Pest Detective: How to Detect Sudden Oak Death

Pest Detective: How to Detect Sudden Oak Death

April 9, 2010
Photo by: courtesy Lake Austin Spa Resort

As homeowners begin their spring gardening, they can act as detectives for invasive plant diseases and insects. One disease in particular, sudden oak death, which has primarily been found along the western U.S. coastal areas, has made an appearance in Pennsylvania on some nursery stock, creating concern for a potential spread of the disease in eastern United States. The news release below gives gardeners specific information on how to detect and report any plants they suspect might carry this disease.

New non-native plant pest introductions are detected at a rate of one every 12 days, adding to the burden of the approximately 400 tree pests already established in the United States.  These pests can wreak havoc in homeowners’ yards, and then move through neighborhoods and to nearby forests, causing costly and widespread destruction.
The Nature Conservancy, along with nursery industry partners and scientists, is supporting revamped USDA regulations in its ongoing efforts to block non-native insects and diseases. If implemented, the USDA rules would create a new category called NAPPRA (Not Authorized for Importation Pending Pest Risk Assessment), under which the nation could quickly stop the import of some plants suspected of harboring pests until procedures can be implemented to ensure they are safe.

“Vigilant homeowners and gardeners have been the ones to detect the presence of foreign pests that had previously gone undetected in many areas,” says Faith Campbell, senior policy representative in the Conservancy’s Forest Health Program. “A Massachusetts homeowner, who found a strange-looking bug in her backyard and reported it to the appropriate government agency, helped prevent the Asian long-horned beetle from spreading through the United States.”
Earlier this year, an alert greenhouse owner in Pennsylvania saw odd symptoms on his seedling bay laurel or sweet bay (Latin: Laurus nobilis).  Experts confirmed that the plants were infected by the pathogen that causes “sudden oak death” (Latin: Phytophthora ramorum), a disease that has killed over a million trees in California. This is not the first detection of the pathogen in Pennsylvania or the eastern United States; however, to date, there have been no detections of the pathogen in the forestry environment on the East Coast.
This disease is known to attack several kinds of oaks, magnolias, rhododendrons, and mountain laurel. Bay laurel is a popular herb often grown by gardeners. If homeowners have recently bought bay laurel seedlings or seeds, they should examine these plants carefully.  If the plants have dead or dying leaf tips or the entire plants are dead or dying, those symptoms may be caused by:

  • too much water
  • too little water
  • too much fertilizer
  • chilling or freeze damage
  • infection by the sudden oak death pathogen or some other disease agent

If homeowners rule out all the causes except for the presence of a disease, they should contact their state department of agriculture to find out where to send a sample of it and how it should be packaged to ensure spores cannot escape during shipment. Click here for a state’s chief plant pest regulator.  
Additionally, as homeowners nationwide begin their general yard clean-up and spring gardening, they should be aware that other plants and trees might be carrying a damaging insect or disease. If they notice any insects or a blight or disease they don’t recognize, they can take a photo or specimen of it to their local nurseries or use Internet resources such as this to help them identify it. If they suspect they may have found an invasive pest or pathogen, they should contact the local government department that oversees agriculture or forestry to alert them to the discovery and gain assistance in confirming its identity.
Following are some of the most prevalent invasive insects and diseases, and the regions which are currently threatened by their encroachment.
Non-Native Pest                                   Regions at risk
hemlock woolly adelgid                      Appalachian Mountain region
laurel wilt & ambrosia beetle               coastal regions from South Carolina to Mississippi; Florida
sudden oak death                              coastal regions of California and Oregon
Asian longhorned beetle                     New England; New York and New Jersey; Chicago metropolitan area
More detailed information about and photos of these and other invasive pests can be found at