Insect

What is causing hardwood species to appear off-color?

Posted on August 29, 2017August 29, 2017 by Kirsten Held

Numerous issues are causing various hardwood species to become off-color this summer. Below I’ve listed a few issues that I’m seeing. Most of these issues do not require any control or any mitigation if your trees are showing these symptoms.

Anthracnose causes irregular dead areas on ash leaflets.

Anthracnose – irregular dead brown blotches on oak leaves and ash leaflets, caused by the fungal leaf disease anthracnose, is making some oaks and ash appear to be browning. Phone calls with concerns about dying trees have been coming in. Symptoms are typically worse in the lower crowns, and the ash I’ve seen with this issue in Marinette, Oconto, and Vilas Counties have very thin looking crowns.

Browning areas on this aspen leaf are caused by aspen blotch miner.

Aspen blotch miner – all ages of trembling aspen are being impacted by aspen blotch miner this year. Aspen crowns appear thin, leaves appear off-color from a distance, “blisters” form on the underside of the leaf, and eventually the leaves curl and brown of the leaves. This is the 4th year in a row that I’ve noticed defoliation by this insect. This year, similar to past years, I’ve seen it in Oconto, Marinette, Florence, Forest, Oneida, and Vilas Counties. Tiny larvae spend their entire life feeding within the leaf and pupate within the area that they mined out. Moths emerge in August and spend the winter in a protected place.

The winding galleries of aspen leafminer make the tree appear grey from a distance.

Aspen leaf miner – for those leaves that aren’t heavily infested with aspen blotchminer, they are often infested with aspen leaf miner. Aspen leafminer is another tiny larvae that spends its life feeding within the leaf, but they create picturesque winding trails that give the leaves a pale appearance.

Balsam poplar browning – a couple of things are going on with the Balsam poplar in Brown and Oconto Counties, including a leaf disease and aspen blotch miner. The trees are thinnest in the lower crowns, but the upper portions don’t look too hot either.

This birch leaf shows both the feeding of Japanese beetles (which don’t eat the veins of the leaf), and a brown blotch where birch leafminer was feeding.

Birch dropping leaves – every year about this time birch will drop a portion of their leaves. Many of those leaves don’t appear to have much damage on them. But there is certainly leaf damage if you look closely at birch. The primary issue that I’ve been seeing this year in Brown, Oconto, Oneida, Shawano and Vilas Counties is from birch leafminer. Dead blotches on the leaves may make you think anthracnose, but holding the leaves up to the light you will discover you can see through them and see signs of insect activity inside the leaves.

Birch look brown – defoliation from Japanese beetle in Minocqua/Woodruff area is causing the birch to appear tan. Defoliation is more significant in the lower canopy, but some trees are heavily defoliated top to bottom. Japanese beetle is something that you may want to do some treatments for. There are many options for treatments, whether excluding them with netting, or using insecticides against the adults, using traps for the adults, or using insecticides or fungal biocontrol against the larvae. UW Extension has a great document with more info on Japanese beetle control.

A young black cherry turns red. While some are being defoliated by lacebugs (causing them to turn red), others like this one have very little defoliation.

Cherry lacewing and cherry turning red – I’m not quite sure what’s going on with all of the cherry. Some of them are turning reddish in color because they are being defoliated by Cherry Lacebug (Oconto County), but others don’t seem to have any damage that I see (Marinette and Oconto Counties), so I’m not sure why they’re turning red.

Maple early fall color – check out Todd Lanigan’s article which highlights the high water levels that are causing stress to lowland trees. Many maples growing in these lowlands are already turning a rich shade of red due to water stress.

Brown blotches on these oak leaves are not anthracnose. The tiny oak leafminer lives within the leaf, feeding on the leaf material. The damaged area eventually turns brown.

Oak leafminer – in Minocqua/Woodruff area I was noticing some oaks were looking a bit brown, which I assumed was probably anthracnose. Always good to double check these things! Once I stopped to check it out I discovered activity from oak leafminer was to blame, causing dead brown areas where the insects feed within the leaf.

Defoliation by oak skeletonizer will leave a layer of cells, which appear like parchment paper if you hold the leaf up to the light.

Oak skeletonizer – scattered light levels of defoliation have been seen in nearly every county in Northeast and East Central Wisconsin. Oak skeletonizer defoliates oak leaves by scraping off a single layer of the leaf, leaving a parchment-like layer on the leaf which turns pale tan. Holding these leaves up to the light makes it clear that they’re defoliated.

A willow leaf is brown where willow flea weevil larvae have been feeding inside the leaves.

Willow browning – although we started this spring with some willow scab that caused significant defoliation, the current issue is the leafmining action of the larvae of willow flea weevil. This is the fourth consecutive year that Brown, Calumet, Marinette, Shawano, and Oconto Counties have experienced significant defoliation of willow from this insect. I’ve also noted this in a few willow in Florence and Langlade Counties this year.

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.

Ladybug larvae don’t look much like ladybugs

Posted on August 29, 2017 by Kirsten Held

Ladybug adults and larvae are great predators of aphids and scales and help keep those pests in check. Ladybug larvae don’t look much like ladybugs though, so you may not notice them, or you may wonder what the tiny monster is that’s munching on aphids. Ladybug larvae come in a variety of colors and shapes. Several people have described them as looking like a small dragon, or for those of you from Rhinelander, perhaps they look like a tiny Hodag.

I recently came across a critter that I would have never guessed was a ladybug larvae; it looked more like a mealybug to me. It was on red pine, and there were no aphids on the red pine, so nothing triggered me to think “ladybug larvae.” After snapping a few pics, I dismissed it as an oddity. But of course oddities are just mysteries waiting to be solved. Mike Hillstrom, my counterpart in Fitchburg, helped narrow this down to a ladybug larvae. Ladybugs in the Hyperaspis genus have larvae that look like mealybugs, and those ladybugs (both larvae and adults) specialize in feeding on pine tortoise scale! How fitting since I found it on red pine!

The following photos illustrate that ladybug larvae come in many shapes, sizes, and colors.

This ladybug larvae, in the genus Hyperaspis, looks like a mealybug and specializes in feeding on pine tortoise scale.

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232

Fall webworm

Posted on August 29, 2017August 29, 2017 by Kirsten Held

Fall webworm started showing up around the middle of July.

Fall webworm web

This is a native insect that feeds on deciduous trees and shrubs, and it is makes an appearance every year in yards and forests. Fall webworm forms loose webbing over branch tips and if it is a small tree, the entire tree can be completely webbed.

Inside the webbing you’ll find caterpillars (alive and dead), partially eaten leaves and frass (caterpillar poop).

Fall webworm caterpillars

Fall webworm is more of a cosmetic problem than a tree health problem, but if you want to control them, the easiest way to do that is to open up the webbing. You can take a rake, fishing pole, long stick, or whatever and open up the webbing. This will allow predators to get at the caterpillars inside the webbing. Or you can use the rake, fishing pole, etc. and roll the webbing up. Then peel the rolled webbing off and place the entire web in a container of soapy water for a couple of days. If you want to use an insecticide, you need to make sure the insecticide is labelled for caterpillars/fall webworm and the spray needs to penetrate inside the webbing. With all pesticides, the user needs to read and follow label directions. There is no need to prune off the branch. If the tree is healthy, the defoliation should not harm the tree. You can find more information on fall webworm here.

Written by: Todd Lanigan, forest health specialist, Eau Claire (Todd.Lanigan@wisconsin.gov)
715-839-1632

New emerald ash borer finds in Wisconsin

Posted on August 29, 2017 by Kirsten Held

Much of Wisconsin has reached peak emergence of emerald ash borer adults.

EAB emergence map as of August 28, 2017. In the north the light green shows peak emergence, and olive is past peak emergence.

EAB continues to be found in new areas. Wisconsin tracks EAB at the municipality or township level. Quarantine counties are shown in tan and infested areas are shown in green on the map below.

EAB quarantine map. Counties shaded in tan are quarantined for EAB, and include much of the southern half of Wisconsin, as well as other counties. Areas shaded in green are the townships and municipalities where EAB has actually been identified, and show that not all counties that are quarantined are fully infested.

EAB quarantine map. Counties shaded in tan are quarantined for EAB, green areas are townships and municipalities where EAB has actually been identified.

Click here for a larger version of the map: EABDetectionsQuarantines

New county quarantines:

none

New finds in counties already quarantined:

Columbia County – town of Caledonia and villages of Poynette and Rio
Crawford County – village of Soldiers Grove
Dodge County – towns of Herman and Theresa
Fond du Lac County – village of Campbellsport
Grant County – city of Boscobel
Green County – town of Sylvester
La Crosse County – city of West Salem
Manitowoc County – city of Manitowoc
Sheboygan County – village of Howards Grove, towns of Mosel, Rhine and Russell

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.

Dutch elm disease is prevalent this year

Posted on August 29, 2017 by Kirsten Held

Dutch elm disease seems to be quite prevalent around the state this year, including the northwoods. Symptoms, including whole tree yellowing and wilting have been occurring this summer, and will continue into this fall. Dutch elm disease is an exotic fungal disease that is spread by the elm bark beetle and can spread underground through root grafts as well. Since bark beetles are generally not attracted to smaller trees (sapling to small pole size) people often get their hopes up that their small elms have “escaped” and will survive and grow to maturity. Unfortunately, as soon as the trees are large enough for the bark beetles to be interested in them the trees may become infected with Dutch elm disease. The first symptom you will see is usually a single branch on which the leaves turn yellow and die. The rest of the tree will die shortly after that. Elm trees attempt to fight the fungus by walling off the portion of the tree where the fungus is located but this can lead the tree to self-induced water deprivation and death. More info on Dutch elm disease, including useful pictures, can be found in the U.S. Forest Service document How To Identify and Manage Dutch Elm Disease.

Dutch elm disease is spread by elm bark beetles, which create artistic galleries under the bark of the tree.

Chemical injections can protect single trees, and some communities in North America still have large stately elms due to this strategy. For new plantings, there are some disease resistant cultivars (those crossed with other elm species) and some disease “tolerant” cultivars of American elm which tolerate the disease without completely killing themselves.

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.

Gypsy Moth Defoliation in Burnett County

Posted on August 29, 2017 by Kirsten Held

An isolated outbreak of gypsy moth was documented on private property in southeastern Burnett County in July. The origin of this population was most likely unintentional movement of outdoor items (e.g., R.V. campers) infested with gypsy moth life stages (e.g., egg masses) from an area where gypsy moth is established. The severity of gypsy moth defoliation ranged from light to heavy across the 60 acre mixed species woodland. Aspen was the most heavily defoliated species, with a 7 acre block of 15 year old aspen sustaining over 75% defoliation. Surprisingly, adult gypsy moths were already flying, and younger caterpillars were still feeding. This was several weeks earlier in the season than normal moth flight would be expected in the state’s north, possibly owing to strong competition between caterpillars within this high population. Burnett County is currently not quarantined for a gypsy moth and the pest is not considered established there.

Gypsy moth caterpillars seeking daytime protection from predators and sunlight on an aspen in the understory.

Gypsy moth caterpillars (Photo by Paul Cigan)

The Slow the Spread program is considering an aerial spray treatment of this property next year to control the population. This isolated outbreak, several counties west of the contiguous quarantined area, provides a good reminder of the important role of human-assisted spread of gypsy moth to new areas – and a reminder of the opportunities to prevent such introductions. Landowners and forestry professionals can help prevent gypsy moth spread by inspecting and cleaning outdoor items when traveling from quarantined to non-quarantined counties, keeping firewood local, and by following other gypsy moth quarantine regulations and reasonable precautions. More information about gypsy moth can be found at gypsymoth.wi.gov.

Written by Paul Cigan, forest health specialist, Hayward (Paul.Cigan@Wisconsin.gov), 715-416-4920.

Elm sawfly with uncommon pink coloration

Posted on August 29, 2017 by Kirsten Held

Elm sawfly is the largest sawfly found in North America and has the disturbing habit of falling out of trees when you walk under the tree. They feed on willow and elm, although in Wisconsin I’ve only seen them causing noticeable defoliation on willow. They may also feed on birch, aspen, basswood, and maple. Most people don’t notice the damage until the larvae begin to migrate down and gather near the base of the tree. Larvae will overwinter as pupae on the ground and emerge as adults the following year.

Pink form of the elm sawfly larvae crawls on the bark of a tree. Photo by Ricky Keller.

Elm sawfly larvae are typically yellow; it is uncommon to find the pink form. (Photo by Ricky Keller)

Larvae grow 1 ½ – 2 inches long and are usually a bright yellow color with a black strip down their back, although occasionally the pink form is found. Adults are a large, dark brown sawfly that looks like a cross between a horse fly and a wasp. Usually defoliation is localized to a single tree or group of trees. Spraying a general insecticide or soapy water should kill these sawflies if you think control is warranted, but these late season defoliators rarely do serious damage to the trees that they defoliate.

H Here you can see how large elm sawfly larvae are, and there are some slight color differences in these. Photo by Chris Plzak. ere you can see how large elm sawfly larvae are, and there are some slight color differences in these. (Photo by Chris Plzak)

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.

Japanese Beetle Damage Extensive in 2017

Posted on August 29, 2017August 29, 2017 by Kirsten Held

Japanese beetles are abundant and causing extensive damage to many species of plants in 2017. Although many landowners in southern Wisconsin have experienced severe damage in the past, this is the first time many in central and northern Wisconsin have experienced an outbreak. The beetles are so common this year in part because populations have recovered after the droughts a few years ago. Many reports are also coming in from newly-invaded areas in northern Wisconsin. Linda Williams noted heavy populations and significant defoliation to birch in the Minocqua/Woodruff area, and growing populations in the Rhinelander area.

Japanese beetles are pests both as larvae and adults. Larvae feed on roots of turf and ornamentals causing pale, dead patches that eventually combine. Adult beetles feed on foliage and flowers of many plant species including trees, fruits, vegetables and weeds. Linden, birch, crabapple, mountain ash, Norway maple and Japanese maple are favorite host trees. Adults eat between the veins causing leaves to look lace-like. Trees severely damaged turn brown and become partially defoliated.

Adult Japanese beetles feed on a wide-variety of plants causing leaves to have a lace-like appearance.

Many treatment options are available, but in outbreak years landowners may be resigned to limiting damage to their favorite plants.

Control options include:

Remove beetles by hand and squish or put in soapy water.
Spray beetles with an insecticide labelled for Japanese beetle control.
Do not irrigate during peak adult flight to make the soil less attractive for egg laying.
Apply carbaryl (Sevin), clothiandin (Arena) or trichlorfon to the soil in early to mid-August to kill larvae.
Apply imidacloprid, chorantraniliprole, clothianidin and thiamethoxam to soil from May to early July to kill larvae.

Some common control options are not recommended. Traps are typically ineffective as they attract more beetles to the area. Biological control of grubs using milky spore disease or others biologicals is often inconsistent.

For more information see UW-Extension’s fact sheet.

Written by Mike Hillstrom, forest health specialist, Fitchburg (Michael.Hillstrom@Wisconsin.gov), 608-513-7690.

White spotted sawyer

Posted on July 27, 2017 by colleenrobinson

Our native pine sawyer has a “spot” between the elytra (yellow arrow) that Asian longhorned beetle does not have. They also will appear dusty or pitted.

White spotted sawyer, sometimes called Pine Sawyer, is a native longhorn beetle. It is often mistaken for Asian Longhorned Beetle (ALB). How can you tell the difference between our native beetle and ALB? First of all, size: ALB is a big burly beetle, while our native sawyer beetle looks slim in comparison. Second, ALB has a very smooth shiny appearance with distinct white spots on black wing covers, whereas our native sawyer beetle will appear pitted or dusty, and the white spots may be less distinct or absent. Finally, our native beetle will have a nice white dot “between its shoulders” where the wing covers meet, and ALB does not have this.

Adult pine sawyer beetles feed on the bark of twigs which can cause branch tip mortality.

Pine sawyer larvae develop in weakened, recently dead, or recently harvested conifers. Larvae first feed in the phloem layer then progress to inner wood. They will pupate within the tree and adults will chew their way out leaving large round exit holes. Adults feed on needles and the bark of twigs. Areas this year which will attract white spotted sawyers include areas of storm damaged pine, and areas of conifer decline due to high water levels, as well as any other areas where conifers are stressed.

If you find a beetle and are unsure whether it’s ALB or our native sawyer, please take some photos to send for identification.

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.

Poplar vagabond aphid

Posted on July 27, 2017 by colleenrobinson

Poplar vagabond aphid feeding on the buds of aspen or cottonwood cause the tree to form a fleshy, hollow gall around the insects.

Galls caused by poplar vagabond aphid form at the ends of aspen and cottonwood branches. The galls are caused by aphids feeding at the tips of twigs. This feeding causes the tree to grow an elaborate structure that the aphids can live inside. One of the galls in the photo is broken open so you can see the aphids inside. This damage does not usually kill the tree, but reduces branch growth because the formation kills the terminal buds. The aphids feed during the spring and early summer within the gall, and then leave to feed on an unknown second host plant. When the aphids leave the gall it will turn brown and woody, and will remain on the tree for several years before weathering off. Adult aphids return later in the fall and lay eggs on the woody gall or in crevices in the bark. Eggs will hatch the following spring and repeat the process. For control, prune the galls prior to egg hatch early in the spring. Because the aphids return to the same trees with the original galls it is common to see a single tree heavily infested while a nearby tree will have no galls at all. I have always seen this problem in trees that are open grown, either along the edge of a stand, along a roadway or fence row, or in a yard. I’m not sure how much of a problem it is in the interior of a stand.

Poplar vagabond aphids, which are covered in a white waxy material, are protected inside the large hollow galls formed by the tree. They suck the trees’ sap.

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.