Root Rot: If you have cool, moist soil, watch out for this problem. Improve soil drainage with compost and wait for soil temperatures to regulate.
Rust/Leaf Blight: Warmer, wetter parts of the country have problems with these diseases. There are many blight resistant varieties available. Ask your local nursery for recommended cultivars.
Wireworms/White Grubs: These pests come from soils recently planted with sod or alfalfa. Look for birds feeding on the grubs. Tilling and planting with a cover crop, such as winter peas, can help with this problem.
Corn rootworm beetles: This pest goes after corn silk on maturing cornstalks. They can cause problems with pollination. The immature beetles can be found in old corn fields, and when mature, they migrate to feed on tender, new corn. Keep on the lookout as your corn first starts to produce silk.
Corn Smut: This is a fungus that causes the kernels to swell and turn grey and black. In Mexico, it is called Huitlacoche and is consumed as a delicacy. Ask your local extension agent or nursery for smut resistant varieties. Corn smut is more common on white varieties. You can remove the smut by hand and you should destroy it so that it won’t infect other corn plants. If you’re curious, you can actually harvest the smut before it turns black and dries out. Check out this article from the University of Illinois at Urbana-Champaign on the economic importance of Huitlacoche in Mexico: sweetcorn.uiuc.edu/Common-smut/Huitlacoche-WSMBMP.doc. Also see Aztec Gardens for more information on this unusual food.
European corn borers: These pests bore into the stalks and can weaken them to the point of breakage. The larva is cream colored and they are about 1” long. They may eventually work their way into the corn cob. Their eggs begin to hatch in June.
Fall armyworms: This moth lays small pinkish eggs on corn leaves. Adult worms are less than two inches long. They have a Y shaped marking on the head. Late sweet corn is especially susceptible. You can plant early to avoid this pest, as armyworms are at their worst in the late fall.
Flea beetles: These pests attack in the early spring and can carry Stewart’s bacterial wilt disease. This disease will eventually stunt the growth of young corn. Ask your nursery for disease resistant varieties.
Corn earworms: These are brownish, flying moths that will lay eggs in corn silk. They are active mostly at night. The worms will feed on the tips of the ears. You’ll usually not find more than one caterpillar per ear as they are known to devour each other when there is competition. You can avoid this pest with a bit of mineral oil in the tip of the silk tube, or by sealing off the husk with a rubber band. Pheromone traps placed around the cornfield are also an effective control.
Birds: Birds such as crows are common pests for corn farmers. You can use reflective bird tape throughout the rows to scare them off and confuse them. A good old fashion scare crow is also effective.