Drought: Short and Long Term Effects

Drought: Short and Long Term Effects

Part of Ep. 2103 Problem Solvers

Drought does far more than turn our lawns brown and crunchy. Severe drought has far-reaching impacts that can affect full-grown trees for years to come. Learn what to water, and what not to water, during a drought.

Premiere date: May 15, 2013

TRANSCRIPT+
Wisc Gardener Transcript: 

Shelley Ryan:

We're here to focus on drought. Now that may seem kind of silly when everything around us is lush and green, but if you look above me, this pagoda dogwood is showing curling leaves, which is a sign of stress from a recent drought. So, just because things are green, don't be fooled into complacency. And I am with Lisa Johnson and she is the Dane County UW Extension Horticulture Educator. And, Lisa, we have kind of two topics to cover with drought the current affects and then, surprisingly and more worrisome, the far reaching affects of drought. So, current affects include things like the curling leaves, what else? Well, obviously dead grass.

 

Lisa Johnson:

Right, early fall color, dieback. Yes, certainly the dead grass. Any of that. But the far reaching affects we're going to see on our woody plants - our trees and our shrubs. We're going to see a lot more attacks by borers. We're going to see spring dieback. We're going to see any number of diseases that normally wouldn't be such a problem becoming a problem one, two, three years into the future.

 

Shelley Ryan:

So, well, we had a drought of historic proportion in 2012. So you're saying one, two, three years after that we're going to be having problems with even mature trees?

 

Lisa Johnson:

That's correct, yeah.

 

Shelley Ryan:

And give us some examples of things to look out for then.

 

Lisa Johnson:

Okay. For things immediately the next spring after a drought you might still see some dieback that occurred over the winter.

 

Shelley Ryan:

Okay.

 

Lisa Johnson:

Particularly on conifers, you might see loss of needles. You might see purpling needles. There's also a beetle called an ips beetle that is a stress related insect that you will see on conifers, on our oak trees. There's two line chestnut borer. And this white paper birch that I'm sitting next to, unfortunately is the victim of both drought and the bronze birch borer. So something like that would be very common to be seeing after a drought.

 

Shelley Ryan:

Well and this one's a little too late to save.

 

Lisa Johnson:

I'm afraid this one's gone.

 

Shelley Ryan:

Toast. But part of the reason it died so quickly is the stress from a drought in previous years.

 

Lisa Johnson:

Correct.

 

Shelley Ryan:

Okay. So and this can also happen to viburnums.

 

Lisa Johnson:

Yeah, the viburnum borer. When you start seeing die back, look at the base to make sure that you're not seeing holes and that saw-dusty material we call frass. That's a good sign that you have viburnum borers which will become worse after the viburnum's undergone some stress.

 

Shelley Ryan:

So basically the stress from drought makes the tree susceptible to damage from insects and diseases for years to come.

 

Lisa Johnson:

Exactly.

Shelley Ryan:

So, and you've got another example, in fact, from pagoda dogwood which is the same tree behind me that has curled leaves.

 

Lisa Johnson:

Right, yeah. And there's a little die back on it right now and this orange material right here, this is a disease that's called Golden Canker. And we do see some of it in years that we have regular moisture, but we're going to be seeing more of it as a result of the stress caused by the 2012 drought.

 

Shelley Ryan:

Okay, so again fungal diseases are going to skyrocket.

 

Lisa Johnson:

Right. And soil borne diseases that attack compromised root systems like verticillium wilt which causes die back. I expect we'll be seeing more of that. We'll probably be seeing more oak wilt, which is vectored by insects that will attack stressed trees. So we may be seeing more of that as well.

 

Shelley Ryan:

What can we do then in years after the drought, especially I think about full sized trees? You know I'm not so worried about my lawn. I can reseed that fairly easily.

 

Lisa Johnson:

Right.

 

Shelley Ryan:

But full sized trees can be a life long investment. What can we do in years after a drought when we see these symptoms?

 

Lisa Johnson:

Well, even during the drought years you should water even though it seems like a large tree should be able to take care of itself. It's not the case. Most of the roots are going to be in the top twelve inches and when we're several inches behind in our water deficit, we do need to water. So, for example, a tree such as the maple behind us, you should probably put down about 60 gallons of water in a 10 x 10 area around the circumference of the trunk in order to make up for some of that deficit. You want to put down about an inch of water a week and that 60 gallons in a 10 x 10 area would cover that. 

 

Shelley Ryan:

So people who think, don't just water at the trunk.

 

Lisa Johnson:

No, a watering can isn't going to do it.

 

Shelley Ryan:

Okay. So a sprinkler or a drip hose or something.

 

Lisa Johnson:

Right.

 

Shelley Ryan:

And we're watering long after we think the drought has ended. We're watering into winter.

 

Lisa Johnson:

Right, just about. Into late fall certainly, especially if mother nature doesn't cooperate and give us an inch of water a week.

 

Shelley Ryan:

So a rain gauge might be kind of handy too because if it rains you don't need to do it.

 

Lisa Johnson:

Yes, exactly.

 

Shelley Ryan:

And so water basically until the ground freezes.

 

Lisa Johnson:

Yep.

 

Shelley Ryan:

And then in the following years, if we see signs of some of these borers or insects or disease, call you?

 

Lisa Johnson:

Call your County Extension agent.

 

Shelley Ryan:

Okay.

 

Lisa Johnson:

And get that identified, whether it's caused by an insect or whether it's caused by a disease, you may still be able to save that tree, especially if you identify the problem early enough.

 

Shelley Ryan:

Okay, and a tree is worth a lot.

 

Lisa Johnson:

A tree is worth a lot.

 

Shelley Ryan:

Okay. Thank you.

 

Lisa Johnson:

Thank you, Shelley. 

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