SUDDEN OAK DEATH: Recent Detections in Nursery Stock in Ohio

By Tom Macy
Forest Health Program Administrator ODNR Division of Forestry

Sudden oak death (SOD) is a fatal disease of oaks and tanoaks in coastal California and Oregon. It was first discovered there in 1995. The disease is caused by Phytophthora ramorum, a fungus-like organism, more related to a water mold. Well over a hundred plant species can be infected by P. ramorum. Though it quickly kills oaks and tanoaks on the west coast, on other host plants it mainly causes leaf spots, wilt, or twig dieback. Despite this disease being quarantined by the USDA Animal and Plant Health Inspection Service (APHIS) in cooperation with state regulatory agencies, it has been known to be transported around the country on nursery stock.

In early spring 2019, it was discovered that a large shipment of containerized plants sent from a nursery in Oklahoma (the plants originated in Washington State and Canada) to vendors in at least 18 states, including Ohio, contained P. ramorum– infected plants. In Ohio, these plants were sent to Wal-Mart and Rural King stores. The infected plants included rhododendrons and lilacs. The exact number of infected plants is not known, but as soon as it was confirmed in the Ohio plants, the Ohio Department of Agriculture (ODA) responded by visiting the stores to seize and destroy potentially infected plants according to established protocols. Unfortunately, some plants had already been sold.

The ODNR Division of Forestry and Ohio State University Extension also worked along with ODA and USDA APHIS to do additional outreach to landowners who might have purchased an infected plant in southeastern Ohio, where most of Ohio’s at-risk oak forests occur, and where much interagency work on restoring oak-dominated forests has been done in recent years. These efforts resulted in some reports from landowners and removal of potentially infected plants from the landscape.

Though it is not known if P. ramorum can survive in Ohio’s climate (it has never been documented to cause damage in the East outside of nursery stock), survey and monitoring for its presence and damage in high-risk sites will begin in 2020. If you think you may have purchased a rhododendron or lilac from Wal-Mart or Rural King in Ohio between March l, 2019 and June 1, 2019, please contact the Division of Forestry at (614) 265-6705.

Published here with permission of ODNR Division of Forestry.
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