WESTON, Conn. -- In a fight, most would assume the bigger man would win. This is not the case in the battle between huge trees and bugs that can only be seen with a magnifying glass.
Take the hemlock woolly adelgid, an invasive insect that sucks the sap from hemlock trees, at the same time exuding a poison that inhibits new growth by the tree.
"The tree sends out auxines or plant growth hormones to buds to grow leaves," according to arborist Bill McKinney . "As the leaves are established they send out auxins to the roots to grow. When this is disrupted by the toxins from the adelgid, there is no growth, and in four to 10 years the tree dies."
"Anytime we lose a plant, we lose 30 species that are dependent on it," he said.
McKinney, chief invasives officer at the Aspetuck Land Trust and owner of Habitat Restoration Services , said the hemlock woolly adelgid came to Connecticut in 1985 and, based on its DNA, has been traced to Northern Japan. It arrived in Virginia in the 1950s, he said, and keeps spreading through the Appalachians. "It's very difficult to do something about it in a forest," he said.
The trees have to be treated one by one. Horticultural oil or low-impact insecticidal soap can be used to kill the eggs and adults of the insect, but it doesn't prevent more from affecting the tree. Safari and Merit 75 insecticides can be absorbed into the tree's vascular system and prevent the attack from the woolly adelgid.
"It makes insects very unhappy when they bite into it," said McKinney.
To see if there are woolly adelgids on a hemlock tree, look closely at the first five inches of a branch, between the needles. If there is a white fluffy matter, that's probably the eggs of a woolly adelgid, McKinney said. The insect has two generations per year, so the eggs would be found in April or July.
Hemlock's have been around for thousands of years. "Trees are such a great resource to the world. They absorb carbon faster than any other area or element," said McKinney.
There are two kinds of pests, said McKinney. Some have been here for thousands of years, and the trees infected by them are typically weakened already. The other pests are the invasive insects that have been showing up in recent years.
The emerald ash borer, an invasive insect spotted as close as Saugerties, N.Y., is devastating the ash population by digging into the tree and making S-turn tunnels that disrupt the tree's vascular system. It goes all the way around the tree, girdling it, so no nutrients or water can go up or down the tree. Millions of trees have been killed, McKinney said. The insect first appeared in Michigan in 2002 and was shipped to the East Coast in wood. Again, the only prevention is to infuse the trees with a systemic insecticide on a tree-by-tree basis.
Blue square traps have been hung around Easton to determine whether emerald ash borers are in the area. They have not been found in Easton yet.
The asian longhorned beetle, another invasive species first spotted in 1996 in Brooklyn, caused 30,000 trees to be taken down in Worcester, Mass. The insect comes from China, where it has killed more than 30 million trees, said McKinney. It burrows a hole into the bark, disrupting the vascular system and causing the tree to starve and die.
There are 40 other bugs that hurt trees, said McKinney, and hundreds of others that live with trees.
"Few are not bad for the tree. Few are good for trees--they raise the trees' defense mechanisms. It's better to have a little stress with a few bugs," said McKinney.
Spraying a tree with insecticides is a "complex process" that takes careful planning, McKinney said. Spraying to eliminate "bad" mites can also kill predator mites, which actually slow the population growth of "bad" mites.
McKinney has a booklet for homeowners on how to stop invasive plants and suggestions for replacing them with native plants. To obtain a copy, email firstname.lastname@example.org .
Do you have invasive insects in your yard? What do you do about them? Leave your tips below.
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