Wisconsin sees increase in ‘gypsy’ moth population
Wisconsin is seeing an uptick in an invasive species of bugs known as the “gypsy” moths thanks to dry weather this spring and summer.
The number of the moths, also known as Lymantria dispar, increased over the last year, according to data from the Wisconsin Department of Agriculture, Trade and Consumer Protection. Over the course of the summer, nearly 100,000 moths were captured in about 11,000 traps, up from nearly 84,000 in 2020 and about 52,000 in 2019.
The number of moths increased because dry weather limited the spread of the diseases that typically kill the bugs. As a result, more caterpillars survived to adulthood, and the population was able to increase, said Michael Falk, trapping coordinator for DATCP.
The moths are an invasive pest that began defoliating Wisconsin trees in 1997. The state captures moths to help track the size and location of the traveling species. The trapping data helps to determine sites for next year’s aerial treatments, DATCP said in a release. In 2021, the state treated about 89,000 acres across 14 counties.
Next year’s treatment sites will be released in the spring.
Commonly known as “gypsy” moths, the bugs are in the process of being renamed by the Entomological Society of America, because the name is considered an ethnic slur to the Romani people, according to a USA TODAY report. The organization is seeking a new name for the moth, but in the meantime recommends calling the bug by its scientific name, Lymantria dispar or L. dispar.
The male moths are dark in color and are able to fly, while female moths are white with wavy black marks and are unable to fly. The caterpillars are about 2 inches long, hairy and have a pattern of dark red and blue spots.
In addition to treatments by the state, residents can help identify and treat outbreaks of the moths as well, said Andrea Diss-Torrance, a forest invasive pest coordinator with the Department of Natural Resources.
If you noticed the small yellow moths flitting around your backyard last summer, or the caterpillars crawling on your trees, make sure to check for egg masses on trees, especially oaks.
The egg masses are about the size of a quarter and a similar color to a manila envelope, Diss-Torrance said, and appear to have a velvety texture.
If you find an egg mass, coat it in a horticultural oil to ensure the eggs won’t become caterpillars next spring. Those are the kinds of treatments being used for outbreaks at Devil’s Lake State Park near Madison and the John Muir Hiking and Biking Trails near Whitewater, where larger outbreaks were noted this summer, Dell-Torrance said.
If you notice a large number of egg masses on your trees, or that you can’t reach the eggs to treat them, it’s recommended to call in an arborist to treat the tree, ensuring its survival.
The moths run on cycles of abundance and scarcity, depending on the weather, Diss-Torrance said.
To learn more about Lymantria dispar, find an arborist or help out with identification and detection of the moths, visit www.gypsymoth.wi.gov.