As one of the coordinators of Wisconsin Insect Fest, I’m thrilled to announce that Insect Fest will be back this year and is coming to the Upham Woods Outdoor Learning Center (Wisconsin Dells) this August. The event will be held from 2–10 PM on Saturday, August 19th, 2023 and is free and open to the public. A family-style cookout will be provided to participants (please RSVP if interested). Insect enthusiasts of all ages are welcome to attend!
Wisconsin Insect Fest is a celebration of insects and attendees will have the opportunity to learn about the different types of insects found in Wisconsin and the many important roles they play in the environment. Insect Fest will feature a variety of indoor and outdoor activities suitable for insect enthusiasts of all ages, including educational presentations, hands-on activities, guided insect hikes, live insects, and an informal BioBlitz activity. This is also a great opportunity to meet entomologists and learn about what they do.
The Wisconsin Insect Fest is a family-friendly event, and we encourage everyone to attend and learn about the fascinating world of insects. We hope to see you there!
Spongy moth (Lymantriadispar) season has officially begun here in Wisconsin. Earlier this week (May 3rd), the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) Pest Survey Program reported caterpillars emerging from an egg mass in far southwestern Wisconsin. Based on forecasting models from the USA Plant Phenology Network, we should expect to see caterpillar emergence begin across much of southern Wisconsin over the next week. As things continue to warm up, the pattern will push further north in the state.
We may be facing a challenging year from this invasive insect. Dry conditions suppressed a beneficial fungal disease (Entomophagamaimaiga) the last two years and allowed spongy moth populations to build up. Along these lines, DATCP reported a 102% increase in male spongy moths caught in trapping surveys last year. Likewise, the Wisconsin Department of Natural Resources (DNR) Forest Health Team reported a significant uptick in defoliation last year—from 294 acres defoliated in 2021 to over 85,000 acres defoliated in 2022.
At this point in the season, it’s hard to know how much damage will ultimately occur on yard and forest trees in 2023. However, you can get an estimate of potential defoliation in your own yard by counting egg masses. Each overwintered spongy moth egg mass contains upwards of 1,000 eggs, so a yard with dozens of egg masses could soon face tens of thousands of hungry caterpillars in the near future.
Over the next few weeks, we can expect spongy moth caterpillar activity increase. These small caterpillars will cause a trivial amount of damage at first but will gradually become larger, hungrier, and more damaging over time. Keep an eye out for activity in your yard. If you are inundated with caterpillars, consider using sticky barrier bands and burlap barrier bands to trap them as described on the UW-Madison Extension Spongy Moth website.
Looking at the bigger picture, Mother Nature could hold a trump card for our spongy moth situation. If we end up having a rainy spring, damp conditions could encourage the fungal disease Entomophaga maimaiga to kick in and crash spongy moth populations (this halted outbreaks in SE Wisconsin in 2004 and 2010) . However, if we experience another dry season, it could allow spongy moth populations to build further—stay tuned and hope for rain!
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.
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.
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).
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.
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.
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.
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 (Calomycterussetarius), 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.
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.
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.
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.
The spongy moth, Lymantria dispar has recently been in the news because of its new name. If you haven’t heard of the “spongy moth” before, it’s probably because you learned of this insect as the “gypsy moth”. It’s the same exact creature, just with a new common name.
Why the change?The word “gypsy” in this insect’s name was originally a reference to persons of Romani descent—“the popular name of the gypsy was no doubt suggested by the brown, tanned kind of color of the male” [Forbush & Fernald, 1896]. In 2021, the Entomological Society of America’s Better Common Names Project started to review the common names used to communicate about insects. Common names that include derogatory or inappropriate terms are being assessed. After a lengthy review process, the term “spongy moth” was ultimately decided upon to describe Lymantria dispar—and fittingly so. The beige egg masses of this insect have a soft, spongy consistency. In French-speaking parts of its range, this species has long been known as La Spongieuse for this very reason. Thus, you’ll be hearing more about the “spongy moth” over time as the term “gypsy moth” is phased out from educational/government websites and other resources.
In addition to the name change, the spongy moth should be on our radar for other reasons. Despite being in Wisconsin for decades, this pest can still be a serious defoliator of hardwood trees, both in yards and forested areas. From the period of 2014 – 2020, spongy moths haven’t been much of an issue. An important reason for this is a beneficial fungus known as Entomophaga maimaiga. This fungus was introduced from Japan and it is strongly associated with the spongy moth. Although it took some time to make an impact in the US, this fungus is now viewed as an important “check” on spongy moth populations. Spring rains encourage this fungus, which can cause high mortality amongst spongy moth caterpillars. However, in many parts of Wisconsin we saw an unusually dry year in 2021 which likely curbed the impacts of this fungus. As a result, I saw an increase in cases and reports of spongy moth caterpillars and their damage, adults, and egg masses at the UW Insect Diagnostic Lab last year and Wisconsin also saw a subtle uptick in defoliation of forested areas.
As illustrated in the chart above, spongy moth populations can be very dynamic and can explode under the right conditions—leading to extensive defoliation. The egg-laying strategy of this species plays an important role in this dynamic. Adult female spongy moths deposit egg masses that can easily contain upwards of 1,000 eggs. In late summer and fall of 2021, I saw plenty of reports where trees contained dozens of egg masses, which could turn into tens of thousands of hungry caterpillars this spring.
Luckily, there’s still a bit of time to take advantage of this knowledge as the young caterpillars typically don’t become active until late April or early May. In the meantime, removal or destruction of the egg masses could help reduce local populations. While often found on trees, the egg masses can also be located on just about any surface in a yard—stacked boards, sides of structures, piles of firewood, and even on vehicles. Don’t delay if you noticed spongy moth activity in your area last year, since it won’t be long before the caterpillars are out and active this spring.
Reference: Forbush, E. H. and C.H. Fernald. 1896. The gypsy moth. Porthetria dispar A report of the work of destroying the insect in the commonwealth of Massachusetts, together with an account of its history and habits both in Massachusetts and Europe. Boston, Wright & Potter. 495pp.