Insect

Native caterpillars not a major concern for trees

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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

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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” →

Northwestern county forests trap for EAB

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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

Posted on by margueriterapp

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

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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

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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.

Trees sought for EAB biocontrol efforts

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The U.S. Department of Agriculture’s (USDA) Biological Control Facility is seeking donations of living green ash trees from Wisconsin landowners. Infested live trees are needed to rear the parasitic wasps that prey upon emerald ash borer (EAB) eggs and larvae. 

USDA staff in Brighton, MI rear stingless, parasitic wasps for release in EAB-infested states. Currently, the biological control facility rears four species of wasp, three of which attack EAB larvae and one that attacks eggs. Finding and harvesting living green ash infested with EAB is a vital part of the biocontrol program, allowing staff to breed EAB colonies from adult beetles. These colonies then support the rearing of almost a million parasitic wasps each year. To learn more about the USDA’s EAB Program, read the EAB Story Map.

The stingless wasp Spathius agrili lays up to 20 eggs on its host. Eggs hatch and the larvae feed and eventually kill the EAB larva.

The stingless wasp Spathius agrili lays up to 20 eggs on its host. Eggs hatch and the larvae feed and eventually kill the EAB larva.

Another wasp, Tetrastichus planipennisi, lays its eggs inside EAB larvae where they feed and develop into red-eyed pupae before completing their lifecycle.

Another wasp, Tetrastichus planipennisi, lays its eggs inside EAB larvae where they feed and develop into red-eyed pupae before completing their life cycle.

The facility is looking for donations from properties that meet the following criteria:

  • Live green ash between 8-20 inches diameter
  • 25 or more suitable ash trees
  • Trees may show signs of decline but must be alive
  • Located in southeastern and eastern Wisconsin north up to Green Bay

USDA staff will conduct landowner site visits after leaves have budded in spring. If a site meets most of the criteria, staff will return in late summer to peel back bark of trees one by one. This is the EAB larval evaluation method used to determine infestation levels. Trees are then selected for harvest based on that methodology.

USDA staff evaluate ash trees for harvest by cutting a ‘bark window’ to estimate the degree of infestation from the live EAB larvae they see.

USDA staff evaluate ash trees for harvest by cutting a ‘bark window’ to estimate the degree of infestation from the live EAB larvae they see.

Harvests will occur weekdays from September to May. The USDA will arrange the harvests, including selecting subcontractors and paying for the work. Sites are remediated to pre-harvest conditions to the best of the contractor’s ability.

Lands enrolled in Wisconsin’s Managed Forest Law (MFL) or Forest Crop Law must file a MFL Cutting Notice (Form 2450-132) 30 days prior to cutting. Contact your local Tax Law Forestry Specialist for assistance.

All private landowners must submit a county cutting notice prior to harvest. This cutting notice is separate from the MFL cutting notice and should be filed with the county clerk. Learn more about cutting notices at this DNR webpage.

For more information about the USDA program and if you are interested in participating, contact Paul Nelson at paul.m.nelson@aphis.usda.gov or 734-732-0025.

Revised EAB insecticide guide now available

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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.

Protect oaks from oak wilt by waiting to prune

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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.

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

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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.