Northwest WI Forest Health

Native caterpillars not a major concern for trees

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

Eastern tent caterpillars (ETC) are hatching and beginning to feed on host trees, including cherry, apple and crabapple. Landowners and homeowners may notice the white silken tents forming in branch forks. Although they form unsightly tents, ETC is a native insect so management is not typically necessary. Even completely defoliated trees will put out new leaves within a few weeks.

A group of eastern tent caterpillars warm themselves on white silk tent before leaving to feed on black cherry leaves.

If landowners want to remove the tents the best time to do so is early morning or evening when the caterpillars are inside. Unless it is raining, eastern tent caterpillars leave their tents each morning to feed throughout the day before returning at night. Caterpillars can be removed either by hand if they are within reach or with a rake if they are high in the tree. They can then be killed by soaking them in soapy water or sealing them in a trash bag. Insecticides are rarely necessary but should penetrate inside the tent if used. Do not prune branches, burn tents or soak them with WD-40. These methods are more harmful to the tree than ETC defoliation and are not recommended.

For more information on eastern tent caterpillar, read this factsheet from UW-Madison Division of Extension.

Protect yourself from ticks and tickborne illnesses

Bill McNee, forest health specialist, Oshkosh, Bill.McNee@wisconsin.gov or 920-360-0942

Adult deer tick. Credit: Scott Bauer, USDA Agricultural Research Service, bugwood.org.

So far this spring we are off to a busy tick season, with many reports and photos being sent in to DNR staff. Ticks can be found year-round in Wisconsin but are most active from May to September. Some species, including the deer tick responsible for Lyme disease, carry infectious diseases that elevate them from mere nuisance to serious health threat.  Lyme disease is most often spread by very small, immature ticks known as “nymphs.” Adult deer ticks can also transmit Lyme disease, but because they are larger, they are more likely to be discovered and removed compared to the tiny nymphs which can be as small as a chia or sesame seed.

Continue reading “Protect yourself from ticks and tickborne illnesses”

Needle and leaf diseases are back!

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

It’s nearly summer and the usual cast of disease characters are on the scene following wet spring conditions. Rhizosphaera needlecast and other needle diseases impacting spruce continue to be a major concern for landowners and homeowners. Diseases in hardwoods are also popping up. For more information on needle and leaf diseases affecting trees in Wisconsin and resources to learn more, click below to read full article. 

A row of spruce trees with dead branches and missing needles caused by Rhizosphaera needlecast.

Spruce trees impacted by Rhizosphaera needlecast.

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Branch tips littering the ground under your trees?

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

Have you been noticing branch tips scattered on the ground beneath spruce, fir or pine trees this spring? You may be seeing one of a few things – damage from small animals or breakage caused by the harsh winter we had. Fortunately, the damage from either is unlikely to do serious harm to your trees. 

Spruce branch tips found on ground were clipped from tree by squirrels.

Spruce branch tips found on ground were clipped from tree by squirrels.

Continue reading “Branch tips littering the ground under your trees?”

Northwestern county forests trap for EAB

Paul Cigan, forest health specialist, Hayward, Paul.Cigan@wisconsin.gov, 715-416-4920

Several forestry partners will be trapping EAB in the northern region in 2018 using baited prism traps similar to this one.

EAB purple prism trap in ash tree.

A number of county forestry partners in northwest Wisconsin are trapping for emerald ash borer (EAB) on their properties this year with technical assistance from the DNR forest health team. Potential captures of EAB may give officials a better understanding of the invasive beetle’s distribution in the region that can support forest management planning and public awareness. Partners conducting trapping include Bayfield, Douglas, Rusk, Sawyer counties and the Barron County Conservation District. Landowners and property managers are encouraged to report signs and symptoms of EAB activity to their regional forest health specialist.

Learn more about emerald ash borer and signs/symptoms of infestation at the DNR emerald ash borer page.

Another low year for forest tent caterpillar

Paul Cigan, forest health specialist, Hayward, Paul.Cigan@wisconsin.gov, 715-416-4920 and Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

Newly hatched forest tent caterpillars on egg mass.

Forest tent caterpillar larvae emerging from egg mass.

Forest tent caterpillar egg surveys conducted in northern counties indicate hardwood defoliation from this native insect will remain low in 2019, sustaining a 16-year trend. The last FTC outbreak affected northern Wisconsin from 1999 – 2002. Cooler and wetter than average spring weather may indirectly reduce caterpillar populations by enhancing the activity of pathogenic fungi. Please report any possible defoliation to your regional forest health specialist.

To learn more about this insect, visit the DNR forest tent caterpillar webpage.

Invasive insects threaten Wisconsin hemlock

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

Two invasive insects, hemlock woolly adelgid (HWA) and elongate hemlock scale (EHS), pose serious threats to Wisconsin’s hemlock trees. Although neither insect is established in Wisconsin, both insects have been found in recent years on infested nursery stock or live tree material that was shipped into the state. Fortunately, these introductions were detected and the plant material destroyed. But with HWA established in hemlock stands of several Michigan counties along Lake Michigan, natural spread to Wisconsin is anticipated.

Because of the risk, forest health staff from the Department of Natural Resources (DNR) and the Department of Agriculture, Trade and Consumer Protection (DATCP) are conducting surveys for early detection of these pests. Both pests could appear in many settings including urban and rural forests, yard trees and holiday tree plantations so everyone has a role to play in looking for these pests and reporting what they see.

HWA and EHS both feed on tree needles with sucking mouthparts. When populations are large enough, this feeding causes excessive fluid and nutrient loss, leading to declining tree health. Both insects can be found together on infested hemlock trees.

A group of adult hemlock woolly adelgid covered in white waxy filaments feeding on hemlock needles.

Characteristic white wax coating of adult hemlock woolly adelgid.

There are a few key ways to spot these insects. HWA is most obvious in winter when white, wax-covered adults are present. You may also see hemlock foliage turning gray-green in color as tree health declines. Adult EHS have a waxy cover and feed on the underside of hemlock, spruce and fir needles. Damage from EHS appears as yellow banding on needles. Crowns appear progressively thinner as infested needles die and fall off prematurely. Both insects also have tiny immature crawlers that may be seen moving on infested trees.

Tiny adult scales protected with a waxy cover feed on needles causing yellow banding.

Adult elongate hemlock scale and yellow needle banding (Credit: WI DATCP).

If you suspect you’ve found either HWA or EHS, please report it immediately to your local DNR forest health specialist. For more information about HWA, visit the DNR and DATCP webpages. To learn about EHS, visit the DATCP webpage.

EAB found in third Douglas County township

By Paul Cigan, forest health specialist, Hayward, Paul.Cigan@wisconsin.gov, 715-416-4920

Emerald ash borer (EAB) has been confirmed in Highland Township in Douglas County, making it the third township with a known EAB infestation in this county. Utility line professionals reported white ash with heavy woodpecker damage, or “flecking,” that was later confirmed to be an EAB infestation. The extent of damage to the tree suggests that the infestation is approximately 4 years old. Surrounding black ash do not display signs or symptoms of EAB. Nevertheless, based on EAB’s natural rate of spread, there is likely to be a low-density population for about 15 miles around the infested tree in all directions. The nearest previous EAB detection, made in the Town of Amnicon in 2017, is located 23 miles away. Firewood transport is the most likely source of this latest outlying introduction.

Known EAB detections as of April 25, 2019.

Known EAB detections as of April 25, 2019.

Forest managers working with ash should become familiar with the revised EAB Silviculture Guidelines, and landowners and managers in northern counties are encouraged to report EAB suspect trees to their regional forest health specialist.

EAB-infested white ash with heavy woodpecker flecking and dead epicormic sprouts.

EAB-infested white ash with heavy woodpecker flecking and dead epicormic sprouts.

Dense EAB larval galleries on the wood surface of infested white ash.

Dense EAB larval galleries on the wood surface of infested white ash.

Revised EAB insecticide guide now available

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

Title page of revised insecticide guide.The North Central Integrated Pest Management Center has released the third edition of its widely distributed guide, “Insecticide Options for Protecting Ash Trees from Emerald Ash Borer.” This updated document addresses frequently asked questions and shares new information about insecticide options that are not covered in the guide’s previous edition from 2014. To review the most current recommendations and study results regarding insecticide use for EAB, download the report here.

Salt spray injury on conifers observed in spring

By Paul Cigan, forest health specialist, Hayward, Paul.Cigan@wisconsin.gov, 715-416-4920

A particularly active winter weather season has left white pine and other conifer species along many of Wisconsin’s roadways with salt spray injury this spring. These salt deposits draw water out of the foliage, causing them to dry out and turn brown, often beginning at needle tips and progressing down to the needle base. Browning is most heavily concentrated on branches facing the road, lower portions of tree crowns and foliage that remained above the snowline.

Browning is likely to intensify as the weather continues to warm this spring, and heavily damaged needles may die and prematurely fall off. Successive years of damage can leave branches sparse of foliage and cause branch dieback.

Salt spray from de-icing salts applied to roadways may drift and settle onto vegetation within 150 feet of a roadway. Injury can be prevented or reduced by placing physical barriers such as snow fencing, plastic or burlap around conifers in fall. Salt residues can also be rinsed off with water during periods of warm weather prior to bud break. More information about salt damage to plants can be found in this UW–Madison Division of Extension publication.

Red pine shoot with needle tip browning from salt spray injury.

Red pine shoot with needle tip browning.

White pine tree with salt spray injury concentrated on limbs of the lower crown that are facing the roadway.

White pine tree with salt spray injury.

White pine seedlings with salt spray injury concentrated on tissues above the former snowline.

White pine seedlings with salt spray injury.