Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665
Ants, aphids, and sooty mold can cause stunting and death of young white pines, but fortunately there are some steps you can take to protect your trees from these pests.
Ants (upper right) guard aphids from predators as they feed. In exchange, the ants collect the sweet honeydew excreted by the aphids.
Continue reading “Ants, aphids and sooty mold on white pine”
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.
Continue reading “Watch for cherry scallop shell moth defoliation”
Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665
Defoliation from larch casebearer (Coleophora laricella) is showing up in some areas of northeast and northcentral Wisconsin. The defoliation is patchy and of moderate intensity, resulting in trees with various degrees of browning due to the insect’s feeding habits. Some appear pale yellow or brown throughout the crown while others only have partial browning.
Defoliation by larch casebearer will cause needles to turn yellow then brown. Trees will usually send out more needles and be green again by mid-summer.
Paul Cigan, forest health specialist, Hayward, Paul.Cigan@wisconsin.gov, 715-416-4920
Jack pine shoots are flagging over a large area of northern and west central Wisconsin this summer due to feeding injury from the jack pine resin midge. Symptoms include scattered dead branch tips and pitch masses on terminal buds and on twigs where larvae feed.
Jack pine with dead branch tips. Photo: Paul Cigan.
Continue reading “Branch flagging caused by jack pine resin midge”
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.
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”
Paul Cigan, forest health specialist, Hayward, Paul.Cigan@wisconsin.gov, 715-416-4920
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.
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
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.
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.
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.
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.
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.
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.
Dense EAB larval galleries on the wood surface of infested white ash.
