Fungicides & Disease ControlEvery veteran gardener knows that gardening is a constant battle with plant disease. Plant disease is caused by pathogens (infectious diseases) as well as environment conditions. Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and parasitic plants. Not included are ectoparasites like insects, mites, vertebrate, or other pests that affect plant health by consumption of plant tissues. Plant disease can be characterized and identified by wilting, scabs, moldy coatings, rusts, blotches, and rotted tissue. 

This is an extensive list of common plant diseases and damage that gardeners around the world have experienced. Use this list to identify diseases and plant damage so that you can prevent plant/crop loss early. Click on the links or pictures below to learn more about each disease and products used to remedy each problem.

 

Anthracnose
Commonly found in the eastern US, this disease damages plants by creating dark spots on stems, leaves, or fruit. These spots generally become covered with pink spore masses.
Apple Scabs
A disease that infects Malus trees, such as apple trees, and can be identified by dull black or brown on tree leaves, buds, fruits, and sometimes wooded parts of the tree. Does not kill host but reduces yield and quality.
Bacterial Canker
Found throughout the US on stone fruit trees such cherries, plums, apricots, peaches, etc. Identified as sunken, sticky, dark lesions that form around the trunk or branches. The underlying tissue will be reddish-brown to black and moist. Leaves above the infected area curl and turn yellow, and if left untreated will kill the host plant.
Bacterial Leaf Spot
Commonly affects members of the Prunus family (cherry, plum, almond, apricot, peach) but also appears on tomatoes, peppers, and members of the cabbage family. Identified by dark colored, wet-looking spots surrounded by a yellow ring on the leaves, stems, or fruit of infected plants.
Blossom End Rot
 A disease caused by insufficient calcium input. This disease can be identified as rotting, black, felt-like lesions on the ends of fruits of plants such as tomatoes, eggplants, and peppers. Destroys fruits and decreases usable yield but does not kill plants and is not contagious to other plants.
Brown Rot
This is a fungal disease that effects all stone fruit plants (cherries, peaches, plums, prunes, nectarines, apricots, etc.) . Developing or mature fruits show circular or brown spots that spread rapidly over the surface and light gray masses of spores are produced on the rotted areas. Rotted tissue remains relatively firm and dry.
Cedar Apple Rust
This is a fungal disease that infects various Juniper species as well as Malus trees like apples or crabapples. Spores overwinter as reddish brown galls on twigs of Junipers and then become orange. The mature spores are passed on to apple or crabapple trees and appear as yellow pin-sized dots that enlarge and turn orange-yellow. The infection process is repeated back and forth between these two types of plants and cause leaf damage and crop loss.
Club Root
This is a common disease in North America caused by Phytomyxea, or parasites. Often occurring in members of the Cruciferae family ( cabbage, radish, turnips, canolas, etc.). This disease can be identified by misshapen and deformed (clubbed) roots that are often cracked and rotting. If left untreated, this infection will cause plant death and an overall decrease in yield.
  Corn Smut
This is a fungal disease that infects  all types of corn and can be identified by grey galls (growths) on all above-ground parts of the plant including stock, leaves, and ears. These growths fill with spores and then rupture, spreading the infection and creating massive crop loss.
Crown Gall
This disease is a bacterial growth commonly found on many woody shrubs and some herbaceous plants, including grapes, raspberries, stone fruits and roses. These galls can be identified as large, swelling growths that become hard and woody and usually are found around the crown of the plant (the area where the stem meets the soil). Crown gall prevents nutrients and water from being absorbed and will cause overall plant death.
Damping Off (Root Rot)
This soil-born fungal disease infects young seedlings of all types and is common throughout America. Fungi cause the seedlings to become water-soaked and mushy, eventually becoming weak at the base. This will cause the plant to break at the stem and eventually causes plant death.
Dollar Spot
This is a fungal disease that infects grass and lawn throughout America. Infection can be identified as irregular shaped tan spots, usually ranging in size from 3-6 inches. Damage from this infection can be compounded by Nitrogen deficiency. Small spots can eventually join together and create a large area of blight, killing grass and lawns.
Downy Mildew
Downy Mildew is a parasitic fungal infection that affects many different types of plants. This disease can be identified as yellow or light-colored spots on older leaves. The underside of these leaves will have a cotton-like fungus growing on them. Infection is easily spread throughout plants and causes foliage loss.
Early Blight
Early Blight is a fungal disease that is commonly found in tomato and potato plants. This infection can be identified as small brown spots that will vaguely resemble a "bull's eye" target. Eventually these spots will enlarge, causing the infected leaf to wither and die. Eventually the stem and fruits can become infected, causing severe crop loss.
Fairy Ring
This fungal disease appears as dark rings on lawns and grass. These rings can be anywhere from a few inches to over 200 feet in diameter and grow 6-24 inches in diameter annually depending on climate conditions. Mushrooms also form on the outside of the ring formation. This infection will prevent grass roots from absorbing moisture and eventually causes plant death.
Fire Blight
Fire Blight is a bacterial disease that is commonly found in apples, pears, and members of the Roseaceous family. This bacteria can be found world wide and is extremely destructive, usually being able to destroy an entire orchard in one growing season. Usually an infected plant can be identified by scorched, burnt looking leaves near the tips of branches where softer, younger tissue is found. Infection eventually spreads to the entire tree, causing severe plant death and crop loss.
Fusarium Wilt
Fusarium Wilt is a fungal disease common in tomatoes, potatoes, eggplants, and peppers. This disease prevents plants from absorbing water and can be identified as drying/wilting of older plants leaves followed by young leaf infection. Usually Fusarium only shows symptoms on one branch or one side of the plant. Eventually, plant death follows.
Gray Mold (Botrytis)
One of the most common fungal diseases in plants, this mold infects a vast array of plants and is easily identifiable as grey, soft spots covered with whitish spores. These spots can appear on leaves, stems, fruits, buds, and seedlings. Back, stone-like sclerotia often develop under the rotten parts. Eventually, plant death and severe decrease in yield may occur.
Late Blight (Potato Blight)
Late Blight, also known as Potato Blight, is a common disease found in the United States. This infection is found frequently in tomato and potato plants and occurs towards late in the growing season. This disease can be identified as water-soaked grey-green spots on the underside of older leaves. These spots may mature and cause a white fungal growth as well. This disease can cause severe plant damage.
Leaf Curl
Curl is a fungal disease that is common in peaches, nectarines, and almonds but occasionally also found in apricots. This infection can be identified as reddish swellings on the leaves, causing the entire leaf to curl and become distorted in shape and appearance. This can cause to reduced fruit production.
Mosaic Virus
Mosaic Virus is a viral disease found commonly in roses, beans, tomatoes, and peppers but is also occasionally found in a variety of other plants. Symptoms of infection are hard to detect, as this disease is similar in appearance to several nutrient deficiencies. Mosaic Virus is identified as yellow or green stripes/spots on foliage. Fruit develop wart-like growths and deform shape, causing a decrease in usable yield.
Potato Scabs
Potato Scabs is a bacterial disease that is common in potatoes but can also be found in beets, radish, turnips, carrots, rutabaga, and parsnips. This disease can be identified as dark brown lesions on the surface of the fruits of these plants, often becoming wart-like in appearance. The lesions can appear in small numbers or cover the entire fruit, causing severe decrease in usable yield.
Powdery Mildew
Powdery Mildew is a common fungal disease that affects a vast array of host plants in an outdoor growing environment. This infection can be easily identified by blister-like growths that mature into a powdery, white/grey mold. This eventually leads to severe plant damage and loss of foliage.
Common Rust
Although there are over 7,800 known species of Rust disease, the most common form of this fungal disease is found on snapdragons, roses, bluegrass, and woody perennials. This disease can be identified as small, white, raised spots that eventually grow rust-colored spores. if left untreated, Rust disease causes leaves to wither and die causing sever foliage loss.