Pyriproxyfen is a biorational insecticide from IGR family, used worldwide against several economic pests. To evaluate the risk of pyriproxyfen resistance in dusky cotton bug, Oxycarenus hyalinipennis Costa (Hemiptera: Lygaeidae), a major concern for cotton producers, and to formulate strategies effective to tackle resistance, a field collected population was selected with pyriproxyfen under laboratory conditions using seed-dip method. A resistant strain designated as Pyr-SEL (G18) was developed after repeatedly selecting O. hyalinipennis with pyriproxyfen over eighteen generations. Thereafter, fitness costs, realized heritability (h2) and cross-resistance were investigated. As a result of selection, Pyr-SEL (G18) developed a very high level of resistance (resistance ratio = 464.23-fold) compared with the susceptible strain unselected over twenty generations Un-SEL (G20). The Pyr-SEL (G18) conferred strong cross-resistance to bifenthrin (146.59-fold), lambda-cyhalothrin (132.96-fold) and fenoxycarb (91.06-fold), whereas showed moderate cross-resistance to diafenthiuron (28.86-fold) and fipronil (22.73-fold). The h2 estimate was 0.16 in Pyr-SEL (G18). The developmental duration of O. hyalinipennis pre-adult prolonged, but traits of λ, r and R0 reduced in Pyr-SEL (G18) compared with the Un-SEL (G20). Also, the population projection obtained lower population size for Pyr-SEL (G18) than Un-SEL (G20). Fitness studies revealed that high resistance development to pyriproxyfen lowered the relative fitness of Pyr-SEL (G18) (Rf = 0.38) compared with the Un-SEL (G20). These findings may be practically valuable in tackling O. hyalinipennis resistance for better pest management.
Keywords: Bioassay; Cotton; Insect pests; Insecticides; Resistance; Selection.
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