South Central WI Forest Health

Please report damage to white and bur oaks

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By Mike Hillstrom, forest health specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov, 608-513-7690; Alex Feltmeyer, forest health specialist, Plover, Alex.Feltmeyer@wisconsin.gov, 715-340-3810; and Paul Cigan, forest health specialist, Hayward, Paul.Cigan@wisconsin.gov, 715-416-4920

Forest health staff are again noticing health issues with white and bur oaks in 2019. A few trees with dieback in 2018 were recently resurveyed and were found to have recovered well. However, variable symptoms are appearing again in some areas. Forest health staff are conducting site visits to determine if the causal agents are the same as in 2018. Last year, leaf damage resulted from leaf fungal pathogens and twig damage was caused by Botryosphaeria fungi and gall wasps.

Please report any white or bur oak issues you notice to your local forest health specialist.

Same bur oak in June 2019 showing good recovery with only minor dieback.

Same bur oak in June 2019 showing good recovery with only minor dieback.

Bur oak with moderate crown dieback in June 2018.

Bur oak with moderate crown dieback in June 2018.

Professionally-designed HRD guidelines now available

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Cover page of HRD guidelines documentThe professionally-designed version of the Heterobasidion root disease (HRD) stump treatment guidelines is now posted on the DNR’s HRD webpage. The revised stump treatment guidelines, developed to reduce the risk of introduction and spread of HRD in Wisconsin, were implemented January 1, 2019. The content is the same as the guidelines that were approved last year, but this document has a layout that is much more user-friendly. Explore the new look of the HRD guidelines.

 

Watch for cherry scallop shell moth defoliation

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

Cherry scallop shell moth, a native defoliator, is back again in Jefferson and Walworth counties. Several residents recently reported large numbers of moths in areas that have experienced multiple years of defoliation by this insect.

Eggs laid by those moths are expected to hatch soon, and the emerging caterpillars will begin feeding on cherry tree foliage. Hopefully, populations of egg-parasitizing natural enemies will be high enough this year to provide relief to stressed trees.

Early instar caterpillars on cherry leaf.

Early instar caterpillars on cherry leaf.

Continue reading “Watch for cherry scallop shell moth defoliation” →

Native caterpillars not a major concern for trees

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Mike Hillstrom, forest health specialist, Fitchburg, Michael.Hillstrom@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” →

Needle and leaf diseases are back!

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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.

Continue reading “Needle and leaf diseases are back!” →

Branch tips littering the ground under your trees?

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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?” →

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.

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.