# Plant Growth Inhibitors



## TreemanFJR (Nov 6, 2004)

I ran across a guy today who is applies these inhibitors. He was a field manager and said he used them for trees underneath powerlines and some valuable trees on golf courses and such. So their function is too inhibit primary growth(apical meristems) right? Does it promote secondary growth? If so, how much and is this a good thing for the root tips/ fibers in the micropores? He made it sound like it won a nobel prize, but I don't know.

What I do wanna know is what you guys think about it. What are the real pros and cons of these inhibitors?


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## Guy Meilleur (Nov 6, 2004)

You can go to the Rainbow TSA forum on this site for answers.


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## murphy4trees (Nov 6, 2004)

*national regs*

I hear in Pa. the law requires a pest app license to spray anything that kills anything else... that would include soap, though I like Reeds idea of "washing the trees"

So in thinking about cambistat... I wonder if one needs a license to apply it??? Are there national regs or is it state by state?


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## Chucky (Nov 6, 2004)

I got into a big debate a few years ago on Guy Meilleur's old arb site with the redoubtable Bob Wulkowicz on plant growth regulators. The thread became quite a long interchange of barbs, anecdotes, analogies, observations, and incisive wit (mostly on Bob's part). Instinctively, I took the "pro-chemical" side of the debate, since I knew, given Bob's well-known natural aversion to anything conventional, I could provoke him to write---in the great Wulky tradition---some really amusing, trenchant, and memorable material. 

I think I got from all my trouble the realization that plant growth inhibitors are pretty much unnecessary if a simple maxim is followed: _The right plant in the right place._


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## TheTreeSpyder (Nov 7, 2004)

Guy with a forum? that must have been something!

Redoubtable- Formidable, eminent

-Wulke is great, a sad day when he gave up here amidst insults and other negativities; that he eventually got drawn into and bowed out.

Of course,the other fella didn't have a chance with such a great mind and repitoire that Wulke can extend.

In fact it was questioned whether Wulke had ever contributed anything, or really had any tree knowledge i think!!!!!!! 

Or, something like that,
:alien:


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## geofore (Nov 7, 2004)

*Wulke*

There is a difference between bowwing out and going on to other things more important to what you want to accomplish in life, and I would say Wulke went on to other things. I can't say he had nothing to offer as I was impressed with the tools he made to clean areas of included bark on trees to help the trees grow over the area to gain strength and holding power sooner. 
Murph, most owners of greenhouses could tell you more about the EPA & DER regs on their use. Greenhouses with tempeture, humidity and CO2 control to grow plants set up near perfect places for bugs and fungi that attack plants thus their need to know how to control pests or lose their livelyhood.


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## Guy Meilleur (Nov 7, 2004)

Whoa, that arb forum was founded by Doug Mellor; similar last name but no relation. (The site is still for sale) I could never convince Wulke that saws are not evil (though much sawing is), but it was good exercise trying. His arguments were well-reasoned, even when he was wrong. Never saw the de-inclusion tool, tho I looked on his site. Help, geofore?

I too wash trees, but do not "apply pesticides". The state laws governing these things can be interpreted different ways. I held a license in IL but never got one in NC.

No TGR's needed if right plant is in right place? a worthy ideal to strive for, but in many urban landscapes trees are better off if they grow less. I love pruning, but if TGR's give better results for the trees then it's time to put down the saw, and make Bob happy. The stuff may or may not be a magic bullet, depending. I wouldn't spray them with an Uzi, but shoot a single-shot rifle.


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## geofore (Nov 7, 2004)

*Wulke's tools*

He emailed me pics a year or two ago, I wanted a set and he said I should make my own from what he presented in the pics. I realize we may not have shared our ideas with this site at the time but Ramshorn was an invitation and you know where that thread went. Back then I would email my ideas, questions or directions on how to do things directly to the original poster rather than join in the free-for-all on the site. TreeSpyder chided me for that as some first time posters asked questions and then where not heard from again. I had been emailing them instructions on how take down the trees they faced and they emailed me back with a "thank you" after they got the trees down without incident following the instructions I provided. This left those on the site wondering what happened to them and did they ever get the trees down or hire someone to take them down. I thought they would continue to post but I was wrong. Some still lurk in the background, reading but not posting and I still email some. At times there is a bit of nonsense going on AS but there is enough good information to keep AS on my favorites list and keep me coming back.


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## arboromega (Nov 7, 2004)

*Re: national regs*



> [
> So in thinking about cambistat... I wonder if one needs a license to apply it??? Are there national regs or is it state by state? [/B]



the primary chemical in cambistat is paclobutrozol and i would think your state would require a license to apply. the manufacturer of cambistat is rainbow and on their website they claim that cambistat is a cheaper more efficient alternative to pruning. no crews, no chippers, no saws...one guy and the application equipment(dbh tape, ppe's measuring cups, water, and application container) i cannot say if their claim is true.

the way paclobutrazol works is to inhibit the shoot growth horemone gibrelin. before the chemical can work the tree or shrub must use up all of its current supply of gibrellin. so uptake may require a year or so. the result will be a gentel slowing of growth and an increase in fibrous root production. from the fibrou root production the tree is supposed to gain an increased drought tolerance and a healthier resistance to pests.


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## alanarbor (Nov 7, 2004)

*Re: national regs*



> _Originally posted by murphy4trees _
> *I hear in Pa. the law requires a pest app license to spray anything that kills anything else... that would include soap, though I like Reeds idea of "washing the trees"
> 
> So in thinking about cambistat... I wonder if one needs a license to apply it??? Are there national regs or is it state by state? *



Yes you do. It has an EPA registration number, which makes it subject to all the regulations that apply in PA. 

Basically if you are applying a material intended to control an insect or disease, and you're getting paid for it, you require a buisiness license (BU#) and a commerical applicator's license. Of course if your applying it on your own property feel free to apply whatever you want. The only items you can't purchase are those with a restricted use label, which would then require a commercial pesticide license.

With all that said, the results I've seen from cambistat uses so far has been pretty good. Waiting to see if it helps out with BLS


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## glens (Nov 7, 2004)

George,

I don't take public things private very often, but when I do, I admonish the person to follow up in the public forum.


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## Nickrosis (Nov 7, 2004)

This thread is going wrong in a couple of ways.



> _Originally posted by TreemanFJR _
> *He was a field manager and said he used them for trees underneath powerlines and some valuable trees on golf courses and such.*


This is one of the greatest uses of growth regulators.


> _Originally posted by TreemanFJR _
> *So their function is too inhibit primary growth(apical meristems) right? Does it promote secondary growth? If so, how much and is this a good thing for the root tips/ fibers in the micropores?*


Why do you say primary growth? And secondary growth? These are temporal differences, meaning that one comes first followed by the second. So on a tree, the spring growth has all the same steps as other growth and is subject to the same restraints by growth regulators. Over the period of years, the growth regulators wear off, but it's not a drop that occurs over a couple of weeks.

It's important to note that all trees respond very differently to paclobutrazol - therefore the different rates recommended. And still, some trees don't really respond.

Back to your question, it's understood that a gibberellin inhibitor will not directly change the number of cells created but rather the size of them since gibberellin is the hormone that induces elongation in cells.

The preliminary research to date shows that some peripheral benefits of growth regulators do exist, from root development to disease benefits, but we need more research to be conclusive.


> _Originally posted by Mike Maas _
> *My feeling is that it's a magic bullet.
> It's not some feel good measure that doesn't do a thing, like Mycorrizal fungi. It really shows promise.*


I agree it shows promise, but nothing is a magic bullet! If your goal is growth reduction, it's a sweet thing. If your goal is to make every tree you treat a beautiful, vibrant tree, you'll be left wanting. It all has to be done in concert - the pruning, the watering, the soil amendments, etc. 


> _Originally posted by Mike Maas _
> *The only problems are with dosing, pricing, and slow uptake. None of which are insurmountable. *


Dosing continues to need refinement. Pricing? We quote $6-8/inch DBH and have had great success selling and making money now that I don't take an hour to calculate the amount required! Slow uptake? What do you mean?


> _Originally posted by Guy Meilleur _
> *You can go to the Rainbow TSA forum on this site for answers. *


But we can talk about PGRs generally here, too. 


> _Originally posted by murphy4trees _
> *I hear in Pa. the law requires a pest app license to spray anything that kills anything else... ... I wonder if one needs a license to apply it??? Are there national regs or is it state by state? *


Yes, you need a pesticide license. There are both national and state regulations. The national regs say you have to be certified. The state regs spell out how to do that. Plus, states can tack on additional stipulations (like Advance Notice Registries - ugh - http://www.datcp.state.wi.us/arm/agriculture/pest-fert/pesticides/lndscp_reg.html)


> _Originally posted by Guy Meilleur _
> *No TGR's needed if right plant is in right place? a worthy ideal to strive for, but in many urban landscapes trees are better off if they grow less. I love pruning, but if TGR's give better results for the trees then it's time to put down the saw, and make Bob happy. The stuff may or may not be a magic bullet, depending. I wouldn't spray them with an Uzi, but shoot a single-shot rifle. *


Very true. And I like the metaphor of one shot at-a-time.


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## arboromega (Nov 7, 2004)

> _Originally posted by Nickrosis _
> 
> 
> It's important to note that all trees respond very differently to paclobutrazol - therefore the different rates recommended. And still, some trees don't really respond.
> ...



nick has correct my spelling...gibberellin, thanks 
regarding that some trees dont respond...this is wrong imo all trees will respond, but the company admits that cambistat use on some trees is still under research - you may be testing experimental rates yourself in the field.
as far as you calculations taking an hour? there is a rate list on the label for cambistat. were you caculating for species not on the list?
and for the mr maas' statement as to cambistat being a magic bullet i am inclined to agree...if it does to all it claims than it does appear as a too good to be true product.


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## TreemanFJR (Nov 7, 2004)

> _Originally posted by Nickrosis _
> *This is one of the greatest uses of growth regulators.
> Why do you say primary growth? And secondary growth? These are temporal differences, meaning that one comes first followed by the second. So on a tree, the spring growth has all the same steps as other growth and is subject to the same restraints by growth regulators. Over the period of years, the growth regulators wear off, but it's not a drop that occurs over a couple of weeks.
> *



Cell division in the apical meristems and subsequent elongation and maturation of the new cells produces primary growth. Secondary is the increase in girth in stems and roots. Carbon is first allocated for primary growth then secondary. From what's been said so far, slowing or stopping primary growth is the function of these inhibitors.


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## Nickrosis (Nov 7, 2004)

> _Originally posted by arboromega _
> *regarding that some trees dont respond...this is wrong imo all trees will respond*


I said some don't really respond. They acknowledge this on the rate card for certain species like spruces. We're trying it out.


> _Originally posted by arboromega _
> *you may be testing experimental rates yourself in the field.*


Yup. I talk to the Rainbow office regularly and know them all by name.  


> _Originally posted by arboromega _
> *as far as you calculations taking an hour? there is a rate list on the label for cambistat. were you caculating for species not on the list?*


I was making use of hyperbole. But it still takes me a while when I'm mixing up for a 5 acre property.


> _Originally posted by arboromega _
> *.if it does to all it claims than it does appear as a too good to be true product. *


But all it claims to do is reduce growth. Some other Rainbow publications reference the thicker leaves and denser roots.


> _Originally posted by TreemanFJR _
> *Secondary is the increase in girth in stems and roots.*


You're right. Good point.


> _Originally posted by TreemanFJR _
> *From what's been said so far, slowing or stopping primary growth is the function of these inhibitors. *


There is evidence that circumferential growth is reduced as well. Here's a link: http://www.rainbowscivance.com/PPT/Cambistat.htm
Go to slide 17.


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## TreemanFJR (Nov 8, 2004)

Good stuff Nick. Thanks for the link


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## Elmore (Nov 8, 2004)

*Atrimec*

Atrimec 
"Atrimec is a systemic plant growth regulator which works by blocking the plant hormones that stimulate growth. Applied as a foliar spray, it is absorbed by the leaves and translocated to the shoot tips where it interrupts apical dominance and temporarily stops shoot elongation. Spraying shrubs, bushes, trees and groundcovers not only reduces trimming and pruning labor by 50% but it also improves the appearance of landscape ornamentals. It promotes lateral branching giving plants a mor dense, fuller look. Hedge and shrubs that show irregular shapes including damage from pests and weather, can fill in lushly, even on the old wood, particularly if treated under optimum growing conditions."


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## Nickrosis (Nov 8, 2004)

Atrimec, _Dikegulac sodium_, must have a different mode of action. What is it?


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## arboromega (Nov 8, 2004)

> _Originally posted by Nickrosis _
> [But all it claims to do is reduce growth. Some other Rainbow publications reference the thicker leaves and denser roots.
> [/B]



not the full picture nick ... they also claim that cambistat creates a higher tolerance to insects and disease(this is a result of thicker leaves which produce more defensive chemicals). improve drought and heat resistance as well as increase FINE root density, not root growth in general. i email those guys too.

as far as atrimmec goes i saw a rep for pbi gordon, the manufacturer, speak and its seem like this product is used twice a year and is mostly intended for shrubs to maintain their shape following a trim job.


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## Nickrosis (Nov 9, 2004)

Right on with the speeling. Thar 2 m's. 

Here's PBI Gordon's info: http://www.pbigordon.com/Product_Pages_Turf/Atrimmec.htm

I like some of their products, but they're kind of a back-woods company compared to their peers. At any rate, they don't divulge how it works on their website, and I'm still wondering how it's supposed to suppress only apical dominance.

Does it work with auxin instead of gibberelins? That could be a possiblity....

Regarding Rainbow, I can understand what you mean about some misleading elements...and I agree to some extent. But the label's clear about being for plant growth regulation. Some of their other publications do get into off-label applications which Reed has talked about.


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## arboromega (Nov 9, 2004)

> _Originally posted by Nickrosis _
> At any rate, they don't divulge how it works on their website, and I'm still wondering how it's supposed to suppress only apical dominance.
> 
> Does it work with auxin instead of gibberelins? That could be a possiblity....
> ...



regarding pbigordon and atrimmec...
i tried to get that out of their rep. but he avoided the question with some corporate double talk. he was more intereste in pushing their broadleaf herbicides which seem to be their main gig.


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