Effects of Herbicide Antidotes on Sorghum Downy Mildew

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Abstract
Relationships between herbicide antidotes and incidences of sorghum downy mildew observed in field plantings of sorghum [Sorghum bicolor] were studied in greenhouse tests. Seed treatment with the herbicide antidote CGA 92194 caused significant increases in downy mildew incidence in susceptible sorghum hybrids grown in soil infested with oospores of Peronosclerospora sorghi or inoculated with conidia of the pathogen. CGA 92194 did not increase disease incidence in resistant sorghum genotypes. Seed treatment with the herbicide antidote flurazole had no significant effect on disease incidence of susceptible or resistant sorghum genotypes planted in oospore-infested soil. Flurazole seed treatment significantly reduced disease incidence in two of three susceptible sorghum genotypes inoculated with conidia of P. sorghi. The field observations of increased downy mildew incidence in sorghum treated with CGA 92194 and the greenhouse test results indicate that CGA 92194 could increase the severity of downy mildew damage in susceptible sorghum genotypes.