Susceptibility of tarnished plant bug to select insecticides and development of diagnostic doses

To determine baseline susceptibility of Lygus lineolaris (Palisot de Beauvois) to conventional and reduced-risk insecticides, serial dilutions of dicrotophos, dicrotophos+bifenthrin, bifenthrin, acetamiprid, acephate, zeta-cypermethrin, dimethoate, cyantraniliprole and others were prepared from a 1000ppm stock solution. A petri dish was sprayed to 100% coverage with each representative solution using a Crown Spray-Tool system (Woodstock, Illinois) and allowed to dry.  A green bean was dipped into solution with 0.25% Silwet L-77 surfactant, allowed to dry, and added to the petri dish.  Fifteen adult plant bugs were added to each petri dish, the dish was sealed with parafilm to prevent escape and held at 26.8±2ºC, 70% RH, 14:10(L:D). Mortality was assessed after 48h. Probit mortality lines for three diagnostic doses, LD₅₀, LD₇₅, and LD_95, for each chemical were estimated using POLO (LeOra Software, 2007).

            The developed diagnostic doses determined thus far are: acetamiprid: 19.39, 33.72, 74.74ppm; imidacloprid+bifenthrin: 10.32, 16.78, 33.77 ppm; dimethoate: 9.55, 23.79, 88.35 ppm; and zeta-cypermethrin: 1.29, 3.16, 11.48 ppm respectively.  Determination of diagnostic doses are still pending for indoxacarb, novaluron, sulfoxaflor, bifenthrin, and acephate. Three populations of TPB with a history of intense spray pressure will be tested with the diagnotic doses for resistance monitoring.