Beneficial arthropods as affected by insecticides and cotton genotypes in cotton fields near the upper gulf coast of Texas

Abstract

The effects of early-season applications of several insecticides for the cotton fleahopper on the beneficial arthropod complex were studied during 1969 and 1970 in cotton fields near the upper gulf coast of Texas. These experiments were conducted in 20-acre replicated test plots. The object of using these large plots was to reduce insecticidal drift and minimize the effects of immigration, and emigration of the arthropods under study. Simultaneous experiments were undertaken to determine the incidence of egg and larval parasitism of Heliothis species and observations of the seasonal and relative abundance of beneficial arthropods in four cotton genotypes were also made. Bidrin, applied twice at 0.1 lb/acre reduced the total predator complex more than the other compounds tested. The effects of one early-season application of Bidrin at 0.05 lb/acre were less detrimental to the predator complex. Other compounds tested also revealed some selective toxicities toward important predator species. Two applications of carbaryl were also somewhat detrimental to the beneficial complex but other materials such as toxaphene-DDT, sulfur, trichlorfon, methyl parathion, strobane-DDT, and toxaphene appeared less harsh to the beneficial complex. Although the insecticide-treated plots usually contained fewer numbers of beneficial arthropods as compared to untreated controls, the reduction of these predators was often not statistically significant. Many of the beneficial arthropods were present in low numbers before applications of the insecticides were made. After insecticide applications, numbers of beneficials were generally reduced but frequently resurged to their original levels within two weeks after treatment. ...