Toxicity of Insecticides toFrankliniella invasor(Thysanoptera: Thripidae) Under Laboratory Conditions

Abstract

Mango cv. ‘Ataulfo’ is perhaps the most popular mango produced in Mexico. The presence of high densities of thrips in mango blossoms, mainly the species Frankliniella invasor Sakimura, has been linked to yield decline. Growers spray synthetic insecticides on a regular basis against thrips to reduce their numbers, but no studies on the effectiveness of these insecticides have been conducted. The present study was undertaken with the objective of assessing the toxicity of 4 insecticides commonly used by growers. Commercial formulations of spinosad, imidacloprid, malathion, and α-cypermethrin were evaluated on adults of F. invasor under laboratory conditions. Six concentrations of each insecticide were assessed: 0.1, 1, 10, 100, 1000, and 10,000 ppm. Snap bean pods were submerged into the different concentrations of insecticides, dried on paper towels, and placed in a plastic container with the thrips adults. A completely randomized design with 10 replicates per treatment was performed. Probit analyses revealed that spinosad and α-cypermethrin were the most toxic insecticides for F. invasor with estimated LC50 values of 0.413 and 0.636 ppm, respectively. No significant differences in toxicity were found between imidacloprid (LC50 = 23.013 ppm) and malathion (LC50 = 34.422 ppm). Mortality in control treatments (distilled water) was never higher than 14%. Our study suggests the use of spinosad and α-cypermethrin as the best control for F. invasor. However, these results should be complemented with field evaluations before being recommended to mango growers.