With recent cool and wet weather, we have observed the presence of anthracnose diseases in several shade trees. Anthracnose is a fungal disease caused by a group of pathogenic fungi that infect a very broad range of shade tree and shrubs, such as maple, elm, oak, sycamore, poplar and ash.
Symptoms of anthracnose start to show up in spring as small dark brown circular or irregular-shape spots (Figure 1). The small spots develop into large blothces along the veins and spread to the edge of the leaves (Figure 2). As the dead areas of the leaves expand, the leaves are distorted, showing blister look. This disease can spread very fast by attacking the newly developed leaves and can affect over 80% of the canopy when the environment favors these pathogens. The fungal spores are transmitted by wind or rain splash to other trees and can infect one tree repeatedly. The young leaves may die and fall from the tree due to heavy infection. As the time passes by, the diesae may stop progressing later in the season and the new leaves will again emerge. The fungal spores can survive in fruiting bodies (pycnidia) on the infected leaves, twigs or cankers on the tree during the winter.
For appropriate diagnosis, the MU Plant Diagnostic Clinic can help you confirm if your plant has this disease. We encourage you to visit our website (https://extension.missouri.edu/programs/plant-diagnostic-clinic) and review submission guidelines before submitting your sample. If possible, you may take photos and send them to email@example.com.
We just uploaded a new webinar about sample submission guidelines on YouTube to help you submit your sample step by step.
Please click here: https://www.youtube.com/watch?v=4dUcYKKFwaI
1) Visit our new online submission system at https://extension.missouri.edu/services/plant-disease-sample. Fill out the submission form online using your computer or mobile device and make payment online securely with a credit card.
2) Download the submission form at https://extension.missouri.edu/programs/plant-diagnostic-clinic/sample-submission. Fill it out and send to us together with your sample and payment. Check or money order. No cash please.
University of Missouri-Plant Diagnostic Clinic
28 Mumford Hall
Columbia, MO 65211
REVISED: May 18, 2021