Sycamore and London Plane Tree Problems Oh My

Taun Beddes 0:00

Hello everyone, I'm with Savannah Peterson, a Utah State University Extension Horticulturist, based in the Utah County Office. She's been spending quite a bit of time doing diagnostics. And we've had a number of calls on sycamore trees. And I'm wondering what's going on Savannah? How are you doing?

Savannah 0:17

I'm doing great.

Taun Beddes 0:18

So first off, how do you identify a sycamore tree?

Savannah 0:22

Sycamores are pretty easy to identify. They have interesting bark that'll peel into different colors naturally, and it looks kind of like a mosaic. Their leaves are similar to a maple but one way to tell them apart is that Sycamores have a round seat head and maples have the little samaras that'll float down and spin

Taun Beddes 0:43

The little helicopter.

Savannah 0:44

Yes.

Taun Beddes 0:45

So Sycamores have been struggling over the last several years. And there's actually several reasons why but you narrow down three primary things. And one of them was a disease called anthracnose. What can you tell us about anthracnose?

Savannah 1:01

It's a pretty common disease on a lot of different kinds of plants. It's a fungal infection and on Sycamore anthracnose, specifically, it affects mostly the leaves and trunk. Pretty common identifier of anthracnose is that on the leaves, it'll show up in dark sunken patches that are pretty angular in shape. It'll also cause some wilting. So you might think it's something like frost damage, which is what you need to look for the other symptoms as well.

Taun Beddes 1:28

If you're looking at a sycamore or a London plain tree from far back, can you readily tell if it has anthracnose in it?

Savannah 1:36

Y ou need to compare it from a little closer up to be sure, but some of the things that will give it away are some wounds on trees, they're called cankers. It looks kind of like the wood has split and then sunk in on itself. You'll also see some twigs die back, leaf dropped a little bit some browning leaves wilt, all of those will be good indicators that that's a place to start.

Taun Beddes 1:59

So what is the life cycle of Sycamore anthracnose ?

Savannah 2:02

it starts as a spore. And it'll overwinter in the buds and on fallen leaves from previously infected years. And then in cool wet springs, especially it'll come out and mostly attack younger growth at first. And then as it progresses and matures, it'll start producing fruiting bodies, which will then after a while, produce the spores again and start the cycle over.

Taun Beddes 2:28

Why is it important to know the life cycle?

Savannah 2:31

it's important to know the life cycle because it'll help you predict how prevalent the disease is going to be that year. And the best time to treat for it. If you know that the leaves are going to maybe harbor some spores for the next year, it's important to rake out all of the leaves the year before so that that won't be a source of infection.

Taun Beddes 2:50

We had really cool wet springs up until a couple of years ago. And how did that impact sycamore trees,

Savannah 2:58

Since that is the perfect environment for that fungus to spread and grow. The more years you have, it will kind of compound the amount of disease in the area. So if you have more spores, more trees will get sick. And they'll have more years of repeated infection which will make them sick or in the long run.

Taun Beddes 3:18

So normally with our dry springs like we've historically had has this been a problematic disease?

Savannah 3:25

It usually isn't. In fact, since we've had drier springs these last couple of years, you won't see anthracnose as much right now, it'll still be there a little bit but it's toned down.

Taun Beddes 3:36

When we talk about disease prevention, we should bring up non chemical controls first. So what would you recommend to people who are trying to control this disease in their yard?

Savannah 3:46

One of them is again rake the leaves in the fall so that leaves won't harbor any spores for the next year. Keep your trees healthy, adequate water and fertilizer go a long way. There'll be less susceptible to most diseases. If you do that. Within anthracnose, you should remove any clearly infected tissue.

Taun Beddes 4:03

It's important to focus on non chemical options with any disease or past but sometimes you do need to spray. So what are some options along these lines?

Savannah 4:14

Most of the options for treating anthracnose chemically are preventative measures, you will want to start treating in the spring right when the buds start to break and the leaves are starting to emerge. That's when the tree will be most susceptible and right before the fungus gets a good foothold. The most common one is clorothalinol. It's found in Dacinol and some other things but that's a pretty good tested treatment for anthrax knows there are some organic options like the Bordeaux mixture, but they're not quite as common or as easy to apply.

Taun Beddes 4:47

As with anything when you use these fungicides. Make sure and follow the label because even though like that Bordueax mix is considered organic. It can actually be pretty toxic if you don't use it correctly. So just that friendly reminder, follow the label all the time. So the next thing you're finding in Sycamore is an insect called Sycamore scale. Tell us about that.

Savannah 5:11

I think we've mentioned other scales on the podcast before, they're a teeny tiny insect with sycamore skills, you can't even see him with a naked eye, you need a microscope or a hand lens. These are actually native to warmer areas. But they've been working their way up the Wasatch Front past decade or so. And you can find them in most places in Utah.

Taun Beddes 5:30

If you're inspecting your own trees, what would you look for to actually identify them in your tree?

Savannah 5:36

they're pretty easy to identify, actually, they have really distinctive circular feeding marks on the leaves, it'll show up as yellow first, and then the spots will start to turn brown. Another thing you can do is since Sycamore bark can peel off pretty easily, you can peel off a couple of chunks and see if you can see a little cottony mass underneath the bark skills. Those are usually the sycamore scale cases where the insects come out when they hatch. And since that's the start of the lifecycle, once the larva hatch, they move out of the bark and move their way up to new foliage. And they'll feed for a while. And then once they start growing, they'll move back down into the bark to reproduce, and they'll have about three to five generations a year.

Taun Beddes 6:24

So how do you monitor for Sycamore scale,

Savannah 6:27

this is a pretty hard thing to do. Because once you start seeing the damage, the scale insects themselves have already moved on to a different part of the tree. Even if you try that like double sided tape trick like you would with other scales, these are so hard to see that that's not really a good way to do it. Another problem is that since they have three to five generations a year, it's really hard to know when they're going to be on the tree if you don't get them the first generation in early spring. That's why it's so important to do preventative control with these, instead of waiting until you see damage. So you want to start taking care of the tree when the first generation is possibly going to be there so that they don't become a huge problem later. Just like within threat knows the best time to start that prep work is at budbreak when the leaves are just starting to emerge, that's the best time to know that they're probably coming out of the bark and about to get to your leaves. So you'd want to start then spraying something like an insecticidal soap or horticultural oil. Those are contact pesticides. So they work really well if you can spray them at the right time. So if you know that bud break is the time that they're going to be there. That is the time to spray. There are some other things like pyrethroids and carbaryl. That will also work well. But there's even a study by UC Davis that showed that out of a bunch of pesticides, two to 3%, horticultural oil was the most effective on these scales.

Taun Beddes 7:56

So what happens if you miss that timing at budbreak?

Savannah 8:00

It's pretty hard to predict later generations just because of like temperature fluctuations and the amount of food that they have available. So if you don't get the first one, it'll be super hard to know when it will be appropriate to spray later, especially since those contact herbicides are the most effective, you have to know exactly that the bugs are there to be able to spray or else you're just wasting your money.

Taun Beddes 8:24

And so if all else fails, what other options do you have?

Savannah 8:27

A systemic pesticide called imidacloprid, you put it on the soil, and then it'll work its way up the tree and make the leaf toxic. So the bugs won't want to live there. But that hasn't been heavily studied for Sycamore scale, specifically, scale is listed as pest to be treated with the medical ibrid. But there's no data on that kind of scale specifically. So you can try it. And it'll hopefully help a little bit.

Taun Beddes 8:53

So do you have anything else on Sycamore scale?

Savannah 8:56

No, that's pretty much the basics there.

Taun Beddes 9:00

So there's a third pest that you wanted to talk about today. And what was that?

Savannah 9:04

It's the sycamore plant bug. And at least for this year, it's the most common one that I've seen.

Taun Beddes 9:10

So describe the sycamore plant bug.

Savannah 9:13

It's decently easy to identify. It looks like a couple other bugs. So it has a similar shape to boxelder bugs. It's quite a bit smaller. But it's a little more yellow Brown with white wings and darker patches on their abdomen and the tip of their wings. So not the black and bright orange color you'd usually see. The nymphs are a little bigger than aphids, and they're a similar green color. So it's kind of hard to tell with those two, but things you can look out for are darker legs, and eyes and antenna. that's those are pretty good indicators that that's the bug that you have.

Taun Beddes 9:52

So are you going to need a magnifying glass to identify them?

Savannah 9:56

They're hard to spot because as nymphs, they're close to the color of the leaves but you can see with the naked eye.

Taun Beddes: 10:03

So what do those Sycamore plant bugs actually do to sycamore trees?

Savannah: 10:07

they have sucking mouthparts and they will physically suck out the sap from the leaves. And they'll leave the leaves looking a little muddled and chlorotic soft, diffuse yellow patches, unlike scale, which would have the harder round edges, and when tricky part is that to identify the problem once they've sucked out the sap, the damaged tissue can turn brown, which will make it look a little bit like scale, but the brown parts will fall out of the leaves. And that can even make it look like a chewing insect was responsible because the leaves will start to look a little ragged and have holes in them. If you see the ragged leaves with holes in them, especially younger leaves, and the mottled yellow chlorosis that's a pretty good indicator that that is sick more plant bug

Taun Beddes: 10:58

Are sycamore plant bugs found nationally.

Savannah: 11:01

Yes, but the more common pest you'll find in other areas is the sycamore lace bug. It's honestly kind of hard to find information on Sycamore plant bug, because lace bugs are such a huge problem elsewhere. So you kind of have to dig for it.

Taun Beddes: 11:17

What did you search to actually find information about it?

Savannah: 11:20

One helpful thing I found is if you at least for us and this is a plug if you type in USU blank, so I select USU Sycamore plant bug that'll usually show up with more relevant information to your areas specifically. Another way that I found it was searching the scientific name. This is me trying to pronounce it but play Plagiognathus albeatus, I'll spell it just in case my pronunciation is really rough. But it's P l a g i o g n a t h u s and then the species name is a l b e a t u s. And that will give you specific results that will be the quickest way to get exactly what you want.

Taun Beddes: 12:02

Because when I've searched Sycamore plant bug 99.9% of the time, Sycamore lace bug comes up and they're completely different species with completely different damage is the sycamore plant bug fatal to Sycamore and London plain trees?

Savannah: 12:20

No, it's almost always just a cosmetic problem, it does make your tree look pretty rough, but it's not going to do a lot of damage to the actual health of your tree. After they feed again, like I said, the leaves look really ragged. But again, it doesn't do significant damage.

Taun Beddes: 12:37

Let's say that people want to try to control it, what's their best option,

Savannah: 12:42

it's actually pretty easy to take care of these without using any kind of chemicals. One quick way to do it is to get a hose with a pretty high power stream of water. You don't want to use like a pressure washer, because that'll rip the leaves off your tree. But just spray your leaves that look like they've been infected. And it'll knock the bugs and the nymphs right off pretty effectively. Another thing you could do is try another horticultural oil or insecticidal soap carbaryl will take them out too. But honestly, they're not that big of a problem. And water should be your first line of defense. If it gets really bad, you could try those other options.

Taun Beddes: 13:23

That's a lot of information to unpack. And so we probably should do a recap. So from all of this, what do you want listeners to understand?

Savannah: 13:32

just to recap the symptoms anthracnose will show up as wilting and brown angular patches scale will show up as damaged smaller leaves, sometimes cankers and small circular spots on the leaves. Plant bugs will usually have that mottled the yellow chlorosis throughout the leaves, or the ragged holes. So those are the best ways to identify each of these three things. Both scale and plant bugs can be treated with carbaryl insecticidal soap and horticultural oil. So that's nice that you just have to look for one of those chemicals for both problems. And with treatment. All of these should be treated starting at budbreak.

Taun Beddes: 14:12

That includes anthracnose?

Savannah: 14:13

Yeah, you want to get it started before you'll see damage because once it's there, once you notice it, it's been there for a while.

Taun Beddes: 14:22

Sycamore and London plane tree are among the largest shade trees we grow in Utah. What is your advice on if it's actually practical for you to self treat your trees.

Savannah: 14:34

If your trees is smaller than about 25 feet, it's probably fine for a homeowner to treat their own trees. If it's any bigger than that it'll hurt. It'll be hard to do effectively. So you'll want to hire a professional like a certified arborist. And one thing is that if it's a severe problem anyways, they're licensed to use a little heavier treatments and they'll be able to get up into the tops of your trees to take care of stuff up there.

Taun Beddes: 15:00

Especially with Sycamore anthracnose, that isn't a once and done treatment. And if you want to keep the trees, how many years do you think it will be before you might get it under control?

Savannah: 15:12

It's hard to say because that disease specifically depends so much on spring weather that you can't know for sure if it'll be gone in a couple years or a year or a decade. You know, it depends. So you have to be constantly looking out for conditions

Taun Beddes: 15:29

For Sycamore, anthrax knows that really sounds like folks could be in for the long haul. And so if people do choose to treat their trees on their own with pesticides, what are your safety recommendations?

Savannah: 15:41

And these will apply for any pesticides you use, even for the other two bugs that we mentioned. Basic pesticide safety is read the label, read the label, read the label. In fact, read it all the way through before you start doing anything. If your pesticide mentions anything about PPE or personal protective equipment, even if that's just like gloves, listen to it's there for a reason. Another thing to do is try to use the non chemical or safest option first, don't just start off with the harshest chemical, because oftentimes, that's not cost effective, and it's more dangerous. So if you could start with something simpler, that'll get the job done.

Taun Beddes: 16:24

Oh, that sounds great. Well, we greatly appreciate your time, and we hope to see everyone next week. The homegrown horticulture Podcast is a production of Utah State University Extension. Show intro and outro music was composed by Savannah Peterson, a Utah State University Extension Horticulturist, and talented musician. Thank you again for listening

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