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Wisconsin is reducing its efforts to slow the westward spread of the leaf-eating gypsy moth and preparing to end altogether a program that helps beat back localized outbreaks in already infested parts of the state.

The end of the aerial pesticide spraying program that has been available in 50 infested eastern counties is being prompted by a decline in requests from local communities and by the emergence of private-sector alternatives to federally subsidized spraying, a state Department of Natural Resources spokeswoman said.

Meanwhile, federal budget cuts and increased demand in other states are contributing to a sharp reduction in western Wisconsin acreage expected to be sprayed in 2018 in a separate program designed to slow the spread of the pest to other states, said a spokeswoman for the state Department of Agriculture, Trade and Consumer Protection.

An average of 176,000 acres in western Wisconsin were treated annually from 2005 to 2017. The state is proposing fewer than 87,000 acres in 2018, agriculture department spokeswoman Donna Gilson said. The previous low was 101,000 acres in 2007.

The U.S. Forest Service and the state agriculture department have been searching out isolated outbreaks in the western part of the state and hitting them with compounds like insecticides and spray that disrupts adult mating.

“The longer you can delay it, the less expensive it is for Minnesota and other states to the west,” Gilson said.

But federal funding for the “Slow the Spread” program is being cut roughly 20 percent nationally from about $9 million to about $7 million, Gilson said.

A 2016 Forest Service report said the program nationally slowed the gypsy moth’s rate of spread by more than 60 percent, from an average of 13 miles per year to less than 5 miles per year, reducing environmental damage and financial losses on more than 125 million acres since 2000.

The invasive species is established in 19 states and the District of Columbia, or about one-third of its potential range in the U.S.

Wisconsin is one of 10 states on the leading edge of the North American gypsy moth infestation, according to the U.S. Department of Agriculture.

Gypsy moths were introduced in Massachusetts more than a century ago. The caterpillars can defoliate, weaken and kill more than 300 different species of trees and shrubs, according to the USDA. Since 1970, more than 83 million acres have been defoliated by the gypsy moth in the U.S.

Healthy trees can bounce back after a season or two without leaves. Heavy infestations can be unpleasant because gypsy moth caterpillars shed skin and hair some people are allergic to, and they excrete droppings called frass.

The species first defoliated trees in Wisconsin in the late 1990s. The pest’s population has grown rapidly a few times and then collapsed.

“They’ve really been a minor issue overall in the last five or 10 years,” said P.J. Liesch, who directs the UW-Madison Insect Diagnostic Lab.

Their numbers have been kept in check by a fungal disease, along with the state DNR’s aerial insecticide spraying program and quarantines designed to prevent people from carrying the insect’s eggs to new places.

Earlier this month, the DNR held public hearings on a proposed rule change to allow the department to end its role delivering up to 50 percent of the cost of spraying requested by local communities in the eastern two-thirds of the state.

Except for when there were small outbreaks in 2004 and 2008 and a larger one 2010, there have been relatively few requests, and private companies are available to be hired to spray for gypsy moths, unlike when the state first started its program, said the DNR’s Andrea Diss-Torrance.

“The private sector is now prepared to handle it, and we should do what private sector can’t,” Diss-Torrance said. Ending the gypsy moth program will allow the department to concentrate more resources on other problems such as the emerald ash borer.

DNR staff analysis of the proposed administrative rule change doesn’t specify when the program would end, that the state could continue the program to suppress gypsy moths on state land, and that the DNR’s policy board, the Natural Resources Board, would have authority to reactivate local community access to the money.

“We expect that business opportunities for local aerial applicators and arborists may increase with the deactivation of the state gypsy moth suppression program,” the analysis said in a section on business impacts. Administrative rule changes must be approved by the governor.

Wet springs tend to increase the prevalence of a fungus that is capable of knocking gypsy moth populations down quickly, she said.

Just two counties requested spraying under the DNR program in 2017. In Dane County, just under 190 acres were sprayed in three parts of Madison. Residential areas and state parks have been the main targets of spraying, Diss-Torrance said.

The department plans to soon add to the web page a guide for groups of landowners who want to organize aerial spraying, Diss-Torrance said.

Liesch said he didn’t believe ending the DNR program would affect the speed with which infestations would spread into the western counties, and with budgetary limits that state agencies face, it’s not surprising that the department would take this step.

Dane County land and water resources department director Laura Hicklin said 2018 requests from municipalities would be examined in February.

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Steven Verburg is a reporter for the Wisconsin State Journal covering state politics with a focus on science and the environment as well as military and veterans issues.