Comparative bioassay methods to determine diamide susceptibility for two coffee pests

Hypothenemus hampei Ferrari (Coleoptera: Curculionidae: Scolytinae) and Leucoptera coffeella Guerin-Meneville (Lepidoptera: Lyonetiidae) are major pests of coffee. Diamides, are a new group of insecticides that activate ryanodine receptors causing muscle contraction, and have been used to control H. hampei and L. coffeella. Bioassay methods need to be standardized for insecticide susceptibility studies on H. hampei with cyantraniliprole and L. coffeella with chlorantraniliprole. Four bioassay methods for H. hampei (topical application with a microsyringe, artificial diet, immersion of green coffee fruits in insecticide solution, and coffee branch bagging) and five for L. coffeella (spraying coffee seedlings, immersion of coffee leaves, immersion of filter paper and topical application with microsyringe were evaluated. The best performing method was selected based on the greater slope (β) of the probit curve, lower LC50, lower natural mortality in the control, and lower variance. The results showed that the best methods for bioassays were the artificial diet for H. hampei and spraying of coffee seedlings for L. coffeella.