Susceptibility of tarnished plant bug (LepidopteraHemiptera: Tortricidae:Miridae) adults larvae to selected reduced-risk insecticides and development of three diagnostic doses

ABSTRACT:   To determine baseline susceptibility of Lygus lineolaris (Palisot de Beauvois) to dicrotophos, dicrotophos+bifenthrin, bifenthrin, acetamiprid, acephate, zeta-cypermethrin, dimethoate, imidacloprid+bifenthrin and sulfoxaflor, adults were subjected to petri-dish bioassays with a range a concentrations for each insecticide.  Mortality was assessed after 48h. Probit mortality lines for each chemical were estimated using POLO Plus (LeOra Software, 2007). Four populations were screened with 3 diagnostic doses (LD50, LD75, LD95) for tolerance to pyrethroids and organophosphates: a long-term laboratory colony from Mississippi State University, and 3 field populations from areas that had experienced spray failures. Baseline susceptibilities (LD50s and LD90s) for tarnished plant bug to acetamiprid, (19.39, 55.48ppm), sulfoxaflor (0.05, 5.90ppm), respectively.  LD50s, LD75s and LD95s for dimethoate were (9.55, 23.79, 88.35 ppm), zeta-cypermethrin (1.29, 3.16, 11.48 ppm), dicrotophos (3.96, 7.86, 14.56 ppm), bifenthrin (0.39, 4.22, 35.97 ppm), and acephate (0.62, 5.09, 33.86 ppm), respectively. Field populations will be collected this summer and lethal dose ratios estimated for dimethoate, zeta-cypermethrin, dicrotophos, bifenthrin, and acephate.  Results reported here provide baseline data for future monitoring of resistance development.