HW Adelgid Treatments

HW Adelgid Treatments

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TOPIC: Adelgid Treatment Questions
http://groups.google.com/group/entstrees/browse_thread/thread/88c83c80391ec885?hl=en
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== 1 of 8 ==
Date: Wed, Sep 17 2008 11:24 am
From: Parajanov

ENTS:

Has anyone in this group seen any adelgid-infested hemlocks treated
with horticultural oil applications survive in excess of five years
beyond the beginning of treatment? It has been five months since two
hemlocks on my property were initially sprayed with horticultural oil,
and now at least one fifth of the needles have died on the larger of
the two trees (approximately 40 feet in height). I've elected to
continue spraying them myself; however, if this isn't the best
treatment, I need to know soon. Please note that these two hemlocks
are at least one-fourth of a mile from any neighboring hemlocks, so
reinfestation due to proximity to other hemlocks shouldn't be a factor
in pest management.

All arborists that I've approached for treatment in my area have
effectively refused to use imidacloprid trunk injection treatment (the
trees are within 100 feet of a large stream). In once instance, an
arborist claimed that injection would make tree death from increased
mite activity inevitable. The one company that would visit my
property mixed their oil solution with a small amount of fertilizer (I
realize fertilizer is not recommended in treatment of adelgid) and did
not thoroughly soak my two trees when they did apply the oil.

If trunk injection is the only effective option, perhaps an ENTS
member knows of an arborist in the central or northern Virginia area
who would be willing to inject imidacloprid? If someone can't refer
me to an arborist, perhaps someone would be willing to provide a
detailed description of how I might perform the trunk injection myself
(including a list of the supplies/materials I would need)?

I'm extremely tired of the indifference I've met trying to seek help
from local arborists. Any help would be greatly appreciated.

Thanks in advance,

D. Walker

== 2 of 8 ==
Date: Wed, Sep 17 2008 5:05 pm
From: Carolyn Summers

Yes, I've had mine for 15 years, since I started spraying. They are still
alive.
--
Carolyn Summers

== 3 of 8 ==
Date: Wed, Sep 17 2008 6:12 pm
From: Andrew Joslin

I'm sure Will will reply with the most up-to-date treament info but I
think I can clear a couple of things up.

The recommended baseline treatment is soil injection or root drench
with imidacloprid. Trunk injection is expensive, is invasive to the
tree and is probably less effective than manually putting the active
agent directly into the root zone. Many arborists are using
techniques that are out-moded etc. and don't have the most current
information. I know otherwise very qualified arborists who had no
idea what I was talking about when I mentioned soil injection as an
application method.

Will has posted preliminary research results that show that when
imidacloprid is applied via root zone soil injection (and perhaps
root drench technique), the active agent binds to organic matter/soil
components and does not migrate from the immediate application site.

My understanding of the horticultural oil technique is that you have
to know when the larval adelgid (crawlers) are active and apply at those times.

Reinfestation is still a possibility, a quarter mile is not far away.
The larval adelgid can travel on winds and piggy-back on birds.
-Andrew

== 4 of 8 ==
Date: Wed, Sep 17 2008 5:22 pm
From: Josh Kelly

In my experience horticultural oil works great if it can be applied
once or twice annually, May-September, and if the top of the tree can
be reached. On my family's property, the hemlocks that are small
enough to use horticultural oil are the healthiest, followed by those
that have had a safari treatment.

100 feet from a stream is no problem with imidacloprid - it isn't
likely to move more than 12" unless it is dumped directly on to
surface water or subsurface seepage.

Josh

== 5 of 8 ==
Date: Wed, Sep 17 2008 5:30 pm
From: "Edward Forrest Frank"

Hello,

Horticultural oil works somewhat if it is applied regularly, but in my reading and research imidacloprid is a better bet. It is best applied as a soil drench. You can buy it at horticultural supply places, or it is sold off the shelf at places like Wal-mart under the name "Bayer Tree and Shrub." The instructions on the bottle I think dilutes the compound too much. Mix up the chemical and apply it slowly to the area around the base of the trunk and out a few feet so that it may be take up by the tree. A treatment should protect the trees for at least three years.

Ed Frank

== 6 of 8 ==
Date: Wed, Sep 17 2008 6:25 pm
From: "Will Blozan"

D. Walker,

I have had extensive experience treating tens of thousands of hemlocks. In
fact, I am delivering a talk tomorrow on just such a topic to ~90 land
managers, land stewards, arborists, etc.

As far as horticultural oil, I never use it as a stand alone treatment. It
does not confer any resistance to reinfestation, is labor intensive, and
very costly in the long run if reinfestation pressure is high. The
advantages are that it also can control other pests of hemlock such as
spruce spider mites and elongate hemlock scale. However, it also eliminates
beneficial insects that can prey on these same pests. Also, if you miss just
one they are back next year.

Imidacloprid- the industry standard for HWA for many years- has fallen into
extreme disfavor due to spruce spider mite explosions. I have renamed the
compound i-MITE-acloprid and will never again use it in a landscape setting-
especially on smaller trees. A stalwart performer for seven years in my
business, it has now been abandoned for a similar neonicotinoid called
dinotefuran. This compound is currently only sold as a product called
Safari, and like imidacloprid is applied as a soil injection or drench.

Unfortunately, the smallest quantity of Safari you can buy is a three pound
jug. This jug costs over $300 here in North Carolina. The bottomline: use
Safari if you can afford it or find someone to apply it as a soil injection
for less than $300. If you stay with imidacloprid you will almost certainly
have a mite explosion and have to spray oil or soap anyway. Systemics are
the best bet for ease of use and longer control than oil/soap sprays.

BTW, hemlocks are apparently sensitive to oil spray during the growing
(elongation) season and can "burn" if sprayed when tender. Insecticidal soap
may be a better bet, but as Josh said- wait until the crawlers have settled
and spray before they produce wax in the fall.

As for a 100 foot distance from water- that is ridiculous. Have the
arborists who tell you so to do some research online. As Ed said, if organic
material is present, movement is highly unlikely with imidacloprid.
Dinotefuran is more mobile but also binds to organic matter. However, it is
much more quickly translocated (<3 weeks) and as such has a short
environmental legacy and quick kill. Its soil half-life is very short. Both
compounds photodegrade rapidly in water, and the miniscule amounts from
properly applied treatments would pose no threat to aquatic organisms. Only
a massive and deliberate spill could possibly have an impact.

I doubt it is soon enough to tell if the crawlers are alive this time of
year on your sprayed trees. Before any treatments I would suggest you make
sure they are really viable by looking for wax this October. A properly
applied oil spray should have nuked them last spring. Some reinfestation is
possible but unlikely if your trees are so far removed from a HWA source.

Good luck!

Will F. Blozan
President, Eastern Native Tree Society
President, Appalachian Arborists, Inc.
-

== 7 of 8 ==
Date: Wed, Sep 17 2008 6:42 pm
From: Carolyn Summers

That is exactly what happened to my large hemlock when I experimented with
Merit soil drench - mite explosion - so I have gone back to regular oil
spray. Fifteen years of no problems with oil spray.
--
Carolyn Summers

== 8 of 8 ==
Date: Wed, Sep 17 2008 7:42 pm
From: "Will Blozan"

Carolyn,

So far we have not seen a single mite flare with Safari- unless it was mixed
with imidacloprid in a combination treatment. It sounded like a good idea at
the time but the trees turned gray!

Will F. Blozan
President, Eastern Native Tree Society
President, Appalachian Arborists, Inc.

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