All posts by pliesch

Dairy, Insects, and Illegal Cheese

As National Dairy Month rolls to a close, you might not have realized the connections between insects and the milk, cheese, yogurt, or ice-cream you’ve had in the last month.  While you might not think of any association between insects and dairy, the connections are surprisingly plentiful.  Some of these links are conspicuous—insect pollinators, for example, play an important role in the production of seeds for growing hay crops like alfalfa.  A plethora of caterpillars, beetles, and true bugs can be pests of those same crops and threaten to reduce hay yields.  In addition, many flies, mites, and grubs can directly bite, pester or even infest dairy of beef cattle and farmers have to manage these pests to maintain herd health and maximize milk or beef production.

Alfalfa leafcutting bee (pollinator) on alfalfa flower. Photo credit: Peggy Greb, USDA-ARS.

Other connections can be downright bizarre—perhaps the most outlandish link between insects and dairy is a cheese so engulfed in a legal cloud that it has been sold on the black market at times: casu marzu.  In Wisconsin we’re blessed with enough cheeses to be the envy of other states, but the thought of an illegal cheese is still mind-boggling.

Casu marzu cheese contains live maggots and can’t legally be sold in the US. Photo credit: Shardan; Wikipedia CC.

The cheese in this case, casu marzu, is a soft unpasteurized variety made from goat’s milk.   It’s made on the Island of Sardinia in Italy and has a unique flavor developed by live maggots of the cheese skipper (Piophila casei)—making blue cheese seem wimpy in comparison.  Cheese skippers like to infest protein-rich materials such as processed cheeses and meats (they’re also called “bacon flies”) and get their name from the ability of the larvae to “skip” or fling themselves into the air when disturbed:

Jumping cheese skipper maggots in the diagnostic lab. Photo Credit: PJ Liesch, UW-Entomology

While cheese skippers have a cosmopolitan distribution, you probably won’t encounter these insects unless you add dairy, meats, or other protein-rich materials to your compost pile (which you shouldn’t do).  This very composting mistake is the reason why I recently received a cheese skipper sample at the UW Insect Diagnostic Lab.

Waiter, are there flies in my cheese?. . .

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.

Sawflies: Caterpillar Copycats

As the old saying goes: if it looks like a duck, swims like a duck, and quacks like a duck, it’s probably a duck.  Following that logic: if it looks like a caterpillar, walks like a caterpillar,  and feeds on plants like a caterpillar, it’s probably a caterpillar—right?

This isn’t always the case and one important example would be the sawflies.  Sawfly larvae look an awful lot like true caterpillars (which turn into moths or butterflies), but these creatures are actually related to ants, bees and wasps.  In contrast, adult sawflies have a distinct wasp-like appearance which hints at the true evolutionary relationships of these creatures.

Elm sawfly adult. The wasp-like appearance reflects the relationship of sawflies to ants, bees, and wasps.

With a little know-how, you can learn to tell apart sawfly larvae from true caterpillars. In addition to three pairs of true jointed legs on the thorax, true caterpillars possess 4-5 pairs (or fewer for “inchworms”) of stubby, blob-like prolegs on their abdomen—each tipped with tiny velcro-like hooks (crochets) that can be seen under magnification.  Sawflies have more pairs of prolegs (7 pairs) and lack crochets.

Larva of the dogwood sawfly. Note the strong resemblance to a caterpillar, but this larva has seven pairs of stubby prolegs on the abdomen.

There are dozens of sawfly species in the Midwest, some of which can be considered plant pests, while others can go unnoticed due to their small size or cryptic habits.  The commonest sawfly species can be pests of pines and other conifers, elms, birches, and other hardwoods, and ornamental flowers and shrubs such as dogwoods, roses, and columbines.  If you’ve ever spent time thumbing through a caterpillar guide book and can’t seem to find a match, there’s always a chance you might be looking at a sawfly.

To further explore the world of sawflies, check out this article from the Wisconsin Master Gardener Program.

Don’t Be an (April) Fool: Look Out For Ticks

April Fools’ Day may be here, but the topic of ticks is anything but funny.  The Midwest is home to over a dozen tick species, although only a few of these are encountered regularly by people and/or pets and are of notable concern.  Nevertheless, the medical concerns posed by some species can be quite significant.  Our two most notorious species of ticks in Wisconsin and nearby states are the wood tick (aka American Dog tick) and the deer tick (aka black-legged tick).

The wood tick (Dermacentor variabilis) is perhaps our most commonly encountered tick and adults of this species are fairly noticeable with their relatively large size (~ 1/4  inch long).  Wood ticks can be associated with certain human diseases, such as Rocky Mountain spotted fever although the threat of this disease in the Midwest is low.  A complication regularly caused by this tick in the field of veterinary medicine is tick paralysis, which is a serious reaction to components of the tick’s saliva in situations where ticks have been attached to pets for extended periods of time.

Adult Female Wood Tick (American Dog Tick). Image source: CDC.

At the moment, the tick of greatest concern in the Midwest is the deer tick (Ixodes scapularis).  This is the species notoriously associated with Lyme disease, although it can also vector anaplasmosis, babesiosis, and other diseases.  This tick is noticeably smaller than wood ticks, making them more difficult to spot; adult deer ticks come in at a mere ~ 1/8 inch long.  Interestingly, deer ticks are relatively new to the upper Midwest and these ticks weren’t spotted in Wisconsin until the late 1960’s .  Fast forward 50 years and deer ticks can be found in nearly every corner of the state.  The high rate of infectivity (i.e., percentage of ticks carrying a disease) is worryingly high: approximately 20% of tick nymphs (juveniles) and 40% of adult ticks in Wisconsin are carrying the microorganism responsible for Lyme disease.  In certain spots in the state, the rate of infectivity has been documented at closer to 60% in some studies.  This high rate of infectivity combined with the recent ubiquity of deer ticks poses significant health risks to residents of the upper Midwest and nearly 30,000 confirmed Lyme disease cases are reported from across the country to the CDC each year.  What’s more alarming is that estimates from the CDC suggest that the actual number of Lyme disease cases may be an order of magnitude higher!

Adult Female Deer Tick (Blacklegged Tick). Image source: CDC.

So how will ticks and Lyme disease be in Wisconsin this year? Some scientists have predicted high tick and Lyme disease pressure in the eastern US in 2017.  While that topic has gotten a lot of attention in the news, this may not be the case in our state.  The thought behind the prediction is that high rodent populations (a host for juvenile deer ticks) may bolster deer tick numbers.  While this relationship was documented in certain geographic locations in a 2005 study, the relationship didn’t hold up across the board as a general predictor of tick activity and neither did weather patterns.  With that said, it’s difficult to get a reliable predictor of tick activity and Lyme disease pressure in a given year.  In addition, based on recent field observations by fellow entomologists, rodent populations don’t seem to be bursting at the seams at the moment in Wisconsin. Last year (2016) seemed to be an average tick year in the state and we may be in for more of the same this year.

Regardless of tick numbers, the threat of ticks and Lyme disease is still out there and isn’t something to be ignored.  Deer ticks can potentially be encountered anytime of the year that the temperatures are above freezing and the ground isn’t covered with snow.  While often thought of as a creature of the deep woods, ticks can also be found in suburban areas near parks and nature preserves, so vigilance is a must—even in your own backyard.  Below are some sound tips to help prevent issues with ticks this year:

  • Personal Protection: Long sleeved clothes can help prevent ticks from getting to skin. In addition, light-colored clothing can make it easier to spot ticks.
  • Repellents: A number of EPA approved repellents (such as DEET) can help repel ticks when properly used. Always consult the product label for important usage instructions (e.g., application to skin vs clothing, how often to reapply).  As another consideration, clothing can be treated with certain permethrin products (often sold at outdoor/camping stores) to provide long-term protection from ticks. Outdoor clothing impregnated with permethrin can also be purchased at outdoor clothing stores and can remain effective for extended periods of time.
  • Tick checks: To effectively transmit Lyme disease, deer ticks have to be attached and feeding for approximately 36 – 48 hours which means that daily tick checks can help find and remove ticks before they’ve had a chance to transmit Lyme disease. Tick checks can be an important precaution for both people and pets.
  • Protecting Pets: Family pets should be treated with a preventative flea and tick treatment. Consult with your veterinarian about the products recommended for your particular pet(s).  Lyme vaccines for animals are also available through your veterinarian.

Perhaps Mother Nature has a cruel sense of humor with her April Fools’ pranks—we finally have an end to the dreary days of winter only to move into tick season!

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]

Wisconsin’s Top Insect Trends of 2016 (#10 – #6)

This post examines 2016’s top insects trends through the eyes of the UW Insect Diagnostic Lab and is the second post in a three part series.  The first post of the series (2016’s diagnostic lab statistics) can be found here.

#10: Boxelder bugs had a surprisingly good year, despite the rainy conditions. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.
#9: Scale insects, like these lecanium scales, have been very abundant the last two years in Wisconsin. Photo Credit: Ronald S. Kelley, Bugwood.org
#8: Reports of juvenile brown marmorated stink bug indicate that this invasive species is reproducing the in the state. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.
#7: Fungus gnats were very abundant in late summer and fall with rainy conditions seen in many parts of the state. Photo Credit: Whitney Cranshaw, Bugwood.org
#6: Silk moths, such as this luna moth, were frequently spotted in 2016. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.

 

10) Boxelder Bugs:
Many insects (like mosquitoes and fungus gnats) thrived in Wisconsin’s rainy conditions last year. However, heavy rains can also be a blessing in disguise when it comes to certain insect pests. Gypsy moth caterpillars, for example, can be killed off by the entomopathogenic fungus Entomophaga maimaiga under damp conditions. Heavy spring rains the past few years likely encouraged this fungus, which has helped keep gypsy moth numbers low in many parts of the state. Rainy conditions can also encourage a fungal disease of boxelder bugs. With the rainy conditions in many parts of the state, boxelder bug populations were expected to be low last year. Disease pressure from the fungus must have been limited in 2016 as boxelder bug numbers were surprisingly high in many parts of the state, much to the chagrin of homeowners hoping to avoid the tiny red-and-black home visitors in the fall.

9) Scale Insects
Scale insects are truly bizarre creatures. For example, the magnolia scale (#1 of 2015’s top insect stories) can look more like a fungus than an actual insect. As in 2015, many reports of scale insects came into the UW Insect Diagnostic Lab last year, especially during the spring and summer months. The most commonly encountered type was the lecanium scale, which can blend in on twigs and resemble deformed plant buds. Both magnolia and lecanium scales produce copious amounts of sticky, messy, honeydew, which can attract ants and wasps, and lead to the growth of black sooty mold. In many cases, scale insects can be notoriously difficult to control. Luckily, over time there are a number of natural enemies (tiny parasitic wasps) that help bring outbreaks under control. With two consecutive years of high scale insect populations, 2017 may be the year that the natural enemies help bring the situation under control.

8) Brown Marmorated Stink Bug
Reports of the brown marmorated stink bug in 2016 were very similar to the previous year. Dozens of sightings of this relatively new invasive species were reported, mostly from the southern part of Wisconsin. Dane County (Madison area) continues to be the hot spot of BMSB activity in the state with additional activity in the Milwaukee/Waukesha area and the Fox River Valley. A few counties had their first confirmed reports of BMSB in 2016: Sauk and Columbia. Also of interest were the first reports of these insects on plants (previous reports involved insects overwintering in buildings). In addition, some of the first observations of juveniles and mating adults occurred in the state. Those observations confirm that the brown marmorated stink bug is breeding in Wisconsin and is likely to continue to increase its numbers in the future. This insect is expected to be a concern for vegetable growers, fruit growers, and home gardeners in the coming years.  For more information on this emerging insect pest, there’s a series of articles available at  Wiscontext.org.

7) Giant Silk Moths
Some of the Midwest’s largest insects had a big year in 2016—the giant silk moths. Wisconsin is home to a number of giant silk moth species, including the cecropia moth, polyphemus moth, imperial moth, promethea moth, and the ever-so-elegant luna moth. Historically, these sizable moths [4-5”+ wingspan] used to be more common in many parts of the country, although their numbers seem to have declined over time. This may be partly due to landscape/habitat changes, urbanization, and accompanying light pollution. Parasites are likely a key factor in this situation.  The parasitic fly Compsilura concinnata, originally imported to control pest caterpillars such as the invasive gypsy moth, also happens to attack and kill a number of wild silk moth caterpillars  and can have significant impacts on their populations. However, numerous reports coming in to the UW Insect Diagnostic Lab indicated that giant silk moth numbers might have been up in 2016 compared to the past few years.

If you ever come across one of these majestic and fascinating creatures, consider yourself lucky—adults are notoriously short-lived as they can be a substantial meal for bats. Species such as the luna moth even have special structures to help evade sonar detection by bats.

6) Fungus Gnats
If you noticed plagues of tiny, dark-colored flies in your backyard in late summer and fall, you certainly weren’t alone. Spurred by the rainy conditions, fungus gnats were extremely abundant in many parts of the state last year. As larvae, fungus gnats live in damp, decaying organic materials—rich soil, decaying plants, compost piles, and similar. Fungus gnats themselves are harmless and don’t bite, but could have been a minor nuisance in the backyard. In many cases, fungus gnats were also spotted indoors this fall. In those situations, the fungus gnat larvae could have easily been living in the damp soil of potted plants brought indoors for the winter months. If over watering of indoor plants continued, the fungus gnats persisted indoors as well.

Up Next:  Wisconsin’s Top Insect Trends of 2016 (Numbers 5-1) 

State of the Lab Address 2016

What’s been “crawling” in the UW-Madison Insect Diagnostic Lab this past year?   Find out in this three part series.

The State of the IDL in 2016

Caseload
It was another busy year around the UW Insect Diagnostic Lab. By the end of 2016, the lab had identified 2,444 specimens, slightly up from 2015’s record number of 2,423 specimens. As in 2015, ~95% of these cases came from within Wisconsin, with just over 4% of samples coming from other states and ~1% coming from other countries.

1-Wisconsin Cases-2016
2-USA Submissions-2016
3-World Map-2016

 

Sample Submission
Overall, lab statistics were very similar to other years in the recent past, with roughly half of the lab samples coming in during the months of June, July, and August. The majority of samples consisted of digital images coming in from the general public. County Extension offices and agents accounted for the next largest number of samples, having submitted over a quarter of all samples processed in the lab. Other sources of samples included the green industry, medical and public health professionals, pest control professionals, farmers and agricultural consultants, and other colleagues in the UW system and state or federal agencies.

4-Monthly Chart-2016
5-Types of Samples-2016
6-Who Submits Samples-2016
7-Sample Source-2016

 

Sample Identity
Very similar to 2015, over 90% of the specimens came from five major groups of insects:

  • Coleoptera: beetles, such as Japanese beetles and carpet beetles
  • Hemiptera: “true Bugs”, such as aphids, and boxelder bugs
  • Hymenoptera: ants, bees, wasps, and yellowjackets
  • Lepidoptera: moths, butterflies, and their young (caterpillars)
  • Diptera: “true flies”, such as house flies and mosquitoes
Click for larger view

Outreach efforts of the IDL in 2016 included over 90 public talks at a variety of events throughout the state, over 30 media interviews, and regular appearances on Wisconsin Public Radio’s “The Larry Meiller Show”.  Numerous articles and other publications came out of the lab in 2016, including a Wisconsin Bee Identification Guide and an urban pollinator conservation guide to help increase awareness of pollinators and pollinator conservation. The services provided to Wisconsin residents by the UW Insect Diagnostic Lab and its outreach efforts are one of the many examples of the Wisconsin Idea.

Up Next: Wisconsin’s Top Insect Trends of 2016 (Numbers 10-6)

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.

Free Couch? Think Twice About Bed Bugs

Right around this time of the year in Madison and other college towns across the country, a smorgasbord of furniture and other goods appear along the sidewalk as tenants are frantically moving in and out of apartments. For historical reasons related to the need to register for classes in-person at UW-Madison, many of the leases end and begin in Madison around August 14th-15th each year, leading to an abundance of items on the curb free for the taking.   This is such a well-known and easily observable occurrence around Madison, that some have even affectionately referred to it as “Hippie Christmas”.

Free Mattress_opt
One of the many free items showing up around college towns these days. Photo Credit: PJ Liesch, UW-Entomology.

As the old saying goes, “one man’s trash is another man’s treasure” and this certainly could be the case with free things on the curb. That free couch along the sidewalk might look like the perfect addition to that larger apartment, and it can be hard to beat the price of that curbside armchair. However, there’s the real possibility of unwanted hitchhikers: bed bugs. While I’m all for reducing waste, reusing items, and recycling, the concern about bed bugs should not be overlooked.

Until the mid 1900’s, bed bugs (Cimex lectularius), been a common pest around the world. With the invention of synthetic insecticides around the time of World War II, these insects had nearly been wiped out. Given time, bed bug populations developed resistance to some of those insecticides. The insecticide resistance coupled with the rise of international travel and the bed bug’s stealthy stowaway tactics, meant that it was only a matter of time before they came roaring back onto the stage. That very phenomenon has happened in the past two decades, and bed bugs can now be found in every US state, and in a wide variety of situations––from student apartments to five star hotels. When bed bugs are detected, they can be eliminated with diligent tactics, although the task can be challenging and is best left to pest control professionals. Costs to eliminate bed bugs can easily be $1,000 or more.

Adult bed bug. Photo Credit: Gary Alpert, Harvard University, Bugwood.org
Adult bed bug. Photo Credit: Gary Alpert, Harvard University, Bugwood.org

Absolutely need to have that nightstand from the curb? A few steps can help prevent issues. The first is to simply know how to look for bed bugs and their telltale signs. Many folks seem to believe that bed bugs are too small to be seen with the naked eye, but this is far from reality. It turns out that adult bed bugs are roughly the same size, color, and shape as an apple seed (as shown above). Juveniles will have the same general shape, but will be smaller. Very tiny whitish eggs (~1mm long) and black spots (from digested blood) on furniture are other classic signs of bed bugs. [A useful guide to identify bed bugs and their signs can be found here]. Before bringing any item in from the curb, examining it thoroughly for any signs of bed bugs is well worth the effort in the long run. Found a smaller item you’d like to grab? One easy step for small items is to place them into a large Ziploc bag and put them in the freezer for 7-10 days as a precaution. Bed bugs, or any other insects present in such an item would freeze during that time.

Bed Bug Signs_opt
Classic bed bug signs: black spots from digested blood and whitish eggs (~1mm long). Photo Credit: PJ Liesch, UW-Entomology.

What if you’ve moved into a new apartment and suspect it has bed bugs? Getting a suspected bed bug specimen properly identified is a crucial step. It turns out that there are a number of nearly identical species that can only be told apart under the microscope. These related species are associated with bats and birds; they don’t pose the same headaches as bed bugs and are controlled differently. If you’ve confirmed that bed bugs are present in your apartment, starting a conversation with your landlord is an important step; ignoring the situation is about the worst thing that could be done in such as case. Overall, it’s much easier for a pest control company to come in and eliminate a small bed bug infestation than a large one. This is especially true of large apartment and condo complexes, where bed bugs can spread from unit-to-unit over time, making control much more difficult. In addition, if you happen to be moving out of an apartment that has bed bugs, it’s best to mark any items being discarded with spray paint so that others looking for furniture will know not to bring those items home with them.

For bed bug questions in rental situations and many other tenant-related topics, the Tenant Resource Center of Wisconsin offers assistance.  Safe moving, happy curbside hunting, and keep an eye out for bed bugs!