Friday, March 30, 2018

Preventing Oak Wilt: A Team Effort

Snowshoes crunched loudly on the hard crust as we made our way toward a cluster flagged trees. After inspecting the furrowed bark of a large northern red oak, Paul Cigan, a forest health specialist with the Wisconsin Department of Natural Resources, pulled out his hatchet and started slicing off chunks of bark. Holding the rich, reddish-brown underside up to his nose, he inhaled deeply. “That’s it,” he exclaimed, “that’s the fruity smell I was telling you about. It’s the smell of oak wilt.”

I’m all about scratch-and-sniff in nature, so when he offered me the piece, I had no reservations about holding it up to my nose as well. It did, in fact, smell quite a bit like bananas. Slightly fermented bananas, to be exact; like when I thaw a brown one from the freezer for baking banana bread.

This pleasant smell has a worrisome source, though. Oak wilt is a fungal pathogen that kills trees in a single season. While it’s already widespread in southern Wisconsin, it has only just arrived here in the north. And we have a lot of big, beautiful oaks. Paul had watched this one die last summer, after he spotted its reddening leaves during an aerial survey.

Hoping to show me an example of the characteristic fungal mat that appears under the bark of an oak-wilt-killed tree, Paul peeled off even more bark. He didn’t find the fungal mat, but he did hand me a bark chunk with a white larva still cradled in its tunnel. “It’s two-lined chestnut borer,” he declared, and we examined the meandering galleries the borer and its buddies had chewed into the tree’s cambium. Chestnut borers only attack already-stressed trees, and while their damage looks a little bit like oak wilt, they take anywhere from two to several years to kill the tree. Rapid death by oak wilt counts as severe stress, so that’s why these little pests are here.

Still hoping to show me what the fungal mat of oak wilt looks like as it bulges underneath the bark, Paul and I headed off to another infection site in Washburn County. I’d been anticipating a nice long walk in the woods on this scouting trip, but instead we pulled into the maintenance road leading to a cellphone tower. Being on town land, the infection of this oak tree was noted quickly by local foresters. The oak-wilt-killed tree was flagged with bright pink tape and spray-painted with an ominous red circle. Oaks in a surrounding cluster were marked with blue paint.

It’s a common story. Early last summer, roadwork led to inconspicuous scuffs on the base of the tree’s trunk. When sweet tree juices began oozing out of the wounds, the scent lured in hungry beetles. Those sap-feeding beetles had already eaten a meal of banana-scented oak wilt fungus somewhere else in the forest, and had picked up fungal spores on their bodies. They transferred those spores onto the new oak’s fresh wound.

The fungus worked quickly to invade the tree’s water conducting system. While white oaks seem to be able to mount a defense and exhibit a degree of resistance to the disease, the red oaks that are dominant up here don’t stand a chance. The oak’s leaves wilted from the crown down, and within a month the tree was dead.

Despite hacking away at the bark, Paul still couldn’t produce a fungal mat to show me. “That’s probably a good thing,” he commented. Oak wilt isn’t supposed to be active yet this early in the spring, and that gives foresters, loggers, and landowners a window of freedom. From August through March, the fungus isn’t in reproductive mode. No fungal mats are giving off spores, the beetles don’t fly in the winter, and the trees aren’t growing vulnerable new cells. Even if an oak is injured, it won’t become infected.

During the fungi’s active time, however, from April through July, how you treat your oak trees can mean the difference between life and death for them. Any sort of wound, whether it’s a scrape from a bulldozer, a pruning cut, a logged stump, or even a broken twig can be the entry point for oak wilt into your forest, and your neighbor’s forest, too. Using wound-sealer to cover injuries immediately can help. (Beetles can find a new wound in 15 minutes or less!) Paul mentioned it several times through the day: the only thing that will prevent oak wilt from becoming a widespread problem in our forests up here is responsible landowners and preventative care.

Luckily, there are many things we can do to prevent oak wilt. In contrast to the beetle that spreads Dutch elm disease, the beetle that spreads oak wilt can’t chew its own holes. We can be careful not to make holes for them. When caught early by observant land managers, infections can be contained.

Beetles aren’t the only way that oak wilt spreads, though. The fungus can travel through the tree’s roots, pass through root grafts with nearby oaks, and kill them, too. The blue-painted trees on this site were already dead, but not from the fungus. They’d been girdled and painted with herbicide. While it sounds drastic, this is the most reliable method to make sure that there aren’t infected root grafts that will spread the fungus below ground. “Collateral damage,” Paul called it with a sigh. It’s better that these few trees die than every oak in the forest. They are still salvageable as lumber, and even the fungus-killed trees can be used for firewood if you quarantine the logs under plastic for a year so that beetles can’t access them and spread their fungal spores.

Right-hand tree died of oak wilt and lots all its leaves last summer. Left-hand tree was girdled and so didn't have a chance to lose its leaves. Two sad, dead oaks. But a contained infection.

Oaks are a major component in our forests, and they are important ecologically, economically, and aesthetically. Last summer, for the first time, an infected oak was detected and treated just southeast of Seeley, Wisconsin—a main hub on the Birkie Trail. While mentioning this, the truth came out. Paul’s a big cross-country skier, and his dedication to the control of this disease is partly fueled by his love for the forests surrounding our beloved American Birkebeiner Trails. Skiing is a personal challenge, but preventing oak wilt will have to be a team effort.

Learn more about oak wilt: 

Special Note: Emily’s book, Natural Connections: Exploring Northwoods Nature through Science and Your Senses is here! Order your copy at

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new exhibit: “Bee Amazed!” opens on May 1, 2018.

Friday, March 23, 2018

Black Knot in my Bag of Tricks

A good naturalist always has a variety of useful things tucked away in their back pocket or in their bag of tricks. For me, this often this takes the shape of a piece of scrap paper, folded into eighths, with a list of facts or an outline of my hopeful lesson plan for the day (“hopeful” because things never go exactly as planned). Sometimes I literally carry a bag of tricks. It’s a backpack full of preserved grouse feet, a bundle of chimney sweep extension rods for measuring bog depth, magnifying lenses, lengths of yarn, bug jars, and a pocket knife, among other seasonally appropriate items.

Ruffed grouse feet! They grow little "pectinations" along their toes that act as snowshoes in the winter. The foot on the right is a summer foot for comparison. Photo by Emily Stone.

Here's me using the chimney sweep poles to test the depth of the Namekagon Fen. I started with 20 feet worth of poles, purchased 20 more feet, and I STILL don't know how deep the fen is...deeper than 40 feet, I guess! Photo by Jane Weber.

Most of the time, though, my bag of tricks is metaphorical. It’s a filing cabinet in my brain that is stuffed to bursting with a messy array of games, activities, facts, stories, jokes, and demonstrations that I can access through a technique that’s part Google search, part random association, and part luck.

I’ve been adding items to this bag of tricks for a long time. My 12-year stint as both a camper and counselor at Girl Scout Camp provided endless games. The Outdoor Education program at Northland College filled me up with facts and activities. Teaching with creative people in the redwoods expanded my assemblage. Little by little I’ve gathered useful tidbits from every person and place I’ve met. Often people will ask me how I know certain things, or how I know so much about nature. My answer is that it’s been both my job and my hobby to collect facts and fill my bag of tricks to the brim.

We had a crazy bunch of naturalists in the redwoods in spring 2006! I learned so much and had so much fun!

Unfortunately, many things I once tucked safely away in a corner of my brain are now buried in dust, and will never be accessed again without the help of some very specific reminder. Other things are so close to the top that I grab them on pretty much every walk.

Recently, while leading a snowshoe hike on the Friday of Birkie Week, I realized that I hadn’t yet written a column about one of my favorite nature nuggets. It’s right here in my metaphorical back pocket, so let me tell you about it.

Especially in winter, shrubs and trees adorned with knobby, swollen, black growths stick out like a sore thumb. They were first pointed out to me by Craig Prudhomme, my instructor for a field semester at the Audubon Center of the Northwoods. Years of teaching college students had honed his sense of humor toward a combination of nerdy and gross. “It’s arboreal fox scat!” he declared, referring to a recent discussion of gray foxes and their tree-climbing skills. Sometimes I repeat his line, but I rarely have the right audience for it. More often I bring up another common nickname for these thumb-sized black growths: dead man’s fingers (always said in the spookiest voice I can muster.)

While fun, neither of those names is even close to being correct. Gray fox scat doesn’t mold itself around twigs, and dead man’s finger more commonly refers to another black, finger-like fungus that occurs at the base of tree stumps in contact with the soil. “Black knot” is the accepted common name of this odd growth, and its scientific name is Apiosporina morbosa.

Black knot on a cherry twig.

This common fungal pathogen is native across the U.S. and Canada, and only attacks plums and cherries. This fungus can help you identify plants! Chokecherry is a very common component of our local forest understory and edge, and it also happens to be one of the most susceptible species. This combination of factors means that I can find some black knot on almost any nature walk.

The crusty, coal-black galls we notice represent a late stage of the infection. The first symptoms include small, tan, swollen galls on the cherry’s newest twigs. At this time, the fungus is growing inside the tree and causing excessive growth in the tree’s own cells. The fungus overwinters in the galls. The next spring, those galls look like olive green velvet before turning brown and then black. The velvet expels asexually produced spores called conida that fly off on a humid breeze to find a new host. They aren’t very effective at infecting new plants, however. I’ve never noticed the olive green stage, but I think that’s because its two-week-long appearance coincides with the peak of mosquito season in June.

Black knot in the olive green stage, from .

The older, blackened galls are made of both fungal and plant tissues, and will girdle and kill the twig or branch they are on. Even if the fungus doesn’t completely encircle a large branch or trunk, the cracks it causes in the bark allow access to different fungi that will have a go at killing the tree. The black galls also release ascospores that were produced sexually. These can infect wounded tissue, but they can also penetrate directly through the intact surface of an elongating shoot when growth begins in spring.

Black knot isn’t a threat to the health of our forests, but if it happens to infect one of your favorite trees, then aggressive pruning of infected twigs during the winter is your best defense. I’ve noticed, though, that when black knot kills some twigs, the increased sunlight fosters a rainbow of lichen growth. Death is a part of life in nature, just as sure as black knot is part of my bag of tricks.

Lichens grow thick on a cherry tree being killed by black knot. And I couldn't even find my most colorful photo!

Special Note: Emily’s book, Natural Connections: Exploring Northwoods Nature through Science and Your Senses is here! Order your copy at

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new exhibit: “Bee Amazed!” opens on May 1, 2018.

Friday, March 16, 2018

Spring MuseumMobile

Three times a year I get to spend a few days at the elementary school in Drummond, Wisconsin, teaching kids my favorite nature facts using my favorite nature props. Once each season, in Fall, Winter, and Spring, I load seven plastic tubs filled with skulls, furs, graduated cylinders, strips of birch bark, and other oddities into the Museum’s mini-van for a visit to each classroom in grades pre-k through six.

Even though we still have deep drifts of snow and below-zero temperatures at dawn, I recently completed my “spring” lessons. The only times when the topics felt out of step with the weather were in the pre-K and kindergarten circles. Keeping the focus on our five senses, I filled the smell and hearing cups and the touch-bags with new items. Sunflower seeds rattled, a cluster of fake flowers gave its best impression of the smell of lilacs, pine cones prickled and, and a plastic grasshopper got lots of attention. Once I revealed each item, our discussion of seeds growing into sunflowers and lilacs blooming (soon!?) felt like a bit of a stretch.

I transitioned to our next activity by asking how a grasshopper starts its life. Does it begin as a seed? No! It begins as an egg. Reading through the book Chickens Aren’t the Only Ones, gave us plenty of opportunities to discuss what types of animals lay eggs. When the book mentioned dinosaurs, I even passed around a replica of a dinosaur egg fossil.

The page about snakes is my favorite. The text reads that “most snakes lay eggs,” which is true in many parts of the world. In cold climates, though, you often find snakes that are ovoviviparous. In this strategy, the female is internally fertilized, and the young are born alive. In contrast to mammals, the young are nourished by an egg yolk instead of a placental connection. The main benefit, and the thing I focus on with the kindergarteners, is that keeping her babies with her allows the mother snake to move them into warmer places so that they can develop faster. Snake eggs laid in the cold ground risk not developing fast enough to hatch before winter. Garter snakes and northern redbelly snakes are two of our neighbors who use this strategy.

First graders also started their lesson with some talk about eggs, since their lesson focused on frogs. After we acted out the life cycle of a frog (scrunch yourself into an egg, hatch and wiggle with a tail, grow hind legs and then front legs, and finally jump out of the pond and back to your desk), we performed a frog concert. Before the eggs can be laid, the frogs must sing.

We all practiced quacking like wood frogs, peeping like spring peepers, snoring like leopard frogs, and humming like bullfrogs. Then I divided the classroom into four groups and conducted their entrances and exits based on the frogs’ spring phenology. Wood frogs wake up first, and spring peepers follow closely. Just as the leopard frogs begin, the first two go silent. Our bullfrogs carry the late summer tune, and the peepers chime back in when the shortening days of fall confuse them into thinking it just might be spring.

The one MuseumMobile lesson about plants includes second graders transforming their class into a working model of a tree. From the inside out and the bottom up, we imitated all of trees’ most important parts. Our heartwood stood tall and strong, roots made slurping noises as they got water from the ground. “WooooOOOOP!” said the ring of xylem cells as they brought the water up. Now that the leaves had the water they needed, we all chanted “pho-to-synthesis” to help them manufacture sugar. The ring of phloem cells “WOOOoooped” the sugar down to the roots. A line of tough-looking kids with their arms crossed growled “we protect” as they played the role of bark. Finally, the whole tree dissolved into giggles.

Third graders became bears and struggled to collect enough “food” that I had scattered around the room. The average bear needs to eat about 80 pounds of food every 10 days. Not all of the third-grade bears survived, so we talked about the components of habitat and the concept of carrying capacity. During our second round, I held back a third of the food and most of the water to simulate a drought. This caused much distress among the bears, but also drove home the importance of a healthy habitat.

Fourth graders rounded out their year of learning about birds by focusing on nests. I’m always amazed at how well a few photos can capture their attention. We compare the wildly different nests of eagles, goldfinches, loons, and orioles, and then attempt to create our own nests using a core of air-dry clay, and tiny strips of birch bark, pine needles, dried grass, and even flakes of paper from the nest of a bald-faced hornet. It was humbling to compare their ramshackle creations to the precisely constructed nest of a red-eyed vireo.

Red-eyed Vireo Nest. Photo by Vernon R. Martin

In a natural transition from energy conservation, fifth graders switched to water conservation this season. We laughed at the absurdity of my one-liter bottle representing all the water on Earth, but as I poured out 30 milliliters to represent the tiny fraction that is fresh water, they became more thoughtful. Six milliliters of that 30 is all we have for fresh water that isn’t frozen. And finally, to represent the 0.003% of water on Earth that is fresh, non-frozen, and above-ground, I let a single drop fall into the bottom of a tin cup. For once, they were quiet enough that even the back of the room could hear the soft “plink.”

My spring visit to the sixth graders is always a little bittersweet, because our MuseumMobile visits don’t follow them into seventh grade. It’s exciting to share bar graphs of the data they collected about goldenrod galls, and to reinforce the notion that they are young scientists. Now that I’ve been at the Museum for seven years, my history with these kids goes all the way back to kindergarten. We started out together by exploring nature with our five senses, and we culminated by using tools and collecting data. After seven years, they are just as curious and excited about nature as they ever were. While their chorus of “thank you!” followed me out the door, I hoped that never changes.

Special Note: Emily’s book, Natural Connections: Exploring Northwoods Nature through Science and Your Senses is here! Order your copy at

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new exhibit: “Bee Amazed!” opens on May 1, 2018.

Friday, March 9, 2018

Sweating through the Birkie

This winter I think I’ve skied more kilometers than ever before. A combination of consistent snow conditions and high motivation levels for doing my best in the American Birkebeiner ski race led me out on the trail more often and for longer distances than usual.

My training sessions were mostly solo, although a couple pairs of vociferous ravens often kept me company at the North End Ski Trails. Scolding chickadees were ubiquitous and always improved my mood on a long climb. When a barred owl made an appearance, its flight was so silent that it seemed to make the whole woods go quiet. While I never saw a live, wild mammal, the tracks of wolves, foxes, fishers, squirrels, and voles still felt like good companions. Deer tracks scuffing up my classic tracks were less appreciated. Cold days brought the metallic smell of snow. Warm days wafted the smell of damp bark under my nose. Stark patterns of black and white, with purple shadows and deep green trees dominated my view.

After all that solo time, the scene at the start line of the Birkie was quite a shock. A rainbow-colored sea of people milled about on the snow. Music and the announcer’s voice blasted from the sound system. Cheering erupted at the sound of each shotgun start. The smell of porta potties came and went on the slight breeze. Skis and poles were everywhere.

I took my place among the crowd of fifth-wave skiers, and as we flew into action at the sound of our start, the snow in the tracks felt silky smooth under my skis. In a fluid chain, we wound up, down, and around rolling hills through the woods. I hoped that other skiers were also appreciating the way the smooth drifts sparkled among dark stripes of trees in the bright sunshine. It was a beautiful morning.

It was also warming up quickly. I’d been able to force myself to start in light gloves despite the chill in the air at start time, but I hadn’t convinced myself to remove the magnetically attached sleeves from my jacket and thus start in just a vest. My fingers went from numb to happy in just the first kilometer, and then my body temperature just kept climbing.

I’m probably the only person who thinks about moose at a time like that, but several years ago I learned that those massive mammals feel heat stress anytime the temperature climbs above 20 degrees in the winter. Their hollow, insulating hairs and huge body mass (1,000 pounds easily), are well-adapted to keep them warm. While I can’t quite empathize with their bulk, I do understand how they easily overheat in a warm coat. Many of my friends have chuckled or shaken their heads at the minimal layers I wear skiing (just a base-layer and my thin jacket even below zero), and multiple moms have cringed at my reluctance to wear a warm hat.

Unlike moose, though, I can don or doff my warm winter layers pretty easily. Which is what I did when I reached a wide spot in the trail.

No amount of taking off layers could have kept me cool on the long climbs leading up to the High Point, though. Hot sun beating down didn’t help. I could feel sweat running down between my shoulder blades and beading up on my forehead.

All that sweat brought to mind a podcast I’d listened to recently—a TED Radio Hour on the theme of adaptations. Chris McDougall, author of the book Born to Run, was the guest, and he shared his theory that long-distance running, especially in heat, was our superpower. Our lack of body hair and our numerous sweat glands allow us to sweat better than any other mammal on Earth. “It was that ability to sweat which made every other great human achievement possible, because the fact that we could sweat allowed us to run super long distances on hot days,” claims McDougall.

Of all the theories about how humans evolved to be the way we are, I think this is one of my favorites. My aptitude for sweating connects me to the success of humans in evolutionary history. Adaptations don’t just include physical traits, though, and cross-country skis are a great example of humans’ ability to make tools and adapt to a wide variety of habitats. The Birkie combines these two adaptations seamlessly as thousands of people “run” on unique tools, for a long distance, over snow.

After crossing the International Bridge, I smiled all the way up Main Street in Hayward to the finish line. A volunteer was waiting there to put a finisher’s medal around my neck. We both grinned.

A couple days later, after it no longer hurt to climb stairs, I headed back out to my beloved trails. The ground flew by beneath my skis and a light breeze kept me cool. Chickadees sang. What a joy it is, to use my adaptations.

Special Note: Columnist Emily Stone is publishing a second book of her Natural Connections articles as a fundraiser for youth programming at the Cable Natural History Museum. Since community members are often the inspiration for her articles, the Museum is conducting an art project for kids and adults to illustrate each chapter with a black-and-white line drawing. Find the details and entry form at

Friday, March 2, 2018

A Winter Walk with Lois Nestel

Curtains of snow sifted down from the laden trees as we entered the forest. The wizened branches of the Grandmother Tree, an old white pine, etched black and white silhouettes against the low, gray sky. Smooth new drifts stretched out in front of our little group of children and adults on the Family Snowshoe Hike.

The Wayside Wanderings Natural Play Area is a special place in any season, but in the magic of a fresh snow, I felt Lois Nestel’s presence more keenly. Lois was the founding naturalist, director, and curator of the Cable Natural History Museum. She was a talented, self-taught naturalist, artist, and taxidermist, and this was her home site. She looked out into this forest on moonlit nights and wrote about the owls that hooted and the rabbits that cavorted in the moonlight.

Lois once summed up snow this way: “However you see snow, as a burden to be borne or as a base for winter sports, see in it also the incredible beauty beyond the power of man to duplicate or even to describe.” Being in her forest on such a lovely day inspired me to look back on some of Lois’s essays.

“Winter has a thousand faces;” observed Lois, “each of us is free to see the face we choose. For example, the colors of winter are subtle and transient. Nothing is as it seems. The snow is white, it is true, but it is also endless hues and shades depending on the light, the type and quality of snow, and even more on the eye of the beholder.”

“Under leaden skies the snow appears dead white or pearly toned with shadows that are slate and steel. Sunrise can turn open spaces to rose and palest gold shadowed with lavender and violet; mid-day brings the clearer blues, and the evening sky may add a depth of tone to morning hues.”

“Frost flakes caught in morning sun outshine the jewel treasures of the world as prismatic reflections bedazzle the eyes with brilliant sapphire, topaz, emerald, and ruby that change with every movement and finally fade with advancing day, as do the rainbow-tinted sundogs that accompany a chill morning sun.”

“Moonlight on the snow brings shadows traced in indigo against the cold white flame of diamonds. The blue-black velvet of the night sky, studded with cold, blazing stars will often show the aurora borealis as wavering, tattered banners or as moving spotlights against the northern sky,” wrote Lois.

We didn’t see the aurora on our hike, of course, but we did see deer tracks, woodpecker trees, and the delicate, snow-laden cup of a birds nest. The woods were full of patterns.

“Most people are aware of the beauty of summer flowers and often bemoan their passing as winter approaches,” Lois continued. This need not be a cause for regret because, while much color may be lost, there continue—as seeds, pods, and capsules—many forms that rival the flowers in beauty and grace. Many of these seed containers last throughout the winter, serving as food for wildlife and pleasure for humans.”

“There is a sculptured beauty in the pods of various milkweeds and wild iris, evening primrose, cockle and Indian pipes. Delicate grace is exemplified in airy sprays of sweet cicely, papery clusters of wild hops and feathery virgin’s bower (wild clematis) twining over bushes, and in the dried grasses and sedges, each with individual form and style.”

“Many fall-blooming flowers (weeds if one must call them that) retain their form if not their color through the winter months. Goldenrod, tansy and yarrow are sepia-toned replicas of summer’s gay colors. Flowers such as asters lift clusters of tan, star-like sepals above the snow.”

“Touches of color do remain in scattered places; the dark velvety red of sumac heads, the red-orange of rose hips and the brighter red of highbush cranberries and hawthorn frozen on their shrubs.”

“To enjoy these and many other beauties of winter there are few requirements; namely these: get outside, have open eyes to see and an open mind, receptive enough to appreciate what is seen.”

Special Note: Columnist Emily Stone is publishing a second book of her Natural Connections articles as a fundraiser for youth programming at the Cable Natural History Museum. Since community members are often the inspiration for her articles, the Museum is conducting an art contest for kids and adults to illustrate each chapter with a black-and-white line drawing. Find the details and entry form at