able to reduce the lethal time of entomopathogen on B. yothersi.

Keywords
integrated pest management; Brevipalpus yothersi ; organic citrus orchards; biological control; synergism