Defoliators and other fall concerns
By John
Fulton
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[September 14, 2011]
Most fall defoliators come to us as the larval
stage (caterpillars) of a moth. When we talk about controls of the
larvae, the fact that they are larvae of moths or butterflies makes
them susceptible to the use of Bt products such as Thuricide. Other
control options include the standbys such as Sevin, permethrin,
bifenthrin, Othene, malathion and others.
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The way that insects live also dictates some of the control do's
and don'ts.Fall webworms live inside a web all the time. They
actually expand the webbing as they need to have more leaves to
eat. They are usually worst on fruit and nut trees. You can even
clip the nest (and the branch it is around) off the tree and
burn it. I guess this tells you that defoliation caused by the
insect isn't that great a threat to the tree or you wouldn't cut
the branch area off. If you want to spray fall webworms, you
need to get the spray through the web. This may be a little
harder than you think. If you don't have enough pressure, the
spray just runs off the webbing.
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In the case of eastern tent caterpillars, they hatch out of a
common nest. They then leave the nest to feed but generally
return in the evening to congregate in the area of the nest.
They are not covered by webbing, and the time they are
congregated is a great time to spray since they are usually in
one area on the trunk or main branches of trees.
In summary, control of fall defoliators usually isn't
justified from the plant's standpoint. Forested areas have heavy
pressure from this group of insects every year, and the trees
are still thriving. The exception is newly transplanted or
struggling plants. If appearances are important, consider a
control spray.
Other fall items
You may have noticed a very large number of brown needles on
evergreens this fall. That may even have translated to large
piles of needles under your evergreens in the past few weeks,
especially white pines. Not to worry. Evergreens usually keep
only one to four years of needles on the ends of branches, or
one to two years of growth for white pines. Depending on the
weather, the old needles will turn brown and drop off. Usually
this is a gradual process that isn't noticed too much. This year
it happened all at once, mainly due to the hot and dry weather.
If the buds on branch tips are plump and green, odds are your
tree is fine.
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Several calls have come in concerning the proper time to prune or
cut things back. Let's start with some flowers. Keep in mind that
perennials keep building their food reserves until all the leaves
and stems are brown. For peonies and other similar flowers, you want
to wait until all the above-ground plant parts are brown. Then you
can mow them off or cut them at ground level. This same principle
goes for most perennial flowers: Wait until the above-ground parts
are no longer green. For trees and shrubs, pruning is best done at
other times. Flowering shrubs should be done after they flower;
high-sap-flow trees are best done in December; and most other trees
are best done in February. The evergreen trees and shrubs are best
done in late June.
Crabgrass is nearing the end of its life cycle. It comes up from
a seed about the first of April each year, depending on
temperatures. Seed has been viable for several weeks already, and
that is what will make next year's crop. The seedling germination
inhibitors do the best job on the annual grasses, and they can stop
the cycle anytime you apply them. For now, let nature run its course
since you really don't have any options anyway.
[By
JOHN FULTON,
University of Illinois Extension]
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