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.
- Articles
Tomato-Potato Late Blight in the Home Garden
This article describes tomato-potato late blight, including symptoms; disease development, cycle, and management; and management after harvest. - Articles
Tree Fruit Disease - Predicting Infection Periods to Apply Protection
This article will help you manually determine infection periods for certain tree fruit diseases. Also included is a table listing coppers available to manage bacterial spot during cover sprays. - Articles
Stone Fruit Disease - Rusty Spot
Caused by the same fungus as apple powdery mildew and only affects the fruit. Peach and nectarine cultivars vary in susceptibility. - Articles
Pome Fruit Disease - Black Rot and Frogeye Leaf Spot
The black rot and frogeye leaf spot fungus, Diplodia seriata (Botryosphaeria obtuse syn), covers a wide geographical range, attacking the fruit, leaves, and bark of apple trees and other pomaceous plants. - Articles
Pome Fruit Disease - Blister Spot on Crispin (Mutsu)
Crispin apples are highly susceptible to blister spot bacterial infection, Pseudomonas syringae, about 2 weeks after petal fall for a period of 2 to 4 weeks. - Articles
Pome Fruit Disease - Apple Union Necrosis and Decline
Apple union necrosis is an economic problem only in commercial apple orchards. It is caused by tomato ringspot virus, which affects the graft union of apple trees, resulting in gradual tree decline. - Articles
Pome Fruit Disease - Rust
There are three rust diseases: cedar-apple rust, hawthorn rust, and quince rust. The most common is cedar-apple rust, Gymnosporangium juniperi-virginianae. - Articles
Stone Fruit Disease - Brown Rot
Brown rot is caused by the fungus Monilinia fructicola. It affects peaches, apricots, nectarines, plums, and cherries. - Articles
Stone Fruit Disease - Black Knot
Black knot of plum, caused by the fungus Dibotryon morbosum, is well-named because of the characteristic black, warty knots it forms on branches of infected trees. - Articles
Peach Disease - Peach Leaf Curl
The peach leaf curl fungus, Taphrina deformans, destroys early peach leaves. - Articles
Cherry Disease - Cherry Leaf Spot
Cherry leaf spot, caused by the fungus Blumeriella jaapii (formerly Coccomyces hiemali), attacks the leaves, leaf stems, fruit, and fruit stems of tart, sweet, and English Morello cherries. - Articles
Apple Disease - Powdery Mildew
Powdery mildew, caused by the fungus Podosphaera leucotricha, attacks buds, blossoms, leaves, new shoots, and fruit of wild and cultivated apples and crabapples. - Articles
Apple Disease: Moldy Core
Moldy core is caused by several different fungal pathogens. Many cultivars of apples are affected, including Delicious, which is very susceptible. - Articles
Powdery Mildew
Powdery mildew occurs on many different flowers, woody ornamentals and trees. - Articles
Pyracantha Diseases
Informational table showing disease name, symptoms, pathogen/cause, and management of Pyracantha diseases. - Articles
Damping Off
Damping-off is the rotting of seeds in the soil and destruction of newly emerged seedlings by fungi. - Articles
Aster Diseases
Informational table showing disease name, symptoms, pathogen/cause, and management of Aster diseases. - Articles
Bacterial Blight of Geranium
Bacterial blight of geranium is the single most important disease of geraniums. - Articles
Viola Diseases
Informational table showing disease name, symptoms, pathogen/cause, and management of Viola diseases. - Articles
Crassula (Jade Plant) Diseases
Informational table showing disease name, symptoms, pathogen/cause, and management of Crassula (Jade Plant) diseases. - Articles
Plum Pox Virus in Ornamentals
Plum pox is a serious disease of Prunus species caused by a virus. - Articles
Palm Diseases
Informational table showing disease name, symptoms, pathogen/cause, and management of Palm diseases. - Articles
Lily Of The Valley (Convallaria) Diseases
Informational table showing disease name, symptoms, pathogen/cause, and management of Lily Of The Valley (Convallaria) diseases. - Articles
Spruce Diseases
Informational table showing disease name, symptoms, pathogen/cause, and management of Spruce diseases. - Articles
Hemlock Diseases
Informational table showing disease name, symptoms, pathogen/cause, and management of Hemlock diseases.