Questions on: Chokecherry

Ron Smith, Horticulturist, NDSU Extension Service

Q: We have a problem with our chokecherry trees. We had black knot disease, so we sprayed the trees with a fungicide after trimming the infected branches. They were OK for a year, but now the disease is back. We tried trimming again, but the trees are in a shelterbelt and we can't keep up with the fast-spreading disease. We can't remember the name of the fungicide. Could you please help us with the name of the fungicide or any other ideas you may have to help stop this ugly fungus from spreading? (e-mail reference)

A: It is an ongoing task to control black knot once the plant has become infected. In early spring, the tree should be sprayed with lime sulfur prior to bud break and after the visible knots have been removed. A fungicide known as Cavalier (thiophanate-methyl is the active ingredient) is then sprayed at bud break, in full bloom and about three weeks after that. I really don't have a vendetta for the hapless chokecherry because I think they are beautiful trees and their fruit makes good jelly and wine. I had one in my backyard years ago, but when black knot disease and suckering started occupying too much of my time, out it came! If Mother Nature gives us a break with some drier summers, but not too dry, it will help slow the spread of this disease.

Q: What is the best way to destroy the diseased branches that have been pruned from a black knot chokecherry tree? (e-mail reference)

A: The choice is up to you, depending on where you live. Cities usually pick up cut branches and limbs. In the country, burn the branches.

Q: I was reading your page on chokecherry trees, but still have a question. I need to clear some of the trees. Is chokecherry wood good for anything, such as furniture or tables, or is firewood the best option? From what I have been able to gather, it seems to be a very hard wood.
(Alexandria, Minn.)

A: I'm not an expert on the use of wood for furniture purposes, but I have been told by those who know more than I do that cherry wood makes very good, durable furniture.

Q: Is there a yellow fruited chokecherry? If so, it must be rare or have I been missing something? (e-mail reference)

A: Yes, but as you say, it isn't very common. The fruit is treated the same for pie and wine purposes. For the record, this is probably a boughen's yellow cultivar.

Q: I know your site is dedicated to horticultural questions, but I am hoping you can direct me. I am looking to buy picked and hopefully dried chokecherries. They do not grow with any reliability in eastern Connecticut. If you or any of your colleagues, friends or family members have any to sell, I would be thrilled to buy them. I'd like to get several gallons of dried berries, but any amount would be appreciated. Thank you for your time. I can be reached at (e-mail reference)

A: I don't know of anybody, but by the time this hits the papers in a couple of weeks, you may get some kind of response that could fulfill your desire. Hang in there!

Q: We purchased a Canadian chokecherry tree last year that looks great in our yard. Since then, we have acquired a puppy and are concerned about the tree being poisonous to the puppy. Do we have to worry about the dog eating the cherries, leaves or any other part of the tree? Also, we plan to have children, so we are wondering if this tree will be harmful to the kids. (e-mail reference)

A: All parts of the chokecherry are poisonous to pet and humans, except the edible flesh of the fruit. However, poisoning cases are very rare and steps can be taken to keep animals and children away from this and other trees and shrubs that would fall into this category.

Q: We chopped down a chokecherry tree and would like to know if the wood can be used in a meat smoker. Someone told us there is something unsafe about using chokecherry wood because it will put a residue in the meat that is poisonous. Is this true or an old wives’ tale? (New Rockford, N.D.)

A: The wood, leaves and pits are poisonous. I am not an expert if chokecherry wood is safe to use in a smoker, but I wouldn't take a chance if it were my decision to make. It probably will not kill anyone, just as the pits that are crushed when making chokecherry jelly have not killed anyone that I know of, but people have different toxic limits. I suggest playing it safe and not using it.

Q: Our chokecherry trees have worms. What should we do? Should the trees be sprayed? Should the surrounding trees also be sprayed? These chokecherry trees are in a windbreak. (Tappen, N.D.)

A: If these worms are in tent sacs, there is little you can do that would be effective at this time. You can spray Malathion for some control, but the most effective treatment is dormant oil applied next spring, before the trees leaf out. The dormant oil kills the eggs the adults lay. There is no need to spray everything - just the species that are affected.

Q: I have a chokecherry tree in my yard and have noticed that the fallen berries from last year have started blossoming. How do I get rid of these little saplings? (e-mail reference)

A: I'll bet a nickel that those are suckers coming up from the roots and not new seedlings. You can check this out by tugging on a few. If they are seedlings, the suckers will pull up easily. If not, you will see that they are attached to a root. You can get a material known as "Sucker-Stopper RTU" at a garden store. After pruning off the suckers, spray those spots with this material. You should not see suckers again for the rest of the year.

Q: I have read your answers regarding black knot. In most cases, you recommend removing the infected tree. I have a Schubert chokecherry tree that is old and close to 30-feet tall, so it would be a shame to lose it. It has developed black knot on a number of small, young shoots, but not on any main branches. I neglected to prune the tree during the dormant season. The tree has just started blooming. Should I be pruning out the black knot at this point or should I wait until winter? If now is a good time to prune, do you have any suggestions on how to do it? I've been told that I should be rinsing my pruning shears with a mild bleach solution after each cut to avoid spreading the disease. (e-mail reference)

A: Please, prune it as soon as possible. Cut back beyond the black knot by at least six or more inches to be sure you are not cutting into any infected tissue. Bleach is tough on pruning shears. Alcohol is better, but not the kind you drink of course. Use good, old-fashioned rubbing alcohol. Spray the tree with a Bordeaux mixture at least twice a year about 10 to 14 days apart.

Q: My daughter lives on a farm near Milnor, N.D. She has a small tree in her front yard that has hard, charcoal stuff on the branches. They have cut the branches off, but then it just comes back on other trees the next year. Can you tell me what it is and what to do about it? (e-mail reference)

A: I'm going to make some assumptions, which are that the tree is deciduous, it is a chokecherry, and black knot fungus is infecting it. This is a difficult disease to control once it has become established. My usual advice is to get rid of the tree rather than continually fight it. Lime sulfur applied in the early spring before leafing is a control measure. Apply a Bordeaux mixture when it leafs out. These sprays are most effective when used as a preventative, not a cure.

Q: We just purchased a Canada red chokecherry and planted it in our backyard. After planting, we started doing some research on the tree and found out that the fruit pits are poisonous. We are concerned because we have a dog and are afraid it may eat the fruit. Should we be concerned for the health of our dog and remove the tree? (e-mail reference)

A: Generally, the birds get the fruit before it falls to the ground. Even if the dog did eat the fruit, it is unlikely that it would be poisoned because it simply would pass through the dog’s digestive system. The fruit is not poisonous, but everything else is!

Q: My students are trying to research chokecherries. We are trying to find out if they are native to North Dakota. How far back can chokecherries be traced in North Dakota history? Could you provide some information or direct me to where I could have the students do some research? (e-mail reference)

A: Chokecherries, Prunus virginiana, are native to most of the eastern U.S. and Canada and extend west into the northern Great Plains, which includes North Dakota. Chokecherries were a source of food for the colonists. American Indians introduced the settlers to the tart fruit. A thesis probably could be written about this small tree, so I would suggest the students do a Google search on the plant and see what pops up!

Q: I had a client call me with a question made for you to answer. His chokecherry tree is leaking sap around the trunk. The fellow tells me that the sap has spread about 4 feet away from the base. Any ideas on why or what to do? (e-mail reference)

A: It could be borers infesting the tree or a bleeding canker. If I had such a tree spreading that much goop, I'd make one pruning cut, which would be at ground level. Anything that is bleeding that much can't have much of a future!

Q: We have a very old and large chokecherry. What are the pruning guidelines? Can it or should it be thinned out? If so, when is the best time? (e-mail reference)

A: Pruning is best done in March when the tree still is dormant and the spread of disease is minimized. It also facilitates healing of the pruning cuts faster with spring growth coming on.
Prune to open the crown, but never leave any stubs. Always cut back to a lateral branch or bud while attempting to maintain a natural size. Survey the tree first before making any pruning cuts so you will know when you have arrived at the last cut. In other words, know what you want the finished product to look like before starting. Also, don’t prune off more than a third of the total canopy at one time and don’t expect something that looks like a sow’s ear to become a silk purse the first year.

Q: Are there any chokecherries I should be concerned about? A friend gave me some to try for winemaking. He said they are Canadian chokecherries. They contained no pits, were dark red and about the size of a pea. It would be great if you could help me out with this so I don’t get extremely sick or get some poisoning (other than from the alcohol). The plant was purchased in the Fargo area. (e-mail reference)

A: If it doesn’t contain a pit, it isn’t a chokecherry. Even though this is coming from a friend, I would be leery about consumption, unless you witness your friend eating them or drinking the wine. As humans, we vary in our tolerance to different things that we consume, so be careful.

Q: We are thinking of planting 20 to 30 chokecherry trees on our property, but it sounds as though they have many disease and mildew problems. Is this correct? I’m also wondering why you did not suggest bacillius thuringiensis to control tent caterpillars and webworms. I have had great success with it on other trees. (e-mail reference)

A: There is a fungus, black knot, which has become so rampant that I no longer can suggest it as a landscape plant without a twinge of guilt. I have recommended Bt (bacillus thuringiensis), but it probably has not made it into the Web site’s history. People want a “shot between the eyes” as far as treatments go, so many are not patient enough to wait for the insect to get sick and die. People want to see results within seconds after spraying! I just hope they are careful. To make it official, I hereby declare Bt effective on all caterpillar stages of insects feeding on trees. To date, as far as I know, it is the only microbial insecticide in wide use for horticultural crops and is safe for use around warm-blooded animals. Thanks for writing.

Q: The branches on my Schubert chokecherry tree are dying. I have seen some pictures of black knot, but I don’t think that is the problem. There seem to be webs on some of the branches and the bark is peeling away in spots. Can you tell me what the problem is and how I can treat it? I’ve attached a photo of the problem. (e-mail reference)

A: Your tree has stem canker. Everything above the canker will die this season or next season. Because the canker is on a main stem and not a side branch, cutting it off would not control it. Sorry about the bad news!

Q: I just found your Web site while doing research about grapevines in North Dakota. In an area about various fruits and jam/jelly making, I read that I shouldn’t grind chokecherry seeds or nuts because they are toxic. Last year was the first year my husband and I picked and processed chokecherries. We used an electric grinder and ground the washed fruit. Then we poured boiling water over the pulp and let it sit overnight. The next step was to extract the pure juice and throw away the remaining dry pulp. The taste is unbelievable. It has a very mellow, much sweeter, almost almond taste. We did not have any ill effects. (Osnabrock, N.D.)

A: The poison is in the dose. Obviously, you tasted the poison and it didn’t kill you, as it didn’t kill generations of Americans before you. If you want to play it safe, separate out the pits from the flesh. The “almond” flavoring will be greatly reduced or eliminated because that is the flavoring of the poisonous seeds. Children especially are prone to poisoning through eating the leaves, skewering hot dogs on chokecherry twigs or eating the seeds (difficult and tough on the teeth!). Poisoning symptoms are difficulty in breathing, voice paralysis, twitching, spasms, stupor, coma or even death. In mild poisoning cases, symptoms may include nausea, vomiting, headache, muscular weakness and irregular heartbeat. Again, the fruit is edible as long as the seeds are discarded. Because of your body mass and the amount of the product you consumed, you did not experience any poisoning effects, but why make your liver work any harder than it has to?

Q: My very large Shubert chokecherry is showing severe signs of western X disease. This is the first time I have seen this disease in all of the years I have worked here. If I cut it down, will it come back with new healthy shoots or should we dig it out and replant with something else? This plant, with its purple leaves, has been such a pretty addition to our landscape. (e-mail reference)

A: This disease, mycoplasma, is the death knell of the tree. You are better off taking it out and replacing it with something else. There are no known control measures at this time. The disease likely is spread by leafhoppers.

Q: We have chokecherry trees in our shelter belt. A few years ago we had so many chokecherries, but we haven’t had any the past few years. The trees have buds and unripe berries at the beginning of the season, but they are gone by the end of June or early July. Are birds eating the unripe cherries or is it a different problem? Our neighbor has a row of chokecherries in his shelter belt that produce a lot of fruit. (e-mail reference)

A: The trees simply over-bore last year, so now the trees have to recover and accumulate energy to bear chokecherries next year. If the trees are healthy, then this should be the cycle. Perhaps you and your neighbor could get together on the off years and share your crops.

Q: I ran across a page of chokecherry advice that you posted on the Web. I was surprised by what I read. I had no idea that chokecherries were so troublesome. My grandpa, who recently passed away, was my supplier of homemade chokecherry syrup. He used to tell us stories of his mother's daily sourdough pancake breakfast. For as long as I can remember, he would fry up bacon, the pancakes (in the fat) and then pour on the chokecherry syrup. I never bothered to ask him where he found the chokecherries. I’m thinking of growing my own. Could he have been harvesting a wild/hardier version than what I'm reading about (black knot, suckers, etc.)? (e-mail reference)

A: Your grandpa was probably harvesting wild chokecherries from shelterbelts. What you describe sounds very familiar. Folks back then ate what they wanted without worrying about low carb, Atkins or South Beach diets and still lived to a pretty ripe old age. Black knot disease has become a real problem over the past 20 years. It is a population phenomenon; high density plantings lead to the easy spread of a very virulent fungus. That doesn't mean chokecherries will be taken off the market anytime soon. I still see them for sale. Many live a good, long life, but more and more often I see them debilitated by this progressively destructive fungus.

Q: My first question is about our chokecherry trees. We have a grove of about 10 thin, tall trees. They have been here for at least 10 years (probably more). About three or four years ago we thinned them out so grass would grow. The power company also trimmed the tops of two of them a year or two ago. Last year they leafed-out in May, turned orange by June, lost their leaves by July and produced no berries. This year, almost no leaves are growing except on a few lower branches on one or two of them. Are they dead? Is there any hope? We use spectracide on our lawn several times a year to kill creeping Charlie and a pre-emergent weed/fertilizer in fall and spring, but we have done that every year. Did we do something wrong? Should we cut them down or give them time? Please answer soon, as the tree trimmers are coming for another tree before long. My second question is about my pea plants. I have tried several varieties, but every year they grow I get yummy peas for a couple weeks and then they get a white powdery coating all over them, turn yellow and dry up. Why does this happen, and is there anything I can do? I love fresh peas and it makes me so sad every year. (Moorhead, Minn.)

A: The chokecherries are probably history. Whether or not it was the herbicide treatments, I don't know. The material that controls creeping Charlie is also soil active and can be taken up via the roots of other plants such as woody plants. There are several products on the market with dicamba as the active ingredient. Peas are susceptible to mildew, a fungus disease. Grow the peas in a very well-drained soil with plenty of direct sunlight and good air circulation. Plant in a different location every year, with a three year rotation before you plant in the same location. Also, look for mildew resistant varieties of peas and try not to splash water on the foliage when irrigating.

Q: What causes a sticky white substance on chokecherries? Is there any way to remove it and is it safe to preserve? (Jamestown, N.D.)

A: It’s most likely powdery mildew. Other than washing them carefully, I don't know of any other way of removing the fungus. I would imagine that the temperatures used in making preserves would render any pathogen inert. I can't say anything about the flavor!

Q: This past week you had a question about suckers growing on a crab apple tree. You recommended using a product called "Sucker Stopper." Would this product be effective on sucker roots growing in a Canadian red cherry tree? We have two different types of tree suckers. It has plain sucker roots and suckers on the trunk and branches of the tree. (Fargo, N.D.)

A: Sucker Stopper is supposed to work on both. I have not tried it although I've been told it works on chokecherry tree suckers. Time will tell.

Q: Some of the choke cherries I planted from bare stock last year were growing well but now have dark red leaves and look sick. What do you recommend if this is something serious and I have to replace them? I was planting them for the berries. (Sheyenne N.D.)

A: There are other berry-bearing trees that you should consider because the choke cherry has gained a reputation for suckering profusely and being vulnerable to black knot fungal disease in our area. Juneberries grow beautifully and are not plagued with as many problems.

Q: I have read your column and know your recommendation that black knot be trimmed from chokecherry trees. On many farms in North Dakota such as mine, the shelterbelts are made up of hundreds of chokecherries, far too many to cut black knot from, using ladders, etc. Thus, these shrubs are dying, a real loss to these prairie shelterbelts. Is anyone developing a spray for this disease? Considering the magnitude in the apple orchards of the USA, I would think the USDA should be doing something. (E-mail reference, N.D.)

A: There is a spray program for these trees, but it often comes too late to save them. Annual spraying of all fruit trees while they are dormant in the early spring with lime-sulfur is about as old as I am, but is a practice that has not been a habit with most gardeners/horticultural farmers. It acts as an excellent general sanitizer, allowing the trees to leaf out surrounded by relatively clean tissue. A product called Cavalier can also be used in conjunction with lime sulfur. That product can be sprayed at pink bud stage, full bloom and three weeks after full bloom. These actions, in addition to selective pruning where possible, will go a long way in saving many of the chokecherries if caught in time.

Q: Every fall we have been getting webworms on our Canadian chokecherry trees. I noticed you suggest spraying with dormant oil and lime sulfur in early spring just before leaf-out to help prevent the web worms from coming back. But, I want to know what a person should do once the web worm is on the tree. We have been cutting the branches off and burning them. What else can we do? Is there some kind of spray that can be used to kill them in the web? Where can I find dormant oil and lime sulfur? (Turtle Lake, N.D.)

A: Once the webworms are noticed, they are very difficult to control, being virtually immune to sprays due to their protective webbing. You are doing the right thing by burning the branches that are infested. Lime sulfur and dormant or horticultural oil is available at most garden supply stores.

Q: Could you tell me if the berries of the Schubert crimson chokecherry are edible and good for jelly making? (E-mail reference)

A: You bet! And, I am told, they make a pretty good wine as well.

Q: A client brought a small branch from his chokecherry tree. It has a black growth about 5 inches from the tip. It kills the trees and gets worse every year. What is it? (Linton, N.D.)

A: That is a fungus known as black knot. He needs to prune out any branches that have that growth on them. Spray lime sulfur on the trees while they are dormant in the spring, followed by a product called Caviler (thiophanate-methyl) at the pink bud stage, full bloom and three weeks after full bloom. If the disease has badly crippled the tree, the client is better off removing it.

Q: Why don't Amur chokecherry trees, Prunus maackii, seem to get black knot? Are there other Prunus species that don't succumb to black knot? (Moorhead, Minn.)

A: A lot of it has to do with population density and the fact that the pathogen (Apiospornia morbosa) may be very host-specific. Or it may be that those species of Prunus are simply more resistant to the disease.

Q: A lady asked if she could spread her fireplace ashes on her garden. Would it help, hurt, or do nothing to her crop? Next, a man asked if there was some chemical he could use to kill a young chokecherry tree growing too close to his house. (Bowman, N.D.)

A: A one-time application of ashes will not hurt, but a continual application would do no good. The pH of ashes is alkaline, something most soils in North Dakota don't need. To kill the chokecherry, allow it to leaf out, then paint or spray the leaves with Roundup.

Q: If a chokecherry has black knot on a main trunk of the tree, and the infected area is cut out down to healthy wood, should anything be applied to that area? Also, do you recommend any fungicide on these trees after removing diseased areas? (Hettinger, N.D.)

A: Lime sulfur can be used after the knot-infected branches have been removed, providing the tree is still dormant. Lime-sulfur is getting increasingly difficult to locate in the retail trade. Caviler is then sprayed if the lime-sulfur is not available, once while the tree is still dormant, a second time when the buds are at the pink stage, at full bloom, and three weeks after full bloom.

Generally if the disease has progressed to any significant degree, one is better off taking the tree down and replanting with a different species.

Q: I am interested in growing chokecherries that are the same quality as the mother tree. Is that possible to do if I use fruit from the original tree? Also, can the chokecherry be crossed with something like a common pie cherry to produce a superior hybrid? (Turtle Lake, N.D.)

A: To get the same quality of fruit as that you sent me you’d have to equalize the genetics and the environment. To do that, don’t use the seed as you will get genetic variation; instead, use the branches for root cuttings. Yes, a cross is possible. They are both in the same genera, so they are closely related. Give both of your questions a try. Who knows? You might become famous and rich someday!

Q: My Schubert chokecherry is in my very small front yard, where I have removed the grass and planted various perennial groundcovers with a view to avoiding the need to water or use any chemicals. The roots of the tree keep putting up little suckers all over the place. Is there any way to discourage this? Someone told me deep watering will encourage the roots to move downward instead of to the surface, but that is rather contrary to my aim of water conservation. (E-mail reference)

A: I wish I could give you a positive answer, but I cannot. There is no effective way to control the sucker growth from these trees. Spreading plastic or landscape barrier will stop it in that immediate area, but they will only come up farther out in the yard. I would honestly suggest simply removing the tree right now. Even doing that, you can be assured of at least 2 years of sucker growth coming up from the remaining roots.

Q: My in-laws have a number of chokecherry bushes on their farm. Last year they noticed some type of black "growth" forming on the branches of the bushes. The affected branches die and eventually the entire bush dies. I love my mother-in-law's choke cherry jelly and I don't want to sit by and let the bushes die. Do you have any idea what the disease is and how we can treat it? (E-mail reference, Nebraska)

A: The disease is a fungus known as black knot that is sweeping across the prairie states. Pruning it out and spraying with lime-sulfur while still dormant will help. If the trees are in leaf/bloom now, then get right on them with a product known as Cavalier. Spray several times and keep the knots pruned out. Good luck. Once this disease gets a foothold it is often hard to control.

Q: Do you have any information on how to get rid of fungal black knot? I think this is what is infecting my chokecherry trees. (Ryder, N.D.)

A: A number of approaches can be used: Remove all knots by pruning about 3 to 4 inches below the knot. Spray with lime sulfur after knot removal. Remove any wild species harboring this pathogen. Realistically, unless this disease is caught in the early stage, it is totally debilitating, and it is best to remove the tree.

Q: I have a question about one of the trees in my yard. I am not sure what kind it is. It is a small tree that starts out in the spring with green leaves that quickly turn purple. The leaves stay purple until fall and are long and slender.

After the leaves dropped this fall, I noticed three branches had a dark growth on them. It is an ugly black thing that has clearly grown around the branches. Is this a bug or a disease? What can I do about this? Will this spread to the other tree like this I have?

I have also planted several other trees for windbreaks and shade. My soil is mostly clay, so I have to be careful about iron with the Silver maples and try to put Miracid on once or twice a year. I have also started mulching my grass clippings and putting them around the trees and rototilling the mulch into the dirt. I have a lot of ants in my yard, and I have not done much bug spraying on the trees because of the expense. Any other thoughts? (Minot, N.D., e-mail)

A: The tree sounds like the Canada Red chokecherry, and the problem sounds very much like black knot fungal disease. Cut out the branches with this growth sometime before new growth begins next spring, and spray the tree with lime-sulfur prior to leaf-out. Once infected, it is unlikely that the tree will be worth very much. You can try for a couple of years, but don't be surprised if you end up taking the tree out completely. I would suggest spraying all deciduous trees with the lime sulfur while they are still dormant prior to leaf-out. This is a very effective fungicide. Sulfur by itself, is a very effective fungicide, but adding lime to it causes a chemical change that allows the sulfur to penetrate the leaf tissue and adhere to the stems of the branches, thus killing any spores that will germinate in the near future or any that have sprouted recently.

I suggest a follow-up of Captan after leaf-out. The spray schedules must be used in coordination with a regular pruning of any of the knots that show up. Go back beyond the swollen canker about 6 to 9 inches to make the cut to be sure that any spore migration has been removed. Keeping a protective spray on the uninfected tree will be beneficial.

This disease has become rampant with this particular species--so much so that it makes it difficult to recommend it as a desirable plant to use in North Dakota landscapes.

Your action with the mulch is good--keep it up. Ants are not a problem unless they get into your dwelling. Allow them to do their thing in your yard, they make good soil aerators and mixers. It sounds like you've taken all reasonable steps to have a healthy landscape. Enjoy!

Q: We have chokecherry trees in our yard and the birds keep taking all of the fruit. How can we stop them? Will they ripen if I pick them green and put them in the patio? (Milnor, N.D.)

A: No, the berries will not ripen that way. Try netting or scare balloons, or both. Sometimes birds can be encouraged away easily and other times not. I've received good reports on these two items doing the job.

Q: Can you tell me what variety my Canada Red or Schubert chokecherry is? Also, the flowers drop almost immediately and it never produces any fruit. Why is this happening? (Cando, N.D.)

A: The full botanical name is Prunus virginiana Schubert. It could be flowering too soon and getting the buds nipped by frost.

Q: Can you tell me what is wrong with my chokecherries? It looks like fireblight, but I didn't think it attacked Prunus varieties. (Wolf Point, Mont.)

A: I agree that it is fireblight bacteria taking out your chokecherries! I must admit this is the first time I have seen this disease hit chokecherries. Try to control it in early spring with bordeaux mixture when the temps are hovering in the 60s. Start at blossom time. As the weather gets hotter, change over the Streptomycin. To get a jump on next year, spray the trees with dormant oil combined with lime-sulfur, just prior to the blooms opening or leaf-out.

Q: Please advise me on what I can use on Creeping Charlie. I am losing ground pulling it! Also, I have fungus on my Canadian chokecherry tree, and it has sucker growth around the base. Can these problems be controlled with chemicals and not damage the tree? (Enderlin, N.D.)

A: Creeping Charlie, or ground ivy, can be spot sprayed with Trimec herbicide, if it's a weed in your lawn.

There isn't any way to stop a Canada Red chokecherry from suckering without killing the tree, but you can spray fungicide to control the fungus. A general all-purpose fungicide is Daconil 2787. It is most effectively sprayed in early spring as a preventive measure.

Q: I have many chokecherries in shelterbelts around the farm. Most of them are the green leaved varieties, but a few around the buildings are the Schubert Canadian Red variety, which are beautiful trees. I notice the green varieties can have black knot, but the Schubert seems to be resistant. Is this true other places, or will they get it too? Is there any spray that would help? I would like to plant some additional Schuberts if they will not die out. (Kensal, N.D., e-mail)

A: Yes, the Schubert chokecherry is susceptible to black knot, as are most Prunus species and cultivars. The first thing you need to do is establish a program of sanitation. By this I mean all existing knots should be cut out of the surrounding trees while they are in the dormant stage, before leafing out takes place.

Then, spray your red-leafed plants with sulfur, captan or any fixed copper fungicide from "green tip" to flower petal drop to provide protection. Be sure to make it a practice to continuously monitor your trees for development of this destructive disease. Judging by the tone of your letter, it sounds as if you are fairly observant about what is going on already.

Q: A warning for those people making chokecherry jelly! Don't throw the pits out the window because they will grow. They can become as bad as any noxious weed. Twenty to 30 years ago my parents made chokecherry jelly, and they threw dishpans full of pits out into a grove near the house. They grew all over the place, and the birds carried the seeds to two other groves on the farm, which became like jungles with chokecherries. I've attempted to clean out the groves, but I still have many that are impossible to get rid of. I would not even want to dispose of these in the landfill unless it was guaranteed that they would be deeply buried for 5,000 years! (Centerville, S.D.)

A: Thank you for sharing your experiences about chokecherry pits with us. It gave me a chuckle, although the battle you have fought is not a laughing matter. Good luck and don't give up!

Q: I'm writing concerning the webworms that are very abundant this year. I do spray them and destroy the webs when small. I'm wondering, what lays the eggs and can they be controlled in the fall?

Also I find brown-like clusters on branches, which appear to be dried up. Where do they come from?

How can I control these worms in the fruit trees: plum, currant, gooseberry, chokecherry?
(New England, N. D.)

A: Whether you are talking about webworms or tent caterpillar, the egg-laying adult is a moth. The webworm makes nests over the ends of branches, while the tent caterpillar makes them at tree crotches. These can be controlled by spraying with dormant oil and lame sulfur in the early spring, just before leaf-out.

The larvae in fruits is controlled by spraying with Sevin or Malathion just at petal drop. Following good sanitation in the fall—picking up leaf and fruit litter also helps.

Q: Could you please identify the problem we are having with these trees? Whatever it is, nearly every tree in our shelterbelt is suffering some stage of damage. The chokecherry bushes are all nearly dead! (Maddock, N.D.)

A: The samples you sent showed two problems: first, sooty molda low-grade fungus that results from "honeydew" secretions of aphids feeding. The Siberian elms showed some herbicide damage.

There are several things that can wipe out chokecherriesblack knot and the x-disease.

At this point, I would suggest spraying with an insecticide like Malathion or Sevin, to control the aphid population. 

In the future, spray your shelterbelt with lime sulfur while they are still dormant in the early spring. This is a good deciduous plant sanitizer. 

Q. Like so many of your readers, I have a question.

I have a tree which my book refers to as horse chestnut or buckeye. It is a very well formed tree, and for years I have been hoping to try and grow one like it. It has to be watched at fruit time, as the squirrels do beat me to the nuts. I have gotten a few this year. A sample is enclosed.

I have tried other years to plant some seeds that would grow. Any idea you might give me would be appreciated.

We also lost a small grove of chokecherries to that so-called "black leg." For over 50 years there had been no damage. Is there some background on that?

Thanks for any help and keep the information flowing. There is always something new it seems. (Litchville, N.D.)

A. Thanks for writing. I am glad the column has helped you.

The sample you sent was of an Ohio buckeye nut still in the outer husk. If you had planted that nut about 4 inches deep where you would want about a 30-foot tree to grow, it would have germinated this spring, assuming, of course, the squirrels didn't find it!

The disease that destroyed your chokecherries was blackknot. That fungus has become so widespread throughout our region that it is difficult to justify recommending this species to anyone any longer. Our current wet, humid summers are believed to be the culprit in making this disease so prolific.

Q. Enclosed in the box are two specimens. What is the hard black lump off my Canadian red chokeberry tree? Any prevention?

The sick impatiens are here and there in a group. Plants around them look healthy. Is there any information on this and is there a prevention? You have been a great help in the past and I thank you. (Oakes, N.D.)

A. Your chokecherry has a fungus disease known as black knot. Normally, not a severe problem on cultivated stone fruits like your cherry. This disease has been showing up more frequently these past couple of years.

The best control methods are to prune out the visible knots, at least 3 to 4 inches below the swelling. Also check around your property and adjacent lots to see if there are other cherries with the same disease. Spray with lime sulfur next spring before leaf-out, and apply a protective fungicide like Bordeaux mixture once the leaves have opened.

Your impatiens sample looked amazingly healthy with the exception of a few leaf spots, which might be a touch of botuytis due to the wet conditions the plants are normally kept in. Just try to avoid splashing water when irrigating.

Thank you for the nice compliment. Glad I have been helpful.

Q.What has happened to my chokecherry tree? It has had such luscious big cherries every year with only a few bloated ones. This year they are all bloated with no good ones at all. What must I do next year to prevent this?

Thanks for answering our questions in the paper. You bring us such good information. (Kulm, N.D.)

A.The badly malformed fruits of your chokecherry are the direct result of the feeding of the larvae of the chokecherry fruit fly.

The maggot begins feeding on the developing fruit near the stone, causing the puffy or bloated appearance. Spraying applications of Sevin at blossom drop and again seven to 10 days later should give you good control.

Be sure to harvest and/or pick up all fruit and destroy it by burning. I also suggest a vigorous raking under the tree canopies in an attempt to remove all possible sources of reinfestation.

Q.Enclosed are samples of our chokecherry trees which are in a shelterbelt. These whitish leaves are localized in certain areas and the trees aren't looking real healthy. The trees should not be hurting for moisture as we had lots of snow and they are kept clean.

I would like your opinion on what this is. (Hettinger, N.D.)

A.Your problem is not too little water, but too much. Your tree has a bad case of powdery mildew, leaf spot and shot-hole disease.

I suggest some severe pruning to increase air circulation and sunlight penetration. Spray now with Daconil 2787, then next spring with lime sulfur while the trees are still dormant.

Q: I have an answer to the person who asked about stopping birds from eating their chokecherries: Spray the trees with grape flavored Kool-Aid. I used six packets
to a gallon of water, and sprayed when the berries were nearly ripe. It sounds crazy, but it works! (Mobridge, S.D.)

A: Wow! Grape flavored Kool-Aid will do it? Do the birds know something we should learn? Thanks for the suggestion. It sure is an easy one to try!

Q: I have a line of chokecherry trees along the side of my house and they have grown up over the roof. They are scraping on the roof and I'd like to trim them to below the gutters. If they are trimmed now, will it hurt them? I've heard that the time of year you trim trees makes a difference. And will they bush out if they are trimmed that much? It would be nice to be able to reach those berries! (E-mail reference, Bozeman, Mont.)

A: It probably won't hurt them, but it won't do them any good either. Pruning this late in the season exposes the plants to potentially insufficient time for proper healing of the cutting wounds. You are better off to let the birds get the ones out of reach this year and prune them early next spring before leafing out takes place. Yes, they will bush out as a result of pruning them back.

Q: We are interested in planting some chokecherry bushes in our garden and note that several nurseries list the Brilliant Red Chokeberry (Aronia arbutifolia ‘Brilliantissima’) and Glossy Black Chokeberry (Aronia melanocarpa elata), but not a chokecherry. The chokecherry bush that we are familiar with grows in the wild producing white flowers in spring and reddish black berries in late summer that are excellent for jelly, syrup, etc. What’s the difference between a chokeberry and a chokecherry? Is it just a matter of correct name? (Baudette, Minn.)

A: Thanks for the very good question. While both are in the rose family, they are distinctly different species. Aronia spp. or chokeberry is an ornamental with little if any wildlife (or human) food value because of extremely astringent fruit (even the birds don’t like them). The chokecherry -- Prunus virginiana -- has edible fruit (with some significant doctoring). Unfortunately this species is being plagued by black knot, a fungal disease that is wiping out domestic and commercial plantings in our prairie region. If you do decide to plant them, don’t invest any more than you can afford to lose in a few years.

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