Balsam fir needles infected with needle rust turn bright yellow. / Photo Credit: Wisconsin DNR
Although this summer has been dry in north-central Wisconsin, there was enough moisture this spring to promote some needle rusts. Needle rusts are fungi that infect needles of various conifers. Most rusts require two hosts to complete their life cycle.
A look at common types of needle rust:
A pitch “glob”, with oozing pitch running down the trunk of a young white pine infected with pitch mass borer. / Photo Credit: Wisconsin DNR
By Linda Williams, Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov, 920-360-0665
Have you seen big globs of gooey pitch on the main stems of eastern white pine trees? Or maybe you’ve seen them on spruce?
For those with an adventurous side, grab a stick and scrape off some of that gooey glob. You might be rewarded with the sight of large larvae feeding beneath all of that goo. This is the larvae of our native pitch mass borer. Adults are clearwing moths that look a bit like wasps.
Using a stick to pry away some of the gooey pitch on a tree exposes a pitch mass borer larva underneath. / Photo Credit: Wisconsin DNR
Adults lay eggs on the bark. When eggs hatch, the tiny larvae chew into the bark and begin feeding on the inner bark. They feed enough to irritate the tree, causing more sap and pitch to be produced, which the larvae feed on.
Pitch mass borer can take two to three years to complete development, remaining in that same location throughout their life and continuously irritating the inner bark to promote continued pitch production. Pupation occurs under the glob of pitch and adults then chew their way out. Old pitch globs will harden and darken over time, remaining on the tree for a year or more before finally weathering off.
Hosts include pines (eastern white, jack, scotch and Austrian) and spruces (blue and Norway).
Management on forest trees is not necessary. Severely damaged and deformed trees can be removed during the first thinning. Management on yard trees includes maintaining healthy trees (which are less attractive to the adults), watering during droughts, avoiding pruning during mid-summer (which can attract adults to lay eggs near the fresh wounds), destroying any larvae under the globs of pitch and removing and disposing of severely infested trees.
Scraping more pitch off a tree’s main stem shows a pitch mass borer larva on the end of the stick. / Photo Credit: Wisconsin DNR
Pitch mass borer larvae can be shades of white to pink, depending on the host. / Photo Credit: Wisconsin DNR
The front page of the Wisconsin DNR’s new Forest Health Fact Sheet on oak decline. / Graphic Credit: Wisconsin DNR
By Art Kabelowsky, DNR Outreach and Communications, Fitchburg
Arthur.Kabelowsky@wisconsin.gov or 608-335-0167
The Wisconsin Department of Natural Resources Forest Health team has published two new fact sheets, bringing the total count of its fact sheet offerings to 26.
The new fact sheets:
The fact sheets are designed in full color, with photos, and are meant to be printed out for reference or to carry into the field. They can also be viewed online. They can be printed on standard letter-sized paper. Most fact sheets are two pages, meant for two-sided printing; a few are four-page documents.
A complete directory of links to all DNR Forest Health fact sheets is available online.
An adult Asian longhorned beetle. / Photo Credit: Wisconsin DNR
By Michael Hillstrom, DNR Invasive Forest Pest Coordinator, Fitchburg
Michael.Hillstrom@wisconsin.gov or 608-513-7690
Asian longhorned beetle (ALB) has not been found in Wisconsin, but early detection is critical to eliminating it from infested areas. Forest Health workers from Wisconsin, Michigan, Minnesota and Manitoba, Canada, recently had the opportunity to visit an active ALB infestation in South Carolina to learn how to identify infested trees. This experience will greatly enhance staff’s ability to detect ALB and respond rapidly.
By Bill McNee, Forest Health Specialist, Oshkosh
Bill.McNee@wisconsin.gov
A spongy moth caterpillar feeds on a leaf. / Photo Credit: Wisconsin DNR
Property owners are encouraged to monitor their trees for spongy moth larvae and damage this summer to determine whether control measures are needed.
Property owners who have oak, birch, crabapple, aspen, willow and linden (basswood) trees should be particularly watchful because the caterpillars of this invasive insect prefer these species.
However, they will feed on many other kinds of trees and shrubs.
Continue reading “Watch For Spongy Moth Caterpillars And Tree Damage This Summer”
Young spruce budworm larvae begin feeding as buds break, causing the new growth to crook where feeding damage occurs. Webbing shown in the photo is also common. / Photo Credit: Wisconsin DNR
By Linda Williams, Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665
The spruce budworm outbreak is continuing for yet another year in some areas of northern Wisconsin.
Continue reading “Spruce Budworm Outbreak Continues In 2026”
Forest tent caterpillar larvae displaying gregarious, clustering behavior on a tree stem. / Photo Credit: Wisconsin DNR
By Paul Cigan, DNR Forest Health Specialist, Hayward
dnr.wisconsin.gov/topic/foresthealth/staff, 715-416-4920
Populations of forest tent caterpillar (FTC) are likely to remain low throughout northern Wisconsin this growing season, continuing a record 23-year statewide trend.
Spring egg mass surveys showed a low presence of overwintering egg masses, suggesting that any defoliation this season is likely to be localized. Overwintering egg masses present on the twigs of deciduous twigs and branch tips are counted during surveys to forecast FTC population density and the associated risk of heavy defoliation going into spring leaf-out.
Wisconsin DNR Forest Insect Pest Specialist Mike Hillstrom gives a presentation during a New Forester Training session in Marinette County in 2024. / Photo Credit: Bill McNee, Wisconsin DNR
By Art Kabelowsky, DNR Outreach and Communications, Fitchburg Arthur.Kabelowsky@wisconsin.gov or 608-335-0167
Mike Hillstrom, the Wisconsin Department of Natural Resources Invasive Forest Pest Coordinator, will give a public presentation on forest invasive species from 10 a.m. to noon Saturday, June 20, at Lake Kegonsa State Park in Stoughton.
The talk will be part of the informational and educational events sponsored as part of the DNR’s Invasive Species Awareness Weekend.
Photo Credit: Wisconsin DNR
* These training opportunities are provided as an information service only and do not constitute an endorsement from the Wisconsin Department of Natural Resources (DNR).
See below for training on urban forestry basics, tree risk fundamentals in Spanish, plant diseases and pests, invasive species, student apprenticeships, nut trees and other urban forestry resources. Continue reading “Upcoming Training”
A putty knife, plastic knife or similar object can be used to gently scrape spongy moth egg masses into a cup of soapy water. The water can be discarded after two days. / Photo Credit: Wisconsin DNR
By Bill McNee, DNR Forest Health Specialist, Oshkosh
Bill.McNee@wisconsin.gov
The Wisconsin Department of Natural Resources (DNR) encourages property owners to examine their trees for spongy moth egg masses and determine whether control measures are needed this spring.
Property owners who have oak, birch, crabapple, aspen, willow and linden (basswood) trees should be particularly watchful because the caterpillars of this invasive insect prefer these species. However, they will feed on many other kinds of trees and shrubs.
Continue reading “Look For Spongy Moth Egg Masses And Take Action”
