Category Archives: Beetles

Under the Microscope: Arthropod Trends of 2017

Over 2,500 cases flowed through the doors of the UW Insect Diagnostic Lab last year, ranging from the typical June beetles through bizarre creatures that most humans will never see in their entire lives (like the itch-inducing pyemotes grain mite).  Perhaps Forrest Gump said it best when he quipped, “life was like a box of chocolates—you never know what you’re gonna get.”  A distinction amongst insects, however, is that the “box” contains 20,000+ possibilities in Wisconsin alone and over well 1,000,000 globally.  With that said, a year at the UW Insect Diagnostic Lab is like having one humongous, box of really awesome chocolates, without all the calories.

Finding a pyemotes itch mite is like trying to find a needle in a haystack, except in this case these microscopic mites were in a farmer’s batch of corn. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

With insects and related creatures, the weather can of course have a big impact and there definitely were examples of this in 2017.  The current cold winter aside, the last two winters had been otherwise mild, giving a few insects suited for warmer conditions a chance to inch their way northward.  Last spring and summer, this meant a bunch of sightings of an otherwise uncommon bee for our area known as the carpenter bee due to its habit of tunneling into unpainted cedar trim and other wood.  In a typical year, I might see a few cases out of the southeastern corner of Wisconsin, but 2017 had regular reports of these bumble bee look-alikes during the spring and summer months.  Similarly, praying mantids often meet their maker at the hands of a cold winter, but were surprisingly abundant in late summer and fall of last year.  Ticks were also extremely abundant last spring and with the rainy start to the summer, mosquito numbers were at an all-time high in some traps.  Mosquitoes were also a big deal in the news, with Wisconsin’s first confirmed reports of the Asian Tiger Mosquito last July.

Asian Tiger Mosquito (Aedes albopictus). Photo credit: James Gathany, Centers for Disease Control

The creature that amassed the most phone calls and emails in 2017 was the notorious Japanese beetle, which likely also benefited from the warmer than average winters these past few years.  For Wisconsin gardeners and farmers, the Japanese beetle is certainly a formidable foe, but at least there are ways to mitigate the damage.  In contrast, there’s another destructive pest wiggling its way into the spotlight in the state, which is much more difficult to control—an invasive earthworm commonly known as the jumping worm.  While they may not be insects, these earthworms are creepy-crawly and can wreak havoc in  gardens and flower beds, so I received a fair number of reports and questions.  What stood out to me in last year was the rapidity with which these destructive worms have been moved around the state (moved—as in humans have moved soil, plants, mulch, and similar materials).  Jumping worms were first found in the state in 2013 (in Madison), but have now been spotted in roughly half of the counties in Wisconsin.  To make matters worse, we don’t have any highly effective tactics to prevent these worms from turning rich garden soil into the consistency of dry, crusted coffee grounds—gardeners beware!

Speaking of invasive species, the emerald ash borer has continued its march through the state and now has footholds in some of our northern counties including Chippewa, Douglas, Eau Claire, Marathon, Marinette, Oneida, and Sawyer counties.  Unfortunately, our greatest concentrations of ash trees are in the northern part of the state (e.g. black ash in swampy areas), and the loss of ash from northern wetland areas could result in significant ecosystem effects.  Other recent invaders like the spotted wing drosophila and the brown marmorated stink bug had busy years as well.

Rusty patched bumble bee (Bombus affinis) visiting a flower in Middleton, WI. Photo credit: Rick Terrien

In other insect news, it seemed to be a good year for monarch butterflies in 2017, and the rusty-patched bumble bee finally made it onto the federal endangered species list. I was pleasantly surprised by a number of confirmed sightings of the rusty-patched bumble bee in the state as well. Perhaps my favorite “bug” story for the year involved black widow spiders.  It’s not common knowledge, but we do technically have a native black widow species in the state (Northern Black Widow, Latrodectus variolus).  It’s a reclusive species and is rarely encountered in Wisconsin, but reports trickled in once or twice a week at some points during the summer months (details to follow in a future blog post).

With so many cases last year, we’re really only touching the tips of the antennae.  If you’re interested in hearing more of the unusual stories from the UW Insect Diagnostic Lab, I’ll be giving a “highlight” talk on May 4th on the UW campus.

 

 

 

Just like Clockwork

We’re all familiar with phenology—that regular progression of plant and animal life through the seasons—to a certain extent.  We might not stop to think about it in detail, but we recognize the crabapples blooming in spring, the fireflies lighting up the nighttime sky in June and July, and the southward flying geese and rutting deer in fall.  When you think of the 25,000+ insects in the Great Lakes Region, there’s a rich diversity of seasonal patterns to pick up on.  Some insect patterns, like cicadas, katydids, and tree crickets calling during the summer months, are hard to miss—although it can be challenging to decipher exactly who’s making that racket (Hint: here’s your translator).  Others are much harder to pick up on unless you’ve been briefed on the subtle clues.  For example, take the tiny foreign grain beetle (Ahasverus advena) which conspicuously pops up in unexpected places in August, September, and October.

To the naked eye, these tiny (1/16 inch long) brownish insects can be a bit tricky to see and it’s hard to tell if they’re beetles, ants, or something else.  Even to budding entomology students pushing the boundaries of what they can interpret under the microscope, foreign grain beetles and relatives might be jokingly referred to as “little brown nothings” and passed over for easier-to-identify specimens.

Foreign Grain Beetles next to a US nickel. Photo credit: PJ Liesch, UW-Entomology.

Around the UW Insect Diagnostic Lab, foreign grain beetles are one of my favorite samples when they arrive in late summer and early fall as they give me the faintest sensation of what it must feel like to be Sherlock Holmes.  Picture a client coming in with a Ziploc bag of tiny brown insects.  After a cursory glance and before the specimens even make it under the microscope, I ask, “are you in a new home by any chance?”  The standard reply is often along the lines of, “Well, yes—but how did you know?”  A quick check under the microscope and the specimen’s identity is confirmed.  It’s elementary, my dear Watson.

Up close view of the Foreign Grain Beetle (Ahasverus advena). Actual size: ~2mm long. Photo credit: PJ Liesch, UW-Entomology.

How is there such a reliable association with an unexpected source: newly constructed homes, where intuition wouldn’t have you expecting insects?  The secret to this seasonal pattern lies in understanding the biology of the foreign grain beetle and its relatives.  These insects love to feed on fungal spores—often in musty stored grains on farms.  It turns out that during the construction of a new home, residual dampness in construction lumber, plaster, sawdust, and other materials can lead to the growth of a trivial amount of mold.  Like vultures to carrion, these beetles fly in looking for a fungal smorgasbord.  Eggs are laid and entire life cycles can be carried out in the wall void of a new home after the drywall, insulation, and siding are put up.

Fast-forward to late summer and just like clockwork the proud new homeowners suddenly have hundreds of tiny brown beetles crawling out through nooks and crannies, causing immediate dismay.  While this can be alarming, these insects are harmless to people, pets, and the home, and are simply a temporary nuisance.  As the construction materials lose that lingering moisture, conditions become unfavorable for the beetles and activity drops off over time.  Pesticides often aren’t needed as the beetles already face an inevitable demise.  Vacuuming or sweeping them up and running a dehumidifier are often the remedy in fall until the dryness of winter puts a final end to the beetle activity.

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