The battle continues against the moth formerly known as ‘gypsy’ – Duluth News Tribune
DULUTH — Entomologists have changed the name of the gypsy moth to gypsy moth, but the battle against forest invaders will continue this summer with aerial spraying in eastern Minnesota and western Wisconsin, including Duluth and Cloquet.
With the term gypsy considered offensive to European Roma, the name of the moth that has roamed the United States for 160 years was officially changed on March 2 by the Entomological Society of America.
The name “spongy,” from the common French term spongieuse, refers to the egg mass of the moth, which apparently has the color and texture of a sea sponge.
Gypsy moths first arrived in the eastern United States from Europe in the 1860s and have moved west ever since, defoliating millions of acres of trees while rolling eastward. west as egg clusters on cars, trucks, trains, trailers and motor homes. They have been present in eastern Wisconsin since the 1970s and have now spread throughout the state and into eastern Minnesota.
Since 1970, more than 83 million acres, an area equal to 37 Yellowstone National Parks, have been defoliated by the gypsy moth in the United States, or about 700,000 acres per year in recent years, according to the U.S. Department of Agriculture.
It is when the moth is in the caterpillar stage that it does the damage, eating the leaves of many species of deciduous trees and plants. Forest health experts say moths can’t be stopped. But their westward movement can be slowed and outbreaks can be reduced, with annual aerial spraying efforts where the greatest concentrations of moths are found.
Gypsy moths have few natural enemies here, and the caterpillars defoliate trees several times in a growing season, unlike native pests like the forest tent caterpillar which typically only defoliate trees once a year. season. If trees are defoliated often enough by gypsy moths, the tree may succumb to disease or stress. In a Wisconsin study, up to 20% of defoliated trees died.
Gypsy moths are “a serious threat to our timber, nursery and tourism industries, and the insect can be a public nuisance during major outbreaks,” said Kimberly Thielen Cremers, head of the regulatory and information section. Minnesota Department of Agriculture Plant Pest Mitigation. “We must slow the spread of the insect in Minnesota to protect our natural resources.”
As it has for the past decade, Northland continues to be the front line in America’s war to slow the butterfly’s westward movement. In Minnesota, the state Department of Agriculture plans to use aircraft to spray four areas this summer, including 75 acres in west Duluth, nearly 500 acres in Cloquet and two areas in Lake County. totaling 45,000 acres.
Minnesota’s highest concentrations of gypsy moths are in Lake and Cook counties, where they may have moved on easterly winds from Wisconsin or Michigan or arrived attached to crowds of vehicles visiting the North Shore from states already infested.
The treatments will be carried out in June and July, depending on the development of the insects and the weather. Both Lake County areas will be sprayed with an organic mating disruption product with pheromones. Spraying in the Duluth and Cloquet areas will see Foray 48B Biological Insecticide, which contains Btk that targets gypsy moth caterpillars.
In Wisconsin, the Department of Agriculture, Commerce and Consumer Protection will again conduct aerial spraying in Washburn, Bayfield, Sawyer, Barron, Burnett, Barron, Buffalo, Burnett, Chippewa, Crawford, Dunn, Eau Claire , Grant, La Crosse, Lafayette, Pepin, Rusk, Trempealeau and Vernon counties.
Beginning in May and continuing through July, low-flying aircraft will spray selected areas in western Wisconsin where a total of approximately 163,491 acres across 57 sites in scheduled counties are to be sprayed.
For more information about gypsy moths and control efforts in Minnesota, including whether or not your neighborhood can be sprayed, go to mda.state.mn.us/plants/pestmanagement/gmunit.
For more information on smaerialspray moths and treatment efforts in Wisconsin, go to smaerialspray.wi.gov.
Concern for butterflies
Because moths resemble butterflies, it is feared that efforts to control gypsy moths could also impact monarchs and other butterflies. But forest health officials say they strive to avoid any collateral damage when spraying gypsy moths.
One of the treatments, a pheromone flake, tricks male squishy moths into thinking there are females around, preventing them from mating with real female moths. The pheromone does not kill anything.
The second major spray used for gypsy moths is called Btk, an organic caterpillar-killing compound that occurs naturally in soil. The product is sprayed on the treetops where the gypsy moth caterpillars feed. When ingested, the bacterium is toxic to certain sensitive caterpillars such as the gypsy moth. The caterpillars stop feeding and die within a few days.
Btk breaks down quickly in the environment and becomes harmless within weeks. And because the Btk spray is done several weeks before most Northland moths are in the caterpillar stage, agency officials say there is little concern.
Btk must be ingested by the insect to cause damage. So it won’t harm the eggs and isn’t effective on the adults because they don’t spend a lot of time eating bacteria-covered leaves.
Yet some critics of widespread Btk spraying say that there are certain species of butterflies that are in the caterpillar stage at the same time and that Btk should not be used at all, as the damage to insect species not intentional outweigh the benefits of reduced forest defoliation.
According to the Minnesota Department of Agriculture, Btk only works in the alkaline conditions found in the stomachs of insects at the caterpillar stage of development. This alkaline condition is not present in the stomachs of humans, mammals, fish, birds or bees, which is why Btk does not affect them.
New western spongy butterfly threat
The Asian gypsy moth, Lymantria dispar asiatica, is also a serious defoliating forest pest that can feed on several hundred different tree species, and has appeared near ports in the western United States and Canada these last years.
Females of this subspecies are capable of powerful directed flight and are attracted to lights, often resulting in the laying of egg masses on the superstructure of ocean-going vessels or on their cargo. Multiple introductions of strains of Asian spongy moths have occurred when egg masses on ships from Japan and ports in the Russian Far East hatch after entering ports in western America North.
The Asian moth was first identified in North America in late 1991 near Vancouver Harbor in British Columbia, Canada. In 2020, the Hokkaido variety spongy moths from Asia were discovered in parts of Snohomish County northeast of Seattle.
John Myers reports on the outdoors, the environment and natural resources for the Duluth News Tribune. He can be reached at