Disease Research
Bacterial Leaf Scorch
Bacterial leaf scorch caused by Xylella fastidiosa is a major
problem in many parts of the US. Water stress has been implicated
in the occurrence of this disease because symptoms typically appear
when conditions become dry. Growth regulation with Cambistat can
enhance the water status of leaves through stomatal aperture control
(abscisic acid), increased leaf thickness, and/or increased leaf
hairs. Thus it makes sense to investigate whether growth regulation
can influence water relations enough to minimize the level of scorch
observed.
Preliminary treatments with paclobutrazol were performed by Bruce
Freadrich with the Bartlett Tree Research Lab in Charlotte, NC on
red oaks and sycamores. With limited replications, Bruce found a
three year reduction in scorch symptoms on treated red oaks, but
similar effects were not seen on sycamores. This data has prompted
further inquiry, and Rainbow, Bartlett, and the New Jersey Forest
Service are collaborating on a much larger field trial with red
and pin oaks. In addition, Dr John Hartman at the University of
Kentucky is investigating the effects of Cambistat on Bacterial
Leaf Scorch in Kentucky.
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The
red oak on the left is infected with Bacterial Leaf Scorch (Xyllella
fastidiosa). In one limited test, this tree was shown to
recover from this disease for three consecutive years after
being treated with a single dose of Cambistat. More extensive
testing is underway.
Note: A similar test on sycamore did not produce any relief
from this disease.
Research and Photographs courtesy of Bartlett
Tree Research Labs |
 Prior
to treatment |
2nd
Year after treatment
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 Ongoing
Projects
There are many published research papers
that refer to the effects of growth regulation with paclobutrazol,
but relatively few that pertain to situations a tree care professional
can use. From what we have seen in the literature, we believe growth
regulation with Cambistat may provide even more uses for arborists.
See our list of ongoing
research projects to see what we are working on for the future.
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