Chlorothalonil (as Bravo 720) was applied at 1255 g/ha 7 times to groundnut cv. Florunner in 0.12, 17.8 or 1.7 kl of water/ha via ground sprays, centre pivot irrigation (chemigation) or pivot-mounted underslung boom, respectively. Some of the chemigated plots were subjected to tractor traffic. Rhizoctonia limb rot (caused by R. 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 [Mycosphaerella berkeleyi]) 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.
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Timothy B. Brenneman (1990) studied this question.