Statewide Forest Health

Native caterpillars not a major concern for trees

Posted on June 4, 2019June 4, 2019 by margueriterapp

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

Posted on June 4, 2019June 4, 2019 by margueriterapp

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.

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Needle and leaf diseases are back!

Posted on June 4, 2019June 7, 2019 by margueriterapp

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?

Posted on June 3, 2019June 4, 2019 by margueriterapp

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.

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

Invasive insects threaten Wisconsin hemlock

Posted on April 29, 2019 by margueriterapp

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.

Revised EAB insecticide guide now available

Posted on April 29, 2019April 29, 2019 by margueriterapp

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

Posted on April 29, 2019April 29, 2019 by margueriterapp

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.

White pine tree with salt spray injury.

White pine seedlings with salt spray injury.

Protect oaks from oak wilt by waiting to prune

Posted on April 1, 2019April 1, 2019 by margueriterapp

By Don Kissinger, urban forester, 715-348-5746, don.kissinger@wisconsin.gov and Paul Cigan, forest health specialist, 715-416-4920, paul.cigan@wisconsin.gov

To protect oak trees from the often-fatal oak wilt disease, don’t prune, cut or injure oak trees from April through July.

Pruning and cutting oaks in spring and early summer leaves them vulnerable to oak wilt, which rapidly kills trees in the red oak group and weakens those in the white oak group. Any damage during this time, including broken branches caused by storms, exposes living tree tissue beneath the bark and provides an opportunity for the oak wilt fungus to infect the tree.

Sap-feeding beetles introduce the disease by carrying oak wilt spores from infected trees or firewood to fresh wounds. Healthy oaks can become infected in as little as 15 minutes after the creation of a wound.

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

The trees most likely to die from oak wilt infection are in the red oak group, including northern pin oak, northern red oak, red oak and black oak. The white oak group is more likely to survive infection and includes bur oak, swamp white oak, white oak and English oak.

Tree paint or wound dressing is not normally recommended on pruned or wounded surfaces, but for damaged oaks an immediate light application of these products may be the only defense against oak wilt infection from April through July.

Pruning in spring can be damaging to any deciduous tree because their energy reserves are low as they produce new buds and leaves following the winter months. In general, the best time to prune is in winter when trees are dormant.

As of January 31, oak wilt has been found in all Wisconsin counties except Ashland, Iron, Forest, Taylor, Door, Kewaunee, Calumet and Manitowoc counties. Several of these counties contain the highest abundance of healthy and productive oak forests in the state. Taking recommended precautions will help keep them that way for years to come.

Oak wilt and other diseases move easily on or in firewood logs year-round, so keeping firewood local, or purchasing Wisconsin-certified firewood, is another important component of protecting trees and keeping forests healthy. Visit the DNR firewood page for more information and a directory of certified firewood vendors.

More information, including a recently released oak wilt video, is available at the DNR oak wilt page. Additional information about proper pruning techniques is available from community foresters or through DNR resources such as this tree pruning poster.

Treat your valuable ash trees against EAB

Posted on April 1, 2019April 1, 2019 by margueriterapp

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

Spring is the best time to evaluate valuable ash trees and determine if they should be treated to protect them from emerald ash borer (EAB). Emerald ash borer is currently the most damaging threat to trees in the state, killing more than 99 percent of the ash trees it infests.

Insecticide treatments to prevent EAB infestation are usually applied between mid-April and mid-May, so it is important to start planning now. The first thing homeowners should do is check their ash trees for signs of infestation. Woodpecker damage is easy to see this time of year and is often the earliest visible sign of EAB. Photos of other signs and symptoms can be found on the DNR EAB website.

Ash trees with woodpecker "flecking" indicate EAB infestation.

Signs of EAB infestation include woodpecker damage where the birds pick away ash tree bark to feed on larvae.

Emerald ash borer has become so widespread that homeowners should consider treating valuable ash trees no matter where they are in Wisconsin. The highest risk of EAB infestation is within 15 miles of a known infestation, but it is widely believed that there are additional, undetected EAB infestations throughout the state. To see a map of known EAB infestations, visit the Wisconsin EAB website.

While the best time to treat ash trees is before they are infested, treatments of infested trees can still be successful if done while EAB populations within the tree are low or moderate. Some ash trees may be too heavily infested to save or they may have other problems that make them poor candidates for treatment.

Trunk injection treatment for EAB. Credit: Matthew Karst.

Trunk injection treatment to protect against EAB. Credit: Matthew Karst.

You should consider several factors when deciding whether to treat your ash trees. Insecticide treatments can be costly, but the investment may be worthwhile if you consider the many benefits that healthy yard trees provide, including higher property values, better air quality, shading and cooling for homes and more. Removing and replacing your ash trees is another option and may be the best choice for heavily infested and lower value trees. For trees that you decide are worth saving, however, the cost to treat may still be less than removing and replacing them with other species. This factsheet from UW-Extension can help you decide whether a tree is worth treating.

If you decide to treat, or if you want to discuss treatment options with a professional, call a certified arborist or search online and in phone books for other businesses. Check the credentials and insecticide applicator certification of any business before hiring them to treat your ash trees.

Treatments are not economically practical for ash found in woodlots. Any questions about woodlot management should be directed to a professional forester.

Despite the cold winter temperatures in late January and early February, don’t postpone treatment of ash trees. Weather data and collection of overwintering EAB larvae at two sites in Waukesha County predict high insect survival rates in most of the state. Female beetles can lay up to 200 eggs, so EAB populations will quickly rebound from any mortality that occurred due to cold weather.

More information about EAB and management options can be found through the Wisconsin EAB website.

Prepare for the return of gypsy moths

Posted on April 1, 2019April 1, 2019 by margueriterapp

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

Gypsy moth eggs should start hatching in a few weeks as temperatures continue to warm. Homeowners should survey their trees for egg masses and either treat or remove the eggs now to help protect trees from defoliation and reduce future caterpillar populations.

Property owners should start by looking for the egg masses. They can be found on nearly any outdoor surface, including tree trunks, undersides of branches, buildings, firewood piles and other outdoor objects. They are tan-colored lumps about the size of a nickel or quarter. Each egg mass can contain 500 to 1,000 eggs that will soon hatch into hungry caterpillars. While statewide gypsy moth numbers are currently low, isolated trees and locations may have high populations.

Gypsy moth larvae hatch from egg masses on outdoor bowl.

If egg masses are found, there are two options to help reduce pest numbers. Available at many garden centers and retail stores, horticultural oils that suffocate the eggs can be directly applied to the masses. These are most effective when temperatures are above 40 degrees and a return to freezing is not imminent. Alternatively, egg masses within reach can be scraped into a can of soapy water and left to soak for a few days before being discarded in the trash.

Insecticide treatments may be appropriate for larger trees that have many egg masses. Some types of treatment are done before eggs hatch, and some are done while the caterpillars are small. Property owners looking to hire a business to treat large yard trees this spring should contact them soon. A list of certified arborists is available on the Wisconsin Arborist Association website. Additional businesses offering insecticide treatments may be found online or in a phone book. Questions about woodlot management should be directed to a professional forester.

Additional information about management options for homeowners, including sticky barrier bands and burlap collection bands, is available at the Wisconsin gypsy moth website.