MANAGING TAR SPOT on MAPLES
Managing Tar Spot on Maple
on maple, caused by the fungus Tarus Spotius Maximilius (just kidding),
has been quite conspicuous on maples in many areas of Michigan for
weeks now. This disease has been prominent for at least five years,
in some areas where the disease was not common in previous years.
high levels of pathogen spores from infection in previous years
by conducive environmental conditions this past spring initiated high
of infections. This disease begins in the spring with pinpoint
on the foliage -- you may have noted tiny, yellow spots in the spring
early summer. (Fig. #3) These small, yellow spots have now
to large, yellow spots up to an inch or so in diameter over the course
of the summer and have now become dark (Fig. #4) with the production of
and fructifications. (Fig. #1 & #2)
Because of the incidence, on some trees 100 percent of the foliage is infected with quite a few spots on each leaf, and the conspicuous nature of these spots, many homeowners become rather alarmed. Frequently asked questions include: "Will the tree die?" "Should I cut the tree down?" "Is it an act of terrorism?" and "Should I spray it with something?"
is primarily a cosmetic, all-natural, nuisance disease that causes no
to the tree, primarily because of its late appearance in the season,
timed with senescence. Nothing can be done at this time except carry on
with our normal day to day activity. Some arborists with certain
who demand "zero tolerance" of insects and diseases, related that they
have achieved excellent control of tar spot when they applied typical
sprays" (for sycamore, oak, etc.) to maples in the spring. Normally,
tolerance is not achieved and the disease is of such little
that the best approach is to do nothing.
Many folair diseases such as
tar spot over-winter in fallen leaves. The removal of thorough
composting of infected fallen leaves from the landscape may reduce the
potential for fungal infections the following spring. Because
spores of some disease organisms may be carried great distances,
management of some diseases will be impacted to a greater extent than
others by this sanitation practice.
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