Webbing Out

The North Country's latest problem is spreading like wild fire

Story by Chris Benini

Look out onto the horizon and see the mountain skyline covered by majestic maple and cherry trees glimmering in the sunlight. Now just imagine those trees covered by silky spider-like webs. The scenery is not as majestic anymore, is it?

Those webs that you see blocking the mountain scenery are Malacosoma disstria Hubner, or forest tent caterpillars. Forest tent caterpillars are one group of three different insect species that are affecting trees in New York, according to Plattsburgh State University College (PSUC) environmental science professor Kenneth Adams. The three species are forest tent caterpillars, eastern tent caterpillars, and gypsy moths.

"All three of them are a concern," Adams said. "Gypsy moths are the biggest concern because they are not native, unlike the eastern and forest tent caterpillars."

The tent caterpillar problem has gradually spread to northern New York, and could soon spread even further northeast.

"When I used to travel to Vermont to go skiing I used to see the tent caterpillars all the time during the trip in Connecticut and even a few in Massachusetts," said Joseph Ricciardi. "However, through the years I noticed the webs were spreading more and more north. Now they are as north as southern Vermont."

The forest tent caterpillar destroys the leaves on trees, as well as create large web-like nests all over the branches. The tent caterpillar is mostly found on hawthorne, maple, cherry, peach, pear, oak, and plum trees. According to PSUC environmental science professor Dennis Aprill, its favorite tree is the cherry.

This pest population is a problem. The caterpillars can be seen all over trees, plants, bridges, and sidewalks. Whether alive or dead on bridges or sidewalks, they get in the way of the scenery. Most importantly they have the potential to destroy trees when they eat the leaves.

"The leaves are important to the tree because they act as a form of defense," said Dr. Tim Mihuc, professor with the Environmental Science program and PSUC. "Without the leaves, the tree can become vulnerable to diseases that can easily kill the tree."

The leaves of a tree can be compared to the white blood cells of a human being. The white blood cells in humans fight off sickness and disease, but without them humans can die from the simplest sicknesses. The same goes for the leaves on trees. Trees can die from the least lethal diseases and sicknesses for this reason.

"Once they are a moth they can easily relocate and can travel a good distance before settling down at another tree."

A forest tent caterpillar can lay anywhere from 150 to 400 eggs. The problem augments when the larvae is fully grown. Insecticide is usually harmless against the adult forest tent caterpillar.

Also, according to Mihuc, the adult larvae are able to fly, which allows the caterpillars to migrate easily.

"The adult larvae eventually become moths," said Adams. "Once they are a moth they can easily relocate and can travel a good distance before settling down at another tree."

The moths travel by wind. The wind blows these moths northward so the problem continues to spread north.

Outbreaks usually last about three years and then diminish because of predators and lack of food sources. New outbreaks usually occur every 10 to 20 years.

"The outbreaks are cyclic," said Adams. "The outbreaks are sporadic and usually start breaking out in mid-May to June. You never know where and what year they are going to break out so a lot of the time it comes to be a surprise."

There have been several predators that have helped control the population and the outbreaks. The first natural predators of the caterpillars are parasites, such as braconids, ichneumonids and chalcid wasps. Various diseases also help control the population of the caterpillars by killing some of them off.

The key to controlling the tent caterpillar is getting rid of them early. If you wait too long, insecticides are harmless and do nothing against the larvae. Removal or destruction is the best way to get rid of the caterpillars.

They can only be removed with insecticide that contains Bacillus thuringiensis var kurstaki (bt), which is a genetically modified strain of bacterium. The caterpillar ingests the bacterium, which acts as a poison. It causes a general infection, and results in the death of the caterpillar. The bacterium is not considered harmful to birds and other animals. While the full larvae can not be destroyed with insecticides, the young larvae can. There are a few other insecticides that would work against the forest tent caterpillar. These are carbaryl, methoxychlor and malathion.

The tent caterpillar is one of those problems where if you don't take care of the problem right away it will continue to grow. As the expression goes, you can pay a little now or you can pay a lot later.

Have you ever seen the tents of the forest tent caterpillar? If so, where?

The use of insecticides does destroy the larvae of insects. In the long run, however, insecticides may be doing more harm than good. What about the insecticides that don't kill the bugs? What about the insecticide that drips down into the roots of the ground? Some insecticide contains the chemical DDT (In America is it banned). Some claim banning the use of DDT in African countries, in particular, for use to combat mosquito populations, has increased the number of deaths by malaria in human beings. Malaria is a disease spread by mosquitoes. Malaria is a disease spread by mosquitoes, and it is a serious problem in African areas, among other warmer climate areas of the world.

As always the best way to contain something is to stop it before it starts. According to Mihuc, the best way way to stop forest tent caterpillars is to band the trees so that the caterpillars can't get to the roots of the tree. Once it get to the base of the tree, to the foundation, it can destroy the tree.

Sometimes you can't always get rid of the problem before it starts though. If you aren't able to stop the caterpillars before they start attacking the tree it is not the end of the world.

"I would recommend insecticides," said Adams. "What I would recommend though is Bt."

Bt is a bacteria that you can spray aerially onto trees and plants, killing off the caterpillars. The bacteria is only hazardous when ingested. The idea of the bacteria is to stay on the leaves so when the caterpillar eats the leaf, the bacteria is ingested; therefore, killing the caterpillar.