What a year it’s been. Things seemed like they were getting back to normal this past summer, only for the Omicron variant to pop up and say—not so fast. Despite all the ups-and-downs, services have carried on at the UW Insect Diagnostic Lab in one way or another through the second year of the COVID pandemic. Things have changed a bit and these days I’m on campus much more than a year ago. Throughout the pandemic, demand for services at the IDL has remained high with over 2,400 ID requests in 2021.
Since COVID first popped up, there have been some subtle shifts in lab statistics—an increase in the percentage of samples solely involving digital images (vs physical specimens) and an overall increase in the proportion of cases coming from the public. Considering the pandemic, this makes sense. Over the last two years, campus buildings and the IDL have been closed to visitors at various points, meaning that clients couldn’t drop off samples. In other cases, it might have been tough to make it to a post office or the UPS store to ship a sample in. Likewise, with many folks working from home, it likely led to more time out in yards and gardens, or visiting local parks or hiking trails—and more time to notice insects.
Looking back at the cases from this last year, 2021 was a unique year due to our unusually hot and dry weather conditions in Wisconsin. Based on data from the Wisconsin State Climatology Office, Madison was quite warm and saw an extra ~500 growing degree days in 2021, but was down about 15 inches of precipitation for the year. Some parts of the state were even hotter and/or drier than Madison and most of the state was categorized as either unusually dry or in some stage of drought during the year [US Drought Monitor].
The weather conditions this year led to some shifts in the insects and related arthropods seen at the UW Insect Diagnostic Lab. A pest that had been relatively quiet the last decade, Lymantria dispar (formerly known as the “gypsy moth”), thrived with the dry conditions this past spring. In “rainy” years, a beneficial fungus (Entomophaga maimaiga) can “kick in” to help keep their numbers in check. If 2022 is another dry year, we could be in store for even more problems from this invasive species. Certain mites also thrived this year and I saw a large number of cases of eriophyid mites causing damage to plants ranging from coneflowers to garlic. Springtails weren’t necessarily more abundant (they feed on decaying plant matter and thrive under damp conditions), but I suspect the hot & dry conditions sent them looking for any place darker, damper, and cooler. This led to lots of reports as they were trying to invade structures.
We’ll likely continue to see the impacts of the 2021 drought for some time. Plants, including established trees and shrubs, also suffered from the drought and this will likely lead to an increase in reports of “secondary” insect pests in the next few years. Certain insects can be generally “well behaved” and leave healthy plants alone, only to attack stressed and weakened plants. As an example, cases of the two-lined chestnut borer (a notable pest of oaks) often increase 1-3 years after a drought, and I’m expecting to see more cases in the coming years.
In the realm of medical entomology, it was a good year for ticks both in Wisconsin and other parts of the US. Black flies (Family Simuliidae) had another strong year in many parts of the state, although calls about these were shifted a bit earlier than in previous years (likely due to an “early” spring). If there’s a silver lining to the drought, it’s that mosquito pressure was down in Wisconsin for much of the summer. As we received a bit more rain in the latter half of summer we saw some late season activity, but disease pressure remained low (only three West Nile Virus cases in Wisconsin, compared to 50+ in a “bad” year). As recreational and work-related travel increased a bit more in 2021 compared to 2020, I did see an uptick in reports of bed bugs.
With the Asian giant hornet garnering attention in the news for the second year in a row, I continued to see lots of reports of cicada killer wasps, pigeon horntails, great golden digger wasps, and other large insects. Unfortunately, with the sensationalized hype about “murder hornets” (ahem—New York Times…) I had plenty of reports of other large harmless insects that were killed simply because they “looked big and scary” (one particular photo of a tomentose burying beetle comes to mind…). Overall, the Asian giant hornet story was really pretty quiet this year, with a limited amount of activity in a small part of the Pacific Northwest. As of December 2021, the Asian giant hornet has not been found in Wisconsin or anywhere close to us.
I had plenty of reports of social wasps (yellowjackets, bald-faced hornets, and paper wasps) as well as bumble bees this year—including three reports of the endangered rusty-patched bumble bee in the same week in early August! We missed the Brood X “cicada craze” here in Wisconsin, but I still had plenty of questions about them from reporters. We will, however, see some periodical cicadas (Brood XIII) in 2024 in southern Wisconsin.
Some other IDL case highlights from 2021 include:
-An explosion of hackberry emperor butterflies in late spring in south central Wisconsin
-More black witch moths than I’ve ever seen before in a single year (over a dozen sightings!)
-First specimens of the invasive Asiatic garden beetle collected in Wisconsin
-An influx of fall armyworms in late summer, and finally
-Unexpected (live) European insect imported in a Jeep
Every year is a bit different here at the UW Insect Diagnostic Lab and 2021 was no exception. I’ll be curious to see what 2022 has in store for insects in Wisconsin!
—PJ Liesch
Director of the University of Wisconsin Insect Diagnostic Lab
