Effectiveness of Fungicides and Their Application Timing for the Management of Sorghum Foliar Anthracnose in the Mid-Atlantic United States

Abstract

Sorghum anthracnose (Colletotrichum sublineola) reduces grain yield up to 50% but suggested management tactics have not yet been developed for the mid-Atlantic United States, where warm, wet conditions favor disease. Under factorial arrangement, five fungicides plus a nontreated control and four application timings were compared for foliar anthracnose control, yield, and profitability of fungicide use in grain sorghum over eight site-years in Virginia and North Carolina. Anthracnose severity was rated at the hard dough stage, and grain yield was determined at harvest. Every percent increase in disease severity resulted in yield losses of 27 to 85 kg/ha. Pyraclostrobin and pyraclostrobin plus fluxapyroxad reduced anthracnose (P < 0.01), and three applications resulted in less disease and greater yield compared with single applications (P < 0.01). However, three applications exceed the labeled maximum application for the fungicides and are not economical. Among single applications, boot or flowering timings reduced disease, and flowering applications resulted in the overall greatest yield. Results suggest that when disease onset occurs at or prior to boot, a single application of pyraclostrobin-containing fungicide at or just prior to flowering reduces anthracnose, protects yield, and increases income. However, when disease is absent or severity is low prior to flowering, fungicide application may not be profitable.

Keywords: chemical; economic impacts; field crops; fungi.