Tuesday, February 1, 2022

Beech Gone Wild: Raging Hormones

American beech

The American beech (Fagus grandifolia) has been slowly dying out for the last 140 years. As a result, beech saplings have overrun many woodlots, making them less diverse, less vigorous, and less valuable.

That’s right – beech decline has led to a beech proliferation so extreme that in some places they are a barrier to forest regeneration. I’d call this an oxymoron, but don’t want to insult the bovine community. Strategies do exist to address this problem, though.

Long-lived and stately, beech grow throughout eastern North America from Wisconsin and Missouri east to the Atlantic, and from northern Florida all the way to northern Ontario and Quebec. In northern New York, the beech family (Fagaceae) contains over a dozen oak species, yet has but one native beech, making me wonder how beech got to lead the clan. Historically, beech was a keystone species in many long-term stable forest communities. From mice to grouse to black bears, a host of wildlife once relied – and still do to an extent – on beech nuts.

In the late 1800s, a European scale insect arrived in Nova Scotia. Simply called the beech scale (Cryptococcus fagisuga), this soft-bodied pest ranges from 0.5 to 1 mm long, or in non-metric terms, wicked-small to crazy-small. The frail, flightless pest can’t even crawl, except for briefly upon hatching; it passively disperses on wind or birds’ feet. Once on a beech trunk, it inserts a thin stylet into the phloem and takes a wee sip of tree juice. So far, it doesn’t sound too menacing.

We’re living through a nasty demonstration of what microbes a bazillion times (well, at least a quadrillion, but I forget what comes after) smaller than us can do. Similarly, the minute beech scale can slay trees millions of times their size through a scheme of rather permissive family planning.

Beech trees could probably handle throngs of insects each robbing a taste of sap. But every time a scale’s micro-straw jabs through the bark, a native fungus in the genus Nectria comes with it and engages in rotten behaviour. This unhurried decimation is termed beech bark disease.

Beech-scale insects exude white filamentous wax, and large infestations look like fuzz or white mold. Rough, puckered areas of bark indicate Nectria has killed the phloem beneath and is busy turning wood to sponge. Dead patches eventually merge, cutting off water to the crown.

But all that’s beside the point. This is really about why hormone imbalance is a threat to forests.

A beech tree’s post-mortem baby boom is related to how it procreates. Like poplars, beech spread by root sprouts, clones of the mother tree, and seed production. Overstory trees crank out growth-inhibitor hormones to stifle the mass-emergence of root sprouts. They don’t want competition while they’re in charge.

When a mature beech dies, hormone constraints go, too. With no mother tree keeping things in check, it’s “bring in the clones.” Given that a tree’s root zone is three times its branch length, every sizeable beech that expires creates a broad, dense monoculture of saplings. Curiously, beech scale doesn’t often attack trees under 8” in diameter, which is why root-sprout saplings are not controlled by beech bark disease.

Never mind that they’re the bane of maple producers trying to run tubing, and mess things up for hunters by retaining leaves all winter; beech thickets inhibit forest regeneration. Anything that interferes with the natural regrowth of a diverse woodland will lead to a less productive and less resilient future forest. Competition for water and nutrients is minor compared to the battle for sunlight. A mini-forest of sprouts will one day succumb to scale, but not before they shade out everything else.

In terms of mechanical control, it’s a lot more effectual to cut in early summer just after leaf-out is complete. This puts the maximum strain on the organism. By late summer, a season’s worth of photosynthate has been tucked away for next year.

Even in small woodlots, severing countless beech stems at the base is daunting. Chainsaws are a poor option, as working bent-over strains the back and quickly fatigues operators, increasing the chance of mishap (plus in my experience, saw chains are magnets for hidden rocks). A pro-model string trimmer with a circular blade is easier on the back, but there remain issues of fatigue and potential injury.

Canadian research concluded that “high stumping” at about 3 feet was as effective as basal cutting. With a two-handled lopper, there’s no bending, and less risk of injury. Cutting stems with a brush head on a small tracked vehicle is likely the best method for large tracts.

Don’t laugh if you haven’t heard of flame-weeders, but they’re used to burn the basal cambium of small trees. With such fire potential, early winter with a veneer of snow may be the only safe window to work. Bark should be heated until well-done, as I’ve seen “undercooked” trees live through flame treatment. Mechanical controls are typically repeated for several years.

Admittedly, chemical control is effective, but organic certification, environmental and/or health concerns, or municipal by-laws might nix it. Concentrated (25% to 50%) glyphosate is dabbed or painted on beech stumps within 72 hours of being cut. Timing is crucial: cut-stump treatment is far more successful in early fall when woody plants move sugars and nutrients into the roots. When done properly, around 90% of beech saplings are killed by one application.

I suggest hiring a professional forester to help with beech-thicket control, especially if chemical use is on the table (figuratively, of course). Peter Smallidge, Cornell Extension Forester for NY State, has great articles and YouTube demonstrations. Find links at https://cornellforestconnect.ning.com/forum/topics/beech-management-1

Paul Hetzler is an ISA Certified Arborist, and a former Cornell Extension Educator.

Photo: Katja Schulz from Washington, D. C., USA, CC BY 2.0, via Wikimedia Commons

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Paul Hetzler has been an ISA Certified Arborist since 1996. His work has appeared in the medical journal The Lancet, as well as Highlights for Children Magazine.You can read more of his work at PaulHetzlerNature.org or by picking up a copy of his book Shady Characters: Plant Vampires, Caterpillar Soup, Leprechaun Trees and Other Hilarities of the Natural World

7 Responses

  1. Ellie and Joe M. says:

    Geez. Just let the deer have a go at them. Our beech saplings are no match for deer browse. And yes, the scale bugs get saplings under 8”. It’s a sorry sight to see. At one time, the yellow saplings quaking like aspen in the winter woods. And now withered, leafless like the majestic trees above them.

  2. Dan says:

    This is actually another deer problem. Exclude whitetail deer from these sites, and beech regeneration is far less likely to dominate. Other species will establish themselves. Ignore whitetail deer, and no other tree species will be able to complete with the beech.

  3. Tom Vawter says:

    Paul, thanks for this excellent article, clear and informative.

  4. JT says:

    I don’t have a lot of Beech on my property in Northern St. Lawrence County but the few I have may max out at 8″ DBH. So far, no Beech Scale Disease. I plan on leaving them because they add to the diversity of tree species on the property, but will continue to monitor. I know of other people in the area who have diseased Beech trees so it is probably a matter of time before it shows up.

  5. JB says:

    Is there any good empirical evidence as to the extent of the problem of BBD-induced beech thickets? …Because, while the loss of an important component of our old-growth forests is beyond tragic, I have my doubts as to the hypothesis that beech thickets caused by BBD die-off will be a serious problem in the Northeast.

    Even considering the spectre of high BBD mortality, it seems like few forests in the Northeast are extensively dominated by old beech. American beech does not appear to become a dominant climax species the way that European beech does. I have never seen an old-growth American beech stand large enough for a die-off to cause an extensive thicket that would not be eventually outcompeted by shade-tolerant species. Further, in calcareous mesic forests outside of the Adirondacks, there are many alternative shade-intolerant species that tend to outcompete beech until there is sufficient canopy to favor maples or conifers. In the Adirondacks, I have found that beech tend to become locally dominant 20 yrs. post-logging–probably one of many arguments against heavy timber management–but I still have yet to find a stand dominated by 8″+ DBH beech, BBD or no BBD. …Other successional trees make their entrance before that can happen.

    Interestingly, in Saratoga Co. I have seen unaffected 12″+ beech trees growing nearly side-by-side with seriously BBD-affected ~8″ DBH trees. And, miraculously, in my neck of the west/central Adirondacks, I still have yet to find any evidence at all of BBD on any of the numerous 18″+ beech! I understand that this is the exception to the rule, but as Gibson has said in his article on the subject, the the game is not lost: there are still many reasons for hope and things worth protecting.

    • JT says:

      I was curious about the Beech thicket problem myself. I tend to think it may be more prevalent as a result of man made conditions from forest management as you mentioned. Hiking through Western High Peaks and West Canada Lakes Wilderness, I saw many diseased Beech trees but no thickets. So perhaps, it’s when the trees are cut down is when the thickets are produced. Actually, the trees were still leafed out and producing Beech nuts, I would presume. Not sure how long these trees can live once infected, but appears to be a significant amount of time. I guess, as Paul states in the article, the growth inhibitor hormones are still effective. The forest types they lived in were a mix of Sugar Maple and Yellow Birch, what you commonly find in the upland glacial till sites. Let’s hope your unaffected 12″+ trees growing beside affected trees have a natural resistance to BBD and will be the future. I try to be optimistic.

  6. Kim Pope says:

    Very good article –
    I will get his book!
    Keep up the great work to Paul!

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