Caterpillar Outbreak
The Forest Tent Caterpillar is a native caterpillar that has been damaging our forests in the Catskills for the last few years. Forest Tent Caterpillars (FTC) emerge when the leaves come out in spring (because it’s a defoliator, which means it eats leaves). Entire mountainsides have been defoliated in the past couple of years and houses, decks and cars were covered by them. Growing a second set of leaves stresses the tree because it must reallocate its energy to make it happen. You probably noticed that the second set of leaves last year where smaller and lighter in color. Trees are left with less vigor to ward off other pests, disease, and environmental changes such as drought, wind storms and flooding.
FTC are black, hairy, and have a keyhole pattern running down their back accompanied by blue and white mottling. FTC emerge from their egg masses in spring as larvae or caterpillars, approximately 1/8 inch long. They can grow to be about 2 inches at maturity. They feed on the leaves of broadleaf trees such as sugar maple, aspen, oak, cherry, basswood, and ash. Ironically, FTC don’t make tents, but instead form huge congregations on the branches or base of trees. About 5 to 6 weeks after emergence, they make a yellow cocoon in the crevice of bark, a folded leaf or under a porch or mailbox, where 10 days later they emerge as a brown moth.
FTC are often confused with Eastern Tent Caterpillars (ETC). The ETC does make tents in the crotch of trees. They mostly feed on fruit trees such as cherry, apple, and pear. These caterpillars are distinct from FTC in that they have a white stripe running down their backs with blue and black spots. Their egg masses are very similar to FTC masses. Both are cylindrical, but FTC egg masses are more squared at the ends. Gypsy moths are also confused with FTC. They do not make tents either, but can be easily identified by their long hair and spots. The spots consist of 2 parallel rows running down their backs. The first 3 sets are red and the last three are blue.
How can you know if you will have caterpillars again this year? And if so, what should you do? First, inventory your property for any FTC. The New York State Department of Environmental Conservation (NYS DEC) has posted a suggested protocol for helping residents predict FTC defoliation at the following DEC website: http://www.dec.state.ny.us/website/dlf/privland/forprot/health/caterpillar/ftcprot2005.pdf. If your property has an abundance of egg masses that will hatch thousands of caterpillars, you may want to consider taking control measures.
Is the cost of reducing caterpillar numbers is less than the benefits the trees provide for you? If you have a valuable timber crop, maple-sugar-bush, or the site of them is too unbearable, you might want to take control measures. There are two different types of pesticides available: chemical and biological. The chemical ones such as “Sevin” kills the insect by contact. However, it also affects beneficial insects such as honey bees. The latter, called BTK is biological and is found naturally as a living microbe, or organism in soil and plants. It only affects caterpillar larvae. Aerial spraying of pesticides can cost anywhere from $35-$55 per acre. A licensed pesticide applicator should be consulted, and a list of these applicators can be found at the following NYS DEC website: http://www.dec.state.ny.us/website/dshmdata/pesticid/busweb.pdf.
Other control measures that do not include spraying are using sticky tape (farm stores sell very wide bands of flypaper for use inside barns), or burlap coated with a sticky substance on the main stem of the tree. As the insect crawls down the tree or branch it becomes stuck to the wrap. Removing the individual egg masses by hand is another method, but is time consuming and difficult to do, since most of them are out of reach in the small upper branches.
The cheapest and surest way to remove FTC may be to let nature run its course. These
outbreaks typically last three years, rarely longer, but sometimes they last
up to 6 years. FTC outbreaks come in cycles of 10 years or so, and
our forests have endured them for hundreds of years. Eventually, natural
predators, low food accessibility, and/or weather kills them. Natural
predators include birds such as tanagers, black and yellow bellied cuckoos,
mice, chipmunks, wasps, and friendly flies. Extreme cold and warm temperatures
may also bail us out of caterpillar damage.
Call The Catskill Forest Association, Inc., a not-for profit, membership
organization at (845) 586-3054 for more information.
Caterpillar damage on a mountainside. Defoliation
usually occurs in bands or patches since FTC usually target sugar maples
first.
FTC and ETC are both found around tree branches no
thicker than the diameter of a pencil. FTC egg masses have squared
edges in comparison to the tapered masses of ETC. Notice the difference
in the photo between new and old egg masses. The more new ones you
have on your property, the more caterpillars will be munching your leaves
this spring!
Newly hatched FTC larvae. They are approximately
1/8 inch long, and feed in the early part of the season on the upper canopy
of a tree. As the season progresses and they run out of leaves to eat,
they spin a silk thread and parachute down where they swing to another tree. This
is called ballooning.