Forest Health News

Two-lined chestnut borer in flooded oak stands

By Mike Hillstrom, forest health specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov, 608-513-7690

2019 was the wettest year ever recorded in Wisconsin. Four of Wisconsin’s top five wettest years have taken place in the last decade, three of them in the last five years: 2019, 2018 and 2016. Flooding can be stressful for trees, and with flooding occurring over the past few years in many parts of the state, forest health staff expect the impacts to forests to continue to escalate. Continue reading “Two-lined chestnut borer in flooded oak stands”

White pine blister rust can girdle branches

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

White pine branches that suddenly turn red may be a sign of white pine blister rust. White pine blister rust is a fungal infection that creates expanding “dead spots” or cankers on the branches or main stem of host trees. Eventually the fungus grows enough to girdle the branch or main stem and the needles fade from green to pale green to rusty red. Orange, spore-producing pustules erupt around the edges of the canker in the spring.

Orange pustules erupt through the bark and around the margins of a white pine blister rust canker. Photo by Jean Romback-Bartels.

Orange pustules erupt through the bark and around the margins of a white pine blister rust canker. Photo by Jean Romback-Bartels.

Continue reading “White pine blister rust can girdle branches”

Gypsy moth spray program begins in May

The 2020 gypsy moth slow-the-spread program, operated by the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) is expected to begin aerial spraying in the second half of May to slow the westward spread of gypsy moth.

Map of counties to be sprayed in 2020.

Map of counties where slow-the-spread treatments will occur in 2020.

Continue reading “Gypsy moth spray program begins in May”

Gall rusts on jack pine

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

There are three things you may find interesting about gall rusts on jack pine at this time of year. The first is that as winter recedes, closer examination of the galls on jack pine shows that squirrels like to chew on them. The squirrels seem to prefer the smaller galls, with most chewing marks being observed on galls less than 2” in diameter. They eat the galls by scraping off the outer layers, leaving behind telltale teeth marks.

Chewing marks on a branch gall caused by gall rust.

Squirrels sometimes feed on galls, scraping away the outer layers and leaving teeth marks behind.

Continue reading “Gall rusts on jack pine”

Damage from heavy winter snow and ice

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

Heavy ice and snow loads can cause significant problems for trees. Branches can break under heavy loads, and entire tree tops loaded with snow can come crashing down in windy conditions. Trees that are repeatedly weighed down or tipped over by snow, only to have more snow pile up on them, can be further impacted.

Four images of winter damage to jack pine, including stem failure from gall damage, root failure due to Armillaria root disease.

Clockwise from top left: jack pine broken at site of gall on main stem; trees that break at their base due to heavy snow loads are not able to recover; previous attack from pine root collar weevil (yellow arrow) weakened this tree near its base; heavy snow load and a major root weakened by Armillaria caused this tree to break (yellow arrow) and tip over.

Continue reading “Damage from heavy winter snow and ice”

Mouse, rabbit and squirrel damage from winter

By Todd Lanigan, forest health specialist, Eau Claire, Todd.Lanigan@wisconsin.gov, 715-210-0150

With the onset of spring and snow melt, you may have noticed bark missing at the base of trees and shrubs. This is most commonly noticed on sections of bark that were below the snow line. This damage, known as girdling, was caused by mice and rabbits feeding on the bark during the winter.

Girdling damage at base of tree surrounded by older greyish black wound.

Mouse girdling damage at base of tree surrounded by older greyish-black wound.

Continue reading “Mouse, rabbit and squirrel damage from winter”

Protect oak trees by pruning after July, not before

By Don Kissinger, urban forester, 715-348-5746, Don.Kissinger@wisconsin.gov or Paul Cigan, plant pest and disease specialist, 715-416-4920, Paul.Cigan@wisconsin.gov

Anyone with oak trees in their yards or on forested lands should avoid pruning or cutting them from April through July to protect them from oak wilt.

Sap-feeding beetle on diseased oak tree in Sawyer County.

Sap-feeding beetle on diseased oak tree in Sawyer County.

Continue reading “Protect oak trees by pruning after July, not before”

Severe spruce needle diseases expected in 2020

By Bill McNee, DNR forest health specialist, Oshkosh, bill.mcnee@wisconsin.gov, 920-360-0942

Wet weather in 2019 created ideal conditions for Rhizosphaera kalkhoffii and other needle cast fungi to infect spruce needles. Since it takes about a year for the needles to show symptoms, heavy and widespread needle diseases are expected to be seen on spruce trees in 2020. 

Lower branches of an infected spruce tree have lots of missing needles and some that are browning.

Loss of older needles on an infected spruce.

Continue reading “Severe spruce needle diseases expected in 2020”

Prepare for the return of gypsy moths in spring

By Bill McNee, DNR forest health specialist, Oshkosh, bill.mcnee@wisconsin.gov, 920-360-0942

Gypsy moth eggs are expected to start hatching as temperatures warm in the next few weeks. Now is a great time for homeowners to check their trees for egg masses and treat or remove any that are found. Removing the egg masses now will help protect trees from defoliation and reduce future caterpillar populations.

Gypsy moth larvae hatching from egg masses on an outdoor bowl.

Gypsy moth larvae hatching from egg masses on an outdoor bowl.

Continue reading “Prepare for the return of gypsy moths in spring”

Nominations Open For “Invader Crusader” Awards

By Tara Bergeson, DNR invasive species team leader, 608-264-6043, Tara.Bergeson@wisconsin.gov

Nominations are being accepted through March 23, 2020 for “Invader Crusaders.” These awards go to individuals, groups and organizations who made outstanding contributions in 2019 to prevent, control or eradicate invasive species that harm Wisconsin’s native wildlife and wetlands, forests, prairies, lakes and rivers.

The Wisconsin Invasive Species Council is seeking nominations for exemplary efforts at addressing issues surrounding terrestrial and aquatic invasive plants and animals. The awards will be presented in both volunteer and professional categories.

To submit a nomination, download and fill out a nomination form available on the Wisconsin Invasive Species Council’s Invader Crusader webpage. Email the completed form to invasive.species@wisconsin.gov by March 23.

A panel of Wisconsin Invasive Species Council members will review the nomination materials and select the award winners. All nominators and winners will be notified by mid-May 2020.

Recipients of the awards will be recognized at an awards ceremony on June 11 at Olbrich Botanical Gardens in Madison.

Invasive species are nonnative plants and animals that cause great ecological, environmental or economic harm, and some can even affect human health. Once an invasive species becomes established in an area, it can be difficult to control. The most important action Wisconsinites should take is to avoid moving invasive species or the materials that might harbor them to new places.

To learn more about what you can do to stop the spread of invasive species, visit the DNR invasive species webpage.