Why Do The Leaves On My Corn Look Unhealthy?

Are the leaves yellow and curled, the plant looks stunted?

Does the whole plant look stunted and yellow?

Did the older leaves turn yellow first, followed by the rest of the plant?

Have you been watering too much or too little or was there any heavy rains or dry spells?

Are the leaves mottled yellow and green?

Do the leaves have yellow stripes lengthwise, plants may wilt?

Do the leaves have yellow, tan or gray spots or blotches?

Do the leaves have orange-brown raised spots on them?

Do the leaves have numerous small holes in them?

Are the holes arranged in rows?

Do the leaves have large, ragged holes?

Curled, yellow leaves and stunted look are caused by aphids. These tiny insects can vary in color, green, pink, black, gray and completely white. They cluster under leaves and on growing tips where they feed on plant sap. Leaves get distorted. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

If the older leaves have turned yellow first, suspect nitrogen deficiency. Drench roots and spray plants with fish emulsion or compost tea to alleviate symptoms.

Too much or too little water in the soil can cause these symptoms. Keep the soil evenly moist and plant in raised beds to ensure good drainage.

If the entire plant is yellow and doesn't green up when sprayed with seaweed or compost and the soil is well-drained and not too dry, suspect pest nematodes. Control by applying chitin or parasitic nematodes to soil.

Maize dwarf mosaic virus causes these symptoms. There is no cure. Destroy infected plants. Prevent problems by controlling aphids, which spread the virus as they feed and perennial weeds such as Johnsongrass that can harbor the disease. Tolerant cultivars are 'Bell-ringer', ‘Bi-guard', 'Bunker Hill', 'Earlibelle’, ‘Enforcer', 'Merit' and 'Silverette'.

Bacterial wilt disease causes these symptoms. This disease can spread quickly, killing the plant in hot weather. Destroy all infected plants. Prevent problems by planting resistant cultivars such as 'Bellringer', 'Bunker Hill', 'Buttersweet', 'Earlibelle', 'Gold Cup', 'Merit', 'Silverado', 'Silver Queen', 'Stylpak', 'Summer Pearl' and 'Sweet Sue'.

Northern or southern corn leaf blight or other fungal leaf spots may cause these symptoms. Spray infected plants with sulfur to prevent blight from spreading. Prevent problems by using a 3-year rotation for corn and by planting cultivars, such as 'Apache', 'Cherokee', 'Comet', 'Florida Staysweet' and 'Wintergreen', which resist blights.

Orange-brown, raised spots on the leaves are caused by the fungal disease - Rust. Leaves may yellow and die. Where the problem is severe, spray with copper. Plant rust-tolerant cultivars such as 'Earlibelle', 'Flavor King', ‘Summer Pearl' and 'Sweetie 82'.

If holes are arranged in rows, look for billbugs. These hard-shelled, nearly black, snout beetles are usually seen only at night. Spray heavily infested corn plants with pyrethrin.

Flea beetles are tiny black insects that hop when disturbed. They can transmit diseases and are likely to be more numerous after mild winters. Cover plants with row cover as soon as they come up to exclude beetles. Remove row cover when tassels form. Treat plants with a commercial neem or pyrethrin spray to control severe infestations.

Various caterpillars cause large, ragged holes in corn leaves. Handpick or spray plants with BTK if caterpillars are feeding.

If the leaves have been skeletonized, the culprits are Japanese beetles. Adults are metallic blue-green beetles with bronze wing covers. Handpick or trap adults. Reduce the beetle population in the following years by applying parasitic nematodes or milky disease spores to garden and lawn areas.