Insect

Gypsy Moth Defoliation in Burnett County

Posted on 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 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.

HHere 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 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.

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 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.

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.

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 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.

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.

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.

Oak leaf tier and oak leaf roller

Posted on by colleenrobinson
Oak leaf rollers and oak leaf tiers fold over or roll leaves which protect them from predators.

Oak leaf rollers and oak leaf tiers fold over or roll leaves which protect them from predators.

Last month I reported on a location in Marinette where oak leaf tier and oak leaf roller were defoliating oak. Since then I had a report of this same combination of pests causing defoliation near Rhinelander. Typically this defoliation is not severe, but when the leaves are rolled up or folded in half it can make it look like the defoliation is more severe.

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

Gypsy moth adults appearing now

Posted on by colleenrobinson
Female gypsy moth lays an egg mass.

Female gypsy moth lays an egg mass.

As of mid-July, DNR forest health staff have received reports of adult gypsy moths present as far north as Burnett County. The brown-shelled pupae and white female moths can be crushed with a stick. The remaining caterpillars will also pupate soon, and where the caterpillars are a problem, they can be crushed, drowned in soapy water, or sprayed with insecticide or insecticidal soap. Continue reading “Gypsy moth adults appearing now” →

Emerald ash borer new finds in Wisconsin

Posted on by colleenrobinson
EAB emergence map as of July 10, 2017. Tan colors in the north are approaching peak emergence, light green is peak emergence, and olive is past peak emergence.

EAB emergence map as of July 10, 2017. Tan colors in the north are approaching peak emergence, light green is peak emergence, and olive is past peak emergence.

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

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 EAB Detections and Quarantine map below.

New county quarantines

  • none

New finds in counties already quarantined

  • Crawford County – city of Prairie de Chein
  • Grant/Iowa County — city of Muscoda
  • Milwaukee County — village of Whitefish Bay
  • Outagamie County — town of Grand Chute
  • Sauk County – village of West Baraboo
  • Waukesha County — village of Merton
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.

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

Defoliation by rose chafers and Japanese beetles is showing up.

Posted on by colleenrobinson

Rose chafers and Japanese beetles are starting to cause problems in some areas this summer. So far reports and damage are generally light for Japanese beetles, but in some areas rose chafer defoliation is noticeable. 

Rose chafers are beetles that can defoliate many plant species. They have fairly long legs, and are a dusty mustard color.

Rose chafers are beetles that can defoliate many plant species. They have fairly long legs, and are a dusty mustard color.

Rose chafer defoliation was reported from Florence, Marinette, Oconto, Vilas, and Waupaca counties this year. Rose chafers are more common in areas with sandy soil where they will lay their eggs. The eggs hatch into white grubs which live in the soil and feed on grass and weed roots. My books inform me that birds can die if they eat adult rose chafers because of a poison in the beetles that affects the heart of small, warm-blooded animals. For information on rose chafer control, check out UW Extension publication A3122.

The last significant defoliation that I noted from rose chafer was in 2012, and before that it was 2005. These beetles feed on a wide variety of plants and prefer blossoms, but they will skeletonize leaves as well. Control is difficult because the adults are good fliers and can easily fly in from neighboring areas to re-infest your freshly sprayed plants. 

Japanese beetle populations will emerge in southern Wisconsin first, typically by the first part of July. Some areas of the state have building populations while others, like the Madison area, may have populations that exploded in the past and are more stable now. These insects are occasionally mistaken for EAB because they have some metallic green coloring near their heads.  More commonly people will refer to the multicolored Asian ladybeetles as Japanese beetles, but the ladybugs are ladybugs and Japanese beetles are scarab beetles.

Japanese beetle adults feed on the flowers and leaves of over 300 plant species, including trees, shrubs, and herbaceous plants. They can cause significant defoliation. The larval stage of Japanese beetle is a white grub that lives in the soil and feeds on plant roots.  University of Wisconsin Extension has a Japanese beetle webpage including information on the damage caused by the adults, the damage caused by the white grubs, and control measures that are useful on the adults and the larvae. 

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

Spruce budworm defoliation is present

Posted on by colleenrobinson
Spruce budworm defoliation is not as noticeable this year, although it is still present as you can see here with many needles missing.

Spruce budworm defoliation is not as noticeable this year, although it is still present as you can see here with many needles missing.

Spruce budworm damage is present this year but in many areas it is less noticeable than in past years. I believe this is due to a couple of things:

  1. The many storms we had this spring with heavy rainfall and strong winds may have washed some of the caterpillars out of the trees. They definitely washed budworm damaged needles off the tree. Damaged needles typically remain on the tree and turn a rusty brown, so not having these needles on the tree makes it less obvious where defoliation is present this year.
  2. Due to the constant rainfall this year, the growth on balsam fir and spruce seems to be quite good in general, which leads to additional green needles on the tree this year. This makes the trees look more green and less defoliated, but spruce budworm is still there.

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