Effect of Cercospora Leaf Spot of Peanuts on Forage Yield and Quality and on Seed Yield1

Abstract

AbstractEpidemics of Cercospora leaf spot reduce the forage and seed yield of peanuts (Arachis hypogaea L.). The purpose of this study was to determine the effect of different levels of control of Cercospora leaf spot disease on defoliation, forage yield, quality, mineral composition, and seed yield of peanuts. Adapted peanut cultivars were grown according to recommended management practices in the Coastal Plain Region of Georgia during 1971 and 1972. Three foliar fungicides (benomyl 50W, chlorothalonil 75W, and copper‐sulfur dust) were compared with an unsprayed control. Fungicides were applied on a 14‐ day schedule, with five applications in 1971 and six applications in 1972. Benomyl and chlorothalonil gave significantly better control of Cercospora leaf spot than copper‐sulfur dust as evidenced by reduced defoliation. Copper‐sulfur dust was superior to the unsprayed control. As a consequence of disease control (very little defoliation), forage yields, in vitro digestibility, protein content, and seed yields were higher, and forage fiber content was lower. Higher calcium levels in forage were associated with good disease control in both years; Mg, Mn, Fe, Al, and Mo were higher in only 1 year. These differences between years could have been due to the use of different peanut cultivars. Several elements (P, B, Zn, Sr, Ba and Na) were not changed as a result of leaf spot control in either year. During both years, potassium decreased with control of leaf spot. Higher levels of Cu were observed in the forage treated with copper‐sulfur dust in both years. Thus, control of Cercospora leaf spot in peanuts was accompanied by an increase in yield and quality of forage and yield of seed, and levels of control achieved were highly correlated with yield and quality.