Hemlocks Still Abundant Despite Adelgid Infestation

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Joe

Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by Joe » Thu Oct 06, 2011 6:37 am

What are the predictions regarding HWA- will it be as devastating long term as the Dutch Elm Disease and Chestnut Blight? or are there enough resistent trees so that the species will make a comeback?
Joe

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dbhguru
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by dbhguru » Fri Oct 07, 2011 8:07 am

Gaines,

You raise an important point and that is what do the data actually show independent of interpretations that may come from groups with divergent agendas. I admit to sometimes jumping the gun when results are announced from studies performed within governmental agencies about our forests. It is a Pavlovian response. Manipulation of data and study results has been going on for decades to justify forest management/exploitation initiatives that benefit the timber industry. I doubt anyone will argue that such practices haven't been going on. However, and this is the confusing part, the bad practices coexist along side topnotch science within the same agencies. They keep us guessing as to who is calling the shots.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

Joe

Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by Joe » Fri Oct 07, 2011 10:51 am

dbhguru wrote:Gaines,

You raise an important point and that is what do the data actually show independent of interpretations that may come from groups with divergent agendas. I admit to sometimes jumping the gun when results are announced from studies performed within governmental agencies about our forests. It is a Pavlovian response. Manipulation of data and study results has been going on for decades to justify forest management/exploitation initiatives that benefit the timber industry. I doubt anyone will argue that such practices haven't been going on. However, and this is the confusing part, the bad practices coexist along side topnotch science within the same agencies. They keep us guessing as to who is calling the shots.

Bob
the governnment land agencies always have internal battles with different schools of thought- policies are then set by whatever Ruling Elite is running the show at that moment

it's inevitable because how to manage "natural resources" is inherently extremely complex in so far as policy making because it's a mix of real science and human values which are infinitely variable; that is, IT'S POLITICS

Joe

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eliahd24
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by eliahd24 » Fri Oct 07, 2011 2:42 pm

... And all the big old hemlocks in the Southern App's are GONE... except (thank God!) the grand Cheoah Hemlock.

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jamesrobertsmith
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by jamesrobertsmith » Fri Oct 07, 2011 6:04 pm

Any official person or group who claims that hemlocks are holding their own or are "still abundant" in areas where the adelgid has infested the groves is a liar with an economic agenda. I hike routinely in areas where the hemlock groves are infested with hwa and in every one of these the mortality rate is, over the course of the infestation, 100%. Find me healthy untreated groves in Shenandoah National Park. Show me healthy untreated groves in the Great Smokies. Locate healthy trees that have not been dosed with ageldicide in Ellicott's Rock Wilderness or along the Cherohala Skyway.

You can't.

Wherever hwa is present, the hemlocks are doomed without treatment with appropriate chemicals.

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gnmcmartin
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by gnmcmartin » Sun Oct 09, 2011 10:37 am

James:

The devastation that the HWA has caused is obvious, I believe the study cites that fact and in no way contradicts it. It is a study that looks at the abundance of hemlock trees over the whole native range here in the U. S. Some areas that are listed as having HWA, such as Garrett County MD, have been more recently infected, and so far the impact is very small, and can not be measured by any study of the abundance and size of hemlock trees, which have generally been increasing. The point that the study makes, it seems to me, is that the increase in hemlocks in some areas has matched or exceeded the losses in others. My local project forester is very concerned that hemlocks in Garrett County will be wiped out.

Joe: I was hoping that someone with more knowledge than me could respond to your question. In the absence of that, I can give you my thoughts. I think the best hope, so far, is the introduction of the HWA eating beetles—some different species. In areas where both are native, the beetles control the HWA to the degree that the HWA's impact on hemlock growth and survival is very, very small, if not practically nil. So far, however, in the Eastern U.S. there has been very little, if any, success in getting the beetles to survive into the year following release (some have, but not many), and then build up a population that can work as an effective control.

I have tried to keep up with the progress, or lack of progress with these programs, but I may well have missed some important reports. Those now conducting the trials say that it will take considerable time before their success or failure can be determined--10 years or more. That presents a special difficulty--the HWA spreads very fast, and its populations in most areas build up very fast. This is a problem because even if the beetles prove successful, they will spread much more slowly--they are not carried by birds, as are the HWA--and their populations will build up very slowly. So far there seems to be no way to let the beetles get a head start in areas where there are not yet any HWA—even if they prove to be, in the long run, successful in controlling HWA

As for the possibility of there being resistant or immune trees--I have heard virtually nothing about this and not heard of anyone engaged in any research expressing any hope that this could be the answer. The trees that have shown more resistance than others seem simply to be the more vigorous trees.

I hope that if there is a solution, it is something other than finding resistant trees. First, I am concerned about all our wonderful hemlocks living now. My timberland has hemlocks as beautiful as any anywhere—although I don’t have contenders for any size or height titles. Finding some resistant strain will do nothing to save the existing stands of hemlock, and the propagation and dissemination of any resistant strain will take several lifetimes to achieve, and many areas may never have hemlock forests restored that would be anything like what was lost.

Also, the finding and development of resistant strains is an iffy and frustrating thing. I cite my experience with the American elm. In the last 10 years I have bought and planted 5 DED resistant elms. Of those, 4 have died of DED, and the one surviving tree has been in the ground only two years. I expect that will die also. The elms I planted were the “Liberty” elms—three different clones—and the Princeton elm. So far, the programs to find a fungus resistant chestnut have not yielded any stunning results either.

But what we are talking about with the HWA is an insect, not a fungal or viral disease. I must plead my ignorance here, but I am not aware of any cases where the predations of an insect have been fought with “resistant” strains of the affected tree. The development of insect resistance may be more difficult than the development of fungal and other disease resistance in trees. Perhaps the genetic changes involved would be larger, or involve more stable genetic elements, or something. But maybe something like that would seem to be possible. But again, I emphasize, it would do nothing to help save existing stands.

Well, Joe, I have gotten long-winded here, and all I may have done is to show how little I know. Sorry!

--Gaines

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AndrewJoslin
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by AndrewJoslin » Mon Oct 10, 2011 3:15 pm

Everything I've seen and everything I know up to now tells me that there will be total wipeout of mid-aged and mature Eastern and Carolina Hemlock in its range. The only limitation on HWA is low enough average winter temperatures, parts of northeastern U.S and Canada have a reprieve for now. There may be some limitation where HWA can't reach geographically isolated hemlock populations, but I think that's a fringe case. As we've discussed in the past imported beetles have failed miserably. One of the big issues identified is that that the eastern hemlock's release of defensive turpenoid compounds are out of sync with adelgid breeding cycles. Imported Asian beetles that feed on HWA cannot do it on their own (if they could sustain their populations) the tree has to be able to participate in controlling HWA.
-AJ

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