By: Paul Markworth, Board Certified Master Arborist WI-0153B
Invasive pests continue to move into new areas of the United States, causing widespread damage despite billions of dollars spent in eradication efforts. New infestations of hemlock woolly adelgid, emerald ash borer, Asian longhorned beetle, gypsy moth, pine shoot beetle, scale and all types of aphids have attacked trees and ornamentals from Florida to Canada and from coast to coast. Exotic plants like garlic mustard, purple loosestrife, honeysuckle and common buckthorn are becoming widespread in both our woodlots and landscapes. Non-native diseases, such as Dutch elm disease and chestnut blight, have ravaged our native American and red elm populations and all but wiped out the American chestnut.
What is an invasive species? Invasive species are plants, insects or other organisms that are introduced to a given area outside of their original range and cause harm in their new home. Because they have no natural enemies to limit their reproduction, they usually spread like wildfire.
Invasive plants quickly establish themselves and typically displace native flora due to faster growth rates, efficient seed dispersal and/or prolific root sprouts, and have a tolerance for a wider range of conditions. These species often lack natural predators and diseases that keep their populations under control in their native environments.
Invasive insects are becoming increasingly troublesome as the increase in world trade brings more and more of them to our shores. While the gypsy moth was introduced into the east coast in the 1890s and took a century to work its way to Wisconsin, many of the new invasive insects are wood borers like the Asian long-horned beetle and emerald ash borer that arrive in shipping pallets and containers and can escape anywhere in the country. Just like exotic plants, these exotic insects have no natural predators or diseases to keep them in check.
Efforts to control invasive species require patience. When dealing with plants such as buckthorn, control strategies involve cutting the plants (small ones can be pulled out by their roots), treating the stumps with an herbicide to kill the roots, and then repeating the process periodically, although on a much smaller scale.
The American chestnut and American elm have not developed a resistance to their respective diseases. The systemic fungicide, ArbotectTM can keep Dutch elm disease from infecting an elm, but it is a treatment that needs repeating every two to three years. Once again—patience.
Invasive insects can be controlled by chemicals, and sometimes host eradication, until natural predators or diseases can be introduced or developed that will slow the spread and/or intensity of the insect.
At Wachtel, we are constantly monitoring the development and spread of invasive species that affect our clients’ landscapes. We keep abreast of the latest technology and control measures to keep your trees and landscapes healthy and beautiful. Feel free to call one of our Certified Arborists to discuss any issues you may have with invasive species control.
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