Badly affected leaves turn brown early and drop off. Plants that lose leaves to rust are weakened and will not produce as well as healthy plants.
Rust-causing fungi persist in soil in warm climates, and spread to other areas when spores are blown on winds. Some varieties offer genetic resistance. Leaves that dry rapidly after rain or heavy dew are unlikely to develop problems with rust. Avoid planting sweetcorn near trees, fences, or low pockets where dew is always heavy, and grow sweetcorn at proper spacing to make sure sunlight reaches all the leaves. The weed called wood sorrel serves as an alternate host for this disease, so eliminating this weed can limit corn rust. At the end of the season, compost all sweetcorn plants to speed the decomposition of diseased tissues.
Stay out of your sweetcorn patch when the leaves are wet, because you can spread the spores from sick plants to well ones. On a dry day, gather badly affected leaves and dispose of them in the trash.