GYPSY MOTH OUTBREAK 2016 - THE BOSTON GLOBE
I've done my best to stay positive these past few months. My very, very, very, very best, despite every fiber of being trying to drag me down to wallow in all my fears, anxieties, and rage, but at this point I think I owe it myself to give in to the bottomless panic that's been threatening to swallow me whole. So for the moment I'm going to stop re-assuring myself that somehow everything will work out, that humanity will finally stop fumbling around in the dark and somehow manage to find its way out of the massive hole we've dug ourselves. Everything is not ok, we are all horrible, and each and every one of us is royally screwed. And so without further adieu I give you multiple (ecological) reasons to lie awake at night, knowing full well the future is not bright, and we are all collectively to blame (and for the record this is only a fraction of the human induced disease and infestations that are currently afflicting our forests here in the northeast. I chose to focus on either recently-ish introduced disease and pests or those that have, for whatever reason, yet to be widely publicized outside of the scientific community). Enjoy.
Disease/Pest: Geosmithia morbida, Thousand Cankers Disease
Description: A fungus spread by the Walnut Twig Beetle, Pityophthorus juglandis.
Primary species affected: Black Walnut, Juglans nigra & Butternut, Juglans cinerea
Mortality: ≈ 100%
Resistant varieties: None
Other Susceptible species: Juglans spp.
Year first reported and location: 2001, Colorado
Successful efforts to combat: Given the recent appearance of the disease there have been no coordinated efforts to fight back, simply curb the spread. Currently, there are no reported cases of resistant J. nigra individuals.
Disease/Pest: Butternut Canker, Sirococcus clavigignenti-juglandacearum
Description: A spore spread fungus.
Primary species affected: Butternut, Juglans cinerea
Mortality: ≈ close to 100% (with an occasional resistant individual)
Resistant varieties: None
Other susceptible species: Black Walnut, Juglans nigra
Year First reported and location: 1967 in southwestern Wisconsin
Successful efforts to combat: Yes, a germplasm of resistant Butternuts has been gathered by the forest service and partnership state and private organizations for breeding. While efforts are promising, they have yet to publicly release any resistant Butternut strains. To further complicate matters some resistant "Butternuts" were actually hybrids between J. cinerea and J. ailantifolia (Japanese Walnut).
The northeastern and mid-atlantic forest once had economic value far beyond the raw materials of the trees themselves. American Chestnuts, Butternuts, and Walnuts once sustained local people well beyond simple subsistence, forming the backbone of local economies up and down the eastern seaboard. But with the appearance of chestnut blight at the turn of the 20th century this economy quickly began to collapse as the once great American Chestnut went functionally extinct. While not as productive or as prevalent both the Black Walnut and Butternut (also highly valued for their nuts) are now at risk of succumbing to the same fate. The 2 diseases that threaten these trees highlight what exactly it is we lose when these foreign pathogens are unleashed upon an otherwise healthy functioning landscape: productivity. Natural systems that could once support diverse populations of native flora and fauna along with local human populations all but collapse leaving the disparate elements to compete for the few resources that remain.
Disease/Pest: Winter Moth, Operophtera brumata
Description: A moth native to Europe and the near East. Males are most commonly observed in late fall and early winter in the evening in search of flightless females.
Primary species affected: Multiple deciduous trees and shrubs including Acer spp., Quercus spp., Fraxinus spp., Malus spp., Vaccinium spp., etc.
Mortality: (?) less than 5% maybe, buy this is a total guess. It may indirectly be much higher (they weaken the trees and make them more susceptible to other disease).
Resistant species and varieties: Conifers
Year first reported and location: Nova Scotia sometime prior to 1950.
Successful efforts to combat: Yes, a parastic fly and natural predator of the moth (Cyzenis albicans) has been studied (see article), and appears to have successfully curbed infestations. It has already been used successfully in Nova Scotia and British Colombia, and results in the northeast look promising. The fly is a specialist and does not appear to target other native lepidoptera species. While not yet available to the larger public, UMass Amherst professor Joseph Elkinton has done several controlled releases across Massachusetts in hopes of curbing the outbreak (see article).
So I only found out recently that the multitude of moths I've been seeing fluttering around at night during the end of November are not only pretty much all the same species (and all male), but a noxious introduced pest that has been responsible for the (often) complete defoliation of a multitude of deciduous tree species, including many natives. This, along with 2 other introduced lepidoptera pest (Gypsy Moth, Lymantria dispar and Browntail Moth, Euproctis chrysorrhoea - both of which have their origins in my great state of Massachusetts...ugh) make a destructive trio that are wreaking havoc across the northeast and continuing to expand their range with each passing year. 2016 was a particularly bad year given the record setting drought (drought compounds the infestation as one of the few natural controls of these voracious little wrigglers is a virus, baculovirus, that relies on rainfall to spread). This confluence of accelerated population growth and extreme drought resulted in some pretty disturbing scenes. There were stretches along the drive to my garden (from Boston to Ipswich) this past summer where it looked like it was winter in mid-July. Thousands upon thousands of big mature oaks were stripped down to their bare branches for pretty much the entirety of the summer.
Disease/Pest: Woolly Adelgid, Adelges tsugae
Description: A miniscule sucking insect. Egg sacks are visible as white cottony masses.
Primary species affected: Tsuga canadensis
Mortality: ≈ 100%
Resistant varieties: None
Other susceptible species: Tsuga carolina
Year first reported and location:
Successful efforts to combat: Tentative yes?, research is currently underway looking into the effectiveness of a few species of predatory beetle (see article). Unfortunately, at least one of the beetles has even less cold tolerance than the adelgid itself, so it may only be effective in the southern Appalachians. There are also efforts to propagate resistant individuals of both native hemlock species as well as various breeding programs looking at crossing both T. canadensis and T. carolina with more resistant Asian species. T. canadensis has not yet made any successful crosses with asian species.
LARGE SCALE HEMLOCK DIE OFF IN THE SOUTHERN APPALACHAINS
This insect has become a relatively recent poster child for how disastrous invasive pests can be. These nearly microscopic little SOBs have rivaled chestnut blight for the speed at which they've spread and their virulence (granted the trees take a few years to succumb, but mortality is nearly 100% and unlike the chestnut, hemlocks lack the ability to re-sprout; once they're dead, they're dead). I've written about this so often mainly because I've witnessed the before and after of this plague first hand, and it has had a profound impact on me personally. Hemlocks were not particularly common in my area to begin with, so when you were lucky enough to come across a stand it made the ecological influence that the trees had on their environment even more profound. Overall, these places were quieter, cooler, and lusher than the surrounding woodland. As tragic as it has been to see this species all but wiped out in my area, where the hemlock are more common and a dominant species, their loss has been catastrophic and will permanently change the landscape they once called home.
While I could go on, and probably should, I'll leave you with an image of the current state of our forests relative to a decade ago. If anything these numbers have probably increased. You can see what it looks like for other parts of the east (here) as well and it ain't pretty. The reality is that soon enough they're may not be any species left to take the place of the ones that get wiped out... and where are we then? And just in case you weren't concerned enough, I'll leave you with a list of a few of the other wonderful human induced plagues that are currently ravaging woodlands up and down the east coast. Keep in mind I didn't even touch upon native disease/pests or other invasive plants... I can only fit so much negativity into one post.
- Asian Longhorned Beetle, Anoplophora glabripennis
- Emerald Ash Borer, Agrilus planipennis
- Beech bark disease, Cryptococcus fagisuga
- Dogwood anthracnose, Discula destructiva
- Viburnum Leaf Beetle, Pyrrhalta viburni
- Oak wilt, Ceratocystis fagacearum
- Dutch Elm Disease, Caused by 3 different species of ascomycete microfungi: Ophiostoma ulmi, Ophiostoma himal-ulmi, Ophiostoma novo-ulmi
- White Pine Blister Rust, Cronartium ribicola
- Chestnut Blight, Cryphonectria parasitica
IMAGE SOURCES: Thousand Cankers Disease Map, Butternut Canker Distribution Map, 2015 Forest Health Aerial Survey, Woolly Adelgid Spread Map, Dead Hemlocks, Northeast Tree Mortality Map
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