– By Donald H. Smith, Connecticut State Forester
Since 1995, large numbers of oaks and tanoaks have been dying in the coastal counties of California. Since then, many Oaks. Photo by S Leavitt other types of plants have been found to be infected or associated with this disease, referred to as Sudden Oak Death, Phytophthora ramorum (Pr). Phytophthora ramorum was first seen in 1995 in Mill Valley (Marin County) on tan oak. Since that time, the disease has been confirmed in twelve coastal California counties and in localized areas of Oregon and Washington. There is no known practicable control for forest environs.
The nation has known other Phytophthora species (root rot and potato blight) for a while. With those species, the means of spread has been through rain splash or other mechanical means. This species seems much more dangerous because it can be airborne. That means that spread can be accelerated via severe weather events that may coincide with spore production. Several tree species are vulnerable to this disease – most notably many red and black oaks – especially northern red oak. Many shrubs species such as rhododendron, laurel, and viburnum are also hosts to this disease.
On oak trees, it seems the infected tree may appear healthy to the casual observer and suddenly wilt and die within two to four weeks. In actuality, infected trees will show evidence of infection that is observable by inspection, (cankers, seeping, etc.) for several years before the final collapse.
The disease was found on stock in numerous commercial nurseries in California and eradication efforts were well under way. Unfortunately, it was announced in early March that one of the largest nurseries in the nation has shipped infested camellias to 1700 retail points across the nation. It is suspected that shipments of rhododendron, laurel, and viburnum landscape stock may have already exposed several regions of the country to the disease, as well.
This is just the latest in a series of “leaks” through the containment net that have been discovered, but this is a big one. In northern climes, camellias are indoor plants and the risk of escape to the forest is small. But, for southern states, the risk is significant. At least seven states have now taken the dramatic step of banning any plant material from California from entering their states. The rhododendron and viburnum stock is of concern to Connecticut – especially since it is so widely available through chain department stores (and then there is the issue of mail order sales).
The Connecticut Agricultural Experimental Station is very concerned about this disease and is gearing up to be able to culture samples and identify the species by DNA analysis. 112 addresses in Connecticut received these camellia plants by mail order. The CT Agricultural Experiment Station (CAES) has sent letters to these people and reports good cooperation. They have been taking samples to determine if the plants are infected. To date, CAES has not found any infected plants and none have been disposed of into the environment. Follow ups will be made to all who failed to respond to the letter. CAES has also notified all of Connecticut ‘s 900+ registered nurseries of the danger of SOD and is instituting an inspection/monitoring program for SOD at and around nurseries.
USDA Animal and Plant Health Inspection Service (APHIS) has instituted a quarantine on all SOD host material originating from the state of California . Approximately 1500 nurseries in the state are affected by the quarantine. A statewide survey of nurseries has found two nurseries in California with infected host plants and an additional 11 have tested positive for the molecular test for the organism. As part of their comprehensive response plan, APHIS has set up a dedicated hotline for SOD issues to be available immediately at (888) 703-4457.
SOD has now been confirmed on nursery stock in Florida , Georgia , Alabama , Virginia and Maryland. To date, it has not been determined if infected plants have been planted out and no infestation of woodland plants has been found.
That’s worth repeating: Sudden Oak Death has never been found in the wild in the eastern United States. To date, it has been found only on nursery stock in nurseries.
I strongly advise anyone reading this article to go to the APHIS web site for this disease http://www.aphis.usda.gov/ppq/ispm/sod/ and familiarize themselves with it. A web search for Sudden Oak Death will yield much information – most of it from the west coast. This is an important emerging issue and you can expect that there will be new material posted (especially on the APHIS site) almost daily. It would behoove all of us to become as knowledgeable about Sudden Oak Death as possible – and to be observant. You should report any suspected cases of infected trees to the Entomology Dept. at the Connecticut Agricultural Experiment Station in New Haven (203-974-8606).
So, does this mean the demise of oak in eastern US forests is imminent?
It is true that researchers and foresters are concerned that sudden oak death has the potential to have a catastrophic impact similar to that of Dutch Elm Disease or Chestnut Blight (i.e., elimination of oak from the forest within just a few decades.) If this were to happen, the economic impact would be staggering, but the economic impact would be dwarfed by the ecological impact. However, it is much too early to push the panic button and, certainly, NO ONE should be rushing to liquidate the oak from their forests.
The facts are:
- SOD has been on the west coast of the United States for 12 years.
- West coast nurseries have been shipping stock throughout the country for those 12 years.
- This is the first time SOD has been found in the east – and only in nurseries.
- So, it is more than possible that the east coast has repeatedly been exposed to SOD throughout the past decade or so. If that’s the case – and SOD has not appeared in the wild – one might take some comfort in the hope that the environmental conditions and species mix in the east is inhospitable to SOD. It may not be able to gain a foothold here. Only time will tell.
Advisory prepared by:
Donald H. Smith, Connecticut State Forester
CT DEP Forestry
79 Elm Street
Hartford , CT 06106
CONNECTICUT FOREST FACTS:
There are 819,628,631 trees in Connecticut’s forests. (9.9% State, 6.8% City, 82.8% Private)
Of those, 145,170,522 are of species known to be susceptible to SOD. (17.7% of all trees)
There are no figures on the number of susceptible trees in yards or on city streets.
(Source: USDA Forest Service, Forest Inventory and Analysis)
This article originally appeared in the June 2004ECFLA/WDLT Newsletter.