Heroic beetles join the battle for the hemlocks

FOREST OF THE DEAD: Multitudes of Appalachian-native hemlocks have been turning up dead and bare, sucked dry by an invasive, non-native insect. But in the last 15 years, entomologists have discovered, captured and released a beetle that may be the key to the hemlocks’ survival. Photo by Brian Gratwicke

When Richard McDonald exits his Seattle hotel, he carries a large, black-and-yellow umbrella, even when the forecast calls for sunny skies. Though he may be fresh off a flight from Western North Carolina, the entomologist will quickly shake off any jet lag in the misty morning air. After 61 trips to Washington in the last nine years, he has this down to a routine.

When the dew lifts, McDonald will tread through mossy underbrush in and around the city, knocking on branches with a bamboo stick and collecting an ensuing shower of beetles into his upside-down umbrella. Carefully, he’ll twirl it from black panel to yellow and back to black again — searching for small black beetles, Laricobius nigrinus — Lari, for short, and their white larvae. Sucking the beetles into an aspirator, he’ll steadily click-click-click his thumb against a tally counter, counting each bug as it passes into the chamber.

“In my life, I never thought I would do anything that’s important like this,” McDonald says. “It’s a story of hope. Actually, it’s even beyond hope. We’re resurrecting the hemlock ecosystem. We’ve turned the tides.”

It's not just the parkway. Hemlock woolly adelgid infestations, seen here at a home in North Asheville, can be identified by the presence of white, cotton-like egg sacs. Photo by Hayley Benton
It’s not just the parkway. Hemlock woolly adelgid infestations, seen here just north of downtown Asheville, can be identified by the presence of white, cotton-like egg sacs. Photo by Hayley Benton

Often referred to as Dr. McBug, the Watauga County resident has dedicated more than 15 years to saving the Carolina and Eastern hemlocks from extinction. The key to their survival, he says, lies in the Pacific Northwest.

“We needed this initiative 10 years ago,” McDonald says. “But the battle’s almost over. It’s like we’ve got Gandalf back on our side, and now we’re going to go kick ass.”

In the early 1950s, an invasive, sap-sucking insect, the hemlock woolly adelgid, was unintentionally introduced to the East Coast, suspected to have arrived on horticultural imports from Asia. In their native environment, McDonald notes, adelgid populations are controlled by natural predators and can stimulate the tree, prune its needles and “make it a little tougher.” But this wasn’t the case for the Southern Appalachians.

Once the aphidlike insect made its way South, where milder winters and a lack of natural predators allow a yearlong population, the path of destruction “spread much faster than anyone thought it would,” says Sarah Sheeran, stewardship associate at Southern Appalachian Highlands Conservancy.

Hemlocks are unique in that they don’t compete for energy, McDonald explains. They’re “like a rechargeable battery. They get all their energy from the winter sun, store it up and use it during [spring and summer] when they’re in the shade of bursting greens.”

But with thriving winter woolly adelgid populations, the hemlocks don’t store enough energy to survive. “It’s this big, giant, winter generation of adelgid that kills the tree,” he says.

The adelgid systematically eradicated millions of hemlocks in the region, turning once-thriving trees into bare, skeletonlike silhouettes. The National Park Service estimates that in some areas, including the Blue Ridge Parkway and Shenandoah National Park, around 80 percent of the hemlocks died due to infestation. Not only was the hemlocks’ disappearance devastating from a visual standpoint, it also meant the threat of ecological imbalance.

The hemlocks “grow on stream corridors, providing very dense shade, which is important for water quality,” Sheeran explains. “[They] keep the water temperatures cool, which favors species like the brook trout, our only native trout species. If the hemlock goes, there’s really nothing else like it that fills that ecological niche.”

Those studying the hemlocks, including himself, McDonald explains, “were operating under three misconceptions: The hemlock woolly adelgid was native [only] to Asia, there were no effective predators in the U.S. and that the hemlocks were doomed.”

Initial (and some ongoing) efforts in the ’80s and ’90s looked to Asia for a solution, seeking something in nature that would serve as a proper adversary to the ever-advancing pest. But around 1997, McDonald says entomologists realized the hemlock woolly adelgid is also native to the Pacific Northwest, where it has its own set of effective predators — including Laricobius nigrinus.

McDonald quickly realized that he and his colleagues could go out West to collect beetles more efficiently than through an expensive trip to Asia or via reproduction in a lab. With that revelation, the race was on. “We were discovering this while the house was on fire,” McDonald says. “It was a mad scramble; nobody was going to save our trees except us.”

In 2006, McDonald flew out to Seattle, collecting 3,586 beetles in a single sweep. “A lab would produce that many beetles in a year,” he explains. “But we’re trying to solve problems in real time, trying to save as many trees as quickly as possible.”

McDonald’s persistence to collect beetles not only benefits the region, but it also often generates some entertaining stories — like the time he bribed army servicemen with cigarettes to collect beetles from an on-base tree.

“If I had to dress in a ninja suit to go in there and get those beetles, that’s what I would’ve done,” he says. “I chained myself to the hemlocks, man. But in a different way — in a scientific way.”

A few years later, McDonald determined that the adelgid had another West Coast predator, a sesame seed-sized beetle called Scymnus coniferarum. While Laricobius takes care of the adelgid in winter, this second predator picks up the slack in summer.

In the last decade, McDonald estimates he’s collected 80,000 beetles from the Pacific Northwest. Meanwhile, the beetles he’s brought back to WNC continue to reproduce. “By 2009, our trees [on Grandfather Mountain] quit dying,” he says. “That was six years ago. When you look at our trees, people are stunned.”

More than 14,000 beetles have been released at that site, McDonald notes, and the observant eye can spot them easily enough. “That’s a 6,000-foot tall mountain, and when the winds get high, those beetles blow all over the place,” he says. “It’s like a beetle volcano.”

So far, it seems this strategy is working. In fact, the evidence in support of predatory beetles “is pretty compelling,” says Sheeran.

“The foliage is rebounding, and the trees are responding positively with new growth,” she notes. “Biological control can make some people nervous. And while there are some instances of biological control gone bad, this one feeds exclusively on the woolly adelgid.”

Currently, McDonald supplies beetles to government agencies, community groups and even individuals for $5 per beetle, a rate that covers travel to and from Seattle for McDonald and his team. Everybody on the East Coast wants beetles, McDonald says — including Buncombe County.

At a May 19 meeting, Buncombe County agreed to purchase 5,000 Lari beetles in the county’s next fiscal year, starting July 1. The nonprofits WNC Communities and MountainTrue will administer the release and monitoring of the beetles, reporting back to the county on their progress.

At the meeting, MountainTrue biologist Josh Kelly said the only way to guarantee an individual tree’s survival is with chemical treatment. But when talking about an entire forest, “this predator-prey relationship, this ecological balance — that’s the bridge to the future.”

From McDonald’s perspective, the region is already seeing some beautiful progress. “This beetle spans, [in patches], from the border of Virginia all the way to Mars Hill,” he says.

If you want to see the difference these little insects are making, he adds, just look to the trees. “If I’m a little bummed out, all I have to do is go for a drive, see hemlocks, and I’m just like, ‘Woo-hoo! We did it!’”

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About Hayley Benton
Current freelance journalist and artist. Former culture/entertainment reporter at the Asheville Citizen-Times and former news reporter at Mountain Xpress. Also a coffee drinker, bad photographer, teller of stupid jokes and maker-upper of words. I can be reached at hayleyebenton [at] gmail.com. Follow me @HayleyTweeet

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20 thoughts on “Heroic beetles join the battle for the hemlocks

  1. AVL LVR

    That first picture is of a Fraser fir forest. They are attacked by the Balsam woolly adelgid, though I don’t consider them in danger like the hemlocks because they still bear cones. A lot of those skeletons are fir waves which are common in the northeast and in Japan. The firs grow so close together that they are all the same age and they all die together. The fir waves on Mt Mitchell are quite obvious.

    The only adult hemlocks I’ve seen living in the wild that have not been treated are above 4500. There are still cones in the ground below that elevation so young hemlocks keep coming up only to die soon. Maybe these Lari beetles will provide enough relief for these sapling or the hemlocks above 4500 to at least bear cones so that the next generation of hemlocks can start the process to become naturally more resistant to the adelgid.

    • HA! Oh no! That’s embarrassing. I’ve now updated the photo to what I believe is *actually* a hemlock. Thanks for pointing that out!

      As for your second point: I’m not sure how old my tree is, but that second picture was taken in my own yard, close to downtown Asheville. Because it’s covered in adelgid eggs, I’m assuming it’s not been treated. I guess that doesn’t really count as “the wild,” but it was my understanding that it’s extremely difficult to treat all the trees in the forest (plus it needs to be redone every 4 or so years, I believe). Just thought that might be an interesting little tidbit. Thanks for the input!

    • Craig Randolph

      There are 2 different species of Hemlocks around here–the Canadian Hemlock and the Carolina Hemlock…are both susceptible to this adelgid?

      • AVL LVR

        Carolina and Eastern hemlocks (I don’t like the term Canadian since it is native here too) are both susceptible. The Carolina seems to hang on longer, but eventually succumbs too.

        The Fraser Firs are NOT in more danger of disappearing than the hemlock. Hike MT Mitchell for example (excluding the areas which have been treated i.e. The Carolina Hemlocks Campground). Hiking up, you’ll notice no untreated mature hemlocks in the wild below 4500 (and above that they are about dead), but you’ll find plenty of healthy mature Fraser Fir bearing cones. I’ve seen extremely a lot of large healthy Fraser Firs in the Middle Prong Wilderness by the base of MT Hardy, but you are right that Clingman’s Dome has a lot of unhealthy ones.

        We should focus on hemlocks because they really are in danger of disappearing from our forests. The Smoky Mountains give an incomplete picture of the crisis because of their extensive treatments of hemlock forests and the high levels of acid rain which weaken the Fraser Firs. I’d reckon that the Smoky Mountains act as a barrier absorbing most of the pollution allowing the Fraser Firs near Asheville to be strong enough to resist the adelgid and expand their range. Actually, the Spruce-Fir forests in the S. Appalachians have greatly expanded since many areas where placed under conservation. I see extensive regrowth of the Spruce-Fir forests in the Middle Prong Wilderness, Shining Rock Wilderness, and the Mount Mitchell area. Areas which were balds or yellow birch (because of past logging) have countless young fir/spruce saplings.

        • AVL LVR

          Eventually, we are going to ban gas motorcycles from the parkway and other sensitive areas. Only electric motorcycles will be allowed. I was hiking the Old Mt Mitchell trail and could barely breathe and hear because of these things. It’s no wonder the firs by the road are worse off. Additionally, they create way too much noise pollution which cars don’t usually create.

          • Craig Randolph

            One last point here, motorcycles burn FAR less gasoline than do cars, hence their ‘carbon footprint’ is correspondingly smaller. It’s every gas/diesel engine contributing to air/noise pollution, to single out motorcycles specifically is ludicrous.

        • Craig Randolph

          I have to disagree with you on two points. Look at old photographs of Mt. Mitchell and you’ll see just how dramatically the Spruce-Fir forest has declined through the years. Granted, some of this decline is due to logging in the past, as well as wildfires. The Graveyard Fields area adjacent to the Shining Rock Wilderness area used to contain one of the largest unbroken stands of Spruce-Fir forests in the S. Appalachians, till a massive wildfire decimated the area in 1925. The entire area is now 99% hardwoods. When you lose a Spruce-Fir forest here, it’s very rare to see it regenerate itself and reclaim what used to be it’s domain…hard for seeds from these evergreens to penetrate the forest floor and make the seed-soil contact necessary for them to regenerate. To say that the Spruce-Fir forests have greatly expanded their range here is just not true. Luckily, a control measure has been found that will hopefully allow our hemlocks a second chance to grow and thrive here, while no such control measure has been found for our Fraser fir forests. Yes, there are areas where young fir trees do spring up thickly and appear to be making a comeback. But, to understand how the balsam woolly adelgid attacks is this–they attack a fir when it reaches a certain age,their saliva injects a poison into the fibers of the tree, causing the fir to rapidly speed up it’s growth cycle, sometimes before a tree has even reached the age to produce cones. A heavy infestation of these adelgids can kill a fir in two years or less.Would imagine the hemlock adelgid acts in a similar fashion. The adelgid was first observed on Mt. Mitchell in 1957. Likely imported into this country from infected stock from Europe into the northeast in the early 1900’s. Also, the other main evergreen tree that grows in our highest elevations is the Red Spruce, which grow into much larger size than do the Fraser Firs. Studies have shown that the Red Spruce here virtually ceased growing in the 1950’s, likely as a result of man-made pollution, as they are not subject to attack from either the hemlock or balsam woolly adelgids. That right there tells me all is not well in the forests of our highest mountains. The Spruce-Fir forest require a very specific set of growing conditions, only found in elevations of approx. 4,500-5,500 ft. for the Red Spruce, and elevations of 5,500-6,600 ft. for the Fraser Firs. They will grow at lower elevations-i.e. Christmas tree farms, but they are not native to such areas. And as any Christmas tree grower will tell you, it takes a lot of work and chemicals to get them to grow at lower elevations. I’m not anti-hemlock as you may think I am, for I love ALL trees, it’s just the Spruce-Fir forests face dangers that their brethren on down the mountain don’t have to. Hemlock suited habitats are virtually endless…know someone in Fayetteville, N.C. that has several of them thriving in his front yard. Try that same thing with a Fraser Fir.

          • AVL LVR

            Graveyard Fields will be a spruce-fir forest within 50 years. After the fires/logging, grasses then bushes grew up. Now hardwoods are growing. Finally, you clearly see spruce popping up along the edges and in other areas (Mt Mitchell/Middle Prong) underneath. The fast growing Faser Fir has yet to have a significant presence in the Shining Rock wilderness (though I can see it will overtake the planted red spruce stands). Once they arrive, they will form dense stands and spread rapidly. Spruce, on the other hand, spread slowly. Black Balsam itself may never again be ‘black’ because they may do a controlled burn to keep it a bald.

            I am not so sure of the hemlock’s control measures being effective. While I support Dr. McBug, I have not seen the healthy hemlocks around Grandfather Mountain he talks about. When I was there last March, I saw tons of dead ones. We need to keep on this unless we lose the rest of the hemlocks.

            “Studies have shown that the Red Spruce here virtually ceased growing in the 1950’s” You should take hikes above 4,500′. You can see Red Spruce spreading along and underneath the hardwood forests of the Buncombe Horse Range Trail and underneath the planted (non-native spruce) of the Mount Mitchell Trail. The firs are regenerating in cycles forming fir waves on the summit of Mount Mitchell and other peaks in the range. Perhaps the fir waves occur sooner because the adelgid attacks it, but you will notice each new generation is more resistant to the adelgid than the last. The important fact is that they bear cones, whereas wild hemlocks (especially below 5,000′) do not.

          • AVL LVR

            That claim was busted by Mythbusters. Motorcycles are more polluting than cars. Drive behind a whole pack of them and see if you can still breathe and hear.

            • Cycles created several hundred times more hydrocarbon pollution than cars. Hydrocarbons cause cancer, breathing and heart ailments, and contribute to smog.

            • Nitrous oxide emissions, which cause smog and acid rain, were equal for the 1980s vehicle pair, but the 1990s cycle produced 138 percent more than its partner car, and the 2000s cycle up to 3,220 percent more.

            • The 2000s-era cycle emitted 8,065 percent more poisonous-to-breathe carbon monoxide than its car partner, while the 1990s and 1980s cycles produced 516 percent and 313 percent more, respectively.

            http://www.greencarreports.com/news/1067907_motorcycles-are-more-polluting-than-cars-new-device-shows

          • AVL LVR

            The Red Spruce have taken complete control of the Camp Alice Trail.
            I have not notice significant action on the Big Tom Spur Trail, but they are still bushes.
            The crest of the Green Mountain Trail in the Middle Prong is now almost entirely spruce.
            Young Faser Firs are forming dense stands along the western edge of Mount Hardy. The Eastern side is still hardwoods, but at 5800′ on the East side there are several of the largest natural and healthy Faser Fir trees I have ever seen.
            The summit of Richland Balsam has many large Faser Fir trees and pure fir stands along the loop trail.
            Faser Firs have formed at least one natural dense stand on the Mountains to Sea Trail in the Shining Rock Extension (not far from Devil’s Courthouse- actually opposite/north of the Blue Ridge Parkway road and slightly west of the planted forest). I’ve seen young Faser Firs especially along the southwestern edge of the planted forest by the Black Balsam Knob Rd while I was bushwhacking. Once the firs become fully established, it will be a real game changer.

        • Craig Randolph

          Well, all I can say is believe what you believe. Go and check out the extensive study done by Dr. Robert Bruck from N.C.S.U. who, along with his students, did a very significant study on the Spruce-Fir forests of Mt. Mitchell and came to most of the conclusions I’ve stated here. Hopefully, there WILL be a cessation of the Fir mortality on our highest peaks. As far as acid rain/cloud deposition, pay particular attention to his records of some of the acidic levels recorded up there. Levels equal to the acid levels found in lemon juice and vinegar. A fog event that occured shortly after ‘bud break’ of the firs that clearly show the tender new tips ‘burned’ by cloud deposition. Also, there may indeed be new Red Spruce coming up, what I was referring to is the scientific evidence of the older, cone bearing age spruce trees nearly total cessation of new growth recorded after the 1950’s. And I’ve yet to see (and I used to work up at Mt. Mitchell State Park, as well as on the Blue Ridge Parkway) any hard evidence, visually or scientific evidence, of the firs on Mt. Mitchell becoming resistant to adelgid infestations. Possibly happening on Mt. Rogers, in southwest Virginia…yet to be proven the same is happening in Fraser Fir forests further south. As I stated earlier, Fraser Firs require a very specific set of growing conditions, and with global warming having been proven beyond a shadow of a doubt,then it’s detrimental starting out in our most fragile ecosystems–the Spruce-Fir forests . That’s the reason we even HAVE a Canadian type Spruce-Fir forest here. After the retreat of the last ‘ice age’, the only areas that were wet and cool enough to support such a forest were the highest peaks of the S. Appalachians. Also, it’s dubious to say that the Graveyard Fields area will be covered in a Spruce-Fir forest in 50 years. If so, hope I live long enough to see it. If what you state as fact is actually true, then why haven’t other high-elevation hardwood forests, such as at Craggy Gardens reverted back into evergreens? You can look across the Craggies (especially from the Glassmine Falls overlook on the Parkway)and see a Spruce-Fir forest growing on the slopes of Blackstock Knob at a LOWER elevation than the hardwood clad peaks of the Craggies. So, the seed source is there, so, what gives? As I’ve read and seen for myself, it is extremely rare for a Spruce-Fir forest to totally reclaim an area formerly dominated by it. Again, due to forest succession, the forest floor gets covered year after year by the shed leaves of blackberry/raspberry brambles, fire/pin cherry trees, then, birch and finally beech trees, making it extremely hard for the light seeds of either the Fir or Spruce to gain a foothold and contact the soil necessary for their seeds to germinate, grow, and reclaim their former domain. So, with this, along with global warming, past logging practices,fire, adelgid infestations, acid rain,heavy metal deposition, along with present-day human impacts-i.e. trampling of seedlings, ‘bushwhacking’ hikers not staying on established trails, have all coalesced into making the Spruce-Fir forests of the Southern Appalachians in real danger of losing any ground you claim they have gained here. Time will tell. In closing, I’d be more than willing, as Eliot Porter once said, to abandon my vehicle and make what is currently an easy drive into the highlands of the Smokies into a multi-day excursion on foot or horseback, leaving these pollution producing tin cans to fend for themselves! Dr. McBug, you have my respect and appreciation for all you’ve accomplished here in the southern mountains. AVL LVR, you as well, good to know there are others paying attention to what is going on with the splendid forests entrusted to the public.

    • Craig Randolph

      Also, I’d say that the high elevation Fraser Firs are in more danger of disappearing than are our hemlocks. They face not only balsam woolly adelgid infestations, they endure much more severe weather than do the hemlocks..(even though the firs are better equipped by nature to survive in the harsh conditions found on Clingman’s Dome, Mt Mitchell and other high peaks) and after a fir has been infested year after year, it weakens them. Then, the acidic levels found in cloud deposition (fog) events, along with a much increased level of acid in the rainfall at these elevations, all combine to render our Fraser firs all but helpless. Hopefully, with this continuing cycle of firs growing, producing seeds, dying, and coming back up again will allow the firs to develop a resistance to these infestations. As far as reducing the levels of acid precip., you get the air quality that you vote for. Also, feel the firs are in greater danger of disappearing because we have so few of them to start off with. A report from many years ago put the acreage of our Spruce-Fir forests in the S. Appalachians at about 65,000 acres. Would imagine it has shrunk drastically since then. Don’t get me wrong, love our hemlocks just as much, but just feel the firs are in greater danger of disappearing completely than are our beautiful hemlocks.

  2. DrMcBug

    These predators are specific to all conifer adelgids (pine bark adelgid, Coolly Spruce Gall adelgids, balsam woolly adelgid – fir, hemlock woolly adelgid). Now that the Laricobius nigrinus beetle is established, we should start investigating its role in suppressing balsam woolly adelgid (BWA) in Fraser Firs. If we do this right, there won’t be any reason for Christmas tree growers to spray Merit and other chemicals against BWA and balsam twig aphid. These beetles will dramatically improve our forest health and promote regrowth of all conifers with adelgids if we are smart enough to pursue this. Onward!

  3. I know there has been significant success in Brevard and other WNC areas with the Sasi beetle (Sasajiscymnus tsugae), and I heard that forest service or extension service staff have confirmed the success in test areas. And, the Sasi beetles are being lab grown for large quantity release. Can you please point me to scientific reports about the Lari beetles and why they might be better then the Sasi beetles, or otherwise please explain the difference in their effectiveness. Thank you!

  4. DrMcBug

    http://www.srs.fs.usda.gov/compass/2014/11/18/one-two-punch-slows-down-the-hemlock-woolly-adelgid/ that clearly proves the effectiveness of Laricobius nigrinus beetles in controlling HWA.
    “Our results show that chemical and biological control of hemlock woolly adelgid can be integrated to promote hemlock health and reduce numbers of adelgids,” said Mayfield. “That said, the Laricobius beetle only feeds on adelgids that are active from fall through early spring. Sustained protection of hemlock through integrated management in the Southern Appalachians may require the addition of an effective predator on the second adelgid generation that is active in late spring and early summer.”

    Even more reason to couple Lari releases with a summer predator such as Scymnus coniferarum in our area.

    Laricobius nigrinus feeds on the winter generation of the adelgid; hemlocks get all their energy from winter sun stored as carbohydrates. That is why the biggest generation of the HWA is in the winter, and this is what Lari goes after, freeing the resources to go back to the tree. That’s why we see massive regrowth as the beetles have knocked the HWA to the point that it doesn’t hurt the tree anymore. In the past 10 years, we have found about 45 Sasaji adults up here in NW NC, versus 63,000 Laricobius nigrinus collected and redistributed in the past several years.

    Sasaji is from southern Japan, where HWA has an alternate host (Tigertail Spruce) and probably works well where it is warmer. We don’t have an alternate spruce host for Sasaji that we know…It has been reared continuously since 1995 – for 20 years and 5 million (!!) Sasaji beetles have been released. Anybody else have any experience recovering large numbers of Sasaji? We put out 100s of Lari and got back 1000s with concurrent hemlock growth…. Where’s the other 5 million Sasaji?

  5. DrMcBug

    This was ALWAYS a team effort… and we wouldn’t be where we are without the critical help of the University of Washington’s Forestry Department, Washington Park Arboretum (where all the early work was done), City of Seattle Parks and Recreation Department, the Blue Ridge Resource Conservation & Development Council, the US Forest Service, the North Carolina Forest Service – Urban and Community Forest Program, NC Agriculture and Consumer Services, Virginia Tech, and NCSU, to name a few. Hope this information and the ultraviolet sidebar help. Thanks for all your interest. Let’s go save a bunch of hemlocks! Especially our very own Carolinas, for starters.

  6. Montreat College Students

    Hello Miss Benton,

    We are creating an interpretive exhibit about hemlocks and we are hoping to gain permission for the use of the first photo, entitled “Forest of the Dead” by Brian Gratwicke. Please email me with your response. Thank you for your time and consideration.

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