Determinación de la resistencia a insecticidas en cuatro poblaciones del psílido de la papa Bactericera cockerelli (Sulc.) (Hemiptera: Triozidae) Determination of insecticide resistance in four populations of potato psillid Bactericera cockerelli (Sulc.) (Hemiptera: Triozidae)

Southeastern potato growing regions from Coahuila and Nuevo Leon contribute with 15% to domestic production. Such production has been impacted by several factors, in particular Bac- tericera (=Paratrioza) cockerelli Sulc potato psyllid, one of the most important pests affecting this crop. Its control is based on Insecti - cide applications, leading to unsatisfactory results and high selection pressure. Five insecticides were evaluated in four field populations of B. cockerelli from the growing region, using a susceptible labora- tory line for comparison. The field populations were collected from greenhouse and commercial orchards located at Huachichil, Saltillo, Raices and San Rafael localities. All the samples were taken to the toxicology laboratory of Antonio Narro Autonomous University, where a series of biological essays were conducted through foliar dipping, in order to determine the CL 50 levels, confidence limits and resistance levels as compared to the susceptible laboratory line. The Huachichil's population did not exceed the resistance ratio (10X) in any insecticide Population without resistance problems. Saltillo and Raices populations exceed the resistance ratio with values of 20.4 and 29.3 times respectively, for the insecticide imidachloprid, and San Rafael population showed values 11.7 times for the insecticide endosulphan, above the resistance threshold.