Comparisons of Insecticides on Fall Alfalfa Insect Populations, and Resultant Hay Yields and Quality

Abstract

Three insecticide active ingredients (cyfluthrin, indoxacarb, and zetacypermethrin) were evaluated for their efficacy on several insects found in fall alfalfa in the low desert. Both liquid and wettable formulations were included for both cyfluthrin and zetacypermethrin, and four rates of indoxacarb were applied. Insect pressures were fairly low throughout the study. Pyrethroid chemistries (cyfluthrin, zetacypermethrin) provided excellent control of threecornered alfalfa hoppers for seven days after application while cyfluthrin applications resulted in lowest numbers of pale striped flea beetles during the same time period. All chemistries resulted in excellent control of the South American bean thrips (Caliothrips phaseoli). Indoxacarb treatments resulted in significantly increased levels of spotted alfalfa aphid, thought due to a reduction of big eye bugs noted with usage of this chemistry. Wettable formulations of both cyfluthrin and zetacypermethrin resulted in significant hay yield increases (0.1 tons/acre) when compared with their liquid formulations. An inverse yield trend was noted with indoxacarb rate. Usage of the liquid cyfluthrin chemistry also resulted in an unexplained quality decrease in this experiment.