Fire Blight - What is it, How to Control & What Trees are Affected?

 Eric Countryman from Davey's East Pittsburgh office talks about fire blight and other bacterial diseases that can impact your trees.

In this episode we cover:  

• What is fire blight (1:06)
• What fire blight looks like (1:39)
• When fire blight is most prevalent (2:13)
• Treating fire blight (2:55)
• How to prevent fire blight (4:35)
• How arborists handle fire blight (6:52)
• Off the beaten path trees to plant (8:22)
• Black knot disease (10:57)
• Apple scab disease (13:02)
• Using fertilizer to help tree health (15:51)
• Eric's experience with tree diseases this season (17:21)

To find your local Davey office, check out our find a local office page to search by zip code.  

To learn more about fire blight, read our blog Why ‘Bradford’ Callery Pear Tree Leaves Are Brown, Black or Falling Off.

Connect with Davey Tree on social media:
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Connect with Doug Oster at www.dougoster.com. 

Have topics you'd like us to cover on the podcast? Email us at podcasts@davey.com. We want to hear from you!  

Transcript

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Doug: Welcome to the Davey Tree Expert Company's podcast, Talking Trees. I'm your host, Doug Oster. Each week our expert arborists share advice on seasonal tree care, how to make your trees thrive, arborists favorite trees, and much, much more. Tune in every Thursday to learn more because here at the Talking Trees podcast, we know trees are the answer. He was the first guest ever on the Talking Trees podcast, and since then, has been on many times. Eric Countryman is a district manager for the East Pittsburgh office of the Davey Tree Expert Company. Eric and I also work together on a local radio show. Eric, welcome back to the show.

Eric: Thanks, Doug. I think we're on the radio again this Sunday I think.

Doug: I was going to check with you on that. Make sure you're going to get up early.

Eric: Oh yes, I got the alarm set.

Doug: All right. Today's topic is fire blight. I don't know a lot about it except that when I hear that word, it sounds devastating. Am I right in thinking that's a really bad one to get?

Eric: It's a very bad disease. It is actually a bacterial infection. You see a lot in pear trees, apple trees, quince, cotoneaster, anything in that Rosaceae family. It's very common in those. I think in Pittsburgh here and in this area, we see it predominantly in Bradford pears and Callery pears, so in an ornamental setting, but it is also very devastating to apple and pear crops in an agricultural setting.

Doug: What does it look like?

Eric: It presents very quickly. You can see it when you're even driving down the road, but you'll see a Bradford pear that looks, in every other way perfectly normal, except you'll see ends that are all dead, shrunken, and have what's called a shepherd's hook, where you see the end start to curl around like a shepherd's hook. It flags like that and it's very obvious that that's fire blight. There's really not much else that causes that.

Doug: Is there any time of the year when it's more prevalent than others when you start to see it or could you see it at any point in the season?

Eric: It presents in the late spring because it starts from an infection of the flower. The tree will open up its flowers in the first one to three days of that flower opening through water splashing or through pollinators. This bacteria is transferred from cankers and sores on the tree into those flowers, which then go back into the stems. The infection progresses in the few weeks after, you start seeing the shepherd's hooks appear.

Doug: Prognosis when we start to see that on a tree?

Eric: If you've got one or two branches that you're seeing that are flagging, you grab your pruners, you sterilize with 10% bleach solution, and you get as far below the infection as you can. If you can go 2 feet, 3 feet, get as far below as you can, and prune it out. Get it away from that tree or any trees like it and dispose of that infected material. If it's presenting all over the tree, it's not really practical. Probably at that point, the sores and the bacteria have infected so far deep into the wood that you're not going to be able to pull it out.

Doug: I know it's a case-by-case basis, but let's say you come upon an apple tree, you see a little bit of fire blight, would you want to take the whole limb off, go all the way back to the trunk just to be sure or I guess it depends on a tree?

Eric: It depends on the tree. It depends how much you're seeing the infection. You can also walk, look at it. Sometimes you can see cankers on the branch below where the infection is and try to get, like I said, 12, 18 inches even below that. You have to whack half the tree off, but you want to get it below. Then again, you make one cut, you sterilize. If you have to make two cuts, you sterilize in between. You do not want to spread this around. Then when you're finished, you sterilize so you don't take it to another tree.

Doug: Anything preventative we can do?

Eric: In an agricultural setting, what they say, and again, you can only do so much because of the rain, it can be a problem, but in those early days of flowering, don't overhead water. Again, we don't overhead water our trees, but it does in an agricultural setting. It can be different in an ornamental setting. There are some limited use of a copper sulfate based fungicide that can try to manage or suppress the extended activity of the disease, but it's not going to cure.

There's no cure whatsoever. If you have a heavily infected tree, but you've got three or four more, sometimes these pears are planted in a row, get the really bad one out totally and get it away. If you leave the bad one and keep spraying all of them, you're never going to have a chance of getting ahead of it.

Doug: From doing this podcast, I know how much arborists hate those pear trees.

Eric: They're not good quality here in Pennsylvania. I believe they're now on the invasive species, do not plant, do not buy list.

Doug: Yet they're still going into developments every day, I think.

Eric: I see that mostly in an ornamental context in those ornamental pears, but it is a problem in apple trees, it's a problem in hawthorns. It can be in all of those family, it's just pear seems to be one of the most susceptible to it.

Doug: Could I buy a tree at a nursery and not know it, and it would be infected, and then when I plant it, I start to see fire blight?

Eric: I guess that's possible. It's not something that's carried around in the root system or in the wood, it really is spread in through the flowers. It can infect, I guess, through open wounds or the stromata, but that's not the primary vector. The vector is splashing spores from some oozing wounds that happen at that time of the year or pollinators who are attracted to the ooze from the sores, and then that take it in and spread it from flower to flower.

Doug: Tell me a little bit about your bedside manner when you have to show up at a property and you see fire blight really bad on a tree, and you've got to break the news that, "Hey, if you want to save these other trees that are close by, this one has to go and it has to go now."

Eric: Direct and truthful is usually the best way. The other thing I like to do is don't just leave it on your word, Davey has good literature that's scientifically based. There's also extension services from Penn State, or Ohio State, or Cornell, or all around the country that have research, one page and so on, so people know you're not just snowing them over and trying to cut the trees down. Then being honest about the cost of the management. The fungicide treatments are hundreds of dollars at a time, you usually need multiple of them. You need to spray before the flower, after the flower.

It has to be done every single year and timing is very difficult to get right. The practicality of it sometimes in the financial headache of it gets people to think, "Maybe I should try something else." Then the best thing is put your arborist hat on and make suggestions for a replacement for that beautiful spring flowering tree that they've just always loved, it's the sign of spring. What are some different options that are in a different family that aren't going to have these kind of problems?

Doug: We've talked about this before too, but I always like to pick your brain a little bit. Of course, the mantra is right plant for the right place, but tell me a couple of your off the beaten path trees again.

Eric: I had actually just had this conversation, one I've been pushing for the last couple of years is black gums here in Pennsylvania. They're just a native tree, hardwood, pretty hardy, easy-going, don't have a lot of problems, and they're not over planted like red maples. The other thing I actually remembered and stumbled upon is American hornbeam or hop hornbeams. I think what's cool about those is they don't hold their leaves in the winter, but they get really tan almost like a beech tree out in the woods can hold. It gives a winter interest, which I always find a little interesting and again natives, which I just like better.

Doug: Does a hop hornbeam have a flower that looks like a hop flower or am I thinking of another tree?

Eric: That's right. They're two different trees. There's the American hornbeam and the hop hornbeam, but both of them are ones that I like.

Doug: I saw one on the lake, and I threw my fishing lure that direction. Now, the hop hornbeam has the fishing lure. Let's go back to black gum because I know it's a favorite of many arborists because of that amazing fall color. What size do you see them at because there's one locally here at the Pittsburgh Botanic Garden that is huge, that is over 30 feet tall? I guess I don't usually see them that big. Is that how in the native forest, they get that big?

Eric: They are sized like maple, oak, beech-type family. If native and out in the woods, they can get that large. It's just that they've not been planted ornamentally very much. You don't see them in yards where they've had the time to get that large, but they absolutely can. I think people are sick of the same old Autumn Blaze or October Glory maple in everyone's front yard. This is a great option that's not going to get tulip poplar huge or sycamore messy, it's just a different thing. Then it'll be a different spot of color, especially in suburban neighborhoods where things can be really matchy-matchy.

Doug: When that thing does change in the fall, is it bright or a dark red, or what is it?

Eric: More dark red purple from what I've seen.

Doug: Wow, cool. There's another disease that I think it's like fire blight, it's a black knot or something. Is that the right term for that?

Eric: It's a black knot disease. Again, it's not fungal, viral bacteria, I think, work together. Really what it presents as is a black big nodule that looks like it's completely surrounding branches. It'll be on your smaller branches at the ends, but it will infect back into larger wood. Then from that knot basically, it chokes that branch off, and then it dies from the knot forward.

Doug: I saw a small orchard, and I think it was the pear trees that had it bad. Can you prune in that situation or if it's really bad, it's like the fire blight?

Eric: If it's really bad, it's like the fire blight, and you need to take it out. It's actually really hard to prune it out. It's actually, I think, even harder than fire blight because you notice the fire blight because it really flags out on the end of the branches. You see this hanging clump of brown things and you go, "Oh, what's that? That's a thing, I should take care of that." The black knot could be really small and you don't notice until it's really gotten through the tree, and then you need to prune below it quite far to get the infection out.

A lot of people make the mistake of like, "Oh, I think I can do it." Then they start clipping, clipping, clipping, and then the next year, it's just goes boom and explodes because they've not got it low enough, they've not been sterilizing their tools, they've cut clean branches, and then it's just so much worse than it was.

Doug: If you did have a small orchard and only one tree had that black knot, is it the same thing with fire blight, you remove the whole tree to try and save the others?

Eric: Absolutely. As quick as you can, cut it down, pull it out, and get it away. Don't chip it up and leave it close, get the debris as far away as possible or burn it offsite.

Doug: This year with my flowering crab apple, it has not defoliated yet where it normally would defoliate. Tell me that fungal disease again, that happens on crab apples.

Eric: The very common is apple scab disease. It is different, but in a lot of ways culturally similar to a cedar-apple rust disease. They're both fungal diseases that invade these same family of plants again. In the early spring, just as the leaf buds are elongating and starting to open up and before the cuticle layer of the leaf is formed, so the harder outer coating of the leaf has got to set yet, spores land on that, they get attached, and then the fungus grows. Then it does form that cuticle layer and locks that fungus in. Then once that happens, they're infected and they won't make it through the summer, they'll defoliate.

Doug: Treatment should be some kind of fungicide before you see signs of damage. Is that the way to do it or?

Eric: The difference between these apple scab or rust problems is that they are manageable and does not really lead to tree death. It can lead to an unhealthy tree because they're defoliating early, the leaves aren't working at their most highest potential, but it never really seemed one to just totally kill a tree. Fungicide applications are necessary and do work, but again, it's right at leaf pop, usually two to three weeks after, then two to three weeks more. You want to fertilize so the tree is good and healthy because healthy trees can fight this infection off a little better. Culturally, the big things with these diseases is your leaf cleanup needs to be thorough and done before spring.

A lot of people wait, and I'm just as guilty, wait till that got cold in the winter, "It's not going to hurt anything, I'll blow the beds out come spring." You need to do it before things start to leaf out and flower because those old leaves hold the spores, raindrops hit it, splash them back up, and you get an infection cycle going. The other thing is that it's a shared disease between the cedar and juniper family with back into the Rosaceae family, and you need to remove one of them.

A lot of times people have this ugly little blue juniper shrub, and it's planted near their crab apple, and both look pretty crummy. You're like, "Well, get rid of that ugly shrub." You've cut that disease cycle down and it's almost natural you'll get a lot more control over that disease.

Doug: You've already touched on it, but I want to talk again about it. With this tree, the example in my property, it's been here forever. It defoliates here and there. That is definitely one that would be a great candidate to fertilize. Talk about how you get that fertilizer to the right place in the root zone.

Eric: Deep root fertilization is the best way to do it. At Davey, we use a product called Arbor Green. It is a suspended powder in water, and we shoot it into the ground using an injector under pressure with water. You're not only getting a bit of mild aeration, but you're injecting it in water. We recommend it about a half gallon every 3 feet in a grid system under the drip zone line, so the canopies of the trees.

The other main thing about it is you want it to be as slow release as you can make it. I think Arbor Green is between, in our climate, and area, and soil type, 12 to 14 months. That way the tree is just naturally absorbing more nitrogen, phosphorus, potassium. It also helps give better channels to bring in the other micronutrients, iron, and manganese, and all of that that trees need as well.

Doug: In this Mid-Atlantic area that we work in, what has this season been like as far as diseases are concerned? What have you seen?

Eric: We had a pretty mild winter. There was a big cold snap here around Christmas, but otherwise, it was pretty mild. Then we had a very dry spring. Where we usually would have a lot of water, a lot of splashing around when things were flowering, it actually was 70 and sunny for, I think it was 20 sun days here in Pittsburgh. Maybe 20 sun days of sun the entire year, but in a row is pretty rare. I've not seen the disease pressure be outrageous. Anthracnose and sycamores have been a little high, but it's the insects this year that's bad. The mild winter and the dryness just really ramped up insect pressure.

Doug: I'm going to assume right off the bat, aphids because all I've been talking to people about is aphids on everything. I actually got a question today where somebody had a Norway maple, had aphids really bad. The ladybugs came and took care of the aphids, but they wondered if they should still spray. I was saying, "Well, if you've got ladybugs eating them, they're not going to eat everything. They'll save something for the next generation." I know you'd have to look at the tree, but a Norway maple with aphids, is that a big deal?

Eric: I think it's the location of the Norway maple. If it's out in my yard, I probably wouldn't care. The thing is that aphids release a honeydew, and that drips. If it's over your patio, and everything turns black the moment after you clean it, and it's filthy all the time, that's a whole different set of circumstances than if it's just out in the yard and the grass is a little sticky or whatever. I'll say today, not that I haven't seen it before, but here in Pittsburgh, spotted lanternfly has gone completely crazy. I was looking at someone's wisteria vine this morning, and they were literally on every single strand, just thick on it. They're going to be gross and problematic here coming up soon too.

Doug: I think for us here, when the spotted lanternfly does get to adult stage, that it's going to get worse before it gets better. I'm answering the same questions and seeing the same thing, just certain plants. I know they can attack a lot of plants, but boy, they love grapes. They've been on my roses, hops, so as long as they stay off my tomatoes and peppers, I think I'm going to be okay.

Eric: Ailanthus trees, they love. There's a lot of varieties, but there's always the special ones. At this point, they're just everywhere. They were crawling up the side of my house last night.

Doug: Let's hope that nature takes charge of this and balances this out in the next couple seasons. It usually does, but we'll see what happens. Eric, great stuff as always. I sure appreciate your time. We will be talking to you again on the radio, and I'm sure we'll be back talking to you again here on the podcast. Thank you.

Eric: Good to talk to you, Doug. Thanks.

Doug: It's always great to catch up with Eric, that's for sure. Now, tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I am your host, Doug Oster. Do me a big favor, subscribe to the podcast so you'll never miss one of these shows. Next week, I can't wait, it's all about caterpillars. I think you're going to be very surprised about what we learn in that show. Have an idea for an episode or maybe a comment? Send me an email to podcasts@davey.com. That's, P-O-D-C-A-S-T-S@D-A-V-E-Y.com. As always, we like to remind you on the Talking Trees podcast, trees are the answer.

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