Sweet corn is a warm-season annual grass grown for its sugary kernels, harvested at the immature milk stage. It is a staple summer crop, but flavor declines quickly after picking, which makes home-grown corn worth the space it takes.
Corn is wind-pollinated, so it must be planted in blocks of at least four short rows rather than a single long row to ensure full kernel set. It is a heavy feeder, needs steady moisture during tasseling and ear fill, and roots shallowly, so avoid deep cultivation near the stalks.
Rust
Orange to brown raised pustules on the undersides of leaves, with yellow spotting on the upper surface. Heavy infections cause leaves to yellow and drop.
Remove and destroy infected leaves. Avoid overhead watering and improve air circulation. Apply a sulfur or copper-based fungicide if it spreads. Clear plant debris in fall.
Corn Smut
Swollen grey-white galls on ears, stalks, or tassels that rupture into masses of black powdery spores.
Cut out and bag galls before they rupture; do not compost. Avoid plant injury, rotate crops, and remove infected debris at season end.
Northern Corn Leaf Blight
Long, cigar-shaped grey-green to tan lesions on leaves, starting on lower foliage and spreading upward in wet weather.
Plant resistant varieties, rotate away from corn for two years, and remove crop residue. Improve airflow and avoid overhead watering.