Tag Archives: Featured

Introducing the Wisconsin Periodical Cicada Website

Now that the solar eclipse has passed, the next big natural phenomenon in Wisconsin will be the emergence of Brood XIII periodical cicadas in late May and June.  These insects last emerged in the state in 2007 around the time that Steve Jobs was releasing the very first iPhone.  While there were some reports of out-of-sync “stragglers” a few years ago, 2024 will be the year of their big emergence.  Since these insects emerge every 17 years, you might only have a handful of opportunities to see them in the Badger State in your entire life.  Despite having grown up in southeastern Wisconsin and turning 40 next year, I still have not witnessed an emergence myself and I’m really looking forward to this year’s activity.

With all the “buzz” about these amazing insects, I recently developed a new Wisconsin Periodical Cicada Website: cicadas.wisc.edu.  This site covers the biology, ecology, and distribution of these insects, with lots of photos, audio recordings, cool historical videos, and other resources.

Wisconsin Periodical Cicada Website
The recently launched Wisconsin Periodical Cicada Website.

I also wanted to get a clearer picture of where these insects occur in Wisconsin.  This winter, I dug through 150+ years of books, newspaper columns, university and government reports, and specimens in our very own Wisconsin Insect Research Collection to develop an updated map for the state.  While this map is an improvement over older ones, there’s still plenty to learn about the local distribution of these cicadas in Wisconsin.  To that end, I also launched a community science project on the website for participants to submit their own sightings from the state.  It’s a brief fillable form and photos can be uploaded right from your phone, tablet, or computer—no app required.  I’d love to receive any reports of periodical cicadas from Wisconsin this year to help improve our map of them in the state.

If you’re a cicada enthusiast and have a lot of reports to share, feel free to contact me via email (pliesch@wisc.edu) to discuss other arrangements.  If you’re unsure if you’ve spotted a periodical cicada, check out the website’s Cicada Basics page or reach out for assistance at the UW Insect Diagnostic Lab.

Adult periodical cicada
Adult periodical cicada. Photo credit: USGS Native Bee Inventory and Monitoring Program; public domain image.

Lastly, if you’re hoping to see and experience the periodical cicadas for yourself, your best bet would be to visit the Lake Geneva area in June.  This part of the state has a very long and well-established history of periodical cicada activity.  There’s also an updated Wisconsin map and a summary for each county on the periodical cicada website’s When and Where page.  Previously, much of this information was buried in the literature, so the Wisconsin Periodical Cicada Website offers a unique look at the known distribution of these insects in the Badger State.

Check out cicadas.wisc.edu for additional details and get ready for all the buzz this spring!

Webinar Announcement: 2024 Monthly Ask the Experts Q&A Sessions

Ask the Experts:  A Monthly Garden and Landscape Q&A Series Sponsored by the UW-Madison Division of Extension Horticulture Program


Join our monthly online programs in 2024 for an opportunity to connect with plant health experts from the UW-Madison Division of Extension. Each session, held on Monday afternoons from 1:00-2:00 PM, is your chance to ask questions about your trees and shrubs, garden vegetables and ornamentals, lawns and more. Whether it’s about plant diseases, insects, or the selection and general care of plants in and around your home, our panel of seasoned experts will provide you with insightful answers. Don’t miss out on this opportunity to cultivate your knowledge and keep your plants thriving.


These online sessions are free but registration is required for each one that you would like to attend (see links below). Upon registration you will receive an email confirmation with the link for joining the session. All sessions are Mondays from 1:00-2:00 PM.

January 22, 2024  To register for this session, click here.

February 19, 2024  To register for this session, click here.

March 18, 2024 To register for this session, click here.

April 22, 2024 To register for this session, click here.

May 20, 2024 To register for this session, click here.

June 17, 2024 To register for this session, click here.

July 22, 2024 To register for this session, click here.

August 19, 2024 To register for this session, click here.

September 23, 2024 To register for this session, click here.

October 21, 2024 To register for this session, click here.

November 18, 2024 To register for this session, click here.

December 16, 2024 To register for this session, click here.

Elm Seed Bug: A New Pest to Watch for in Wisconsin

Note: As of late 2023, elm seed bug (ESB) has not yet been found in Wisconsin, but could show up in our area in the near future.


The elm seed bug (Arocatus melanocephalus  | Hemiptera: Lygaeidae) is an invasive insect species native to parts of Europe. It was first detected in North America in 2012 in western Idaho and is now established in western parts of the continental US and Canada. In the eastern US, we haven’t seen much of this insect yet. It was technically spotted in the general Detroit area in Michigan in 2015 and reports continue to pop up in southeastern Michigan. This last summer, I helped confirm the presence of the elm seed bug (and the Asiatic garden beetle!) in the Twin Cities area for the Minnesota Department of Agriculture. Given the proximity to the Wisconsin state line, the elm seed bug could make an appearance in our state in the not-too-distant future.

Overall, elm seed bugs have habits similar to boxelder bugs and birch catkin bugs in that they feed on trees outdoors before invading structures later in the year.  True to its common name, the elm seed bug is associated with elm trees and is especially fond of feeding on the seeds. They have little overall impact on the health of the trees. Later in the year, adult elm seed bugs seek out sheltered overwintering spots. In natural settings, they would typically overwinter beneath loose bark of trees or similar locations. However, they can readily invade homes and other structures in large numbers.  Indoors, elm seed bugs are harmless to humans, but can be a general nuisance. Like brown marmorated stink bugs, elm seed bugs can also produce an unpleasant odor when crushed. Because ESBs are a nuisance invader like boxelder bugs and multicolored Asian lady beetles, management is going to be very similar and should focus mostly preventing these insects from getting indoors, e.g., physical exclusion and exterior crack and crevice treatments.

Elm Seed Bug Infographic
Infographic describing the main features of the elm seed bug (Arocatus melanocephalus). Infographic created by PJ Liesch, UW Insect Diagnostic Lab. Click for larger version.

Since we have not yet seen elm seed bugs in Wisconsin, having this insect on our radar and being able to recognize it are the most important things at the moment. Elm seed bugs are similar in body shape to boxelder bugs, but are slightly smaller at roughly ¼ – ⅓ inch long. The adults are a dark brownish-black color with rusty-colored patches behind the head. There is a blackish, triangular structure (scutellum) on the middle of the back which sits within a rusty-colored, square-shaped patch. The edge of the abdomen is marked with a series of small, pale spots and the underside of the abdomen is a rusty, reddish color as well.


Wisconsin residents believing that they’ve found elm seed bugs are encouraged to collect a sample and contact me at the UW Insect Diagnostic Lab to definitively confirm the identity of the specimens: insectlab.russell.wisc.edu.

Blow Flies (Calliphoridae) Indoors

Each insect species has a “story” to tell—where they came from, what they do, and what their presence means for humans. Knowing this story can make a big difference when it comes to our own actions.  For example, imagine finding an insect near your bed.  If you recognized the insect as a harmless ground beetle that accidentally snuck in from outdoors, you might shrug your shoulders and carry it outside in a Tupperware.  But, if the insect were a blood-feeding bed bug, it could mean an expensive bill to have your home professionally inspected and treated by a pest control company.  Knowledge is power!

In my mind, the first step towards getting this knowledge is through proper identification.  I say this with a certain amount of endearment, as I am an insect diagnostician after all.  However, once you’ve properly identified an insect, it’s easy to look up its “story” (biology, behavior, etc.) in books, websites, or even the scientific literature.  This process can allow you to more efficiently identify the root of a problem (if there is one) and figure out a solution.

Adult cluster fly (Pollenia sp.)
A cluster fly (Pollenia sp.). These flies are common parasites of earthworms, but frequently enter structures in late summer and can be a nuisance. Preventing their entry into homes is the single most important management step. Photo credit: Katja Schulz, via Wikipedia.

A good example of this concept would be flies in and around homes.  There are easily dozens of different types of flies that can be encountered in typical yards and homes in the Midwest and each has a slightly different story to tell.  Some can breed in piles of grass clippings or seaweed (e.g.,  stable flies), some parasitize earthworms but like to sneak indoors (e.g., cluster flies), and others can hitchhike on plants.  A common and widespread group of flies is the Family Calliphoridae—the blow flies.

Luckily, blow flies can be identified easily in many cases due to their metallic green or bluish coloration. Some members of this group are even known as “green bottle flies” or “blue bottle flies” due to their distinctive colors.  Overall, the blow flies are mid-sized flies and are often slightly larger than house flies (~1/4 – 3/8” long).  The larvae are your stereotypical pale and slender “maggots”, although they can be definitively distinguished from similar-looking fly larvae under the microscope.

Adult blow fly (Family Calliphoridae)
An adult blow fly. The metallic green coloration is a helpful identifying feature. Finding these indoors often indicates a dead mouse. Photo credit: Brian Gratwicke via Wikipedia.

When blow flies are found indoors, it’s often easy to understand the situation and remedy the problem.  One of the biggest factors in the “story” of blow flies is dead stuff.  Out in nature, blow flies play an incredibly important role in helping break down dead animal matter.  These flies are often the very first insects to show up at dead animals—sometimes within seconds.  After laying eggs, the resulting larvae do a lot of work feeding on and breaking down animal tissues.  Being poikilothermic (“cold-blooded”), they also develop at a predictable rate depending on the temperature, so these flies are even used to estimate lengths of time in forensic investigations.

There’s always a chance that a blow fly spotted indoors might have accidentally snuck in from outdoors, but in many cases it’s an indication of something dead.  Blow flies are able to detect the faint odors of death from long distances, so a single dead mouse, bat, or other creature in a home can attract these flies.  Rather than spraying an insecticide, the best remedy is to find the root of the issue and clean it up.  In many cases, it’s just a matter of checking mouse traps and discarding the mouse that had recently met its demise.

Another situation that I often see indoors is a scenario that has simply proceeded further than the last one.  If an adult female blow fly is able to locate a dead mouse (or other animal) and lay eggs unnoticed, the resulting larvae can consume most of the remains and complete their development.  If this happens, the first thing noticeable is often a bunch of maggots wandering the nearby area (the maggots often wander away from their food source when ready to pupate).  When they pupate, small brownish “pods” (puparia) may be noticed and upon reaching maturity, dozens of adult blow flies can seemingly appear out of nowhere.  In such a case, it’s generally an indicator that a dead mouse or other animal had been present for some time (often a few weeks). Unless there are additional resources for them, these flies usually perish quickly indoors.  This scenario frequently comes into play in second homes or cabins that are unoccupied for longer periods of time or if the dead animal is location in a tucked away or inaccessible spot (such as in a wall or ceiling void).

Wandering Weevils: Summertime Visitors

If you’ve spotted small, crunchy beetles in your home this summer you aren’t alone.  Broad-nosed weevils (Curculionidae: Entiminae) have been a surprise this summer at the UW Insect Diagnostic Lab.  While I see cases of these insects every year, things have been a bit more intense this summer with a flood of reports from around Wisconsin.

What’s a weevil?  Out of the 100+ different families of beetles, the weevils (Family Curculionidae) are extremely diverse with over 50,000 species in this group alone.  In terms of their appearance, most weevils might remind you of Gonzo from the Muppets with their very pronounced “snouts”.  A great example of this in Wisconsin is the genus Curculio (the “nut and acorn weevils”).  Some species in this group can have a snout (technically “rostrum”) as long as the rest of their body.

The pecan weevil (Curculio caryae). The pronounced rostrum or “snout” is a classic feature of many members of the weevil family. Photo credit: Jennifer C. Girón, Museum of Texas Tech University. Bugwood.org.

On the other hand, some members of the weevil family lack the pronounced snout .  One such group, the subfamily Entiminae, is commonly referred to as the broad-nosed weevils.  Our common broad-nosed weevils tend to be small (around ⅛ – ¼ inch-long) and have pear-shaped bodies with very hard, crunchy exoskeletons; they also have “elbowed” antennae similar to ants.  The color of the broad-nosed weevils can vary by species, but many are blackish or grayish.

The imported longhorned weevil (Calomycterus setarius)—a type of “broad-nosed weevil” that occasionally sneaks indoors. Photo credit: Natasha Wright, Braman Termite & Pest Elimination, Bugwood.org

When it comes to broad-nosed weevils, we have over 100 species in the Midwest alone.  In general, these are “outdoor” species associated with plants.  The larvae tend to feed on the roots of plants while the adults often chew small notches out of the edges of foliage.  Interestingly, a few species in this group have the habit of sneaking indoors during the summer months.  Once inside, these insects are completely harmless but can be a minor nuisance as they seem to mindlessly wander on walls or floors.

During the summer months, some broad-nosed weevils can sneak indoors—occasionally in large numbers. In this case, hundreds of strawberry root weevils (Otiorhynchus ovatus) were wandering on the side of a home. Photo submitted to UW Insect Diagnostic Lab.

Conditions in Wisconsin over the last year and a half must have been just right for some of these species, since I’ve had a flood of requests to help identify broad-nosed weevils in homes and other structures during the summer of 2022.  Often when I see “weevil” cases it’ll be a handful of weevils indoors, but this year I’ve also seen plenty of reports of large numbers of weevils (hundreds or thousands!).  The top three species I’ve been seeing in Wisconsin have been the strawberry root weevil (Otiorhynchus ovatus), the imported longhorn weevil (Calomycterus setarius), and the black vine weevil (Otiorhynchus sulcatus).  There are a number of other species in this group that can invade structures as well.  Due to the similar appearance of these beetles, it’s often necessary to get a sample under the microscope to help confirm the exact species.  If you come across broad-nosed weevils in your home and want to know the exact type, feel free to send in a sample to the UW Insect Diagnostic Lab: insectlab.russell.wisc.edu/samples.

While these weevils can be a bit of a nuisance, there usually isn’t much of a need to spray (especially indoors).  In the grand scheme of things, good physical exclusion (i.e., sealing things up better with caulk, expanding insulation foam, better weatherstripping, etc.) can go a long way to help prevent broad-nosed weevils from getting indoors in the first place.  For the weevils that do make it indoors, insecticide really aren’t necessary and sweeping or vacuuming up these slow-moving pests is the best course of action.

Do mosquito yard sprays harm other insects?

If you’ve noticed all the lawn signs for mosquito treatments, you may be wondering if mosquito yard sprays harm other insects. If so, you’re not alone.  As an Extension entomologist, this is a common question that I get from the public every year.  To get to the bottom of this question, it helps to understand the different types of mosquito spraying that’s done.

One approach (Ultra Low Volume or ULV) is sometimes used by municipalities or abatement districts to control mosquitoes.  These ULV applications generally involve using specialized equipment mounted on trucks or aircraft to apply extremely tiny droplets which kill adult mosquitoes by direct contact as the droplets float in the air.  Such applications use very small volumes of insecticides either undiluted or with minimal dilution and are often applied after dark when mosquitoes are most active.  The microscopic droplets from ULV treatments disperse relatively quickly and have little residual activity—think of them like a “one time strike” to knock down mosquito numbers.

The vast majority of research on mosquito sprays and non-target organisms has looked at these ULV-type treatments.  Some good news is that these studies suggest that impacts to non-target insects are relatively small and short-lived.  It turns out that the ULV treatments are most effective on insects with very small body mass, so insects larger than mosquitoes tend to be spared.  A good summary of the impacts of ULV treatments on non-target organisms can be found in a 2012 review paper by J.A.S. Bonds in Medical and Veterinary Entomology. 

Many mosquitoes like to rest on vegetation during the day, so some mosquito sprays specifically target these resting sites. Photo credit: Public Domain Image.

Case closed, right?—Not quite. Here in Wisconsin, we don’t really use ULV treatments a whole lot for mosquitoes.  The common yard treatments are what we’d call “perimeter”, “barrier”, or “residual” treatments.  Such treatments are applied via a backpack sprayer to create a coating or “barrier” on treated surfaces which affects mosquitoes that land on it.  These treatments involve applying a residual insecticide (usually from the pyrethroid group) to vegetation in yards and around structures.  The pyrethroid products are broad-spectrum and often last for a few weeks or longer depending on the formulation.  These same ingredients (and sometimes the exact same products) can also be used to control a wide range of yard, garden, and structural pests (e.g., Japanese beetles, garden pests, household ants, etc.).

While the pyrethroids are very common and widely used for a range of purposes, there’s a knowledge gap when it comes to the impacts of mosquito “barrier” treatments on other insects.  While this knowledge gap exists, a few studies raise concerns.  One study by Dr. Karen Oberhauser and colleagues found that monarch caterpillars could be harmed or killed even 3 weeks after spraying.  A more recent (2022) study by Qualls et al. found that honey bees were harmed 28 days after “barrier” treatments were applied.  Thus, if a yard is being sprayed for mosquitoes monthly during the warm season, there are reasons for concern.  More research is needed to help understand the effects of these “barrier” yard treatments on insects that often land on vegetation in yards, such as moths, butterflies, fireflies and other beetles, true flies, bees, wasps and other pollinators.  

Fireflies can be very common on vegetation in a yard during the summer months. Scientists view pesticides as a concern for fireflies globally. Photo credit: RachelEllen via FLickr CC.   

References:

  • Bonds, J.A.S. 2012. Ultra-low-volume space sprays in mosquito control: a critical review. Medical and Veterinary Entomology. 26: 121-130. 
  • Oberhauser, K.S., Brinda, S.J., Weaver, S., Moon, R.D., Manweiler, S.A., and N. Read. 2006. Growth and Survival of Monarch Butterflies (Lepidoptera: Danaidae) After Exposure to Permethrin Barrier Treatments. Environ. Entomol. 35(6): 1626-1634.
  • Qualls, W.A., Moser, B.A., Periera, R.M., Xue, R-D, and P.G. Koehler. 2022. Impacts Of Barrier Insecticide Mixtures On Mosquito, Aedes Aegypti And Non-Target Honey Bee, Apis Mellifera.  Journal of the Florida Mosquito Control Association 69: 34-42.