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Evaluation of Propiconazole Operational Treatments of Oaks for Oak Wilt Control Jordan Eggers, Jennifer Juzwik, Shawn Bernick, and Lori Mordaunt. 2005. USDA Forest Service
Oaks commercially treated with propiconazole on 29 sites in Minnesota in 1998 were evaluated for efficacy in controlling oak wilt. Root graft spread occurred in 39 percent of preventively treated red oaks over 5 years; spread in white oaks occurred only once. Propiconazole generally prevented further disease symptom development in white oaks. [read the report]
Efficacy of Alamo for prophylactic and therapeutic treatment of oak wilt in red oaks K. Ward, J. Juzwik, and S. Bernick. 2004. USDA Forest Service
An experiment (prophylactic study) to determine the efficacy of Alamo in preventing spread of C. fagacearum through grafted roots of oak wilt-affected and of apparently healthy red oaks was initiated in eight locations in east-central and southeastern Minnesota in Jul 2002. Paired treatment plots were established in separate oak wilt centers within a larger forest stand of red oak species in each location. [read the report]
Root Flare and Root
Injection Techniques E.
S. Kondo. 1978. Proceedings of the Symposium on Systemic Chemical
Treatments. Michigan State University. Braun-Brumfield Inc.
This American elm study
demonstrated better distribution of systemic fungicides to the upper
canopy could be attained by injection into the root flares versus
the trunk. It also noted wounds on the trunk take longer to seal
and require closer spacing than an equivalent number of injection
sites on root flares.
Propiconazole as a
Treatment for Oak Wilt in Quercus rubra and Q. ellipsoidalis
N.K. Osterbauer, and D.W. French.
Journal of Arboriculture vol. 18 no. 5: 221-226.
Red and pin oak were treated
preventively with Alamo in 1989 and 1990 using a root flare macro-injection
technique, while control trees under similar disease pressure were
left untreated. Fifteen of 49 trees injected in 1989 wilted, in
comparison to 18 of 50 control trees. In 1990, however, 9 of 88
treated trees wilted as compared to 42 of 80 controls. They also
reported the frequency of wilting in treated trees increased with
time after injection. A separate procedure showed propiconazole
was found in treated trees up to 12 months after injection but was
not detected in samples taken 20 or 23 months after injection. This
degradation of the fungicide prompted them to suggest treating trees
once every two years. They concluded treatment of oak wilt with
Alamo requires optimization, but this fungicide is an effective
preventive treatment to oak wilt in red and pin oak, especially
when used within the context of a broad management plan.
Intravascular injection
with propiconazole in live oak for oak wilt control. D.N. Appel
and T. Kurdyla. Plant Disease vol. 76 No. 11: 1120-1124.
Propiconazole injection
into mature live oaks at high risk of root graft infection resulted
in lower crown loss and mortality compared with untreated controls.
In some cases nearly complete protection for up to 36 months after
treatment was achieved. The authors reported, however, that propiconazole
was not an impervious barrier to root graft infection because some
treated trees became infected. Despite this, they recommended use
of Alamo as part of a broad management program.
Recognition in Live
Oak 1986.
D.N. Appel. Journal of Arboriculture vol. 12 no. 9: 213-218.
Since the initial discovery
of Ceratocystis fagacearum near Dallas in 1961, oak wilt
has become the most serious disease of live oaks in Texas. The response
of live oak to the disease, however, is inconsistent as some trees
die within a few weeks while others deteriorate slowly over several
years. Foliar symptoms include veinal necrosis, tipburn, interveinal
chlorosis, or combinations of these. Fungal spore mats are not found
in live oaks, but their presence in Spanish oaks provides inoculum
for overland transmission of the disease. Appel noted traditional
methods for oak wilt management are not practical in some Texas
locations due to rocky soils and large sizes of infection centers.
Thus new methods for control must be explored.
Use of Alamo as a
preventive and therapeutic treatment of oak wilt.
Ongoing research at Rainbow Treecare
Alamo is an effective
therapeutic and preventive treatment of oak wilt in the white oak
family. The natural resistance of white oaks to the pathogen coupled
with the fungicidal properties of Alamo appears to be a potent combination
to keep oak wilt suppressed. Alamo shows the most promise as a preventive
treatment in high-value red oaks that are asymptomatic but at high
risk of infection. Ongoing studies are slated to be published at
the end of this multi-year project.
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