SORGHUM DOWNY MILDEW, A DISEASE OF MAIZE AND SORGHUM

During these years, programs for the study and control of downy mildew have been centered in Texas. The continual spread of downy mildew throughout the Southern States and into several Central States bordering the maize belt has focused national concern on the potential threat posed by tropical downy mildews. Since 1964, 36 sorghum lines resistant to downy mildew under field conditions have been identified and made available to persons engaged in sorghum improvement programs. Also, more than 30 maize inbreds with moderate to high levels of resistance to sorghum downy mildew have been identified under field conditions. The manner in which resistance is inherited has permitted breeders to develop resistant hybrids of both maize and sorghum. Today some agronomically desirable, downy mildew resistant hybrid cultivars of both maize and sorghum are commercially available. Specific cultivation control practices have reduced disease severity. These include removing inoculum, particularly by deep plowing to bury soilborne spores, and avoiding cultivation of susceptible crops. In fields in which highly susceptible sorghum-sudan-grasses and broomcorn have not been grown, build-up of disease has been less than in fields in which they have been grown. Chemical control of downy mildew is being studied, but to date results have not been encouraging.