Quantifying Tarnished Plant Bug Resistance to Acephate in Louisiana Cotton

Acephate is one of the most important control tools of the tarnished plant bug.  Recent evidence, however, has suggested that resistance of the tarnished plant bug to acephate could potentially affect cotton production in La.  This study was conducted to evaluate the correlation between acephate field efficacy and resistance monitoring data.  Tests were conducted throughout the state in producers’ fields.  Field efficacy experiments evaluated five acephate treatments (0, ½, ¾, 1, and 1 ¼ lb ai/a).  Treatments were arranged in a Latin square design with plots four rows wide by 50 feet long.  Treatments were applied with a back pack sprayer calibrated to apply 12 oz of water/acre, and all plots were sampled 5-7 days after treatment to determine efficacy.  Resistance monitoring, using glass vial bioassay tests were also conducted to determine LD₅₀ of each population collected.  In field tests were set up adjacent to an alternate host source of the tarnished plant bug in order to make collections of tarnished plant bugs that were to be used in glass vial bioassays, when possible.  In field test data was compared to glass vial bioassay data to see if there was any correlation between in field efficacy and LD₅₀ of each population.