Plant Disease Identification and Control

Preventing and controlling plant diseases is key to growing healthy plants. In this section, find information on plant disease identification and control, including rot, freeze damage, rust, blight, mold, scales, bacteria, viruses, fungus, wilt, mildew, gall, mites, moths, and cankers. You’ll also find tips on integrated pest management and herbicide summaries.

Types of Plant Diseases

Plant disease is “anything that prevents the plant from performing to its maximum potential.” We classify plant diseases as either abiotic or non-infectious diseases and biotic or infectious diseases.

Abiotic diseases are those caused by external conditions rather than living agents. These diseases are not infectious and include nutritional deficiencies, salt injury, ice, sun scorch, or soil compaction.

Biotic diseases are caused by living organisms, otherwise known as plant pathogens. These pathogens can spread from plant to plant and affect all parts of the plant, including roots, tubers, leaves, shoots, stems, crowns, fruit, and vascular tissue. Plant pathogens include fungi, fungal organisms, viruses, bacteria, phytoplasmas, viroids, parasitic higher plants, and nematodes.

Being able to quickly and accurately diagnose plant health gives you the best possible chance to solve any issues before losing the plant.

Field Crop and Forage Plant Diseases

A wide variety of diseases attack field and agronomic crops and forages. Successful disease control requires correct identification and knowledge of the cause and life cycle of the disease. It’s also essential to have control procedures available. There is plenty of information available for producers to increase their knowledge base, such as the Penn State Agronomy Guide. You can also turn to professional crop advisers or agronomy scouts for further guidance.

To make the right decisions about the controls to use, you need to have first-hand knowledge of the condition of the crops or forages in the field. Some common diseases to look for in corn include gray leaf spot and corn ear rot. Mycotoxins can cause moldy corn. Yield-limiting plant diseases do not become problematic until the reproductive stages of development, which means there is little benefit to early season fungicide applications.

Forage grasses are susceptible to a variety of leaf, stem, floral, and root diseases. Recent developments have led to improved management practices, such as using disease resistance species.

Small grains such as wheat may display symptoms of diseases such as head scab, black chaff, and Stagonospora glume. The quality and size of your yield depend on the severity of the disease.

There are some late-season diseases to look out for in soybean crops. Stem canker doesn’t show symptoms until well into the reproductive stages of growth. Soybean sudden death syndrome has pretty striking symptoms, but other diseases, such as brown stem rot or injury from chemicals can mimic it.

Fruit and Vegetable Diseases

As with all other types of crops, early identification is key for successful management and control of fruit and vegetable diseases. There’s plenty of help available for seasoned and beginning vegetable farmers, whether you’re growing brassicas, potatoes, or any other fruit or vegetable crop.

Regular and proper scouting techniques allow you to note significant changes and symptom development early enough to keep vegetable and tree fruit diseases at bay. It can help manage pre- and post-harvest fruit rots, spot the symptoms of pear blister mite and pear rust mite, as well as many other vegetable and tree fruit diseases.

Timing is key with any disease management plan and typically varies depending on the disease you want to control. You must also take product efficacy and disease development into account. There are, however, things a farmer can do to delay resistance to fungicides in vegetable and fruit crops.