Category Archives: Moths

2018’s Top Trends from the Diagnostic Lab (Part 2)

In this post, we’re continuing to count down the University of Wisconsin Insect Diagnostic Lab’s top arthropod trends of 2018. This is the second half of a two part series; the first half can be found here.


5) White-Lined and Other Sphinx Moths:
The white-lined sphinx moth (Hyles lineata) can be a common species, so encountering one of the 3 inch long hornworm caterpillars isn’t unusual. However, these caterpillars can also be encountered in massive road-traversing hordes if the conditions are just right. From midsummer onwards, large numbers of these caterpillars were observed around the state—in some cases by the tens of thousands. If you didn’t spot any of the caterpillars themselves, you might have encountered the large adult moths with their hummingbird-like behaviour in late summer. Several other sphinx moths species also had a strong presence in 2018, such as the clearwing hummingbird moths and the tobacco and tomato hornworm caterpillars which can regularly be encountered in gardens as they munch away on tomato and pepper plants.

Large, dark-colored hornworm caterpillar of the white-lined sphinx moth on a plant
Large, dark-colored hornworm caterpillar of the white-lined sphinx moth. Photo submitted by Ted Bay, UW-Extension

4) Sawflies:
Sawflies, the caterpillar copycats of the insect world, are a diverse group, so they’re always present to some extent. Last year saw an unexpected abundance of two particular types in Wisconsin—the dogwood sawfly and the non-native Monostegia abdominalis, which feeds on creeping Jenny and related plants from the loosestrife group (Lysimachia species). While sawflies are plant feeders, dogwood sawflies can also damage the soft wood of a home’s siding or trim when these insects excavate small chambers to pupate in. The UW Insect Diagnostic Lab saw a distinct bump in reports of wood damage from the dogwood sawfly last year.

Whitish larva of the dogwood sawfly curled up on a dogwood leaf
Larva of a dogwood sawfly showing the whitish, waxy coating. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

3) Armyworms:
True armyworms (Mythimna unipuncta) can be a dynamic and sporadic pest in the Midwest. This species doesn’t survive the cold winters of our area, so adult armyworm moths must invade from the south each spring. Depending on national weather patterns, the arrival of the adult moths can vary significantly from year to year. If an early mass arrival is followed by abundant food and ideal conditions for the ensuing caterpillars, large populations can result. Once they’ve arrived, true armyworms can go through 2-3 generations in the state and this second generation of caterpillars made an alarming appearance in mid-to-late July. Under the conditions last summer, massive hordes of these caterpillars decimated crop fields before marching across roads by the tens or hundreds of thousands to look for their next meal. In some cases, that next meal included turfgrass, meaning that some Wisconsinites came home from work to biblical hordes of caterpillars and half-eaten lawns in late July.

Striped caterpillar of the true armyworm
Caterpillar of the True Armyworm (Mythimna unipuncta). Photo Credit: Lyssa Seefeldt, University of Wisconsin-Madison Extension

2) Monarch Butterflies:
Much to the delight of fans and conservationists, the iconic monarch butterfly (Danaus plexippus) appeared to have a banner year in the Midwest in 2018. Reports and observations of high numbers of monarchs poured into the Insect Diagnostic Lab during the summer months. As comforting as these reports were, the butterflies still faced a perilous 2,000 mile journey to reach their overwintering grounds in Mexico.  The most consistent measurement of the eastern monarch population comes from estimating the area occupied by the densely-packed overwintering butterflies.  In late January the latest count was released with encouraging news—the eastern monarch population is up 144% over last year and is estimated to be the largest in over a decade.  In contrast, the western monarch population overwinters in southern California and has recently dipped to alarmingly low numbers. Regardless of the winter assessments, monarchs face tough challenges and Wisconsinites are encouraged to help conserve this iconic species.  The Wisconsin Monarch Collaborative recently launched a website with resources for those wishing to join the effort.

Seven monarch butterflies nectaring on a flower
Multiple monarch butterflies nectaring on a single plant in August. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

1) Floodwater Mosquitoes:
Mosquitoes snagged the top spot on 2018’s list for good reason. The upper Great Lakes region is home to over 60 different mosquito species, but one subset—the “floodwater” mosquitoes—drove the storyline last year and impacted outdoor activities through much of the spring and summer months. Mosquitoes in this group, such as the inland floodwater mosquito (Aedes vexans), flourish when heavy rains come. Last year’s mosquito season kicked off in force with a batch of pesky and persistent floodwater mosquitoes just before Memorial Day weekend. Mosquito monitoring traps in southern Wisconsin captured record numbers of mosquitoes shortly thereafter. Later in the year, the Midwest experienced an unprecedented series of severe rainstorms, setting the stage for an encore performance of these mosquitoes. It was this second explosion of mosquitoes that caught the attention of anyone trying to enjoy the outdoors in late summer—a time of the year when mosquitoes are typically winding down in the state.

Ephemeral pools of water created ideal conditions for floodwater mosquitoes in late summer. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

2018’s Top Trends from the Diagnostic Lab (Part 1)

Each year the University of Wisconsin’s Insect Diagnostic Lab receives thousands of arthropod samples and reports from around the state and region, providing a unique perspective into insect and arthropod trends in Wisconsin and beyond.  This post is the first half of a series counting down the top arthropod trends in our area last year.  The second part will be posted in early February and can be found here.


10) Dagger and Tussock Moths:
A few species of fuzzy caterpillars were surprisingly abundant last year and there’s a good chance you might have bumped into these in your own neighborhood.  Two similar-looking yellowish species, the American dagger moth and the white-marked tussock moth, were extremely common around Wisconsin and were two of the most widely reported caterpillars last summer. Another tussock moth associated with milkweed was also surprisingly common in 2018. With many Wisconsinites growing milkweed to attract monarch butterflies, the black and orange caterpillars of the milkweed tussock moth were also noted in abundance around the state last year.

Fuzzy black and orange Caterpillar of the milkweed tussock moth (Euchaetes egle)
Caterpillar of the milkweed tussock moth (Euchaetes egle). Photo Credit: Katja Schulz via Wikipedia

9) Fungus Gnats:
Pick any spot on a Wisconsin map and 2018 was most likely a soggy year. Understandably, rain encourages insects and other creatures that thrive under damp conditions. Last year’s rains created great conditions for fungus gnats, which became quite abundant by late summer. While fungus gnats are harmless to people and pets, they can be an annoyance if present in high numbers. Fungus gnats thrive in damp organic materials, meaning that rich soil, compost piles, and decaying plants can produce masses of these tiny, dark-colored flies. The larvae of these insects can also be common in the soil of houseplants.  As Wisconsinites brought their favorite potted plants indoors in autumn to avoid approaching frosts, reports of indoor fungus gnats were common.

Small dark coloured gnats captured on a yellow sticky card trap
Tiny (2mm long) fungus gnat adults captured on a sticky card trap near indoor plants in fall of 2018. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

8) Purple Carrot Seed Moth:
With several new, non-native insects showing up in Wisconsin every year, the impacts of each species can vary significantly. Some exotics, like the emerald ash borer make massive waves, while others cause merely a ripple. The impacts of one of our newest invasive insects, the purple carrot seed moth (Depressaria depressana), are not yet fully known. This European species was spotted in Wisconsin for the first time last summer and the tiny caterpillars love to feed on the flowers (umbels) of plants from the carrot family. Below-ground plant structures (e.g., the taproots of carrots) aren’t impacted, but notable damage to herbs like dill, fennel, and coriander can occur. As a result, this pest may be a concern for seed producers, commercial herb growers, or home gardeners with a fondness for dill and related herbs. The purple carrot seed moth has been reported in 8 Wisconsin counties thus far [Brown, Columbia, Dodge, Kewaunee, Milwaukee, Racine, Sheboygan and Washington Counties], so new county-level reports are encouraged at the UW Insect Diagnostic Lab.

Tiny (<1/4" long) spotted caterpillar of the purple carrot seed moth on dill.
Caterpillar of the purple carrot seed moth. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

7) Odorous House Ants
Imagine the stereotypical black ants zeroing in on sugary foods at a picnic and you’d have a fitting profile of the odorous house ant (Tapinoma sessile). Of the 100+ ant species in the Midwest, the odorous house ant stood out in spring and early summer last year with its sheer abundance. The UW Insect Diagnostic Lab was flooded with calls about these sugar-loving ants during 2018’s rainy spring, especially when these ants wandered indoors. The spring rains may have forced the ants from waterlogged colonies to seek out higher-and-drier locations, making odorous house ants the most commonly reported ant at the diagnostic lab last spring.

SMall black ant—an odorous house ant worker
Odorous House Ant (Tapinoma sessile) worker. Photo Credit: JJ Harrison via Wikipedia

6) Stink Bugs:
While the Midwest is home to over 50 species of stink bugs, one particular species—the invasive brown marmorated stink bug—stands out to give the rest a particularly bad reputation. If you live in a part of the state with the brown marmorated stink bug, you may have already encountered this species. With its habit of sneaking indoors in the fall, this insect replaced boxelder bugs in some areas as the top home-invading nuisance pest of 2018. This Asian species has made the diagnostic lab’s Top 10 list for several years now and unfortunately doesn’t show any signs of slowing down. In 2018 alone, BMSB was detected in 8 new Wisconsin counties, which hints at potential damage to fruit and other crops in those areas in the coming years.

Adult brown marmorated stink bug
Adult brown marmorated stink bug. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

To see the rest of Wisconsin’s top arthropod trends of 2018, check out part 2, available here in early February.

Sphinx Moths—Hovering at a Flower Near You

If you’ve watched the flowers in your yard or local park recently, you might have noticed some surprising visitors hovering at the flowers—the hummingbird-like sphinx moths.  Several species in the “sphinx” or “hawk” moth group (Family Sphingidae) are known for their day-flying, hummingbird-like behavior.  From a distance these moths can easily be mistaken for hummingbirds as they skillfully maneuver from flower-to-flower sipping nectar with their long mouthparts.

One of the commonest members of this group in Wisconsin is the white lined sphinx moth (Hyles lineata).  With a wingspan of nearly 4 inches, it’s easy to understand why this species can be mistaken for a hummingbird as it feeds.  The greyish adults are easy to pick out and a white stripe on each forewing helps identify them in the field.  The caterpillars (hornworms) of this species reach nearly 3 inches in length and can feed on a wide range of plants.  While this species is regularly encountered in the Midwest, this year has been especially good for white-lined sphinx moths in Wisconsin.  In mid-to-late July I received many reports of the caterpillars—sometimes in astounding numbers.  In several instances, “outbreaks” of tens of thousands of these large caterpillars were spotted as they migrated across roadways from agricultural fields.  The multitudes of caterpillars have since pupated and transformed into nectar-loving moths—leading to a recent spike of sightings.

White-lined sphinx moth (Hyles lineata). Photo Credit: Andy Reago & Chrissy McClarren; Wikipedia

In addition to the white-lined sphinx moth, several other hummingbird-like sphinx moths have been common this year—the “clearwing” hummingbird moths (Hemaris spp.) and the Nessus sphinx moth (Amphion floridensis).

The rusty-colored “clearwing” moths (Hemaris spp.) are smaller than the white-lined sphinx moth, and have a wingspan of approximately 2 inches.  Their shaggy appearance and patches of yellow coloration lend a resemblance to large bumble bees.  Characteristic transparent “windows” in the wings help identify these moths.  Several Hemaris species can be encountered in the Great Lakes region with subtle differences in appearance and biology.  Both the “hummingbird clearwing” (Hemaris thysbe) and the “snowberry clearwing” (Hemaris diffinis) can be common, while the “slender clearwing” (Hemaris gracilis) is associated with pine barrens and is rarely encountered.

The hummingbird clearwing moth (Hemaris thysbe) showing the transparent “windows” in the wings. Photo Credit: Andy Reago & Chrissy McClarren; Wikipedia

The “Nessus Sphinx” (Amphion floridensis) is another hummingbird mimic that was commonly reported earlier in the summer.  Although somewhat similar in size and coloration to the Hemaris clearwing species, the Nessus sphinx moth has opaque wings and two distinct yellow bands across the abdomen.

The Nessus sphinx moth (Amphion floridensis) in action. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

In addition to being a joy to observe, sphinx moths are a great example of “non-bee” pollinators.  Their unique behavior and anatomy allows them to form interesting relationships with some of the plants they pollinate.  In an extreme example, the Christmas Star Orchid (Angraecum sesquipedale) from Madagascar possess extremely long tube-like floral structures which contain the nectar.  Upon learning of the unique anatomy of this orchid, the famed naturalist Charles Darwin speculated that a moth with equally long mouthparts must exist to pollinate them.  It took over a century to document, but a sphinx moth wielding foot-long mouthparts was finally observed pollinating the Christmas Star Orchid.

Purple Carrot Seed Moth Appears in Wisconsin

In a given year at the UW Insect Diagnostic Lab, I typically document 2-3  new, non-native, potentially-invasive insects in Wisconsin. In some cases, these species make an appearance only to fade into the background with little impact, while other exotics become heavy-hitting invasive pests (e.g., emerald ash borer and gypsy moth). The latest non-native pest to make an appearance in the state is the tiny “purple carrot seed moth” (Depressaria depressana) and its impacts are not yet fully known. This species has a wide native range and can be found from western Europe through Russia to China.  It was first documented in North America in 2008 and is so new that few images exist and it’s not included in the common caterpillar and moth field guides on the market.

Purple carrot seed moth. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

In the last decade, the purple carrot seed moth has been documented in many locations in southern Canada and the northeastern US and has also been spotted in a few scattered locations in Michigan, Indiana, and Illinois. In mid-July of 2018, two reports came into the UW Insect Diagnostic Lab in rapid succession—Kewaunee and Dodge counties in Wisconsin. These cases were confirmed through images and caterpillar specimens that were reared to adult moths. After discussing the purple carrot seed moth on a recent episode of Wisconsin Public Radio’s The Larry Meiller Show, several additional suspected cases were reported in the state: Racine (Racine Co.), Random Lake (Sheboygan Co.), Burnett (Dodge Co.), and Franklin (Milwaukee Co.).

These insects get their name due to their association with flowers (umbels) of plants in the carrot family (Umbelliferae). The caterpillars of the purple carrot seed moth are small (3/8 inch long when mature), but dozens can feed on a single umbel. The caterpillars are dark green or reddish with many conspicuous white spots on their bodies. In addition to feeding on the flowers, the caterpillars tie together floral parts with silken webbing, which can make herbs like dill unusable. Eventually the caterpillars pupate within the webbing and emerge as adult moths a short time later. The adult moths are 3/8 inch long with a pale patch near the head; their purplish-grey wings are folded back along the body when not flying.

Caterpillar of the purple carrot seed moth, note the many conspicuous white spots on the body. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

The impacts of this non-native insect are not fully known for our area. The reports of plant damage in Wisconsin thus far have only been on dill. Due to the plant parts attacked (flowers), the impact on carrots, celery, and parsnip crops will likely be minor. The biggest impacts would be expected with umbelliferous crops commonly grown for seeds: dill, fennel, and coriander. Luckily, several organic control products may offer help on herbs: insecticidal soap and Neem oil are two low-impact products expected to help control this pest, if needed.  Cutting out and destroying infested flower heads may be another helpful tactic.

Damage from the purple carrot seed moth on dill. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

Because this pest is “new” in Wisconsin, if you believe you’ve found it on dill or other plants from the carrot family, please snap some pictures and contact me to help document this species in the state.

If you’d like to learn more about this insect and its potential impacts check out this video through the Wisconsin First Detector Network.


May 2019 Update: A current distribution of known PCSM sightings can be found below.  If you encounter this insect this summer in Wisconsin, feel free to let me know, so I can better keep track of its activity in the state.        —PJ

County records of the Purple Carrot Seed Moth from 2018. Map Credit: PJ Liesch, UW Insect Diagnostic Lab

Wisconsin’s Top Insect Trends of 2015 (#5 – #1)

In this post, we’re continuing to count-down 2015’s top insect trends in the state.  This is the final post in a three part series.  Part I (2015’s diagnostic lab statistics) can be found here and Part II (Top Insect Trends Numbers 10-6) can be found here.

5) Pollinators
With all the headlines about bees, it’s not surprising to see pollinators in the top insect stories again in 2015.  Similar to other years in the recent past, honeybees and other pollinators have been facing declines.  Unfortunately, Wisconsin saw some of the highest honeybee losses in the country, with over 60% colony loss during the 2014-2015 period.  Some good news over the past year has been the development and release of pollinator protection plans.  A federal pollinator protection plan was released in May with the goals of reducing honeybee losses, increasing the population of Monarch butterflies, and increasing pollinator habitat.  In addition, a Wisconsin pollinator protection plan was announced in 2015, and was just released in January of 2016.   Due to the recent declines and their importance to agriculture in the state and nation, pollinators will continue to be in the spotlight in the future.

A ground nesting bee (Colletes sp.) near the stump of the former President's Oak on the UW-Madison campus. Photo Credit: PJ Liesch
A ground nesting bee near the stump of the former President’s Oak on the UW-Madison campus. Photo Credit: PJ Liesch

4) Spring caterpillars
An unexpected insect trend in the spring of 2015 was the surprising abundance of a number of caterpillar species feeding on plants in the landscape.  Caterpillar species, such as the humped green fruitworm, speckled green fruitworm, eastern tent caterpillar, forest tent caterpillar, gypsy moth caterpillar, and the euonymous caterpillar are typically present to some extent, although their numbers have been low the past few years.  For a number of potential reasons, these species had a great spring and during a period in May and June, caterpillars made up roughly 30% of the cases coming in to the diagnostic lab.  Weather patterns (i.e., rainy weather) and natural predators/parasites/diseases can have significant impacts on caterpillar populations each year, so it’ll be interesting to see if we’re faced with a plethora of caterpillars again in 2016.  Additional details of this story were featured in a blog post last June.

3) Viburnum Leaf Beetle
In terms of a new emerging pest with the potential to impact a commonly planted landscape shrub, Viburnum Leaf Beetle is near the top of the list.  As of late 2014, we only knew of a single infested viburnum bush in northern Milwaukee County, which raised the question: is the infestation small enough to contain and/or eradicate?  Some ground truthing this past spring identified many new infestations in SE Wisconsin, in many cases miles from the original site.  At the moment, the viburnum leaf beetle seems to be centered around the four county area where Milwaukee, Waukesha, Washington, and Ozaukee counties meet.  While this insect only feeds on viburnums (and related plants like Arrowwood), the damage can be significant.  It may be some time before this pest spreads elsewhere in the state, but if you have viburnum plants in your yard in SE Wisconsin, be weary!  Additional details of this case were featured in a post last June.

VLB Damage
“Skeletonizing” feeding damage from adult viburnum leaf beetles. Photo courtesy of Paul Weston, Cornell University, Bugwood.org

2) Brown Marmorated Stink Bug
Populations of the invasive Brown Marmorated Stink Bug increased dramatically in 2015 and this insect takes the overall #2 spot in this list (up from #8 last year).  This invasive species was first spotted in the state in 2010, and each year a handful of lone adults have been found in Wisconsin.  In the fall of 2015, we had more sightings of BMSB (30+), than in the past 5 years combined! (Spoiler: this trend has continued into early 2016)  At this point, the “hot spots” in the state are: Dane County, the greater Milwaukee area, and the Fox River Valley.  In addition to being an indoor nuisance pest, BMSB can also feed on and damage a wide variety of plants in home gardens, agricultural fields and orchards.  In other places in the country, the first reports of plant damage have typically been noted ~3-5 years after the initial detection of this species.  With that said, 2016 could be the year that BMSB really takes off and starts wreaking havoc for gardeners and agricultural growers alike.  Additional details of this case can be found in this post from last October.

1) Magnolia Scale
While scale insects have already been mentioned in the “sucking insects” section (#9 on the list), one species in particular, the Magnolia scale (Neolecanium cornuparvum), seemed to stand out amongst all other insects in 2015.  This species is often present in low numbers in the state, but the conditions must have been perfect for their populations to explode last year.  During the months of June and July, reports of Magnolia scale were coming in on almost a daily basis.  Being one of the unusual scale insects, Magnolia scale adults look more like a fungus than an insect (note the whitish blobs in the image below).  Not only did this bizarre looking species pummel Magnolia shrubs and trees in many parts of the state, but the honeydew produced by these insects rained down below, attracting ants and yellowjackets and leading to the growth of unsightly black sooty mold.  A number of predators, parasites, and diseases typically keep Magnolia scale in check, but with the extremely high infestations noted last year, it’s likely that we’ll continue to see some Magnolia scale activity into 2016.  If you experienced magnolia scales first hand, there’s a helpful factsheet available here.

Magnolia twig coated with whitish, fuzzy magnolia scale adults.

Wisconsin’s Top Insect Trends of 2015 (#10 – #6)

What were Wisconsin’s top insect trends of 2015?  In this post, we’ll look at the first half of our count-down.  

This is the second post in a three part series.  The first post of the series (2015’s diagnostic lab statistics) can be found here.

10) Mosquitoes and ticks:
Like most years, Wisconsin had a pretty good mosquito season.  Overall, we were close to the average rainfall mark during much of the year, which meant the typical batch of mosquitoes starting after Memorial Day.  In many parts of the state, mosquitoes were prevalent throughout June, July, and August.  However, this is Wisconsin after all, and mosquitoes seem to be one pillar of summer culture along with beer, cookouts, and fishing.  The silver lining of the mosquito story is the fact that West Nile Cases were low for the year, with only four confirmed human cases reported in the state in 2015.

Deer Tick
Adult female deer tick. These ticks can now be found throughout the state and roughly 40% of adults are carrying the microorganism responsible for Lyme Disease. Photo credit: Scott Bauer, USDA Agricultural Research Service, Bugwood.org

While there wasn’t anything out of the ordinary with the mosquitoes last year, ticks seemed to have a particularly good year in the state.  Deer ticks, which can vector Lyme disease can be found essentially statewide.  From the standpoint of an emerging health threat, deer tick populations have exploded in the past few decades (our first deer tick wasn’t found in the state until the 1960’s).  A recent nation-wide study found that deer ticks were found in nearly half of the counties in the U.S.  One of the more alarming trends is urban encroachment.  Historically, ticks seemed to be the type of creature you’d pick up if you were out hunting or hiking through the woods.  In the recent past, we’ve noticed an increase of ticks found in more urban environments, such as parks and backyards.  With roughly 40% of the adult ticks in Wisconsin carrying the microorganism responsible for Lyme Disease, this is an issue that will continue to exist in the state for years to come.

9) “Sucking Insects”
A certain group of insects (the Order Hemiptera) are sometimes known as the “sucking insects” because they possess tube-like mouthparts which are used by many species use to drink fluids from plants.  Two of the members of this group, the aphids and the scale insects had a great year in 2015.  When these insects feed on plants, a common sign is the presence of sticky, sugary honeydew, which attracts ants and yellowjackets, and can result in the growth of black sooty mold.  Aphids and scale insects are common and typically present in low numbers, but the conditions must have been just right for their populations to thrive in 2015.  As a result, there were many reports throughout the state of honeydew “raining” down from trees and shrubs onto vehicles, decks, outdoor furniture, and people below.  If you felt “rain” on a sunny day last summer, the actual cause may have been honeydew dripping down from aphids or scales in the trees above!

Lecanium Scale
Lecanium scales producing sticky honeydew (clear droplets).  Photo credit: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Bugwood.org

 

8) Long Lost Pests: Japanese Beetle and Gypsy Moth
Two of our best-known landscape pests, the Japanese Beetle and the Gypsy Moth had been very quiet in 2014, but resurfaced last year.  Japanese beetles had been low across the state in 2014, likely due to the brutal winter of 2013-14 killing many of the soil-dwelling grubs.  While we did see an increase in beetle activity in 2015 compared to 2014, their numbers still seemed low compared to the long term average.  However, with a milder el Niño winter, it’s possible that we could see increased winter survival and higher Japanese beetle populations in 2016.

Japanese Beetle
The infamous Japanese Beetle. Photo credit: David Cappaert, Michigan State University, Bugwood.org

Gypsy Moth populations have been low the past few years in Wisconsin.  Damp spring conditions can result in a fungal disease killing many of the caterpillars, which likely helped lessen populations in the recent past.  It’s also not unusual for some long-term cyclic patterns to be involved with insect populations.  For a number of potential reasons, Gypsy Moth populations seemed to rebound a bit in 2015, and many reports of sightings and damage came in to the diagnostic lab, particularly from the south central portion of the state (Dane, Rock, Walworth Counties).  Because Gypsy Moth can be a destructive defoliator of hardwood trees, it’ll be good to keep an eye out for this one in 2016 to see if the populations continue to climb.

7) Emerald Ash Borer
This is our most destructive forest pest in the state, and unfortunately, there doesn’t seem to be anything capable of completely stopping this pest.  While we didn’t see many additional counties added to the quarantine map in 2015, there were many municipalities that detected EAB for the first time.  At the moment, 39 of the 72 Wisconsin counties are quarantined for EAB and this number will continue to increase over time.  Like Dutch Elm Disease in the past, Emerald Ash Borer is changing and will continue to change the appearance of our urban forests and woodlands for years to come.

6) Spotted Wing Drosophila
This invasive pest first showed up in the state in 2010, and became a significant fruit pest almost immediately.  Since its introduction, SWD has spread widely and can be found in most counties in Wisconsin.  Very similar to 2014, SWD was detected in dozens of counties across the state.  SWD can attack a wide variety of fruit, but due to the fact that this insect doesn’t seem to become active until July, the late-season raspberry and blackberry crops are hit the hardest.  Luckily Wisconsin’s famous cranberry crop does not seem to be favored by this invasive pest.

Up Next, Part III:  Wisconsin’s Top Insect Trends of 2015 (Numbers 5-1) 

Spring is Caterpillar Season

Caterpillars, and the moths and butterflies they become (Order Lepidoptera), normally make up less than 20% of the cases in the diagnostic lab, while beetles (Order Coleoptera) usually make up the largest chunk of the pie (almost 30%).  However, spring often tells a slightly different story around the lab:Pie Chart-May 2015So what does this mean? Well, as far as caterpillars are concerned, it’s been a great spring in Wisconsin. Perhaps you’ve even noticed some happily munching on the trees and shrubs in your yard. If you’re curious to meet the culprits, there’s a good chance they’re on this list:

1) Speckled Green Fruitworm
2) Humped Green Fruitworm
3) Linden Looper
4) Gypsy Moth
5) Eastern Tent Caterpillar
6) Forest Tent Caterpillar
7) Euonymus Caterpillar

Of all the caterpillar species that have popped up this spring, the speckled green fruitworm (Orthosia hibisci) has been the biggest surprise. It’s usually present, but in low enough numbers that damage isn’t common. Despite having the word “fruit” in its name, this species feeds on more than just fruit trees—it also feeds on a long list of hardwood trees and shrubs and even some conifers. This spring I’ve had reports of it damaging: maples, oaks, hackberry, lindens, elm, serviceberry, apple, spruce, peonies, roses, and other plants.

Speckled Green Fruitworm
Speckled green fruitworm on a rose bush in Madison, WI. Photo credit: PJ Liesch, UW-Entomology

The humped green fruitworm (Amphipyra pyramidoides), has a similar feeding pattern to its speckled cousin and has also been common this spring. An interesting thing about the green humped fruitworm is that the caterpillars turn into copper underwing moths. Perhaps that name sounds vaguely familiar? If you’ve been following this blog, you may remember the invasion of the copper underwings from last summer. It’s too early to tell, but with the numbers of green humped fruitworm caterpillars I’ve been seeing, I wonder if we might see the copper-colored adults sneaking into buildings again in the coming months. . .

Green Humped Fruitworm
Green humped fruitworm on a rock near Coloma, WI. Photo credit: PJ Liesch, UW-Entomology

Like the fruitworms, the linden looper (Erannis tiliariaa type of inchworm) and the nefarious gypsy moth (Lymantria dispar) also feed on a wide range of plants and have been popping up this spring. I haven’t had any reports of large-scale significant defoliation by gypsy moth, but there are pockets of damage and gypsy moth certainly seems to be more active than last year at this time. Hopefully with the rains we’ve had lately, the fungal disease, Entomophaga maimaiga, will pop up to smack down the gypsy moth numbers.

Linden Looper
Linden looper caterpillar from Middleton, WI. Photo credit: PJ Liesch, UW-Entomology
Gypsy Moth
Gypsy moth caterpillar from Monona, WI. Photo credit: PJ Liesch, UW-Entomology

Then there are the “tent” caterpillars, which have also been common this spring: the eastern tent caterpillar (Malacosoma americana) and the forest tent caterpillar (Malacosoma disstria). The eastern tent caterpillar is the species that makes the silken tents in apple, crabapple, and black cherry trees where the branches meet the trunk of the tree. Despite its name, the closely related forest tent caterpillar doesn’t make any tents…

Eastern tent caterpillar near Coloma, WI. Photo credit: PJ Liesch, UW-Entomology.
Eastern tent caterpillar near Coloma, WI. Photo credit: PJ Liesch, UW-Entomology
Forest tent caterpillar near Coloma, WI. Photo credit: PJ Liesch, UW-Entomology.
Forest tent caterpillar near Coloma, WI. Photo credit: PJ Liesch, UW-Entomology

Lastly, if you’ve got a burning bush (Euonymus alatus) or another type of euonymus, you might have noticed some webbing on your plant from the euonymus caterpillar (Yponomeuta cagnagella). In some cases, the webbing from these polka-dotted caterpillars can cover the entire plant, making you think that giant mutant spiders have taken over. Complete defoliation can occur with this species, but thankfully, most healthy plants leaf out again and are generally fine.

Euonymus caterpillar and webbing on burning bush near Cambridge, WI. Photo Credit: PJ Liesch, UW-Entomology
Euonymus caterpillar and webbing on burning bush near Cambridge, WI. Photo Credit: PJ Liesch, UW-Entomology

Now for some good news: while all of these spring caterpillars have the potential to significantly damage plants, they only have a single generation per year—meaning that they’re just about done wreaking havoc for the year in the southern part of the state. That’ll give us just enough time to get ready for the next batch of insects coming up soon: squash vine borer, squash bugs, Japanese beetles and many more!

Invasion of the Copper Underwings

An invasion has been going on unnoticed across a portion of the state this summer and early fall.  It all started back in mid-July, when I had several inch-long moths show up at my back deck lights.  I captured a few and set them aside to examine under the microscope but hadn’t thought much of it at the time.  Later, as I was preparing the specimens, I noticed a distinct copper color of the hind wings.  Over the next week, several more of these moths mysteriously appeared in the house. . .

Within days other reports started popping up elsewhere in the state.  By the time October rolled around, I had reports of “home invasions” from over a dozen counties in the southern and western portion of Wisconsin.  The common feature in these cases was the metallic copper color of the hind wings, indicating the Copper Underwing (Amphipyra pyramidoides).  The species is fairly widespread, but isn’t usually encountered in large numbers.  In most cases (mine included) it was only a handful of these moths that snuck indoors. However, in a few situations, the moths were congregating by the hundreds (or even thousands) on homes or garages and were being quite a nuisance.  David Wagner does mention this phenomenon in the Owlet Caterpillars of Eastern North America.

Copper Underwing
Copper Underwing (Amphipyra pyramidoides); Photo credit PJ Liesch

I’m not exactly sure what caused the boom of activity this year, but the caterpillars (commonly called “humped green fruitworms”) must have had perfect conditions to develop earlier in the year.  Luckily, with fall and the cooler weather the invasion seems to have stopped.  Who knows what next year will bring?