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Posted by Kathleen10 z9b AZ (My Page) on
Sat, Jul 30, 05 at 12:48

Well, thought I'd put this out here and see how folks feel about this stuff. Living out on natural desert land, we have many paloverdes, mesquites and smaller greythorns and such. The mistletoe is pretty abundant growing in perhaps 50% of the trees including a few very large paloverdes. We have also planted many more trees like mexican and blue PVs, chilean mesquite, sweet acacias and so they are also getting mistletoe here and there. I try to trim out smaller branches with it but some larger branches also end up with it.

Last week's high winds took one of the larger mexican PVs and bursted one of the largest branches. What I mean is the branch being about 6" in diameter stayed on the tree. But at a point 8' above the ground where the branch was still arching upward in growth, it split vertically in half for about 18" just at the spot where a small bunch of mistletoe was growing. I am 99% sure the mistletoe weakened the branch and that's why it split. So if you can imagine, the branch now looks like a mascerated stem, like a giant decides to gnaw on it so it was a stringy mess, still holding together but with a gapping ripped hole in the vertical fibers over a foot long in that one section.

Of course the branch is now drooping almost to the ground. I think we will wait a few months to trim it off as it is at least 30% of the tree - hopefully the cooler months will mean less stress on it when losing that much.

OK so got offtrack describing, but the question is: what do the tree gurus say about mistletoe? Should we try to control this stuff where we can? How? I've read it MUST be cut out but sometimes that is not very feasible given location or the fact that the branch is a main one. Is it a losing battle? Does just knocking off the growing portion of mistletoe do any good at all? I realize it grows down into the flesh of the tree which is why this branch was weakened but can you stunt the mistletoes by keeping the growing portions knocked off in cases where you don't want to prune out a major branch it appears on or where it's 20' up in a very prickly PV?

I would appreciate any discussion on this topic.

Footnote: I do realize that mistletoe beeries are one of the primary sources of food for phainopepla (black cardinal like bird) so I wouldn't want to eliminate all mistletoe. I'm just trying to minimize the possibility of losing any of the big trees or losing huge branches like what just happened. Our native trees and almost all of those we've planted (now well established) do not get regular watering or much pruning outside what we need to do to walk/drive on our land. Some of the more prized ones might get an overnight drip soak 1 or 2x a year IF drought is particularly bad in a year. But by and large these are native and totally adapted trees.

Follow-Up Postings:

RE: Mistletoe...

The palo verde next door has mistletoe infestation; anyone know whether it likes Chinese elms? *chews nails cuz I like that tree so much*

I know that in southern California, in my previous life in the Forest Service, mistletoe had us crazy as it was infesting acre upon acre of trees on top of the drought, killing so many. Talk about potential fuel for fire! No wonder the San Bernardino burned up last year. But I digress...

Remember that it is a parasite, and that it doesn't do the tree a lick of good in the long run. Folks more knowledgeable on this will be sure to have better advice than I do, because I, for one, would cut and cut as much as I could.

But that's my probie opinion. :)


RE: Mistletoe...

Well, the real questions are: do you want the land to remain more or less natural desert? And is the level of mistletoe normal for this habitat? If the answer to both of those is "yes" then clearly you shouldn't do anything.

You'll have to decide what the answer to the first one (my bias would strongly be in favor of a "yes", but I'm not you), the second question probably needs someone with better knowledge of the ecology of the area than I have.

My impression in New Mexico so far is that at lower elevations having mistletoe in the majority of the trees is perfectly normal, but I haven't been here long and haven't spent too much time in southern Arizona. I kind of suspect that problems with mistletoe infestation, when they do occur, are most likely a downstream result of some sort of deeper problem (e.g., too little fire --> too dense growth --> lots of weakened trees that are easily killed by mistletoe), and if that's the case trying to get rid of the mistletoe isn't the solution. This would be essentially the tree analogue of what happens to deer when you get rid of predators--suddenly starvation (=drought) and disease (=mistletoe) can start causing massive fatalities, though they are not the true cause of the problem. That's just speculation on my part, but as a graduate student in biology I figure it's at least enlightened speculation.

Patrick Alexander

RE: Mistletoe...

Hmmmm.... not being a guru, I can only say what I think... ....

I'd knock the mistletoe off. It spreads, easily, and there's plenty of it about. The more you leave, the more you'll have - the birds who eat it also spread it. And you have, unfortunately, experienced the results. And left on its own, it can decimate your trees. Anyway, knocking it off does not kill it, it just sets it back - unless you're using some kind of systemic poison, uh, weed killer, it's soon part of the tree.

There's my .02!

And just a thought on the Palo Verde - I understand your fears of having the tree sunburn by pulling off so much, but I also have some concerns about leaving a jagged "wound" - you might want to try to clean up the cut as soon as you can - perhaps the bough can still stay leaning against the trunk?

HTH, good luck!

RE: Mistletoe...

er... what does a mistletoe looks like? any pics? thanks!

RE: Mistletoe...

"And left on its own, it can decimate your trees."

Unless there's something else wrong with the trees to weaken them, I'm not convinced that's the case.

Patrick Alexander

RE: Mistletoe...

Sure, but we've been experiencing drought for many years now, so many of our trees are stressed anyway. So, with that stressor along with other reports of people losing trees, I'd say my comment isn't necessarily an exaggeration. It won't happen overnight, for sure, but over a period of time it can lead to death. Especially as in Kathleen's case, the general weakening of the tree leaves it susceptible to other elements.

DesertH, mistletoe in Palo Verde trees looks much like a very dense growth patch, like kind of a strange growth of the tree itself.

The link below gives more info.


Here is a link that might be useful: U of A Extension on Mistletoe

RE: Mistletoe...

  • Posted by usha z8AZ,Nscottsdal (My Page) on
    Sun, Jul 31, 05 at 11:17

Thanks for the link PC.
Kathleen, I know what you mean about mistletoe. What I do is keep them in control. Once a year I take a rake..Knock off some of the real big ones...they will still grow back but won't take over the trees. I think too much of the mistle toe will damage the trees. Finding a right balance will help the trees and the birds.

RE: Mistletoe...

Thanks everyone. It's been a working weekend so I am just now reading the replies. Usha's idea of knocking some large ones down occasionally is what I am thinking and have a done just a bit of it over the many years here.

PC, thanks for reminding me that the long term drought has probably put my beautiful natural trees more or less in stress and more susceptible to mistletoes even while I sit here fat dumb and happy thinking they look just great and marveling that they seemingly thrive without additional watering. Ignorance is bliss - but I knew about parasitic mistletoe all along, just hadn't considered that more than one big whammy might be too much for some of these desert giants. A couple of my PVs have trunks 20 inches across...

To explain further, this land was natural desert when we got it 18 years ago -- no trimmed trees, nothing groomed or irrigated, just what grew here naturally. We haven't done much of anything to the existing plants in all that time except trim a few where we must have access (and we keep that to a bare minimum) and to take out a few fully deadwood branches from key spots close to our viewing places. We just don't irrigate the natives I guess because we're lulled into thinking they can survive anything -- after all they were here for decades before we showed up and never got pampered. The only stuff we really concentrate on watering are the things we've put in, both native plants to establish and grow them and a few non- native types around the living areas.

So, I guess it's the long handled rake and maybe the saw for a bit of damage control or should I say death prevention. I sure do not want to lose any of my wonderful trees. They may droop to the ground like bushes but they are tall trees in the desert world.

Thanks again for the discussion.

RE: Mistletoe...

Oh, so that's what on some of thre trees in the neighborhood. Thanks for sharing! I've it added to my list of things to watch out for ...

RE: Mistletoe...

I have seriously been wanting mistletoe for years and would love it if I could get some growing on my sweet acacia... or maybe I'll plant more palo verdes-? I'll need to research how one might accomplish such a thing. In the meantime, can someone bring some mistletoe *clumps* to the plant swap for me?

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