Category Archives: In the News

Weathering the Emerald Storm: EAB in Wisconsin

Like a kid watching a summer thunderstorm slowly rolling in and wondering how long until the rumbles would be directly overhead, I’ve had a morbid fascination with watching the progression of the emerald ash borer in the Midwest for over a decade.  Although emerald ash borer wasn’t found in Wisconsin until 2008, my connection with EAB precedes that by a few years.  It turns out my first job as a budding entomologist was as a summer intern for UW-Extension looking for signs of the insect in the state during the summers of 2005 and 2006.  Fast forward twelve years and that storm is finally overhead, at least in my neck of the woods.  I knew such a time would come, but it really hits close to home when the sounds of chainsaws mark the final days of your neighborhood’s ash trees—at least the ones that aren’t being treated. 

EAB Detection and Quarantines as of May 19, 2017. Click for larger version. Image source: WI-DATCP.

At the time of writing, 42 counties in Wisconsin have been quarantined for EAB.  While the southeastern part of the state has already been hit hard (green on the map above), a large chunk of the state has not yet seen the emerald ash borer or has only seen light pressure (click the map above to see more details on this topic). Unfortunately, this means that the emerald storm will only be getting worse over the coming years.  Along these lines, when EAB first arrived in Wisconsin, spread was slow and the annual number of new community-level detections was small.  However, as the populations of this insect have built up in the state, the number of new detections has increased dramatically as illustrated below:

Chart created using data from WI-DATCP on May 22, 2017. Click for a larger version.

Unfortunately, the outlook for the Midwest’s ash trees doesn’t look good and we’ll still be dealing with this insect for years to come.  Ironically, this isn’t the first time that we’ve watched a scenario like this play out.  As the baby boomer generation grew up, they watched as elms were devastated by the likes of Dutch elm disease.  As with emerald ash borer, Dutch elm disease had significant impacts on forested and urban areas and led to irreversible changes in the landscape around us.

With all this Doom-and-Gloom, is there a light at the end of the tunnel?
Possibly—but it may be a ways off.  For the time being, there are insecticide treatments available that can maintain the health of ash trees, although treatments are costly and are only feasible for relatively small numbers of trees.  Biological control is being explored as a potential way to control EAB populations, although results have been limited thus far.  However, with any biological control program, it can take years to work the kinks out of the system and see results.

A long-term plan may be to develop varieties of ash trees that are resistant to attack by the emerald ash borer.  In several locations in Ohio and Michigan, scientists have found a small percentage of “lingering” ash trees that have survived the initial onslaught of EAB and are monitoring those trees over time for continued survival and genetic traits that may help stave off infestations.  Interestingly, one particular species of ash (blue ash, Fraxinus quadrangulata) may hold important clues for long-term ash survival.  In some spots in Michigan, >60% of blue ash trees have survived in areas attacked by emerald ash borer.  While tree breeding programs may ultimately develop a resistant ash variety, this is likely years away and for the time being we’ll have to face the emerald storm.

Larval tunnels of the emerald ash borer beneath the bark of an ash tree. This damage disrupts the flow of water and nutrients and ultimately kills the tree. Image source: PJ Liesch, UW Entomology.

Wisconsin’s Top Insect Trends of 2016 (#5 – #1)

In this post, we’re continuing to count-down 2016’s top insect trends in the state.  This is the final post in a three part series.  Part I (2016’s diagnostic lab statistics) can be found here and Part II (Top Insect Trends Numbers 10-6) can be found here.

#5: The spread of the emerald ash borer increased dramatically in the state last year. Photo Credit: Howard Russell, Bugwood.org.
#4: Fall invading insects, such as boxelder bugs are well known, but the strawberry root weevil and other weevils can sneak indoors during the summer months. Photo Credit: Whitney Cranshaw, Bugwood.org.
#3: Several scarab beetles, including the rose chafer caused notable plant damage last year. Photo Credit: Clemson University Extension, Bugwood.org.
#2: An elusive adult rabbit bot fly. Photo Credit: Quentin Sprengelmeyer.
#2: An inch long bot fly larva from a mouse. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.
#1: Fierce mosquito pressure in many parts of the state combined with the Zika stories in the news gave mosquitoes the top spot in 2016's insect trends. Photo credit: Susan Ellis, Bugwood.org.

 

5) Metallic Wood Boring Beetles
Two different metallic wood boring beetles (Family Buprestidae) had strong years in 2016. The first, the emerald ash borer, is no stranger to Wisconsinites these past few years. While there were only 3 new counties (Portage, Wood, Sawyer) added to the state quarantine map in 2016, there were over 80 municipalities with their first confirmed EAB infestation last year (out of 227 municipalities with documented EAB finds at the end of 2016). With that said, EAB has greatly picked up steam these past few years and is attacking ash trees at a rapid rate in Midwest.

Another metallic wood borer that seemed to have a good year was the twolined chestnut borer. Unlike the invasive emerald ash borer, the twolined chestnut borer is is native to North America and tends to attack stressed trees (oaks). In these cases, trees might be stressed by factors such as disease, drought stress, winter injury, or damage from other insects. The UW Insect Diagnostic Lab noticed a distinct increase in cases of the twolined chestnut borer this past summer, although the underlying stress might have begun affecting trees several years ago. With the high value of oak trees in the landscape, this insect is definitely a pest that tree care companies should have on their radar for the near future.

4) Home-Invading Weevils
Many Wisconsinites experience or at least are familiar with insects that sneak indoors in the fall, such as boxelder bugs and multicolored Asian lady beetles. There’s also a group of broad-nosed weevils that happen to sneak indoors during the summer months. Species in this group include the strawberry root weevil, the imported longhorned weevil, and others. Once indoors, these weevils tend to stumble around in a slow, somewhat tick-like manner, causing concern to homeowners. But fear no weevil, for these insects are completely harmless. A broom or vacuum cleaner are often the best tools to deal with them. While broad nosed weevils can be somewhat common, reports coming in to the UW Insect Diagnostic Lab suggest that numbers of these home-invading beetles were up in 2016.

3) Scarab Beetles
A number of scarab beetles had noteworthy activity in 2016, including several important landscape pests. Scarab beetles can be an extremely common group of insects, with well over 100 species in Wisconsin alone. Perhaps the best known (and most infamous) member of this group would be the Japanese beetle (Popillia japonica), which seemed to rebound last year after a few quiet years. In parts of the state with sandy soil, the rose chafer was present in high and damaging numbers. Similar to Japanese beetles, rose chafers are fond of feeding on a wide range of plants from landscape shrubs to fruit trees.

Two other scarab beetles were noteworthy in 2016: the Northern masked chafer and the European chafer. This past year marked the first year that the larvae of these beetles (white grubs) had been found damaging turfgrass in the state: Rock County (NMC) and Door county (EC). Previously, turfgrass managers only had to contend with the white grubs of Japanese beetle and the occasional May/June beetle.

2) Bot Flies
[Disclaimer: bot flies are not for the faint of heart! If you’re preparing to eat lunch, you may want to skip down to #1.]
Bot Flies-Click to Read

If you’re not familiar with bot flies, these creatures may seem like something out of a science fiction movie. In their simplest terms, bot fly larvae are essentially large, flesh-inhabiting maggots. When fully mature, the maggots can be over an inch long and are covered with tiny backward-facing spines, making removal nearly impossible from their host. Adult bot flies are very short lived and somewhat resemble bumble bees or certain horse flies in their size and coloration. In a typical year, the UW Insect Diagnostic Lab might receive 1-2 reports. For whatever reason, bot flies had a great year in 2016 and several dozen reports came in to the lab. The common species observed in Wisconsin last year were from the genus Cuterebra and parasitize small mammals such as: mice, chipmunks, squirrels, and rabbits.  The maggots live and feed beneath the skin of their mammal host for weeks before popping out to pupate.  The mammal hosts generally seem to tolerate their companions, although the concept of bot flies may give you a creepy-crawly feeling.
[Bonus material: there is a bot fly (Dermatobia hominis) in South and Central America that affects humans]

 

1) Mosquitoes
With all the stories about the Zika virus in the news, it was difficult to avoid hearing about mosquitoes in 2016. In addition, with the heavy rains many parts of Wisconsin received last year, it was equally challenging to venture outdoors and avoid mosquitoes. In many parts of the state, mosquito pressure was severe last year, giving mosquitoes the top spot on the 2016 list. If there’s a silver lining to the mosquito story last year, it has three parts:

  • The mosquitoes that were dreadfully abundant last year (floodwater mosquitoes) aren’t important vectors of human disease. Yes, they might have ruined that evening cookout, but at least they weren’t making anyone ill.
  • Reports of mosquito-borne diseases (such as West Nile Virus) were relatively low in the state last year.
  • Zika virus was not a major issue in Wisconsin, as the mosquito species responsible for that disease haven’t been found here [Read more about this topic in this post]

Zika: An Issue in Wisconsin?

With mosquito season nearly upon us and all the headlines about Zika Virus in the news, a big question at the moment is: will Zika be an issue for us in Wisconsin?  Based on what’s known about the Zika Virus and the mosquitoes that transmit it, it’s unlikely that Zika will be a major issue for us in the state.  Certainly, we’ll get cases of Zika in Wisconsin, but these will almost certainly be from individuals that have travelled to areas with active Zika infestations.  Overall, if we look at the bigger picture, a much bigger concern should be deer ticks and Lyme Disease, which affects thousands of Wisconsinites each year.

The Zika situation is an interesting one.  The Zika virus itself was first discovered in Africa in the 1940’s and has been found in parts of the eastern hemisphere for decades.  It wasn’t until very recently that it popped up the western hemisphere.  Because the Zika Virus is linked to a number of serious health issues, such as microcephaly in newborns, it certainly can pose significant health risks—hence the headlines and the concern.

However, the virus is only half of the story—the other half being the mosquito species (vectors) capable of transmitting the virus to humans.  Two mosquito species are associated with Zika virus and other viral diseases such as Chikungunya and Dengue: the Yellow Fever Mosquito (Aedes aegypti) and the Asian Tiger Mosquito (Aedes albopictus).  The good news for us in Wisconsin is that neither of these mosquito species are native to our area, and these species have never been found in the state (additional surveys are being conducted to look for them).  With that said, there may end up being some Zika cases in Wisconsin associated with travel to areas where Zika is widespread, but the absence of the two mosquito vectors responsible for transmission will greatly reduce the chance for transmission occurring within the state.

Estimated range of Aedes albopictus and Aedes aegypti in the United States, early 2016. Map source: Centers for Disease Control and Prevention.
Estimated range of the Asian Tiger Mosquito (Aedes albopictus) and the Yellow fever Mosquito (Aedes aegypti) in the United States, early 2016. Map source: Centers for Disease Control and Prevention.

While the Yellow Fever Mosquito and the Asian Tiger Mosquito don’t occur here, there still is reason to be vigilant about mosquitoes.  With as many as 60 or more different mosquito species in the state, there are a number of other mosquito-borne diseases that do occur in our area.  Our best example would be West Nile Virus transmitted by the Northern House Mosquito (Culex pipiens).  While West Nile cases can vary dramatically from year-to-year, we’ve historically had issues with West Nile in our area, and human deaths have occurred in the past.

When it comes to mosquitoes in general, there are several approaches to keeping yourself and your family members safe. Around the yard, one of the most important things is to reduce or eliminate standing water to help eliminate mosquito breeding sites.  Toys left out in a sandbox, old tires, clogged gutters, birdbaths with stagnant water and anything else that collects and holds water could be a potential breeding site for mosquitoes.  Using EPA approved repellents, such as DEET, Picaridin, or others when working or relaxing outdoors will offer protection from bites.  Lastly, wearing long sleeves, avoiding outdoor activities during prime mosquito feeding times (dawn/dusk), or simply staying indoors can also protect you from mosquitoes.