Since last week’s press release on the Brown Marmorated Stink Bug by the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) and my own blog post on this invasive pest, I’ve been getting many reports of this insect from Wisconsin residents. It’s always great to get reports from the community as it helps us keep track of this invasive pest.
Interestingly, there have also been many cases of an insect that somewhat resembles BMSB: the Western Conifer Seed Bug. Both insects try sneaking into buildings to look for shelter and possess “checkerboard” patterns at the back of the body. However, when you have the insects side by side, they can be easily separated. The western conifer seed bug is longer and more slender in appearance, has dull reddish and orange patches on the body, and has distinctly dilated hind legs (think “bell-bottoms”). In addition, these insects possess a unique zig-zag (“lightning bolt”) pattern on each wing, which can easily be seen with the naked eye as illustrated in the ID guide below.
While the western conifer seed bug can sneak into buildings in the fall, they tend to invade in relatively low numbers. This species feeds on the seed cones of pines and other conifers, but doesn’t seem to cause much (if any) harm to the trees. Overall, they can be a bit of a nuisance, but that’s about it, unlike BMSB, which can potentially damage many different types of plants.
Have western conifer seed bugs around the house and want to know more about their biology and management? Check out this handy factsheet from UW-Extension.
Every fall, residents throughout Wisconsin and many other parts of the country face an invasion by a number of insects: boxelder bugs, multicolored Asian lady beetles, western conifer seed bugs and cluster flies, to name a few. With the coming frosts, these insects are simply trying to find a sheltered location to settle for the winter. Out in nature, many of these insects would simply crawl into a rock pile or beneath the loose bark of a dead tree to overwinter.
But why rough it out in nature if there are perfectly good buildings to sneak in to? Next time you’re cleaning the gutters, take a moment to peek around the outside of your house. Small gaps in siding, soffit areas, around door and window frames, and cracks in the foundation are all potential spots for insects to sneak through. And if they make it through? Well, you could be in for some extended visitors. . .
In addition to the usual fall invaders, a relative newcomer starting to pop up in Wisconsin and other parts of the Midwest is the invasive Brown Marmorated Stink Bug (Halyomorpha halys). Like the boxelder bugs and multicolored Asian lady beetles, brown marmorated stink bugs (BMSB) like to find their way indoors for the winter. This Asian species was first detected in Wisconsin back in 2010 and for reasons we don’t fully understand, their numbers have been quite low the past few years. As of late 2014, BMSB has been confirmed or suspected in 10 Wisconsin counties, with most of the reports coming out of the Madison and Milwaukee area. A handful of sightings each year has been the pattern.
Unfortunately, we may be at the beginning of a shift in BMSB populations in the state. In early 2015, there were at least 6 specimens found in Wisconsin by early March. Despite the quiet summer, the sightings have started popping up again in late September and October of this year. What’s more concerning is that we’re starting to see groups of these insects clustered together (previous sightings had consisted almost exclusively of lone individuals).
Not only are these unwanted houseguests a nuisance, but quite frankly, they smell bad. True to their title of “stink bug”, brown marmorated stink bugs possess glands that can emit a pungent odor. Some consider the odor to be coriander-like, while others say it resembles musty gym socks. Invasive species [check]. Nuisance invader [check]. Smells bad [check]. That’s all, right? Unfortunately, not quite. Just like a bad late-night infomercial: Wait! There’s more!
It turns out that brown marmorated stink bug has the potential to be quite a nasty plant pest and rivals the Japanese beetle in the breadth of its palate. Brown marmorated stink bug seems to feed on just about anything under the sun: field crops like corn and soybeans, vegetables like tomatoes and peppers, and even ornamental trees and shrubs. Fruits like apples and grapes can be hit especially hard. In some cases, the mere presence of BMSB can be a problem: imagine being a vintner and having your batch of wine tainted by the presence of a few squished stink bugs! In the eastern U.S. there are regular reports of agricultural problems and growers have to spray to control these insects. We haven’t had any reports of plant damage in Wisconsin yet, but that could change over time if BMSB populations continue to climb.
So what can you do about brown marmorated stink bugs? For starters, learning to tell them apart from our native stink bugs is relatively easy. Look for the alternating “checkerboard” pattern along the back edge of these half-inch long insects and the two light bands on the otherwise brown antennae.
With relatively few sightings in Wisconsin at this point, we’re still trying to get a feel for where this insect is. If you suspect that there may be brown marmorated stink bugs around your house, take a picture of the insect and email it to me at (email@example.com) for identification. Another option is to collect a physical sample and mail them in to the Insect Diagnostic Lab for identification (instructions on how to submit samples can be found here).
If brown marmorated stink bugs or other fall invading insects are trying to get into your house, one of the best things to do is to inspect the outside of your home and physically seal up cracks and crevices where they’re trying to sneak in. Once fall invaders are indoors, hauling out the hose attachment on the vacuum cleaner is often one of the best steps to remove them.
The case load is generally pretty quiet around the UW-Madison Insect Diagnostic Lab during the first few months of the year. There are still the cases of conifer seed bugs or multicolored Asian lady beetles which are the norm for January, February and March. Occasionally I get some interesting specimens (like the cedar tree borer) which emerge from firewood that had been brought in and stored next to the fireplace. My most interesting case lately has been a sample which I was convinced contained small, hairy carpet beetle larvae. I placed the specimen under the microscope to confirm my suspicions, only to be surprised to find that it had a lot more than six legs. With that one glance, the mundane had become the bizarre. I vaguely recognized the creatures I was staring at through the microscope, as I must have seen them in a book once before.
A few minutes of digging and I had my ID: an unusual type of millipede called a “duff millipede” or “dwarf millipede” from the genus Polyxenus. At only a millimeter or two long, these millipedes are hardly noticeable unless they’re moving against a light colored background. Typically, when I hear of millipedes, I think of the slow-moving, dark-colored, creatures that curl up when disturbed and are frequently associated with moisture and decaying organic matter. When it comes to duff millipedes, you have to take most of your preconceptions about millipedes and throw them out the window. Not only are they incredibly small, but their armature of spines makes them resemble a miniature hedgehog (cuteness, included) or some kind of character from the Muppets.
So what do these little spine-balls do anyways? If you dug into the literature, you’d find that they’re often associated with tree bark, leaf litter, or old stone walls and are thought to feed on algae. Other than that, there isn’t much known about them—except for their fascinating defensive mechanisms. Most millipedes rely on chemical defenses to keep predators at bay (including the ability to secrete cyanide). Some polyxenids take a very different approach and use a physical defense consisting of detachable, barbed spines reminiscent of those novelty “finger trap” toys from childhood. Thomas Eisner and colleagues found that these detachable spines can get hooked on the bodies of would-be predators (such as ants), allowing the millipede to escape while the hungry predator attempts to extricate itself. Like the “finger trap” toys, the more the predator struggles to free itself, the more entangled the barbs become. In some cases, the predators can even die from this entanglement. [You can read a detailed description of this defensive mechanism here:http://www.pnas.org/content/93/20/10848.full.pdf]
Entanglement by microscopic millipedes: what a way to go. . .
Below you’ll find the second part of a three part series describing the Top 10 insect-related stories of 2014 from Wisconsin. Part three will be released next week.
7) Missing Pests: As every landscaper and farmer knows, there’s a certain batch of insect pests that tend to pop up consistently each year. One of the biggest stories of 2014 was the scarcity of some of these “regulars” like the gypsy moth and the Japanese beetle. The reason behind this? We likely have Mother Nature to thank. Gypsy moth populations fare poorly during periods of wet weather due to the proliferation of a fungal disease that kills the caterpillars. We certainly had abundant and consistent rainfall in 2014, and several images of diseased insects made their way into the lab. In addition, gypsy moth numbers have been in a general decline for several years in the state, which is good news for oak trees.
If there’s one good thing that came out of the brutally cold winter of 2013-14, there’s the fact that it may have helped knock down the Japanese beetle populations. Japanese beetles overwinter as white grubs in the soil and tend to move just deep enough to avoid the frost line. With the pipe-bursting cold and deep frosts of last winter, it seems that the deep freeze knocked their numbers down. As a result, reports of damage from Japanese beetles were scarce this past summer. While it’s too early to tell, it’s possible that it may only be a one-year reprieve. Turfgrass researchers have reported decent grub numbers in turfgrass areas this fall, which could mean that Japanese beetle numbers could creep back up in the future.
Agricultural pests were also down in 2014, with no major pest outbreaks. Two of our best known corn pests, the European corn borer and corn rootworms, had very slow years. Even migratory crop pests, such as the potato leafhopper and black cutworm, which overwinter in the gulf coasts states and migrate northward in the spring failed to take off in 2014. (A full summary of agricultural pests can be found here.)
6) Interesting “Structural Pest” Trends: Two of our insects that commonly invade homes in the fall (boxelder bugs and multi-colored Asian lady beetles) had drastically different trends this year. Box elder bugs thrive under dry conditions, like we had in the latter parts of 2012 and 2013. Similar to the gypsy moth mentioned above, the damp conditions in 2014 likely helped keep the box elder bug number in check and prevented the widespread numbers that we’ve seen the past few years. While the numbers of box elder bugs were low this fall, the multicolored Asian lady beetle, which had been low for the past few years, started popping up in decent numbers in certain parts of the state. One warm October day, I wandered out to the front of the entomology department building on campus to view thousands of the lady beetles flying around looking for overwintering spots.
5) Invasion of the Copper Underwing: Most folks have never heard of a moth called the copper underwing. Rightly so, as it tends to be a fairly obscure species. The caterpillars are commonly called the green humped fruitworms and can feed on fruit trees and other trees. When adults rest on trees, their grayish appearance isn’t much to write home about. However, when they display their hind wings, you’d notice the brilliant copper color and understand the common name of the insect.
For whatever reason, 2014 seemed to be perfect for this species. Perhaps I should have suspected that the few adults I spotted at my porch lights in late spring were the beginning of a trend. As the summer went on, I started getting reports of large numbers of these moths congregating on the sides of homes, sneaking under siding, and even leaving excrement stains on siding. All in all, I had reports of “home invasions” from over a dozen counties, mostly in the southwestern part of the state. Because this species tends to be present in low numbers, I suspect that we won’t see them amassing by the thousands again anytime soon.