Interaction of Paraquat-Based Weed Control with Chlorothalonil-Based Disease Control in Peanut

Abstract

Understanding how weed and disease management strategies may be implemented in combination is important for improving pest management strategies in peanut (Arachis hypogaea L) production. In greenhouse and field studies, tank mixtures of paraquat and other herbicides, with the fungicide chlorothalonil (tetrachloroisophthalonitrile), were evaluated for their effect on weed control and peanut injury, defoliation due to leafspot diseases (Cercospora arachidicola and Cercosporidium personatum), and yield of peanut. In the greenhouse studies, the bipyridylium herbicide, paraquat, was tank-mixed with each of two formulations of the substituted aromatic fungicidal compound, chlorothalonil. Tank mixtures consisted of 0, 0.06, and 0.12 lb a.i.lacre paraquat and each of two chlorothalonil formulations (a liquid and a dry-flowable) at 0, 0.38, 0.75, and 1.12 lb a.i.lacre. Control of smallflower morningglory [Jacquemontia tamnifolia (L.) Griseb.] increased with increasing rate of paraquat application but was not affected with chlorothalonil in the tank mix. Control of Florida beggarweed [Desmodium tortuosum (Sw.) DC.] and injury on peanut increased with increasing rates of both pesticides, especially with paraquat at 0.06 lb/acre. In 2 yr of field studies, peanut injury due to paraquat, paraquat plus bentazon, paraquat plus bentazon plus 2,4-DB, 2,4-DB, or bentazon was not affected by the addition of chlorothalonil to tank mixtures. Three years of field studies on peanut show that end-of-season defoliation and yield, after a season-long schedule of chlorothalonil applications, were not affected when the initial fungicide application was tank-mixed with paraquat-based herbicide systems or 2,4-DB alone, regardless of chlorothalonil formulation. These data suggest that tank mixtures of chlorothalonil and early-season herbicides are compatible for use on peanut.