Category Archives: Beetles

Weathering the Emerald Storm: EAB in Wisconsin

Like a kid watching a summer thunderstorm slowly rolling in and wondering how long until the rumbles would be directly overhead, I’ve had a morbid fascination with watching the progression of the emerald ash borer in the Midwest for over a decade.  Although emerald ash borer wasn’t found in Wisconsin until 2008, my connection with EAB precedes that by a few years.  It turns out my first job as a budding entomologist was as a summer intern for UW-Extension looking for signs of the insect in the state during the summers of 2005 and 2006.  Fast forward twelve years and that storm is finally overhead, at least in my neck of the woods.  I knew such a time would come, but it really hits close to home when the sounds of chainsaws mark the final days of your neighborhood’s ash trees—at least the ones that aren’t being treated. 

EAB Detection and Quarantines as of May 19, 2017. Click for larger version. Image source: WI-DATCP.

At the time of writing, 42 counties in Wisconsin have been quarantined for EAB.  While the southeastern part of the state has already been hit hard (green on the map above), a large chunk of the state has not yet seen the emerald ash borer or has only seen light pressure (click the map above to see more details on this topic). Unfortunately, this means that the emerald storm will only be getting worse over the coming years.  Along these lines, when EAB first arrived in Wisconsin, spread was slow and the annual number of new community-level detections was small.  However, as the populations of this insect have built up in the state, the number of new detections has increased dramatically as illustrated below:

Chart created using data from WI-DATCP on May 22, 2017. Click for a larger version.

Unfortunately, the outlook for the Midwest’s ash trees doesn’t look good and we’ll still be dealing with this insect for years to come.  Ironically, this isn’t the first time that we’ve watched a scenario like this play out.  As the baby boomer generation grew up, they watched as elms were devastated by the likes of Dutch elm disease.  As with emerald ash borer, Dutch elm disease had significant impacts on forested and urban areas and led to irreversible changes in the landscape around us.

With all this Doom-and-Gloom, is there a light at the end of the tunnel?
Possibly—but it may be a ways off.  For the time being, there are insecticide treatments available that can maintain the health of ash trees, although treatments are costly and are only feasible for relatively small numbers of trees.  Biological control is being explored as a potential way to control EAB populations, although results have been limited thus far.  However, with any biological control program, it can take years to work the kinks out of the system and see results.

A long-term plan may be to develop varieties of ash trees that are resistant to attack by the emerald ash borer.  In several locations in Ohio and Michigan, scientists have found a small percentage of “lingering” ash trees that have survived the initial onslaught of EAB and are monitoring those trees over time for continued survival and genetic traits that may help stave off infestations.  Interestingly, one particular species of ash (blue ash, Fraxinus quadrangulata) may hold important clues for long-term ash survival.  In some spots in Michigan, >60% of blue ash trees have survived in areas attacked by emerald ash borer.  While tree breeding programs may ultimately develop a resistant ash variety, this is likely years away and for the time being we’ll have to face the emerald storm.

Larval tunnels of the emerald ash borer beneath the bark of an ash tree. This damage disrupts the flow of water and nutrients and ultimately kills the tree. Image source: PJ Liesch, UW Entomology.

Wisconsin’s Top Insect Trends of 2016 (#5 – #1)

In this post, we’re continuing to count-down 2016’s top insect trends in the state.  This is the final post in a three part series.  Part I (2016’s diagnostic lab statistics) can be found here and Part II (Top Insect Trends Numbers 10-6) can be found here.

#5: The spread of the emerald ash borer increased dramatically in the state last year. Photo Credit: Howard Russell, Bugwood.org.
#4: Fall invading insects, such as boxelder bugs are well known, but the strawberry root weevil and other weevils can sneak indoors during the summer months. Photo Credit: Whitney Cranshaw, Bugwood.org.
#3: Several scarab beetles, including the rose chafer caused notable plant damage last year. Photo Credit: Clemson University Extension, Bugwood.org.
#2: An elusive adult rabbit bot fly. Photo Credit: Quentin Sprengelmeyer.
#2: An inch long bot fly larva from a mouse. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.
#1: Fierce mosquito pressure in many parts of the state combined with the Zika stories in the news gave mosquitoes the top spot in 2016's insect trends. Photo credit: Susan Ellis, Bugwood.org.

 

5) Metallic Wood Boring Beetles
Two different metallic wood boring beetles (Family Buprestidae) had strong years in 2016. The first, the emerald ash borer, is no stranger to Wisconsinites these past few years. While there were only 3 new counties (Portage, Wood, Sawyer) added to the state quarantine map in 2016, there were over 80 municipalities with their first confirmed EAB infestation last year (out of 227 municipalities with documented EAB finds at the end of 2016). With that said, EAB has greatly picked up steam these past few years and is attacking ash trees at a rapid rate in Midwest.

Another metallic wood borer that seemed to have a good year was the twolined chestnut borer. Unlike the invasive emerald ash borer, the twolined chestnut borer is is native to North America and tends to attack stressed trees (oaks). In these cases, trees might be stressed by factors such as disease, drought stress, winter injury, or damage from other insects. The UW Insect Diagnostic Lab noticed a distinct increase in cases of the twolined chestnut borer this past summer, although the underlying stress might have begun affecting trees several years ago. With the high value of oak trees in the landscape, this insect is definitely a pest that tree care companies should have on their radar for the near future.

4) Home-Invading Weevils
Many Wisconsinites experience or at least are familiar with insects that sneak indoors in the fall, such as boxelder bugs and multicolored Asian lady beetles. There’s also a group of broad-nosed weevils that happen to sneak indoors during the summer months. Species in this group include the strawberry root weevil, the imported longhorned weevil, and others. Once indoors, these weevils tend to stumble around in a slow, somewhat tick-like manner, causing concern to homeowners. But fear no weevil, for these insects are completely harmless. A broom or vacuum cleaner are often the best tools to deal with them. While broad nosed weevils can be somewhat common, reports coming in to the UW Insect Diagnostic Lab suggest that numbers of these home-invading beetles were up in 2016.

3) Scarab Beetles
A number of scarab beetles had noteworthy activity in 2016, including several important landscape pests. Scarab beetles can be an extremely common group of insects, with well over 100 species in Wisconsin alone. Perhaps the best known (and most infamous) member of this group would be the Japanese beetle (Popillia japonica), which seemed to rebound last year after a few quiet years. In parts of the state with sandy soil, the rose chafer was present in high and damaging numbers. Similar to Japanese beetles, rose chafers are fond of feeding on a wide range of plants from landscape shrubs to fruit trees.

Two other scarab beetles were noteworthy in 2016: the Northern masked chafer and the European chafer. This past year marked the first year that the larvae of these beetles (white grubs) had been found damaging turfgrass in the state: Rock County (NMC) and Door county (EC). Previously, turfgrass managers only had to contend with the white grubs of Japanese beetle and the occasional May/June beetle.

2) Bot Flies
[Disclaimer: bot flies are not for the faint of heart! If you’re preparing to eat lunch, you may want to skip down to #1.]
Bot Flies-Click to Read

If you’re not familiar with bot flies, these creatures may seem like something out of a science fiction movie. In their simplest terms, bot fly larvae are essentially large, flesh-inhabiting maggots. When fully mature, the maggots can be over an inch long and are covered with tiny backward-facing spines, making removal nearly impossible from their host. Adult bot flies are very short lived and somewhat resemble bumble bees or certain horse flies in their size and coloration. In a typical year, the UW Insect Diagnostic Lab might receive 1-2 reports. For whatever reason, bot flies had a great year in 2016 and several dozen reports came in to the lab. The common species observed in Wisconsin last year were from the genus Cuterebra and parasitize small mammals such as: mice, chipmunks, squirrels, and rabbits.  The maggots live and feed beneath the skin of their mammal host for weeks before popping out to pupate.  The mammal hosts generally seem to tolerate their companions, although the concept of bot flies may give you a creepy-crawly feeling.
[Bonus material: there is a bot fly (Dermatobia hominis) in South and Central America that affects humans]

 

1) Mosquitoes
With all the stories about the Zika virus in the news, it was difficult to avoid hearing about mosquitoes in 2016. In addition, with the heavy rains many parts of Wisconsin received last year, it was equally challenging to venture outdoors and avoid mosquitoes. In many parts of the state, mosquito pressure was severe last year, giving mosquitoes the top spot on the 2016 list. If there’s a silver lining to the mosquito story last year, it has three parts:

  • The mosquitoes that were dreadfully abundant last year (floodwater mosquitoes) aren’t important vectors of human disease. Yes, they might have ruined that evening cookout, but at least they weren’t making anyone ill.
  • Reports of mosquito-borne diseases (such as West Nile Virus) were relatively low in the state last year.
  • Zika virus was not a major issue in Wisconsin, as the mosquito species responsible for that disease haven’t been found here [Read more about this topic in this post]

The “New” Japanese Beetle in the Midwest

Move over Popillia japonica, there’s a new “Japanese beetle” in town.

As is typical in a given year, Wisconsin sees a few new invasive species in the state each year.  In 2016, one of the surprises was the arrival of the “two banded Japanese weevil” (Pseudocneorhinus bifasciatus), often simply called the “Japanese weevil”.  Weevils themselves are technically a type of beetle from the hyper-diverse family Curculionidae, which contains a plethora of weevils, curculios, and multitudes of bark beetles.  When talking to the public, it’s amazing how often the Japanese beetles feeding on landscape plants during the summer are mixed up with the Asian lady beetles (Harmonia axyridis), which invade homes in the fall.  Given the name of this new “Japanese weevil”, I’m expecting this creature to confuse the situation even more.

What is the Japanese Weevil?

The Japanese weevil (P. bifasciatus) is a non-native beetle that feeds on a wide variety of landscape plants, particularly shrubs.  Adult Japanese weevils are ~ ¼” long with a gray or brownish, pear-shaped body with black bands across the wing covers (elytra).  The pale larvae (grubs) live in the soil and feed on roots of suitable host plants.  We haven’t had this pest in Wisconsin long enough to fully understand the local life cycle, but given the pattern in other states, this insect will most likely complete one generation per year, with adult presence and feeding damage occurring during the summer from late June through August.

Photo Credit: Michael C. Thomas, Florida Department of Agriculture and Consumer Services, Bugwood.org
The invasive two banded Japanese weevil (Pseudocneorhinus bifasciatus). Photo Credit: Michael C. Thomas, Florida Department of Agriculture and Consumer Services, Bugwood.org

Where’s the Japanese weevil from?

Very similar to the Japanese beetle (Popillia japonica), the Japanese weevil is native to Japan and first popped up in the US in 1914, via the transport of infested nursery stock.  Like the Japanese beetle, the Japanese weevil feeds on a wide range of landscape plants.  When it first showed up in Wisconsin in 2016, the Japanese weevil was found on a variety of ornamental plants in Madison, WI.  How this species got to Wisconsin remains a mystery, but the movement of infested potted plants is the most likely explanation, as this insect is not capable of flight.  While the Japanese beetle is common across many parts of eastern North America, the Japanese weevil has a much more scattered distribution and can be found primarily in the Mid-Atlantic region with scattered cases in the Illinois, Iowa, Wisconsin and Oklahoma.

What does this insect mean for Wisconsin?

Luckily, it seems that the Japanese weevil may not be nearly as big of a threat to landscape plants as the Japanese beetle.  When lots of Japanese beetles are present, entire trees can have their leaves nibbled into a lace-like skeleton.  In contrast, when the Japanese weevil feeds, it tends to cut notches out of the edges of leaves.  This damage can resemble the feeding of many caterpillar species, and healthy plants should be able to tolerate the feeding.  Reports from other states suggest that this insect unlikely to cause very severe damage.

The invasive two banded Japanese weevil (Pseudocneorhinus bifasciatus). Photo Credit: Michael C. Thomas, Florida Department of Agriculture and Consumer Services, Bugwood.org
The invasive two banded Japanese weevil (Pseudocneorhinus bifasciatus). Photo Credit: Michael C. Thomas, Florida Department of Agriculture and Consumer Services, Bugwood.org

Think you’ve found the Japanese weevil?

If you come across any beetles in Wisconsin feeding on landscape plants that resemble the Japanese weevil, send digital images and/or physical specimens to the UW Insect Diagnostic Lab for confirmation, so we can track this new arrival in the state.

Japanese Beetles: 100 Years and Counting

Ask any gardener or landscaper in the Midwest what their least favorite insect is, and the Japanese beetle will probably be near the top of the list.  Think of the plants that this insect feeds on: ornamental trees and shrubs like lindens, birches, crabapples, and roses, fruit crops like apples, pears, plums, raspberries, and strawberries, and garden and vegetable crops like beans and corn, as well as hundreds of other plants.  It’s no wonder gardeners have to be on alert for this insect.

japanese-beetle
Photo Credit: PJ Liesch, UW-Madison Entomology

So why the resurgence of Japanese beetle activity in 2016?  Every winter, a common topic I’m asked about is my “insect forecast” for the coming year.  Before winter had even ended, there was good reason to believe that the Japanese beetle would pop back up the state in 2016–and Mother Nature may be the cause.  Japanese beetle larvae (white grubs) spend the winter in the soil below ground.  In July, August, and September, these grubs can be found in the upper portion of the soil where they feed on the roots of turfgrass.  As winter approaches, the grubs tunnel deeper into the soil where they avoid being killed by a hard freeze.  In most parts of Wisconsin, we had a reprieve from Japanese beetles the past two years.  I suspect this may be due to the brutal winter of 2013-14, which had some extended periods of sub-zero temperatures.  It’s quite feasible that this deep frost killed many grubs and led to lower adult populations the following summer (2014).  Given enough time, the Japanese beetle populations were destined to rebound at some point, and the mild (el-Niño) conditions this past winter might have been just what they needed to bolster their numbers.  Unless we face another brutal winter in the next few years, I suspect that Japanese beetle numbers will be up for the foreseeable future in the state.

Ironically, there’s an important milestone to recognize for this invasive pest this year–the Japanese beetle was detected for the first time in New Jersey 100 years ago, in 1916.  Slowly, but surely, this insect spread through many parts of the eastern US, and has been spotted on occasion in isolated spots in the western states.  We also have an interesting history of Japanese beetles in Wisconsin.  Technically, our first detections occurred in the southeast part of the state in the 1960’s, although these populations struggled to take hold.  At the time, this seemed to be a comforting sign–perhaps, our famed “frozen tundra” was simply too cold for them.  However, by the 1990’s, Japanese beetles had gotten a solid foothold in the state and they’ve been around much to the chagrin of gardeners ever since.

Photo Credit: Michael C. Thomas, Florida Department of Agriculture and Consumer Services, Bugwood.org
The “new” Japanese Beetle on the block: the invasive Japanese weevil (Pseudocneorhinus bifasciatus). Photo Credit: Michael C. Thomas, Florida Department of Agriculture and Consumer Services, Bugwood.org

Interestingly there’s also a new “Japanese beetle” that showed up in Wisconsin this year: the invasive Japanese weevil (sometimes called the “two-banded Japanese weevil”).  Stay tuned more information about our newest invasive species in Wisconsin.

Buckets of Beetles

Many naturalists will relate to this post: as nature enthusiasts, everyday tasks sometimes end up taking much longer than expected due to fascinating biological distractions just beneath our feet.

As I was mowing the front lawn over Memorial Day weekend, I stumbled upon a prehistoric-looking stag beetle, which is always a neat creature to come upon.  As an entomologist, my first instinct was to pick it up to make a closer examination.  Typically, I run into stag beetles a few times each year and it’s usually the large, “reddish brown stag beetle”: Lucanus capreolus (see image below).  The beetle I found was a bit smaller, darker, and lacked the bicolored legs of L. capreolus, but was still a good-sized insect at over an inch long.  After a beverage break and some Internet browsing, I figured I must have been looking at the closely related Lucanus placidus.  Interesting, I thought, and placed the stag beetle back on a portion of the lawn that had already been mowed, lest it face the wrath of a metallic tornado.

At roughyl 2 inches long, the "reddish brown stag beetle" (Lucanus capreolus) is amongst our largest beetles in Wisconsin. Photo Credit: PJ Liesch, UW-Entomology
At roughly two inches long, the “reddish brown stag beetle” (Lucanus capreolus) is amongst our largest beetles in Wisconsin. Photo Credit: PJ Liesch, UW-Entomology

Another pass or two with the mower and I spotted a few more stag beetles.  I was no longer simply stumbling upon these beetles—something else must be going on.  Once again, I stopped mowing to take a closer peek in the taller grass, only to find even more beetles.  Within the span of five minutes, I had found nearly forty stag beetles in the lawn near a low spot where a tree must have previously stood.  As with the first specimen, I gently relocated these beetles and rushed to finish mowing in the dwindling light.

Around 10:30 PM, I wandered back outside with a flashlight to see what the beetle situation looked like.  I had no idea what I was about to stumble upon—hundreds of battling stag beetles!  Male stag beetles use their large mandibles to compete for females, which made my front lawn seem like a combination of the Bachelorette mixed with Gladiator.  It was astonishing to see the sheer numbers of stag beetles present in a single spot at a given time.  In an attempt to count them, I starting placing them into an empty flower pot.  The forty I had spotted earlier seemed like a drop in the bucket—quite literally!  The bucket was nearly full to the brim with 250 beetles, and I eventually stopped counting.  I’d estimate that I spotted nearly 400 stag beetles in a single night.

A handful of battling stage beetles. Photo credit: PJ Liesch, UW Entomology.
A handful of battling stage beetles. Photo credit: PJ Liesch, UW Entomology.

I did eventually confirm that the species of stag beetle in the lawn was Lucanus placidus.  According to the scientific literature, aggregations have been noticed in lawns on occasion.  In Kriska and Young’s “Annotated Checklist of Wisconsin Scarabaeoidea” (2002) an aggregation of 15 males and females was once noted beneath a black oak tree in the state.   I’m not entirely sure what kind of tree used to occupy the low spot in my front lawn, but the stag beetles obviously loved it (note: stag beetle larvae live in decaying wood).  As an interesting side note, the same low spot was also home to the “Dead Man’s Fingers” fungus (Xylaria polymorpha), another biological curiosity in its own right.

It’s amazing what you can find in your own back yard or front lawn if you take the time to look!

Wisconsin’s Top Insect Trends of 2015 (#10 – #6)

What were Wisconsin’s top insect trends of 2015?  In this post, we’ll look at the first half of our count-down.  

This is the second post in a three part series.  The first post of the series (2015’s diagnostic lab statistics) can be found here.

10) Mosquitoes and ticks:
Like most years, Wisconsin had a pretty good mosquito season.  Overall, we were close to the average rainfall mark during much of the year, which meant the typical batch of mosquitoes starting after Memorial Day.  In many parts of the state, mosquitoes were prevalent throughout June, July, and August.  However, this is Wisconsin after all, and mosquitoes seem to be one pillar of summer culture along with beer, cookouts, and fishing.  The silver lining of the mosquito story is the fact that West Nile Cases were low for the year, with only four confirmed human cases reported in the state in 2015.

Deer Tick
Adult female deer tick. These ticks can now be found throughout the state and roughly 40% of adults are carrying the microorganism responsible for Lyme Disease. Photo credit: Scott Bauer, USDA Agricultural Research Service, Bugwood.org

While there wasn’t anything out of the ordinary with the mosquitoes last year, ticks seemed to have a particularly good year in the state.  Deer ticks, which can vector Lyme disease can be found essentially statewide.  From the standpoint of an emerging health threat, deer tick populations have exploded in the past few decades (our first deer tick wasn’t found in the state until the 1960’s).  A recent nation-wide study found that deer ticks were found in nearly half of the counties in the U.S.  One of the more alarming trends is urban encroachment.  Historically, ticks seemed to be the type of creature you’d pick up if you were out hunting or hiking through the woods.  In the recent past, we’ve noticed an increase of ticks found in more urban environments, such as parks and backyards.  With roughly 40% of the adult ticks in Wisconsin carrying the microorganism responsible for Lyme Disease, this is an issue that will continue to exist in the state for years to come.

9) “Sucking Insects”
A certain group of insects (the Order Hemiptera) are sometimes known as the “sucking insects” because they possess tube-like mouthparts which are used by many species use to drink fluids from plants.  Two of the members of this group, the aphids and the scale insects had a great year in 2015.  When these insects feed on plants, a common sign is the presence of sticky, sugary honeydew, which attracts ants and yellowjackets, and can result in the growth of black sooty mold.  Aphids and scale insects are common and typically present in low numbers, but the conditions must have been just right for their populations to thrive in 2015.  As a result, there were many reports throughout the state of honeydew “raining” down from trees and shrubs onto vehicles, decks, outdoor furniture, and people below.  If you felt “rain” on a sunny day last summer, the actual cause may have been honeydew dripping down from aphids or scales in the trees above!

Lecanium Scale
Lecanium scales producing sticky honeydew (clear droplets).  Photo credit: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Bugwood.org

 

8) Long Lost Pests: Japanese Beetle and Gypsy Moth
Two of our best-known landscape pests, the Japanese Beetle and the Gypsy Moth had been very quiet in 2014, but resurfaced last year.  Japanese beetles had been low across the state in 2014, likely due to the brutal winter of 2013-14 killing many of the soil-dwelling grubs.  While we did see an increase in beetle activity in 2015 compared to 2014, their numbers still seemed low compared to the long term average.  However, with a milder el Niño winter, it’s possible that we could see increased winter survival and higher Japanese beetle populations in 2016.

Japanese Beetle
The infamous Japanese Beetle. Photo credit: David Cappaert, Michigan State University, Bugwood.org

Gypsy Moth populations have been low the past few years in Wisconsin.  Damp spring conditions can result in a fungal disease killing many of the caterpillars, which likely helped lessen populations in the recent past.  It’s also not unusual for some long-term cyclic patterns to be involved with insect populations.  For a number of potential reasons, Gypsy Moth populations seemed to rebound a bit in 2015, and many reports of sightings and damage came in to the diagnostic lab, particularly from the south central portion of the state (Dane, Rock, Walworth Counties).  Because Gypsy Moth can be a destructive defoliator of hardwood trees, it’ll be good to keep an eye out for this one in 2016 to see if the populations continue to climb.

7) Emerald Ash Borer
This is our most destructive forest pest in the state, and unfortunately, there doesn’t seem to be anything capable of completely stopping this pest.  While we didn’t see many additional counties added to the quarantine map in 2015, there were many municipalities that detected EAB for the first time.  At the moment, 39 of the 72 Wisconsin counties are quarantined for EAB and this number will continue to increase over time.  Like Dutch Elm Disease in the past, Emerald Ash Borer is changing and will continue to change the appearance of our urban forests and woodlands for years to come.

6) Spotted Wing Drosophila
This invasive pest first showed up in the state in 2010, and became a significant fruit pest almost immediately.  Since its introduction, SWD has spread widely and can be found in most counties in Wisconsin.  Very similar to 2014, SWD was detected in dozens of counties across the state.  SWD can attack a wide variety of fruit, but due to the fact that this insect doesn’t seem to become active until July, the late-season raspberry and blackberry crops are hit the hardest.  Luckily Wisconsin’s famous cranberry crop does not seem to be favored by this invasive pest.

Up Next, Part III:  Wisconsin’s Top Insect Trends of 2015 (Numbers 5-1) 

Viburnum Leaf Beetle

Note: A factsheet with additional information about the Virburnum Leaf Beetle can be found here.


One of Wisconsin’s newest invasive species has been popping up in Milwaukee and Ozaukee counties this spring and summer.  The invasive Viburnum Leaf Beetle  (VLB) is originally from Europe and was first detected in North America in eastern Canada in the 1940’s.  By the 1990’s, it had been detected in New England and is now scattered across much of the northeastern part of the country.  This insect can cause significant damage to viburnums.  In some cases, entire plants can be defoliated and plant death can occur.

An isolated infestation of viburnum leaf beetle was detected in Dane Co. in 2009, but was quickly eradicated.  Last summer, VLB was detected in Glendale (Milwaukee county) on a mature plant and has since been found on other viburnums in area .

VLB Damage
Feeding damage from adult viburnum leaf beetles. Photo courtesy of Paul Weston, Cornell University, Bugwood.org

The larvae (up to 1/3″ long; yellowish in color with black spots and dashes) and adults (~1/4″ long; yellowish-brown beetles) can cause significant damage to viburnum plants, especially Cranberrybush and Arrowwood viburnums.

VLB Larvae
Viburnum leaf beetle larvae. Photos courtesy of Paul Weston, Cornell University, Bugwood.org.
VLB Adult
Adult viburnum leaf beetle. Photos courtesy of Paul Weston, Cornell University, Bugwood.org.

At this point, all of the known finds are confined to northern Milwaukee county and southern Ozaukee county, but gardeners, landscapers, and residents in southeastern Wisconsin should keep an eye out for this highly damaging pest!

A UW-Extension factsheet with additional information can be found here.

Wisconsin’s Top 10 Insect Stories of 2014 (Part II)

Below you’ll find the second part of a three part series describing the Top 10 insect-related stories of 2014 from Wisconsin. Part three will be released next week.


7) Missing Pests: As every landscaper and farmer knows, there’s a certain batch of insect pests that tend to pop up consistently each year. One of the biggest stories of 2014 was the scarcity of some of these “regulars” like the gypsy moth and the Japanese beetle. The reason behind this? We likely have Mother Nature to thank. Gypsy moth populations fare poorly during periods of wet weather due to the proliferation of a fungal disease that kills the caterpillars. We certainly had abundant and consistent rainfall in 2014, and several images of diseased insects made their way into the lab. In addition, gypsy moth numbers have been in a general decline for several years in the state, which is good news for oak trees.

If there’s one good thing that came out of the brutally cold winter of 2013-14, there’s the fact that it may have helped knock down the Japanese beetle populations. Japanese beetles overwinter as white grubs in the soil and tend to move just deep enough to avoid the frost line. With the pipe-bursting cold and deep frosts of last winter, it seems that the deep freeze knocked their numbers down. As a result, reports of damage from Japanese beetles were scarce this past summer. While it’s too early to tell, it’s possible that it may only be a one-year reprieve. Turfgrass researchers have reported decent grub numbers in turfgrass areas this fall, which could mean that Japanese beetle numbers could creep back up in the future.

A female Japanese beetle digging into the turf to lay her eggs. Photo Credit: PJ Liesch.
A female Japanese beetle digging into the turf to lay her eggs.
Photo Credit: PJ Liesch.

Agricultural pests were also down in 2014, with no major pest outbreaks. Two of our best known corn pests, the European corn borer and corn rootworms, had very slow years. Even migratory crop pests, such as the potato leafhopper and black cutworm, which overwinter in the gulf coasts states and migrate northward in the spring failed to take off in 2014.  (A full summary of agricultural pests can be found here.)

6) Interesting “Structural Pest” Trends: Two of our insects that commonly invade homes in the fall (boxelder bugs and multi-colored Asian lady beetles) had drastically different trends this year. Box elder bugs thrive under dry conditions, like we had in the latter parts of 2012 and 2013. Similar to the gypsy moth mentioned above, the damp conditions in 2014 likely helped keep the box elder bug number in check and prevented the widespread numbers that we’ve seen the past few years.   While the numbers of box elder bugs were low this fall, the multicolored Asian lady beetle, which had been low for the past few years, started popping up in decent numbers in certain parts of the state. One warm October day, I wandered out to the front of the entomology department building on campus to view thousands of the lady beetles flying around looking for overwintering spots.

5) Invasion of the Copper Underwing: Most folks have never heard of a moth called the copper underwing. Rightly so, as it tends to be a fairly obscure species. The caterpillars are commonly called the green humped fruitworms and can feed on fruit trees and other trees. When adults rest on trees, their grayish appearance isn’t much to write home about. However, when they display their hind wings, you’d notice the brilliant copper color and understand the common name of the insect.

Copper Underwing
Copper Underwing (Amphipyra pyramidoides); Photo credit PJ Liesch

For whatever reason, 2014 seemed to be perfect for this species. Perhaps I should have suspected that the few adults I spotted at my porch lights in late spring were the beginning of a trend. As the summer went on, I started getting reports of large numbers of these moths congregating on the sides of homes, sneaking under siding, and even leaving excrement stains on siding. All in all, I had reports of “home invasions” from over a dozen counties, mostly in the southwestern part of the state. Because this species tends to be present in low numbers, I suspect that we won’t see them amassing by the thousands again anytime soon.

Part 3: Coming soon

Wisconsin’s Top 10 Insect Stories of 2014 (Part I)

The year-end stats are in: a grand total of 2,092 insects, mites, spiders and other curiosities were submitted to the Insect Diagnostic Lab in 2014. With the ubiquity of smart phones and internet access, nearly 60% of the cases handled in the lab this year consisted either solely of digital images or as digital images accompanying a physical specimen. While the vast majority of cases came from within Wisconsin, there were occasional images and questions sent in from other states and even other countries (including Mexico, England, Ireland, South Africa, India, Guatemala, the Philippines, Spain, Portugal, Afghanistan, and Jamaica).

When it comes to the insects in Wisconsin this past year, several stories pop out. First of all, several of our “usual” pests were noticeably down this year: gypsy moth, Japanese beetle, and box elder bugs, to name a few. In contrast, the emerald ash borer had quite a year and was detected in many new locations, leading to over a dozen counties being added to the quarantined zone in the state. Then there were some cases that seemed to appear overnight: the spring mosquitoes and the massive mayfly hatch in late July.

Below you’ll find the first part of a three part series describing the Top 10 insect-related stories of 2014 from Wisconsin. Parts two and three will be released over the next two weeks.


10) Mosquitoes: Our unofficial “state bird” made news headlines across the state starting Memorial Day weekend. In some spots, the mosquitoes were so bad, that outfitters of recreational canoeing trips were turning customers away, lest they fall victim to the winged vampires.

What caused the mosquito problems in 2014? It boils down to some ideal conditions, as far as the mosquitoes are concerned. With over 50 species of mosquitoes in the state, each species has its own unique habits. Some rely on the moisture from melting snow to develop. Others wait for rain to flood depressions in the woods, where female mosquitoes had laid their eggs. Some other species rely on more permanent bodies of water, such as drainage ditches and rain-filled containers. With the late snowmelt and the heavy rains this spring and summer, our mosquitoes had plenty of moisture to use.

If there’s a silver lining of the 2014 mosquito season, it’s that the number of West Nile cases were down in the state. It turns out that our heavy rains created temporary pools out in the woods, which are favored by our “floodwater” mosquitoes. For the most part, these species are a nuisance, but don’t carry diseases like West Nile. The mosquitoes that spread West Nile tend to prefer more permanent bodies of water.  When you have lots of rain, it can sometimes cause these more permanent bodies of water to overflow, flushing the mosquitoes away. It may be counterintuitive, but our worst West Nile year of the past decade was actually the droughty year of 2012.

9) Invasive Leaf Beetles: Two different species of invasive leaf beetles (Family Chrysomelidae) were detected in Wisconsin this past year: the lily leaf beetle and the viburnum leaf beetle. Both of these beetles have unusually similar histories: they’re both known from Europe but were found in Canada in the mid-1940’s. Both made their way into New England in the 1990’s and have been popping up in other locations since then.

The lily leaf beetle was detected for the first time in Wisconsin in July in the Wausau area. This species feeds on true lilies in the landscape and has been found at a handful of sites in Marathon and Wood counties. The viburnum leaf beetle had technically been found once before in the state a few years ago in Dane county. At the time it had been found on a recently planted viburnum bush, which was removed and the insects were eradicated. Technically, the case that popped up in the Milwaukee area in late summer on an established viburnum bush is our second record in the state. Unfortunately, the original source of the insects and extent of the current infestation are not fully understood at this point.

Lily Leaf Beetle (Lilioceris lilii)
Lily Leaf Beetle (Lilioceris lilii); Photo Credit PJ Liesch

While these two beetles have only been found in a few isolated spots in the state, they have the potential to cause significant damage to their host plants, so gardeners should keep a watchful eye out for them in 2015!

8) Brown Marmorated Stink Bug (BMSB): This invasive pest was first discovered in the state in 2010. When I describe BMSB during presentations, I joke that it’s as if a mad scientist in a bad Sci-Fi movie had somehow crossed a Japanese beetle with a box elder bug.  Like Japanese beetles, BMSB will feed on hundreds of different types of plants: field crops, vegetables, fruits, and ornamental plants can all be damaged. In addition, BMSB has the habit of sneaking indoors in the fall like box elder bugs. In other parts of the US (such as Pennsylvania and Virginia), BMSM has been wreaking havoc on agricultural producers and homeowners alike. Luckily, this stink bug has been quiet the past few years in Wisconsin and we saw more of the same for 2014. While I only had half a dozen samples documented in the state this year, this is certainly a pest that everyone should be keeping an eye out for in the future.

Brown Marmorated Stink Bug (Halyomorpha halys); Photo Credit PJ Liesch
Brown Marmorated Stink Bug (Halyomorpha halys); Photo Credit PJ Liesch

Part 2: Coming soon

The Oddest Beetle on Campus

Meet Thylodrias. Kind of sounds like a character from the Game of Thrones. But alas, it’s just an odd beetle about the size of the letter “d” in size ten print.

The Odd Beetle (Thylodrias contractus); Photo credit PJ Liesch
Adult male odd beetle (Thylodrias contractus); Photo credit PJ Liesch

Although, technically speaking, this one’s not just an odd beetle. It’s more like the king of odd beetles, so much so, that it’s actually known as the odd beetle. Kind of weird for a species belonging to a very common family: dermestidae. Other relatives in the dermestid bloodline include the common hide, larder, and carpet beetles, which occasionally find their way into that old, half-empty box of spaghetti noodles at the back of the kitchen cupboard. However, if you made a closer examination of the dermestid family tree, you’d find that the odd beetle sits alone: a solitary species in its own genus.

By now, you may be wondering: what really makes this one so odd? For starters, it’s a bit infatuated with humans and we only know of the species from human habitations. We even know of specimens from archaeological sites in Iran, but these days it’s most commonly found in museums. It’s somewhat ironic that such an interesting and unusual insect has a history of lurking around the home of the UW-Madison entomology department: Russell Labs1. Like many other museum pests, the odd beetle wanders around looking for a protein-rich meal to feed on.   It turns out that Russell Labs is home to plenty of potential food: millions of preserved insect specimens in the Wisconsin Insect Research Collection as well as preserved mammal and bird specimens in the Forestry and Wildlife Ecology wing of the building.

In addition to popping up in weird places, Thylodrias contractus also looks downright bizarre. With the naked eye, an adult female looks more like a bed bug or a small silverfish than a beetle. Technically, the females lack wings and have a larva-like appearance, which is strange in and of itself. Even the males of this species have a peculiar appearance and bear the meekest resemblance to other members of the family. Then there’s the quirky life cycle: developing larvae can go over a year without food. If times are really hard, they can borrow a page from The Curious Case of Benjamin Button and undergo retrogressive molting. With that elasticity in its development, the complete life cycle can vary from several months to several years.

All in all, rather peculiar.

1 Mertins, J. W. 1981. Life History and Morphology of the Odd Beetle, Thylodrias constractus. Ann. Ent. Soc. Am. 74(6): 576-81.