Tag Archives: Insect Pests

Asiatic Garden Beetles Collected in Wisconsin for the First Time

Serendipity can play a big role in being an entomologist or any kind of naturalist. Sometimes, you’re simply in the right spot at the right time to make an interesting observation or scientific discovery. There’s lots to learn about the natural world around us and plenty of room for discoveries.

Think about birds for a moment. According to the Wisconsin Society for Ornithology, there are 441 species of birds known from the state. Birders can spend an entire lifetime learning about the biology and habits of these species and how to identify them by sight, song, and other features. Now, think about insects. Here in Wisconsin, our best estimate is that we have somewhere in the ballpark of 20,000 insect species in the state (let alone all the other arthropods!). During talks to the public, I often joke that birders have it easy—with so many insects out there, you could have ten lifetimes and still have plenty to learn and discover!

With that said, there’s lots to be discovered in the world of insects. Even though I’ve been collecting and studying these creatures for over 15 years, I still make discoveries on a regular basis. This often requires hours of diligent observations and the ability to focus on the tiniest of details, but in other cases it comes down to plain old luck. For example, I’ve written about discovering and collecting specimens of the rare fly, Asteia baeta, in my house after setting up a Christmas tree (no such luck this year…).

Photo of adult Asiatic garden beetles
Asiatic garden beetle adults. Photo credit: Emmy Engasser, Wichita State University, Bugwood.org.

A more recent example of entomological serendipity occurred this last July in my own backyard in Dane County. I was enjoying a cold beer on our back deck one warm evening  when I noticed a few small scarab beetles on our window screens. Since I keep a lookout for invasive species as part of my job at the UW Insect Diagnostic Lab, I always have a list of species in mind that I’m keeping an eye out for. In this particular case, the beetles piqued my interest due to their resemblance to the non-native Asiatic garden beetle (Maladera formosae), although we have native species in the genus Serica that can look similar to the naked eye. Just a few weeks before this, I had identified some specimens of the Asiatic garden beetle from a suburb of Chicago, which placed the species on my immediate radar.

Hold my beer, I’m getting some vials. I collected all the specimens I could spot (4), and was able to confirm their identity as the Asiatic garden beetle after tracking down appropriate keys and dissecting out the male genitalia—a surprisingly common and delicate entomological task used to distinguish certain insects that look similar. While I’ve seen a possible report of the AGB on iNaturalist, the specimens from my back deck marked the first specimens of the Asiatic garden beetle collected and confirmed from the state of Wisconsin.

Adult Asiatic garden beetles colleted in Wisconsin.
A few of the Asiatic garden beetle specimens known from Wisconsin. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

The Asiatic garden beetle first showed up in the United States in New Jersey in the early 1900’s and has spread westward ever since. This species is a notable pest and feeds on a wide range of plants. The adult beetles are “sneaky”—hiding by day and causing most of their damage after dark. They are primarily active on warm evenings (>70˚F) and can be strongly attracted to lights. In this case, not only was I enjoying a cold beer on a warm summer night, but the string of patio lights over our deck likely attracted the beetles from the nearby area. The larvae (white grubs) can be pests of turfgrass, home gardens, and agricultural crops such as corn and potatoes.

Adult Asiatic garden beetle and plant damage.
An adult Asiatic garden beetle and feeding damage on a landscape plant. Photo credit: Whitney Cranshaw, Colorado State University, Bugwood.org.

At this point, I have many more questions than answers about the Asiatic garden beetle and what the future holds for this species in Wisconsin. To date, only a handful of specimens have been collected (four in July and another specimen in mid-September) and no plant damage has been observed. However, I’ll be keeping a close eye on this species, since reports from nearby states suggest that we may be seeing more of this species and damage in the coming years.

Jeep ‘Adventure’ Leads to an Unexpected Insect Discovery in Wisconsin

On average, I see 2 – 3 new, non-native insect species show up in Wisconsin every year through my work at the UW Insect Diagnostic Lab (3 so far in 2021!). I’ve mentioned this in previous blog posts, but humans make excellent accomplices in moving species from one spot to another on the globe. This last spring, I saw one of the most interesting cases of my career which highlights this point exactly.

Like any good globetrotting adventure, this story involved a rugged, adventurous mode of travel—a Jeep. This particular Jeep had been imported in late 2020 and after a period of time in the eastern US, it eventually wound up in a small town in central Wisconsin. Unbeknownst to the owner of the vehicle, this Jeep also contained unexpected insect stowaways.

These insects managed to survive for months sheltered within the Jeep and would become active when the vehicle was in use—unexpectedly wandering out of nooks and crannies, much to the displeasure of the driver. Obviously, this isn’t something a new car owner wants to see, so a pest control professional was consulted about the insects and they got in touch with me at the UW Insect Diagnostic Lab to figure out what the specimens were. In the initial conversation, the mystery insects had been described as “stink bugs” and I figured that overwintering nuisance insects like the brown marmorated stink bug might have been involved. The photos, however, hinted at something far more puzzling.

The initial photo I received of the mystery insect on a car window.  Limited resolution, but definitely not a stink bug or anything else that I recognized. This certainly was a “we’re not in Kansas anymore” type moment.

By this point, I had been running the UW Insect Diagnostic Lab for six years and hadn’t seen anything quite like the insect in the photo. I requested a sample to get to the bottom of this mystery under the microscope.  I handle so many cases at the diagnostic lab (~2,500 annually), that I can generally identify most specimens to family (or perhaps even genus or species-level) with a quick peek. In this case I was utterly perplexed, meaning I had to run it through a general family-level taxonomic key for the true bugs (Order Hemiptera). In Borror and DeLong’s Introduction to the Study of Insects the specimens keyed out to the Family Heterograstridae.

From the Hemiptera family key from Borror and DeLong’s Introduction to the Study of Insects. The asterisk symbol (*) is always a surprise.

An asterisk is always a surprise when you encounter it in a taxonomic key. It generally means one of two things: you either took a “wrong turn” in the decision-making process (and misidentified the specimen) or it’s something rare or highly unusual. Something seemed amiss, so I consulted a few other keys to further confirm the Family Heterogastridae. In North America there’s only a single genus (Heterogaster) from this family and three species known from the west coast of the US. The specimens in my possession looked markedly different. Because the Family Heterogastridae is mostly a footnote in the western hemisphere, it’s hard to find information on this group of insects.

This is why geographic clues can be so important in diagnostics and why I request this information with every sample at the UW Insect Diagnostic Lab. Knowing where a specimen was collected and/or originated helps tremendously in learning more about it. Through follow-up conversations, I learned that the Jeep was manufactured in and imported from Melfi, Italy—meaning there was a good chance I was looking in the completely wrong hemisphere for the information needed to identify it.

This led to many evenings of armchair sleuthing. During this process, I’d like to imagine myself as Jason Bourne tracking down members of an international conspiracy while a suspenseful soundtrack blared in the background, but in reality I was mostly just locating pdfs of scientific papers and using Google Translate. Such work could have taken months or even years a few decades ago, but was now possible in the matter of a week or two.

Thanks to Interlibrary Loan and other online resources, I tracked down manuscripts from a half-dozen European and Middle Eastern countries in multiple languages and spent hours pouring over posts on Italian and French insect forums looking for clues. I finally found my answer in a scanned pdf version of Jean Péricart’s Hémiptères Lygaeidae euro-méditerranéens, vol. 1., which identified the specimens as Platyplax inermis—a species associated with Salvia spp. plants in the Mediterranean region.

Map showing reports of Platyplax inermis from its native range. Map credit: iNaturalist.

Having finally identified the stowaway insects and their origin, my work was mostly done at that point. The species happened to be on the USDA-APHIS regulated plant pest list (technically, the entire family Heterogastridae is listed), so I reached out to colleagues at the USDA-APHIS office in Madison to hand off the case. Specimens were sent off to an APHIS field office in Chicago and then off to the Smithsonian for further confirmation, a few specimens are also being deposited in the Wisconsin Insect Research Collection.

While most cases at the UW Insect Diagnostic Lab aren’t anywhere near this exciting, even insect diagnosticians get to live vicariously every once in a while.

 

Fall Armyworms: A Late Summer Surprise in Wisconsin

It’s been hard to miss the recent news headlines about fall armyworms “FAW” (Spodoptera frugiperda). States east of the Rockies have seen historical outbreaks of this insect in 2021, including a bit of fall armyworm activity here in Wisconsin. In some cases, the caterpillars have decimated entire crop fields or home lawns overnight before marching onwards in search of “greener pastures”.

We usually don’t see much of the fall armyworm in Wisconsin and it’s primarily a pest of warmer areas, such as the gulf coast states.  The FAW is native to tropical and subtropical parts of the western hemisphere and the larvae (caterpillars) can feed on dozens of different types of plants—ranging from field crops to fruits and vegetables and even turfgrass. They can be particularly important pests to crops such as corn, grains, and alfalfa.

Fall armyworm caterpillar
Fall armyworm caterpillar. Photo credit: Frank Peairs, Colorado State University, Bugwood.org.

The fall armyworm can’t survive the winters in the US, other than the southernmost areas (e.g., southern Texas and Florida). However, in spring and summer the adult moths migrate northwards and lay eggs. Over the course of many generations and subsequent northward migration, fall armyworms can make it to the upper Midwest and even parts of southern Canada. Historically, fall armyworm has rarely been a notable pest in Wisconsin or the upper Midwest—it simply arrives too late or in too small of numbers to be a concern. To a certain extent, every year is a roll of the dice, but the odds are usually in our favor in Wisconsin and other northern states.

Fall armyworm adult moth
Fall armyworm adult moth. Photo credit: Lyle Buss, University of Florida, Bugwood.org.

This year has been different though, with large numbers being spotted northwards and reports of significant damage coming in from nearby states such as Illinois, Indiana, Iowa, and Ohio. Many other states ranging from Kansas to the mid-Atlantic region have also been impacted in the later parts of summer. While there have been scattered reports of fall armyworm damage to field crops in southern parts of Wisconsin, the lateness of this pest’s arrival and our declining temperatures have likely spared us from the widespread damage seen in other states.

Under hot conditions (e.g. temps in the 90’s), the life cycle of the fall armyworm—from eggs to adult moths—can take only a few weeks. However, fall armyworms are “cold blooded” creatures and cooler temperatures slow down their growth and development. Depending on how chilly it is, their life cycle can be “stretched out” to take 60 days or longer—leaving them much more vulnerable to predation, parasitism, or exposure to frosts.

Eggs of the fall armyworm
Fall armyworm eggs from a residential yard. Photo submitted to UW Insect Diagnostic Lab in September, 2021.

One study* found that fall armyworm eggs didn’t hatch at all if temperatures were cool enough (though not particularly chilly by Wisconsin standards). That particular study simulated daytime/nighttime temperatures of 21˚C (70˚F) and 8˚C (46˚F)—temperatures that are “in the ballpark” for many parts of Wisconsin by mid-September and are often considered downright “pleasant” by Wisconsinites.  Eggs held at warmer temperatures in the experiment hatched just fine.

For eggs that did hatch this year in Wisconsin, cool temperatures also could have helped us out by slowing down their development. As they grow, fall armyworms pass through six sub-stages (instars). The early instar caterpillars are so small, they simply can’t eat much and cause little damage. It’s not until FAW caterpillars become more mature fifth and sixth instars that they really start to chow down and cause significant damage to plants. Thus, falling temps could help prevent the fall armyworm caterpillars from making it to the destructive late instar stages and could also leave them more exposed to a variety of threats.

Chart showing quantity eaten by fall armyworm larval instars.
Graphic representation of the amount eaten by fall armyworm caterpillars in an early USDA experiment. Early instar caterpillars eat little compared to late instars. Cool temperatures limiting their development could help prevent damage by the FAW. Credit: USDA Technical Bulletin No. 34

The fall armyworm outbreak of 2021 could very well be a “once every few decades” type of event, and our northern location likely helped us avoid the significant problems seen in other states. However, if changing climate gives the fall armyworm a “head start” by overwintering farther north, it’s possible that we could see more of this pest in Wisconsin in the future.


*Barfield, Mitchell, and Poe. 1987. A Temperature-Dependent Model for Fall Armyworm Development.  Annals of the Entomological Society of America. 71(1): 70-74.

The Summer of Springtails

With the unusually dry weather we’ve had in Wisconsin this year, I would not have predicted that springtails (Collembola), would have been one of the commonest samples at the UW Insect Diagnostic Lab this summer. In general, springtails tend to thrive under damp conditions. These tiny (<1/10 inch long), insect-like creatures are commonly associated with leaf litter, rich soil, compost, and mulch or plant beds outdoors where they feed on fungi and decaying plant materials.

Photograph of a springtail on a log.
A tiny springtail on a decaying log outdoors—a common place to spot these creatures. Photo credit: Melissa McMasters via Wikipedia.

Springtails are ubiquitous and can be found around the globe under a wide variety of conditions. In many parts of North America, you can even bump into large numbers of dark-colored springtails (snow fleas) bouncing around on the snow in winter.  Springtails are a fairly diverse group with over 15 Families in North America, so there’s a lot of variability in terms of the color and overall appearance.

Indoors, it’s usually too dry for springtails to survive or reproduce unless damp conditions exist. Occasionally, they can be found indoors in association with overwatered houseplants, new construction (due to residual moisture in construction materials), plumbing leaks, and other moisture issues. In many cases, when springtails are spotted indoors, they originated outside and simply snuck in but perish shortly thereafter due to desiccation.

Chart shwoing drought conditions in Wisconsin in June of 2021.
Drought conditions in Wisconsin—June of 2021. Much of the state experienced drier than usual conditions this year, with some parts experiencing extreme drought conditions. Photo credit: US Drought Monitor Program: https://droughtmonitor.unl.edu.

With the lack of precipitation and this year, I haven’t gotten the impression that springtails are necessarily thriving outdoors. However, the hot and dry conditions are likely forcing springtails to sneak into structures or other spots that may be slightly damper, darker, and cooler. When they do make it inside, springtails are often spotted near moisture sources—kitchen or bathroom sinks, showers or bathtub drains, and basement floor drains. Some good news is that springtails are completely harmless to humans, pets and homes, and in most cases won’t survive long.

Hundreds of springtails along a home's foundations.
Hundreds of springtails along a home’s foundation. Photo submitted for a recent case at the diagnostic lab.

The following tips can be helpful when springtails are a problem indoors:

  • Monitor both indoors and outdoors—Visually inspect for areas with lots of springtails and see if potential entrance points into structures are nearby. Indoors, glue board traps from the hardware store or garden center can be helpful tools for monitoring and management.
  • Manage vegetation near the foundation of homes and other structures—Plants near a foundation can hold in moisture and create good habitat for springtails, spiders, millipedes, and insects that can wander indoors. Having a gap of 1-2 feet or more between a structure and plants increases airflow and can decrease humidity.
  • Avoid excessive mulch—A thick layer of mulch can hold in moisture and may create good habitat for springtails and other arthropods.
  • Physical exclusion—Sealing up potential entrance points into a structure can help with many pests, including springtails. Caulk and expanding insulation foam can be helpful in this regard. Inspect and replace weather stripping to make sure that windows and doors seal properly. Pay particular attention to high priority areas such as along the foundation, around window and door frames, and basement window wells.
  • Keep indoor humidity low—Running a dehumidifier and/or air conditioning can help decrease moisture and make it harder for springtails to survive. Repair or correct any drainage, plumbing, or moisture issues that may be increasing humidity levels within a structure. Allow houseplants to dry out between waterings; soil that is kept damp can be a potential hangout for springtails indoors.
  • Insecticides—Since springtails sneaking in from outside don’t survive long, spraying indoors is generally not warranted or helpful. If springtails are highly problematic, treating cracks and crevices on the exterior of a structure may decrease the number making it inside but won’t eliminate them outright.

Fungus Gnats: Tiny Flies Around Your Houseplants

With winter’s arrival, the caseload at the UW Insect Diagnostic Lab is low, although ID requests continue to trickle in. Recently, dark-winged fungus gnats (Family Sciaridae) are one of the commonest insects I’ve seen at the lab. These tiny (1/16 – 1/8 inch long), dark-colored flies are almost always associated with houseplants.

Adult fungus gnat showing the distinctive, curved “Y” fork in the wings.  Photo Credit: B. Schoenmakers, via Wikipedia.

Despite their small size, adult fungus gnats can readily be identified by their wing venation. Using a bit of magnification, the translucent wings of these insects possess an oblong, rounded “Y” towards the tips of the wings. While the delicate adults gnats may catch our attention, the larvae are at the root of the problem. The slender, worm-like larvae possess a dark head capsule and live in moist environments.

The connection with houseplants has to do with the feeding habits of the larvae. Fungus gnat larvae generally aren’t plant pests, but scavenge on fungal spores. If the soil of a houseplant is kept too moist, it can create ideal conditions for them. An abundance of fallen decaying plant materials (leaves, etc.) on the soil surface can also contribute. Some of the commonest sources of fungus gnats (and other houseplant pests) are “outdoor” plants which were brought indoors in the fall.

Adult fungus gnats may be a nuisance, but are harmless and short-lived. They will often be observed near potted houseplants (where females can lay eggs) or at nearby windows. When it comes to fungus gnat problems, the following approaches can be helpful:

Sticky card traps can be a useful non-chemical approach for monitoring fungus gnat populations over time and capturing adults. Photo credit: PJ Liesch, UW Entomology.

1) Dry out the Soil: Fungus gnat larvae thrive in damp soil or potting mix. Cutting back on waterings is often the single most important step in dealing with fungus gnats and the mere presence of these gnats is often an indicator of overwatering. Allowing the soil to dry out between waterings decreases survival of the larvae. For succulents and other popular plants that are tolerant of dry conditions, cutting back on waterings can often correct a fungus gnat issue over time without any additional steps.

2) Sticky Card Traps: These traps look like bright yellow index cards, but are covered with a sticky adhesive. When purchased at local hardware stores, garden centers, or online, they usually include small stakes to help place these cards into pots. The adult fungus gnats are attracted to the color of the traps and can become stuck in the adhesive. Used alone, these traps will not eliminate fungus gnats. However, these traps are a non-chemical way to capture adults and can help when used in combination with other approaches. If you have significant fungus gnat numbers, swapping out sticky cards on a regular basis can help monitor for trends over time.

3) Soil Monitoring: If you have lots of houseplants, determining which plant(s) is/are harboring the larvae can be a challenge. One helpful approach is to place slices of potato on the soil surface of potted plants. If larvae are present in a given pot, some may come to the surface to feed on the readily-available starches of the potato. Checking the potato slices for the presence of the dark-headed larvae can help determine where to focus your attention.

4) Cultural Practices: If fungus gnats are really bad, it can sometimes make sense to discard a problematic plant to prevent it from serving as a continual source of fungus gnats. Alternatively, a favorite plant could be washed to bare roots and re-potted in fresh potting mix. When obtaining new plants, it can be helpful to isolate and monitor new plants for fungus gnat or other insect activity before placement amongst other houseplants.

5) Soil Treatments: With severe or persistent infestations of fungus gnats or in cases where watering can’t be reduced, treating the soil is an option to directly target the larvae. The commonest option is to use a product labelled for use on houseplants containing Bacillus thuringiensis israelensis (Bti). These products are based on a naturally-occurring bacteria that is toxic to fly larvae. Such products can be applied as a liquid drench (e.g., Gnatrol) or as granules (e.g., Mosquito Bits) to the soil surface and watered in. Such products won’t eliminate fungus gnats overnight, but can be effective over the course of several weeks.

6) Sprays for Adult Fungus Gnats: Spraying for adult fungus gnats with is not generally effective or recommended.  Targeting the adults will only provide temporary relief and it is much more effective in the long-run to target the larvae at the heart of the problem.