Anthracnose Fact Sheet

Anthracnose is a disease of hardwood trees and various crops that occurs throughout the United States and the world. It is commonly referred to as leaf blight, twig blight, stem blight or the blight. Among crops affected by anthracnose disease are tomatoes, peppers, strawberries, sorghum and alfalfa.

Trees

Symptoms of anthracnose in hardwood trees are dead areas or blotches on leaves. The leaves take on a brown or black color and appear to be scorched. While symptoms vary depending upon the type of tree affected, the whole leaf may die and fall off prematurely. On other species, anthracnose may damage twigs, shoots, buds and fruits. The disease can lead to reduced growth, weakened trees and increase the tree's susceptibility to attack by other pests or injury during the winter.

Trees that are susceptible to anthracnose attack include ash, basswood, birch, catalpa, elm, hickory, horse chestnut, London planetree, maple, oak, sycamore, tulip tree and walnut.

Other Crops

In tomatoes, peppers and other similar crops, symptoms include small, circular lesions on the skin of the fruit as it ripens. These lesions appear to be water soaked, sunken and dark.

Symptoms in alfalfa include diamond-shaped lesions near the base of the stem. The lesions have a straw-colored center and a dark border. The infection results in wilting of the upper portion of the stem. The anthracnose fungi will continue to grow into the plant crown and the plant will die.

Cause

Anthracnose disease is caused by fungi. The fungi spores spread the disease when they are moved by wind, rain or animals from one tree to another. Because the fungi that cause anthracnose disease are carried by wind and rain, disease is often worse during seasons when rains are heavy. Drier springs and summers mean less likelihood of widespread anthracnose disease.

Life Cycle

The fungi survive over winter on the debris from trees they have infected or in infected buds and twigs. When spring rains arrive, the fungi release spores that are blown by wind or rain to the growing leaves of nearby trees. The spore germinates and produces the fungi that will attack the leaves.

In fruit crops, the fungi survive between crops on plant debris in the soil. Early in the growing season spores form the soil splash onto the lower leaves of the plant.

Control

In forests, spraying and pruning cannot reduce the likelihood of disease. Thinning trees to allow for better air movement and sunshine may help. On trees in lawns and in nursery stock, anthracnose disease can be controlled by destroying the fungi in its over-wintering stage. Leaves should be raked, and infected twigs and branches pruned. Fungicides can also be applied in the spring.

In crops such as tomatoes and peppers, control measures include rotating three years between crops, planting in well-drained fields, applying overhead irrigation during the early part of the day so that plants are dry by sundown and harvesting fruit before it fully ripens. Fungicides can be applied in certain conditions.

In crops such as alfalfa, control may mean leaving a crop unharvested or harvesting it last. Cutting the crop could mean spreading the disease to uninfected fields. The fungi can be moved from one field to the next via tools and implements and these devices must be disinfected between fields to avoid spreading the disease.

References

• Anthracnose Disease of Eastern Hardwoods
• Anthracnose of Tomato
• Alfalfa Antracnose