Is Early Season Whorl-Stage Application of Acaricide a Viable Practice for Managing Spider Mites1 in Maize?

Abstract. Banks grass mite, Oligonychus pratensis (Banks), and twospotted spider mite, Tetranychus urticae Koch, are major pests of maize, Zea mays L., throughout the Great Plains states. Acaricides are primarily applied at late-vegetative to posttassel growth stages, but producers and crop consultants sometimes apply acaricides when maize is at the V3–V5 growth stages. This study investigated whether or not early applications of acaricides or applications at V9–V11 growth stages would be sound practices for managing spider mites. Studies from 2010 to 2012 used Comite® II (propargite) at 4.76 liters/ha, Oberon® 4SC (spiromesifen) at 0.53 liters/ha, and Onager® (hexythiazox) at 1.05 liters/ha at the designated growth stages. In two of the three years, spider mites in the nontreated check or treated plots never developed to damaging numbers when acaricides were applied at the very early V3–V5 or the late V9–V11 growth stages. The spider mites were suppressed naturally by predators during the 2 years. In 201...