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.
By Linda Williams, Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov, 920-360-0665
Red turpentine beetle and pine root collar weevil both attack pines near ground level. So, how can you identify them and differentiate the damage?
If you prefer the abbreviated version, check out the table below. For more details, read further and be sure to check out the photos.
| Pine Root Collar Weevil | Red Turpentine Beetle | |
| Hosts | Pines | Pines, tamarack, spruce, fir
|
| Tree size | Younger pines (generally less than 8 inches diameter at breast height). | Larger trees (generally greater than 8 inches diameter at breast height)
|
| Location of damage | Ground level and below | Lower 1-3 feet of the trunk
|
| Signs and symptoms | Trees leaning heavily or broken over at the base. Black, pitchy soil at base of tree. Black, pitchy, sunken area at base of tree. | Scattered trees in a stand decline and die. Pitch tubes near base of tree
|
| Prevention | Maintain stocking and crown closure to prevent grass and weeds around the base of trees. | Keep trees healthy
|
| Management | Remove grass and weeds from base of trees. Prune lower branches to increase air flow. Insecticides may be an option. | Salvage |
Damage at the base of young red pine, by pine root collar weevil can weaken it and trees with green needles can suddenly break over. / Photo Credit: Wisconsin DNR
Pine root collar weevil prefers younger pine stands that are open, with grasses or weeds near the bases of the trees to give the insects additional protection. Pine root collar weevil will attack red, jack, scotch and Austrian pine, but rarely white pine.
Pine root collar weevil damages roots and creates a weakened area of the tree at ground level. Damaged trees can break over at ground level if damage is on the trunk or may just lean heavily if roots are damaged and can no longer keep the tree upright.
To look for pine root collar weevil pull the weeds, duff and soil away from the base of the tree and away from the major roots. Infested trees will have black pitch-soaked soil around the base. Removing the bark from the root collar area and from the major roots, will show boring damage from pine root collar larvae just under the bark. The base of the tree may be slightly sunken where weevil larvae have been feeding under the bark.
Management options depend on the age and stocking of the stand when you notice the infestation. Planting at the proper depth and maintaining good crown closure to minimize the amount of grass and weeds around the base of trees can help prevent infestation. If you already have an infestation, eliminating weeds and grass around the base of trees and/or pruning lower branches can increase air flow to dry out the base of the trees and make them less attractive to the weevils.
Looking closely at the base of a tree being attacked by pine root collar weevil shows blackened pitchy dirt around the base of the tree. / Photo Credit: Wisconsin DNR
Pitch blobs near the base of a red pine indicate attack by red turpentine beetle. / Photo Credit: Wisconsin DNR
Red turpentine beetles generally prefer pine trees that are pole-sized and larger. They attack the lower 2-3 feet of the trunk of pines that are under stress, but can also attack stressed tamarack, spruce and fir. The original stressors could be abiotic, such as drought, flooding or fire, could be due to stress from thinning, or from trees being planted too deep or off-site.
Look for pitch tubes around the base of the tree. Adult beetles bore into the bark to lay eggs under the bark, and the tree will start to exude pitch, which the beetles push out to create a blob of pitch called a pitch tube. Pitch tubes will last for many months to years and are a noticeable clue indicating attack.
Larvae feed under the bark. The damage they do can girdle areas, which puts additional stress on the tree. If multiple pitch tubes are noticed at the base of a tree, the damage could be severe enough that Ips bark beetles could attack the tree and kill it.
Red turpentine beetle can also carry the spores of Leptographium root disease and, when introduced to a red pine, the disease can begin to spread through the roots and create expanding pockets of mortality, referred to as Red Pine Pocket Decline And Mortality.
Maintaining tree health is the best way to prevent attack by red turpentine beetles. When stress is severe, and attacks are numerous, salvage of trees may be necessary.
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.
The updated map of spongy moth quarantined counties in Wisconsin, showing the April 15 addition of Green and Sawyer counties to the quarantined list. / Map Credit: Wisconsin DNR
By Wisconsin DNR
Green and Sawyer counties have become the latest additions to Wisconsin’s spongy moth quarantine, joining most eastern and central Wisconsin counties already considered to be infested by the invasive insect.
The announcement was made April 15 by the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP), based on trapping data collected last year.
Continue reading “Green, Sawyer Counties Added To Spongy Moth Quarantine”
A 3-D printed trap used to collect hemlock woolly adelgid DNA. / Photo Credit: Wisconsin DNR
By Michael Hillstrom, DNR Invasive Forest Pest Coordinator, Fitchburg
Michael.Hillstrom@wisconsin.gov or 608-513-7690
This spring, the Wisconsin Department of Natural Resources (DNR) is collaborating with the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) to set traps to detect the invasive insect hemlock woolly adelgid (Adelges tsugae; HWA).
The project, funded by the Wisconsin Specialty Crop Block Grant Program, calls for traps to be set to detect the invasive insect. No detection of HWA has been made to date in Wisconsin forests. Continue reading “Cooperative Hemlock Woolly Adelgid Trapping Effort Begins”
An adult deer tick looks for a spot to attach. / Photo Credit: Wisconsin DNR
By Michael Hillstrom, DNR Forest Health Specialist, Fitchburg
Michael.Hillstrom@wisconsin.gov
Adult blacklegged (deer) ticks are already active this year, as of March 2026. The adults start looking for a host as soon as it warms up to around 40 degrees Fahrenheit.
In Wisconsin, between 20-60 percent of adult ticks are infected with the bacteria that causes Lyme disease. However, the risk of getting Lyme disease is higher with bites from nymphal ticks, which are most abundant in June and July, because they are so tiny and difficult to find. While only 10-28 percent of nymphs are infected with the Lyme disease bacteria in Wisconsin, rapid removal of a tick can reduce the risk of infection because it takes at least 24 hours for the Lyme bacteria to spread.
A map showing the 2026 spongy moth caterpillar aerial spraying area planned for Perrot State Park in Trempealeau County. / Map Credit: Wisconsin Department of Agriculture, Trade and Consumer Protection.
By Bill McNee, DNR Forest Health Specialist
Bill.McNee@wisconsin.gov
This spring, a portion of Perrot State Park in Trempealeau County will be aerially treated for spongy moth with “Foray” bacterial insecticide, containing Bacillus thuringiensis var. kurstaki.
A reproducing population of the leaf-eating caterpillar was detected in the park last fall, leading to the decision to conduct aerial spraying in 2026.
Continue reading “Aerial Spraying For Spongy Moth Planned at Perrot State Park”
Large white grub larvae discovered while splitting firewood. The insects are living in a piece of firewood with a lot of decay. / Photo Credit: Wisconsin DNR
By Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665
Hermit flower beetles (Osmoderma spp.) are very large scarab beetles, sometimes called leather beetles.
Three Osmoderma species can be found in Wisconsin, though none are common. Adult beetles look big and beefy but are harmless, eating a little pollen, feeding on ripe fruit and sipping nectar and tree sap during their adult life.
Continue reading “Huge White Grubs Found In Firewood, Rotting Logs”
Cold temperatures across the state of Wisconsin on Jan. 25, 2026. / Graphic Credit: National Weather Service
By River Mathieu, DNR Forest Health Specialist, Fitchburg
River.Mathieu@wisconsin.gov or 608-772-2758
Wisconsin experienced a polar vortex in late January 2026, and temperatures got chilly throughout the state, even reaching close to -40⁰ F in some places! Although it has warmed up, the cold weather is still fresh in everyone’s minds, leaving insect and forest lovers alike wondering how insects survive temperatures that cold.
The Wisconsin Department of Natural Resources Forest Health staff has received several questions over the past month about how insects survive cold weather in winter and whether the January temperatures were cold enough to kill insect pests.
