Wet Weather Issues

 

Farmers are starting to make progress on planting, but it's quite variable. Warmer temperatures and humid conditions are expected. Both the winter wheat and weeds are growing quickly. Not only weeds, but also many insects and diseases are becoming a problem this year. Wet soils tend to compact and create poor soil structure, which is a major problem if soil dries off. Farmers have a lot of things to worry about when it stays wet and it's time to get crops planted.

On fast-growing weeds, corn has more restrictions for post applications of herbicides. Higher rates of herbicides will be needed along with post-emergent herbicides to control the weeds. Higher rates of Glyphosate (Roundup), Liberty Link corn, and Extend corn can help control most weeds but it is more difficult when weeds get big. The weeds are much easier to terminate when they are small.

On insects, watch for wireworms and seed corn maggot. Seed corn maggots are often a problem early with the larva feeding on the seeds and seedlings. Wireworms tunnel into the seed, roots, and stems and weaken the plant. These two pests are the most damaging insects in Ohio on corn and soybeans. Black cutworms tend to grow with the weeds. Black cutworms emerge from the soil and cut off newly growing corn seedlings. Often, they feed on weeds first before moving on to corn. A natural predator to black cutworm is the paper wasp. Usually, insecticides as a seed treatment are used to control these pests. Crop rotation, fast seed emergence, and weed control may help control these insect pests.

On diseases, there are many that thrive under wet humid conditions. Tar spot is becoming a major corn disease and starts early. It lives on the corn residue and looks like little black tar spots growing on the leaves. Fast decomposition of the residue helps reduce this disease. While tillage may help, this disease can be windblown from miles away and even resides in fence rows, waterways, and other non-cropped areas. Tar spot has many cycles and if it starts early and the weather remains warm and humid, it can grow quickly. Planting earlier maturing crops and good soil health allows the crop residue to break down faster.

Farmers also need to watch for Gray leaf spot (GLS) and Northern corn leaf blight (NCLB). Other diseases that grow well under warm humid conditions are ear rots which contain mycotoxins that contaminate grain and Anthracnose, a fungus that causes leaf blight and stalk rot. Under wet humid conditions, GLS leaf spots turn gray and fuzzy. NCLB starts on the lower leaves and begins as a small dot with a yellow halo which elongate and run along the leaf, turning brown and gray. Anthracnose is a fungus that affects corn seedlings and comes from undecomposed crop residue. The anthracnose spores germinate in the spring and can splash up from the soil during rain or from wind. Ear rots show up when grains start to develop. Planting high-quality seed, crop rotation, getting residue to decompose quickly, and planting resistant varieties to these diseases are the best management practices along with chemical treatments. Good balanced soil fertility and good drainage also help reduce the incidence of most diseases. A number of diseases affect both corn and soybeans including Phytophthora, Rhizoctonia, Fusarium, and Pythium diseases. Northwest Ohio is considered one of the Phytophthora capitals of the world due to heavy clay soils and poor drainage. Phytophthora is a root rot that resides in the soil and decays roots and stems. Rhizoctonia is a fungus that causes brown lesions on roots and stem rots. Infected plants are stunted and lower leaves turn yellow. Fusarium infects the roots and stems and causes a reddish-brown color to lower stems followed by wilting, yellow lower leaves turning brown, stunted growth, and even dead plants eventually. Pythium is a fungal pathogen that thrives under waterlogged soil with high humidity. Symptoms include stunted growth, wilting, uneven plant growth, and reduced root growth. All these diseases affect and hurt both corn and soybeans.

How to treat these diseases: Crop rotation and good drainage management help reduce these diseases. Soils with good soil structure and water infiltration will help lessen the disease. A good balanced soil fertility program helps plants grow quickly and often they can outgrow many pests. Planting high-quality seed and fast emergence help fight all diseases and pests. Insecticides and fungicides can help but sometimes these same products are detrimental to natural soil predators. Most farmers use seed treatments and genetics to help reduce the detrimental effects of these diseases. Safe planting!