Turn under corn debris soon after harvest to promote rapid decay and destroy overwintering fungi. Prevention & Treatment: Rotate corn with nongrass-type plants (crop or cover crop) in the garden. With corn ear infections, the fungus causes oblong, bleached spots that penetrate through the shuck layers and finally into the ear. Spots often enlarge and increase in number and can cause severe leaf blighting. Spots on the leaves are tan to light brown and occur first on the lower leaves of the plant. Symptoms occur as leaf spots or cob rots and are fairly easy to recognize on plants. This disease is caused by the fungus Bipolaris maydis (syn. All insect controls should be carefully followed as described in HGIC 2205, Insect Pests of Sweet Corn. Keep soil fertility balanced based on soil tests. Do not exceed recommended plant densities (i.e., use the recommended in row and between row spacing). Prevention and Treatment: Plant in well-drained areas because stalk rots are most severe in poorly drained soil and where poor air movement slows drying. Insect damage can increase infection by wounding the plant and allowing fungi to enter. Some of these disease-causing organisms enter through the roots and move up into the stalk, while others enter the stalk directly at the nodes. Infected corn stalks fall over (called lodging) and losses result from unharvested ears and poor ear development on infected plants. They are caused by various species of fungi, including Diplodia zeae, Fusarium species, and Colletotrichum graminicola. Root and stalk rots are among the most destructive corn diseases. Corn planted at the appropriate time and not too late in the season is often damaged less by viruses. Prevention & Treatment: Control grassy weeds near corn plantings (Johnsongrass). In the spring, insects transmit the virus to young corn plants. The viruses survive the winter on many perennial grass species, especially Johnsongrass. Both virus diseases generally cause plant stunting. MCDV-infected leaves often have a pale green streaking of the upper leaves, and often these leaves turn a reddish color. The upper leaves of MDMV-infected plants show pale green blotches or mottling. Symptoms of these virus diseases can easily be mistaken for other growth problems such as nutrient deficiencies. In South Carolina, there are two main viruses that are a problem on corn, Maize dwarf mosaic virus (MDMV) and Maize chlorotic dwarf virus (MCDV). Sweet corn should be planted on raised bed rows after the soil temperature is above 55 ✯. Seeds will be pink to indicate they have been treated. Prevention & Treatment: Control of these problems is obtained by using high-quality seed that has been treated with protective fungicides. In warmer soils, seedlings may emerge but have rotted roots and stems at the ground line. Low-quality seed also produces seedlings that are weak and survive poorly, especially in cold soils. In cool, wet soils, seed germination and seedling development slow down, increasing the length of time exposed to fungi in the soil. In cold soils that have a temperature of less than 55 ✯, seeds can decay, and seedlings may die before they reach the soil surface. Poor stands of corn can result from various species of fungi, including Pythium, Fusarium, and Diplodia, which affect seed germination and seedling development. Rust develops best when temperatures are cool (60 to 70 ✯) and humid. ![]() Plant corn early and avoid letting plants get under stress from drought. It is caused by various species of the fungus Puccinia and causes raised, brick red spots primarily on upper leaf surfaces. Rust occurs in most home gardens on corn but is seldom a serious problem.
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