Subject:
Date: Wed, 1 Aug 2001 09:44:12 -0700
From: Linda Haugen/NE/USDAFS
Reply-To "TREEPHYS (Open Discussions of Tree Physiology)"
To: TREEPHYS@LISTSERV.OKSTATE.EDU

Treephys list:
I asked a colleague who is an expert on elm tree injection to respond to the question... his reply is below (after the original message).
-- Linda
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Linda Haugen,
Plant Pathologist
Forest Health Protection, S&PF, USDA Forest Service 1992 Folwell Avenue, St. Paul, MN 55108
Phone: (651) 649-5029 Fax: (651) 649-5238
E-mail: lhaugen@fs.fed.us
----- Forwarded by Linda Haugen/NE/USDAFS on 08/01/2001 08:50 AM ---
From: Treespeak@aol.com
To: lhaugen@fs.fed.us
Subject: Re: 3 year arbortech injection and American elms.
07/31/2001 06:19 AM

----- Forwarded by Linda Haugen/NE/USDAFS on 07/30/2001 11:55 AM ---
John Paul Sanborn sanborns-trees@WI.RR
To: TREEPHYS@LISTSERV.OKSTATE.EDU.COM>
Sent by: "TREEPHYS Subject: 3 year arbortech injection and American elms.
07/23/2001 03:21 PM

Is there any consensus as to the best time of year to treat? I have heard that there could be a problem with blowing bark out when it is "slippery" in say July.

John Paul Sanborn- Staff Arborist
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Good morning Linda,

I'm not sure there is a consensus on the best time to treat. If there is a time possibly to avoid, it may be the traditional time in early June (in MN) when most treatments are administered. That's when the bark is really slipping and the trees energy reserves are lowest, but also when they are most susceptible to both infection and disease development. I know that for Arbotect, the later in the season the treatment is administered (into early October), the longer the chemical shows up in new wood in subsequent seasons.

I believe the same is true for Alamo, but its lasting effects are different, I believe related to its growth regulator properties.

On another related front, Alamo and Arbotect 20-S differ widely in their effects on the tree at and around the injection site. Arbotect is a water soluble acid salt, and even when properly diluted, goes into the tree at a very low pH. As a consequence, there is substantial mortality to the radial meristem around the hole and to the living parenchyma cells in the sapwood above, below and to each side of the hole. Alamo has no effect on then radial meristem, and does much less damage to the parenchyma cells. The study will be published when I can find the time during the coming dormant season (I promise).

Mark Stennes
Plant Pathologist
Top Notch Treecare
952-922-3239
Treespeak@aol.com

Reply to post by JPS, on August 01, 2001 at 20:08:17:

Linda,
Thanks for the help!

Mark,
Thank you too.

Current wisdom is that we can get 3 years of protection with the macro-fusion treatment, wich is 6x the one year rate in a 1:64 dillution. Saying that we get better persistance in subsequent year wood with later season injection, is this that we are more likely to get the full three seasons of coverage if injected in the fall?

I have heard that Alamo has no reliable persistance in the 2-4 y/o twigs where the beetles feed. Have you any comment? I feel than annual boring is worse then localized dieback if we can have a reliable two year "rest" period in the treatment. I' have had to do a lot of theraputic treatments this season because this is the "off" year on the two on one off cycle.

Are there any studies on including minor elements and/or insecticides for control of scale to the mix?

Will you be at the ISA thing in MKE on the week of the 12th?

_________________________________

Greetings John,

If you would like to see some data on how the benzimidazole fungicides behave in mature elms trees, please see:

Stennes, M.A. & French, D.W. 1987. Distribution and retention of thiabendazole hypophosphite and carbendazim phosphate injected into mature American elms. Phytopathology 77: 707-712.

Thiabendazole hypophosphite (Arbotect 20-S) is the best of the two because it will show up in new wood for up to three years, but only if administered at what is now the highest rate on the label. But the truth is that even at the highest rate, uniformity of distribution and strength of activity diminishes rapidly after 12 to 14 months. The degradation of fungitoxic activity in new wood appears to be a function of the number of months of growing season after treatment, which is why if the tree is apparently healthy I always like to treat late in the season, and do not have serious trouble with my three-season warranty.

Twenty-five years of experience have given me the impression that we seem to get three season protection because the treatment stops latent infections and protects against new infection for up to 14 months, which is in the second season. The third season comes because of the incubation time between infection and disease expression. Back in the late 70's, and again in the mid-nineties, I inoculated mature trees in hundreds of places throughout consecutive growing seasons to assess the efficacy of various treatments and discovered that most infections that are conspicuously killing trees are at least two, if not three or four years old. The host-parasite relationship is not a simple one, and trees recover from infection far more often than they die (thankfully). If you want to see some data, and a literature survey on Dutch elm disease chemotherapy, please see:

Stennes, Mark A. 2000. Dutch elm disease chemotherapy with Arbotect 20-S and Alamo. IN: Dunn, Christopher P. (ed.). The Elms: Breeding, Conservation, and Disease Management. Copyright 2000. Kluwer Academic Publishers. Boston. It's chapter 10 in a hard cover book. There is also some really good stuff in there about the taxonomy, ecology and epidemiological history of the pathogen.

To reply to your comment on the "persistence" of Alamo, I must point out that the chemicals are not related in any way. The benzimidazoles work as a fungicide because of the morphology of the molecule, which binds to the spindle microtubule during mitosis, preventing it from happening. It works by sitting on the fungus like an 800 pound gorilla. Alamo (propiconazole) is technically a sterol-inhibiting fungicide, and is applied as a fungicide, but pathologists who have studied the entire group of triazoles seem to believe that its efficacy is due mostly to its growth regulator properties. It can never be detected in the tree by traditional bioassay techniques. If I was a professor at a University, I would have a graduate student working on how and why it works for both Dutch elm disease and oak wilt. For now I cannot be concerned with the how. It's whether it works that matters, and it works every bit as well as Arbotect and for just as long. I no longer have any use for Arbotect, except perhaps for Sycamore anthracnose. Injection site injury is a very serious concern I have had since 1978, the first time took a tree apart that had been treated with Arbotect.

I have no information about mixing anything with the fungicide injection solution, and would be very careful if I were you.

I will be in Milwaukee, starting with the President's Reception on Friday, 10 Aug. I am the current President of the Minnesota Society of Arboriculture, Chapter ISA, and will be there throughout the Conference.

Thanks for your interest in my opinions.

Linda, could you reconnect me with the ForPath list serve? I lost touch when I changed e-mail address. Thanks.

Mark Stennes
Plant Pathologist
Top Notch Treecare
ISA Certified Arborist #MN-0147
952-922-3239


BTW, I've ordered the mentioned book, it is $125 @ Amazon.