|SUDDEN OAK DEATH
Sudden Oak Death is caused by a funguslike pathogen recently identified by scientists and named Phytophthora ramorum. Since its appearance in 1995, Sudden Oak Death (SOD) has killed hundreds of thousands of coast live oak, black oak, tanoak and Shreve oak in northern California. It can also infect leaves and branches of rhododendron, buckeye, madrone, manzanita, bigleaf maple, bay laurel, and evergreen huckleberry. Two species of East Coast oaks, northern red oak and southern red oak, are also susceptible to P. ramorum..
SYMPTOMS: Bleeding or oozing of a dark reddish-brown thick sap is the first symptom to appear on true oaks. It typically occurs on the lower portion of tree trunks but has been found as high as 60 feet. On tanoak, the first symptom is drooping of new growth. Beetles attack weakened trees. Wood decaying fungi are seen in the later stages of decline on the trunks of oaks and tanoaks.
PREVENTION: Preventing the movement of infected leaves, wood and soil will be critical to slowing the spread of the fungus to other oak woodlands, such as the Sierra Nevada. Plant material and soil should not be moved from coastal areas. Any wood already moved elsewhere should be burned. Visitors to coastal forests should clean their tires, shoes and animals' feet thoroughly before leaving the area. Construction workers should wash equipment well and should not move dirt from one place to another. Ornamental plants, such as rhododendrons, that may be hosts should not be moved from infected counties unless certified to be free of the pathogen.
DISTRIBUTION: Sudden oak death has been found as far north in the state as Humboldt County and as far south as Big Sur in Monterey County. To date, SOD has been identified in 14 California counties: Alameda, Contra Costa, Humboldt, Lake, Marin, Monterey, Napa, San Francisco, San Mateo, Santa, Clara, Santa Cruz, Sonoma, Mendocino. Solano. In Oregon, Sudden Oak Death has been confirmed in Brookings, a small town in the southwestern corner of the state.
TREATMENT: Phosphite controls many species of Phytophthora, including Phytophthora ramorum and Phytophthora cinnamomi. Injecting a tree with phosphite provides three to five years protection from Phytophthora dieback. In contrast, spraying with phosphite provides protection for only one and possibly to two years. Because it only provides temporary protection, treatment needs to be ongoing.
The solution for spraying is much weaker than for injecting and contains a small amount of wetting agent or penetrant to hold the droplets on the surface until they are absorbed. Phosphite spraying should not be conducted along creeks and streams. The penetrant used is toxic and it can cause adverse effects on some amphibious animals. Phosphite is not toxic to people or animals and its toxicity has been compared to table salt. There is a very low pollution risk associated with phosphite.
A DISEASE: Phytophthora cinnamomi can produce identical symptoms in oak trees. Scientists differentiate this fungus from Sudden Oak Death by using a lab test. P. cinnamomi can infect about 1,000 plant species. It can kill oaks, rhododendrons and other nursery plans and agricultural crops including almond, walnut and avocado trees.
More About Sudden Oak Death:
Callifornia Oak Mortality Task Force http://nature.berkeley.edu/comtf/
Forest Pathology and Micology Labratory http://nature.berkeley.edu/garbelotto/
U.S. Department of Agriculture http://www.na.fs.fed.us/spfo/pubs/pest_al/sodeast/sodeast.htm
Phosphite Treatment http://www.oakwilt.com/s_o_d.html
Potassiun Phosphite " VITAL" http://www.oakwilt.com/vital.html
Photo - Copyright - Chemjet Trading Pty Ltd., Australia.
A typical application of the Chemjet® injector
Disclaimer: This article may contain pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator’s responsibility, by law, to read and follow all current label directions for the specific pesticide being used. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The Writer assumes no liability resulting from the use of these recommendations. The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement is implied.
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