Phytophthora ramorum (P. ramorum) is the organism that causes Sudden Oak Death (SOD), a serious disease of oaks and other woody and herbaceous plants. Thousands of tan oaks and other oak species have been killed by this disease in California since the mid 1990s. Mortality has also been reported in arbutus, beech, rhododendron, Vaccinium and Viburnum. These plants and others may also exhibit symptoms such as dieback, wilting, and lesions and may play an important role in the spread of the pathogen, both by natural movement in the environment and by the movement of infected plant material via the nursery trade.
SOD has caused great economic hardship for nursery and landscape businesses in those regions where it has become established. For example, in 2001, Canada closed its markets to most plant crops from the states of Oregon and California. Without reopened market access, Oregon nurseries alone faced losses in sales to Canada of $15 to $20 million.
A pest risk assessment was completed by the Plant Health Risk Assessment Unit of the Canadian Food Inspection Agency (CFIA) in March 2002 and was updated in June 2005. This assessment concluded that if P. ramorum were introduced, the disease could have a significant impact on Canada's forest resources and landscape. The pest risk assessment indicates that plants, plant parts, soil and growing media play a role in the movement and dispersal of P. ramorum. Laboratory studies have demonstrated that the disease has the capacity to spread to many oak species, including those growing in Canada. Oak and other related species are a significant component in the Great Lakes-St. Lawrence and Acadian Forest Regions of Canada, are valuable as shade trees in urban areas and parks and are a critical habitat providing food and shelter for wildlife. Wood from oak trees is an important resource for the production of furniture and flooring for use both in Canada and overseas. Rhododendrons, azaleas, camellias, and other ornamental hosts are important landscape plants in Canada and represent a significant portion of the total of the horticulture crops produced. The CFIA Pest Risk Assessment identifies rhododendron, including azalea, Pieris, Viburnum, and Kalmia, as high-risk nursery host plants. Other SOD host species are significant components of forest ecosystems, of commercial forestry seedling nurseries, of small fruit and nut production, and of the lumber industry (both domestic and export).
On March 11, 2004, the United States Department of Agriculture (USDA) informed the CFIA that camellia plants infected with SOD had been found at a nursery in California. The CFIA immediately implemented emergency quarantine measures to prevent the entry of any shipments of plants known to be susceptible to SOD from California. The CFIA also took immediate action to prevent the spread of the disease in Canada, including the quarantine and destruction of imported plants and the sampling of plant material from Canadian nurseries and garden centres that imported and/or received plants from the affected nursery in California.
On March 31, 2004, the CFIA confirmed the presence of P. ramorum in California-origin plant material at nine retail garden centres in the south coastal area of British Columbia. Although this represents a small percentage of all garden centres in British Columbia, if P. ramorum were allowed to spread unimpeded, it would have devastating economic consequences on the entire British Columbia landscape and nursery industry. The value of the nursery and floriculture sectors of British Columbia is estimated at $500 million, with approximately $170 million in export sales to the United States. Additionally, there could be impacts on Canada's conifer log exports to Asian countries. The value of export sales of conifer logs to these markets in 2005 was more than $150 million.
From April to June 2004, a public recall in British Columbia involving the CFIA and the British Columbia Landscape and Nursery Association (BCLNA) resulted in the recovery of approximately 1 400 camellias and identified ten homeowners with infected plants. National survey activities identified an additional five nurseries and three homeowners with infected plants in south coastal British Columbia. Plants that tested positive for P. ramorum and any adjacent host plants were also destroyed.
In 2005, the National (detection) Survey, conducted from June to September, focused on nurseries that had imported host material from California, Oregon and the European Union within the previous six years. At each of these sites, up to 30 samples from plants showing symptoms consistent with P. ramorum infection were collected and submitted for analysis to the CFIA Centre for Plant Quarantine Pests in Ottawa. P. ramorum was not detected during the National Survey, but two sites in British Columbia were found to be positive during the trace-back and trace-forward activities in 2005.
In cases where plants and plant material are found to be infected, the CFIA has issued Notices to affected individuals to eradicate infected plants and plant materials. The intent of the CFIA eradication actions is to prevent the spread of SOD to other areas of the province and Canada and to eventually eliminate the disease in the British Columbia south coastal area.
No comments:
Post a Comment