Category Archives: Invasive Species

To Boldly Go Where Man Has Gone Before: Pests on the Move

Since the earliest days of mankind, we’ve excelled at exploring and expanding our presence to nearly every spot on the map With all our wanderlust, we’ve been equally adept at taking other species with us as we go—often with unintended consequences. 

In some situations, species have been deliberately moved by humans: livestock to the new world, the introduction of birds from Shakespeare’s plays into Central Park,  and even the notorious gypsy moth was transported from Europe in a failed attempt at an American silkmoth industry On top of that, there’s an extraordinarily long list of species that have been accidentally moved, with significant impacts Stowaway rats on the ships of European explorers and traders would be one of the most notorious examples Rats introduced to new island environments wreak havoc on native birds and reptiles by devouring vulnerable eggs Insects have also been transported around the globe with devastating results and some of North America’s most important and emerging insect pests originate elsewhere on the planet: Japanese beetle, emerald ash borer, brown marmorated stink bug, and the spotted lanternfly.

Aedes sp. mosquitoes preparing for a blood meal. Aedes albopictus (left) and Aedes japonicus (right). Photo Credit: Ary Farajollahi, Bugwood.org.

One of the insects best adapted to follow humans is the notorious mosquito Certain mosquito species (peridomestic species) possess traits that allow them to take advantage of conditions in areas disturbed by humans and thrive in those spots.  With humans came environmental modification, construction, and discarded trash of one kind or another.  Some mosquitoes might have originally relied on the water pooled in natural containers, such as rotted out tree stumps to reproduce, but can just as easily take advantage of water-filled containers, ditches, and other artificial habitats.

In modern times, automotive tires have become a key habitat for certain mosquito species Tires not only are perfect objects for holding water for extended periods, but they also provide the dark, sheltered habitat favored by some female mosquitoes looking to lay eggs Tires are an important way for mosquitoes, like the Asian Tiger Mosquito (Aedes albopictus) to be moved into and around the US (including the Midwest) Other species, like the Asian Rock Pool Mosquito (Ochlerotatus japonicus), are also easily transported in human materials.

Hyacinth flower sold from a local store, including a vase pre-filled with water. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

A recent case at the UW Insect Diagnostic Lab illustrates the ease with which non-native mosquitoes can be moved around the country In the first part of 2018, stores have been selling hyacinth bulbs in vases pre-filled with water as a way to force the bulbs to bloom into a flash of color during the dreary winter months In a recent discovery in southeastern Wisconsin, a vase purchased at a local store ended up yielding half a dozen larvae of the non-native Asian rock pool mosquito.  The exact origin of the mosquitoes isn’t known at this time.

A bonus surprise with the flowers—larvae of the Asian rock pool mosquito (Ochlerotatus japonicus). Animation credit: PJ Liesch, UW Insect Diagnostic Lab.

These mosquitoes won’t be much of a concern in the grand scheme of things as Ochlerotatus japonicus has been present in Wisconsin for over a decade and is already established hereHowever, such cases do leave open the possibility of non-native mosquitoes being moved into parts of the country where these pests have not been encountered beforeWhere humans go, pests will boldly follow.

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.

 

 

 

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.

Wisconsin’s Top Insect Trends of 2015 (#5 – #1)

In this post, we’re continuing to count-down 2015’s top insect trends in the state.  This is the final post in a three part series.  Part I (2015’s diagnostic lab statistics) can be found here and Part II (Top Insect Trends Numbers 10-6) can be found here.

5) Pollinators
With all the headlines about bees, it’s not surprising to see pollinators in the top insect stories again in 2015.  Similar to other years in the recent past, honeybees and other pollinators have been facing declines.  Unfortunately, Wisconsin saw some of the highest honeybee losses in the country, with over 60% colony loss during the 2014-2015 period.  Some good news over the past year has been the development and release of pollinator protection plans.  A federal pollinator protection plan was released in May with the goals of reducing honeybee losses, increasing the population of Monarch butterflies, and increasing pollinator habitat.  In addition, a Wisconsin pollinator protection plan was announced in 2015, and was just released in January of 2016.   Due to the recent declines and their importance to agriculture in the state and nation, pollinators will continue to be in the spotlight in the future.

A ground nesting bee (Colletes sp.) near the stump of the former President's Oak on the UW-Madison campus. Photo Credit: PJ Liesch
A ground nesting bee near the stump of the former President’s Oak on the UW-Madison campus. Photo Credit: PJ Liesch

4) Spring caterpillars
An unexpected insect trend in the spring of 2015 was the surprising abundance of a number of caterpillar species feeding on plants in the landscape.  Caterpillar species, such as the humped green fruitworm, speckled green fruitworm, eastern tent caterpillar, forest tent caterpillar, gypsy moth caterpillar, and the euonymous caterpillar are typically present to some extent, although their numbers have been low the past few years.  For a number of potential reasons, these species had a great spring and during a period in May and June, caterpillars made up roughly 30% of the cases coming in to the diagnostic lab.  Weather patterns (i.e., rainy weather) and natural predators/parasites/diseases can have significant impacts on caterpillar populations each year, so it’ll be interesting to see if we’re faced with a plethora of caterpillars again in 2016.  Additional details of this story were featured in a blog post last June.

3) Viburnum Leaf Beetle
In terms of a new emerging pest with the potential to impact a commonly planted landscape shrub, Viburnum Leaf Beetle is near the top of the list.  As of late 2014, we only knew of a single infested viburnum bush in northern Milwaukee County, which raised the question: is the infestation small enough to contain and/or eradicate?  Some ground truthing this past spring identified many new infestations in SE Wisconsin, in many cases miles from the original site.  At the moment, the viburnum leaf beetle seems to be centered around the four county area where Milwaukee, Waukesha, Washington, and Ozaukee counties meet.  While this insect only feeds on viburnums (and related plants like Arrowwood), the damage can be significant.  It may be some time before this pest spreads elsewhere in the state, but if you have viburnum plants in your yard in SE Wisconsin, be weary!  Additional details of this case were featured in a post last June.

VLB Damage
“Skeletonizing” feeding damage from adult viburnum leaf beetles. Photo courtesy of Paul Weston, Cornell University, Bugwood.org

2) Brown Marmorated Stink Bug
Populations of the invasive Brown Marmorated Stink Bug increased dramatically in 2015 and this insect takes the overall #2 spot in this list (up from #8 last year).  This invasive species was first spotted in the state in 2010, and each year a handful of lone adults have been found in Wisconsin.  In the fall of 2015, we had more sightings of BMSB (30+), than in the past 5 years combined! (Spoiler: this trend has continued into early 2016)  At this point, the “hot spots” in the state are: Dane County, the greater Milwaukee area, and the Fox River Valley.  In addition to being an indoor nuisance pest, BMSB can also feed on and damage a wide variety of plants in home gardens, agricultural fields and orchards.  In other places in the country, the first reports of plant damage have typically been noted ~3-5 years after the initial detection of this species.  With that said, 2016 could be the year that BMSB really takes off and starts wreaking havoc for gardeners and agricultural growers alike.  Additional details of this case can be found in this post from last October.

1) Magnolia Scale
While scale insects have already been mentioned in the “sucking insects” section (#9 on the list), one species in particular, the Magnolia scale (Neolecanium cornuparvum), seemed to stand out amongst all other insects in 2015.  This species is often present in low numbers in the state, but the conditions must have been perfect for their populations to explode last year.  During the months of June and July, reports of Magnolia scale were coming in on almost a daily basis.  Being one of the unusual scale insects, Magnolia scale adults look more like a fungus than an insect (note the whitish blobs in the image below).  Not only did this bizarre looking species pummel Magnolia shrubs and trees in many parts of the state, but the honeydew produced by these insects rained down below, attracting ants and yellowjackets and leading to the growth of unsightly black sooty mold.  A number of predators, parasites, and diseases typically keep Magnolia scale in check, but with the extremely high infestations noted last year, it’s likely that we’ll continue to see some Magnolia scale activity into 2016.  If you experienced magnolia scales first hand, there’s a helpful factsheet available here.

Magnolia twig coated with whitish, fuzzy magnolia scale adults.

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) 

Why Such a Stink About a Bug?

Every fall, residents throughout Wisconsin and many other parts of the country face an invasion by a number of insects: boxelder bugs, multicolored Asian lady beetles, western conifer seed bugs and cluster flies, to name a few.  With the coming frosts, these insects are simply trying to find a sheltered location to settle for the winter.  Out in nature, many of these insects would simply crawl into a rock pile or beneath the loose bark of a dead tree to overwinter.

MALB Overwintering_opt
Multicolored Asian Lady Beetles often spend the winter in sheltered spots, such as beneath the bark of dead trees. However, they can just as easily sneak into buildings. Photo Credit: PJ Liesch, UW-Entomology

But why rough it out in nature if there are perfectly good buildings to sneak in to?  Next time you’re cleaning the gutters, take a moment to peek around the outside of your house.  Small gaps in siding, soffit areas, around door and window frames, and cracks in the foundation are all potential spots for insects to sneak through.  And if they make it through?  Well, you could be in for some extended visitors. . .

In addition to the usual fall invaders, a relative newcomer starting to pop up in Wisconsin and other parts of the Midwest is the invasive Brown Marmorated Stink Bug (Halyomorpha halys).  Like the boxelder bugs and multicolored Asian lady beetles, brown marmorated stink bugs (BMSB) like to find their way indoors for the winter.  This Asian species was first detected in Wisconsin back in 2010 and for reasons we don’t fully understand, their numbers have been quite low the past few years.  As of late 2014, BMSB has been confirmed or suspected in 10 Wisconsin counties, with most of the reports coming out of the Madison and Milwaukee area.  A handful of sightings each year has been the pattern.

Unfortunately, we may be at the beginning of a shift in BMSB populations in the state.  In early 2015, there were at least 6 specimens found in Wisconsin by early March.  Despite the quiet summer, the sightings have started popping up again in late September and October of this year.  What’s more concerning is that we’re starting to see groups of these insects clustered together (previous sightings had consisted almost exclusively of lone individuals).

Not only are these unwanted houseguests a nuisance, but quite frankly, they smell bad.  True to their title of “stink bug”, brown marmorated stink bugs possess glands that can emit a pungent odor.  Some consider the odor to be coriander-like, while others  say it resembles musty gym socks.  Invasive species [check].  Nuisance invader [check].  Smells bad [check].  That’s all, right?  Unfortunately, not quite.  Just like a bad late-night infomercial: Wait! There’s more!

Bad Bug Checklist-Upload

It turns out that brown marmorated stink bug has the potential to be quite a nasty plant pest and rivals the Japanese beetle in the breadth of its palate.  Brown marmorated stink bug seems to feed on just about anything under the sun: field crops like corn and soybeans, vegetables like tomatoes and peppers, and even ornamental trees and shrubsFruits like apples and grapes can be hit especially hard.  In some cases, the mere presence of BMSB can be a problem: imagine being a vintner and having your batch of wine tainted by the presence of a few squished stink bugs!  In the eastern U.S. there are regular reports of agricultural problems and growers have to spray to control these insects.  We haven’t had any reports of plant damage in Wisconsin yet, but that could change over time if BMSB populations continue to climb.

So what can you do about brown marmorated stink bugs?  For starters, learning to tell them apart from our native stink bugs is relatively easy.  Look for the alternating “checkerboard” pattern along the back edge of these half-inch long insects and the two light bands on the otherwise brown antennae.

Brown Marmorated Stink Bug ID
Identifying features of the Brown Marmorated Stink Bug; click for larger version. Photo Credit: PJ Liesch, UW-Entomology

With relatively few sightings in Wisconsin at this point, we’re still trying to get a feel for where this insect is.  If you suspect that there may be brown marmorated stink bugs around your house, take a picture of the insect and email it to me at (pliesch@wisc.edu) for identification.  Another option is to collect a physical sample and mail them in to the Insect Diagnostic Lab for identification (instructions on how to submit samples can be found here).

If brown marmorated stink bugs or other fall invading insects are trying to get into your house, one of the best things to do is to inspect the outside of your home and physically seal up cracks and crevices where they’re trying to sneak in.  Once fall invaders are indoors, hauling out the hose attachment on the vacuum cleaner is often one of the best steps to remove them.

 

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.