#9 :: Wood Boring Beetles

Intro music: "InsectaLoop" by Jake McCarthy.

JAKE Hello. you are listening to InsectaPod Cast Episode 9- Wood Boring Beetles. InsectaPod Cast is a product of the Michigan state University Department of Entomology and its home on the web is www.insectapodcast.com. I'm Jake Mccarthy, the next voice you'll hear is Anna Fiedler's, and this is InsectaPod Cast

ANNA The global economy we live in has many benefits, including ready access to products from all over the world. One drawback, however, is that material those products are shipped in can harbor unwanted pests. Today, we talk about the effect of wood boring beetles that aren’t native to North America, and how they get here, as well as what one researcher is doing to enable quick response to future introductions.

Dr. Anthony Cognato is an Assistant Professor of Entomology and Director of the A.J. Cook Arthropod Research Collection at Michigan State University. His research focuses on learning more about potential invasive insects, as those that are not native to an area are often called, as well as recognizing when a new 6-legged critter has entered the U.S. He is especially interested in beetles that make their home in wood.

Many goods enter Michigan on wooden pallets, and if items arrive on a ship, there may be additional packing material known as dunnage. This dunnage often consists of wooden scraps. When shipments arrive from areas with similar climates, such as Europe and northern Asia, Michigan is a habitable place for any insects living in those packing materials. Often, the packing equipment that is no longer useful is just left behind at the port.

ANTHONY So what happens when countries import items, what they usually do, will have them packed in material, and also their ships will carry dunnage. And this packing material or dunnage usually consists of raw timber that has been cut in the forest and usually left for awhile, and the insects will infest this wood. And so, what happens, if it takes about a month to get over to Michigan, if the insects, the eggs have hatched and the larvae have developed and these new adults are ready to emerge as soon as these ships get into port. And what happens is that a lot of this packing material or dunnage is thrown off to the side and the insects emerge.

ANNA These insects, often beetles, emerge as flying adults and are sometimes able to establish in their new home before anyone realizes it. Often, it doesn’t even occur to people that a small beetle could kill trees. These beetles feed under the bark as young and the only external sign of their presence is a hole in the bark that forms when they emerge as adults. As such, an insect population may be huge before it’s recognized as the tree-killing culprit. Here’s what happened with the Asian Longhorned Beetle:

ANTHONY I n New York city they started seeing trees along the streets dying and being, actual large holes in the trees, and so a concerned citizen stood out there watching because he thought there were kids vandalizing the tree. And so, through that observation he actually saw the adult beetle emerge, and I think he asked people what it was, I think in Cornell, and from there they discovered it.

ANNA Wood boring insects can have impacts much larger than those a few vandals would have. Besides killing street trees, they can affect trees in natural ecosystems, changing the balance of species that has been established over millions of years, possibly leading to extinction of native insects or plants. One family of wood feeding beetles, bark beetles, can be especially troublesome to Michigan’s economy.

ANTHONY The biggest effect we’ve felt from an exotic insect was a bark beetle, Tomicus piniperda. It’s the pine shoot beetle, and it was discovered in Cleveland in 1992 and then, subsequently, by the end of the year, it was found in six states. What this beetle does, as an adult, it feeds on the shoots of the pines. And so, it doesn’t usually kill the pines, but for Christmas trees this ruins that nice manicured cone shape that you usually see on Christmas trees. So, it affected our economy because there was a ban on shipping Christmas trees to other states, because they didn’t want the beetle to spread.

ANNA Bark beetles such as the pine shoot beetle are of special concern for several reasons relating to their lifecycle. Females lay eggs under the bark or in wood. Those eggs hatch and the young feed under the bark. If the tree happens to be for shipping material and the female bark beetle found it when it was freshly dead, the larvae feed and are ready to emerge as adults when goods arrive at their destination. The second reason is the varied mating systems bark beetles have. Some can lay eggs of male beetles without even mating, then mate with their sons to produce a new population. This means that a very small number of isolated beetles can reproduce, sometimes in large enough numbers that they survive and continue infesting trees in a new location they are not native to. One final reason bark beetles can be such a problem is their size: many adults are less than 1/8 inch long, and the only evidence on the outside of trees is the tiny hole they make to emerge as an adult.

ANTHONY Well, bark beetles, in particular, are a concern because of their lifecyle. They bore under the bark or into the wood to lay their eggs and to rear their young. So that, within a month, if you’re on a ship traveling across the Atlantic, your offspring will develop and mature and be ready to emerge once you reach port. And also because they bore into the wood, they’re usually harder to detect, so if you’re a port inspector you may miss the entry, the hole that a beetle has made into a piece of wood.

ANNA One additional problem is that humans have brought new tree species, such as Scotch pine, from Europe to grow in the U.S. When the pine shoot borer that infests Scotch pine in its native Europe came to the U.S., it already had just what it needed to thrive here. A group of bark beetles in the genus Ips are currently of especial concern.

ANTHONY And also, too, with Ips species, you know they tend to be host specific, but if they can’t find their host tree, they might use pine trees, and so it has been recorded to feed in pine trees too, so it could be even more disastrous. And, we also have its native host, Norway spruce, is commonly planted throughout landscapes and also for wood and timber in the United States and, most likely, in Michigan, too, so it could really do a lot of damage.

ANNA You can prevent infestations of new bark beetles by doing two things: not moving wood, particularly firewood, and keeping an eye out for signs of insect damage, especially sawdust coming out of the trunk, on trees that you know were healthy. Scientists like Anthony are still searching for new bark beetles in Michigan, even though there are about 100 species documented there so far. Knowing which species already are in an area will help us know whether new bark beetles we find really are non-native to Michigan. In fact, Anthony is part of a national program focused on early detection and rapid response to new non-native bark beetles in the U.S. Each summer, ¼ of the states are surveyed for potential non-native bark beetles. This is done in a very specific way, using traps with pheromones, chemicals bark beetles use to find one another, and tree volatiles, which bark beetles use to locate trees with bark beetle feeding.

ANTHONY So, bark beetle traps that consist of several funnels that are attached together are hung with pheromone baits and tree volatile baits. So, a combination of, say, ethanol and alpha pinene, which is a pine chemical, are hung from these traps, from locations where bark beetles may have been introduced but we’ve not detected them. And so what I have done in collaboration with the DNR last summer is to survey areas around Detroit, Lansing and Grand Rapids for exotic bark beetles.

ANNA Anthony is one of the official taxonomists of bark beetles on this project. In addition to surveying for bark beetles in the U.S., Anthony and graduate students working with him survey areas, such as Southeast Asia, where non-native bark beetles may come from. Since many insects worldwide are unknown, Anthony and his students will likely identify many new bark beetle species. Even more importantly, they will know where the beetles came from if they do get accidentally introduced into the U.S. His work has, in fact, already led to more rapid identification of several introduced beetles. Here’s one example.

ANTHONY We were looking for a particular species in Hawaii and I knew we could catch them with these traps. So a friend set some traps just pretty much in his backyard and nothing special habitat, mostly exotic plants that were growing there, and he sent me the specimens, and I found a new exotic species for Hawaii

ANNA Anthony discussed this bark beetle with his graduate students, and one immediately recognized it from bark beetle collecting they had done in Southeast Asia. Essentially, Anthony is part of a network of beetle taxonomists interested in preventing potential disasters related to introductions of bark beetles into new regions. That requires not just inspecting dunnage and respecting firewood quarantines, but also taking the time to identify insects in their native habitats before they show up in the US.

JAKE Thank you for listening to InsectaPod Cast Episode 9, Wood Boring Beetles. InsectaPod Cast is a product of the Michigan state University Dept. of Entomology and is funded in part by the Ray and Bernice Hutson Memorial Entomology Endowment. Our home on the web is www.insectapodcast.com. I'm Jake McCarthy, my partner is Anna Fiedler, and this is InsectaPod Cast. Thank you for listening.