Effects of Tractor Traffic and Chlorothalonil Applied via Ground Sprays or Center Pivot Irrigation Systems on Peanut Diseases and Pod Yields

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Abstract
Chlorothalonil (Bravo 720) was applied at 1,255 g/ha seven times to peanut [Arachis hypogaea L.] cultivar Florunner in 0.12, 17.8 or 1.7 kl of water per hectare via ground sprays, center pivot irrigation (chemigation), or pivot-mounted underslung boom, respectively. Chemigated plots either were or were not subjected to tractor traffic. Rhizoctonia limb rot (caused by Rhizoctonia solani anastomosis group 4) was generally not controlled by chlorothalonil and tended to be more severe with tractor traffic. Plants in untreated plots had final defoliation of 96 and 68% because of late leaf spot (caused by Cercosporidium personatum) in 1987 and 1988, respectively. Ground sprays gave the best leaf spot control in both years, followed by the underslung boom and chemigation applications. In 1987, yields were significantly lower in plots that received the underslung boom or chemigation treatments than in ground-sprayed plots. With less disease in 1988, pod yields were equal in chemigated and ground-sprayed plots and were significantly higher in plots treated by means of the underslung boom.