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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.
Scenic Hills Nuirserry -
WARRANTY DISCLAIMER : http://www.scenichillsnursery.com/disclaimer.html
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