A new invasive species on the landscape

Not a Phytophthora, but still -beware!

Gnome Management in the Garden

'PC' disease devastating African palm plantations

Another destructive Phytophthora disease (P. palmivora) attacking oil palms in the tropics:

http://seattletimes.nwsource.com/html/nationworld/2011597413_palmoil14.html

Nursery news

A Clark County, WA production nursery was found to have P. ramorum infested soil on 3/10/10. A delimiting survey was conducted. This nursery was also found P. ramorum positive in 2008 and 2009.

From the April COMTF newsletter

Update on conifer hosts of P. ramorum in the UK

This is of interest to Washington because Douglas-fir and western hemlock are important forest species here:

"The 2009 UK sites where Japanese larch (Larix kaempferi) were found with Phytophthora ramorum foliar and stem infections, yet not in close proximity to Rhododendron ponticum, have more recently been found to have a range of other woodland and commercial plantation species affected by the pathogen (primarily bole canker infections). Tests conducted by UK Forest Research have shown that the Japanese larch foliage strongly supports P. ramorum sporulation, possibly even to the extent seen on California bay laurel (Umbellularia californica). Foliar infections on larch appear to be able to generate hundreds and even thousands of sporangia on a single infected needle. This inoculum load high in the crowns of affected Japanese larch has likely lead to widespread local infection on the foliage and boles of nearby susceptible tree and understory species, as well as caused bole infections on the larch.
Affected species of the larch understory include beech (Fagus sylvatica), sweet chestnut (Castanea sativa), and oak species (Quercus spp), all of which are known to suffer from bole cankers, as well as birch (Betula pendula), which has not previously been found as a bole host. Over the past 6 months a number of conifer species have also emerged as bole hosts, including western hemlock (Tsuga heterophylla), Port Orford cedar (Chamaecyparis lawsoniana), and Douglas-fir (Pseudotsuga menziesii); however, only one or two individuals of these conifer hosts have so far been confirmed P. ramorum positive. Western hemlock has also been confirmed as a foliar host of the pathogen.
This upsurge in P. ramorum and the many new hosts that are emerging is strongly correlated with proximity to larch exhibiting crown dieback. The number of sites where this is known to be occurring is limited. Control measures are now underway, which includes felling the larch to prevent further sporulation following budburst in the spring. For more information and details of symptoms, go to http://www.forestry.gov.uk/forestry/INFD-7XVEWH and http://www.forestry.gov.uk/website/forestry.nsf/byunique/infd-5vfmzu "

from the April COMTF newsletter

HERB GARDENING ENTHUSIASTS CAN HELP DETECT INVASIVE PLANT DISEASE

HERB GARDENING ENTHUSIASTS CAN HELP DETECT
INVASIVE PLANT DISEASE

Since destructive pests are often impossible to control once established, early detection is key to stopping their spread


ARLINGTON, VA—April 7, 2010 – Until proposed revisions to the regulations governing international plant trade, currently under review, are approved by the U.S. Department of Agriculture (USDA), homeowners can play an important role in detection and reporting of invasive insects and diseases. 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 these revamped 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. A state’s chief plant pest regulator can be found at www.nationalplantboard.org/member/index.html.

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 http://invasivepests.org/photosmore.html 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 http://www.invasivepests.org/.

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The Nature Conservancy is a leading conservation organization working around the world to protect ecologically important lands and waters for nature and people. The Conservancy and its more than one million members have been responsible for the protection of more than 18 million acres in the United States and have helped preserve more than 117 million acres in Latin America, the Caribbean, Asia and the Pacific. Visit us on the Web at http://www.nature.org/.

The Continental Dialogue on Non-Native Forest Insects and Diseases is a group of organizations and individuals that cultivates and catalyzes collaborative action among diverse interests to abate the threat to North American forests from non-native insects and diseases.

Phytophthora ramorum has been detected in Pennsylvania on Bay (Laurus nobilis)

Another pathway by which P. ramorum can be introduced is described below:

"On Feb. 18, 2010 the Penn State Plant Disease Clinic received a sample of Laurus nobilis, known commonly as bay laurel, true laurel, sweet bay,laurel tree, Grecian laurel, or bay tree. Some people use its leaves in cooking. The tips of the leaves submitted were dead or dying and it was reported by the grower that 95% of well rooted plants in 12 or so flats exhibited the symptoms. The United States Department of Agriculture-Animal Plant Health Inspection Service (USDA-APHIS) confirmed the plants to be infected with Phytophthora ramorum, the Sudden Oak Death pathogen known to occur in trees and shrubs on the west coast of the U.S. and in Europe. The sample came from a commercial, primarily wholesale, greenhouse in eastern Pennsylvania. Phytophthora ramorum can infect many important ornamental trees and shrubs under the right conditions. There is a great deal of concern that this fungus-like organism could cause significant economic damage to eastern forests and landscapes if not excluded from the region.The’ bay laurel’ submitted was not Umbelluiaria californica, the California bay or California bay laurel that grows on the west coast and is a major host of Phytophthora ramorum that then spreads to oaks. However, Laurus nobilis is known to be a host of Ph. ramorum.The actual source of the Ph. ramorum in Pennsylvania is still under investigation and is very much in question. The infected plants had been grown in Pennsylvania from seed obtained from a source in California. As yet, there are no known cases of Ph. ramorum being seedborne. I learned recently that the ‘seed’ is sometimes received not as cleaned seed but as seed still in the drupe (fruit). That raises the possibility that the pathogen may have been in parts of the fruit other than the actual seed. It is also possible that the pathogen was infecting other plants in the greenhouse and spread to the Laurus. APHIS is doing ‘trace backward’ investigations to determine where the pathogen may have come from and‘trace forwards’ to determine whether various plants sold by the Pennsylvania greenhouse are carrying the pathogen.

Phytophthora ramorum has, to date, been excluded from the eastern U.S. but this occurrence may indicate that the plant pathogen is now or will soon be in the region from multiple sources. In 2009, Laurus nobilis was named as the Herb of the Year by the International Herb Association (IHA). Laurus nobilis seed can be purchased from a number of sources including through Amazon.com. Web information indicates that the seed is difficult to germinate. It is my understanding that people have been encouraged to grow this plant and that it has been used in various Master Gardener projects. If seed or tissue associated with seed is actually the source of the pathogen, it is possible that Phytophthora ramorum has arrived in the east with seed purchased bybackyard gardeners, etc. Where is the ‘failed to germinate’ material discarded? Where are plants with dying leaf tips discarded? The photo below (and attached) is of the actual sample as it arrived at Penn State. It is not very impressive. If you are presented with Laurus nobilis plants with dead or dying leaf tips or entire plants dead or dying…those symptoms may be caused by:

too much water

too little water

too much fertilizer

chilling or freeze damage

Phytophthora ramorum infection

There is much we don’t know about the circumstances surrounding this occurrence and, therefore, we can’t release specifics such as the name of the greenhouse. But, the information above can be used in newsletters,training sessions, news releases, grower presentations, etc."

Gary W. Moorman, Prof. of Plant Pathology

The Pennsylvania State University, Department of Plant Pathology