Wafer Ash Tree Question

Asked June 10, 2019, 3:10 PM EDT

Our client has 10-12 wafer ash trees with spots on all their leaves. He also has a native shrub nursery on this site and would like to discuss if quarantine is needed for infected plants. He noticed the spots onset in the last week. Melissa Franklin, Van Buren MSU Extension 801 Hazen Street, Suite D Dowagiac, MI 49079 269-657-8213

Van Buren County Michigan trees and shrubs ash

1 Response

Thank you for contacting us about your wafer ash. It is difficult to diagnose problems from photographs, but it appears that the tree may have leaf spot. Leaf spot can be bacterial or fungal. Both types of leaf spot are most active when there is plenty of moisture and warm temperatures. Wind and rain transmit the bacteria to plants. Some plants are more susceptible than others.

This disease overwinters in the soil around infected plants as well as on garden debris and seeds. It will also remain in the twig cankers, leaves, stems and fruit of infected trees so good sanitation is required to control its spread. Essentially, control methods recommend:

  1. Keep the soil under the tree clean and rake up fallen leaves or fruit.
  2. Use a thick layer of mulch to cover the soil after you have raked and cleaned it well. Mulch will prevent the pathogen from splashing back up onto the leaves.
  3. Prune plants to improve air circulation. Disinfect your pruning equipment after each cut. (Use 70% isopropyl alcohol on a rag.)
You can read more about leaf spot at:
https://extension.umn.edu/plant-diseases/leaf-spot-diseases-trees-and-shrubs

Since there is no cure for leaf spot, I would definitely segregate the affected plants.