Diseases of garden plants |
 | All of a sudden my 5-year-old mums are dying. Can you help me? They are all different mums. Antoinette, Milton |
 | Hello, Antoinette: Not having any details or a sample I can only speculate, but chrysanthemums are subject to many different insect and disease problems. Aphids and spider mites are the most common problem, but usually these insects are not detrimental to the plant. Excess moisture and lack of winter hardiness is usually the reason for plant failure. The most common chrysanthemums, or mums, are all hybrids, and depending on the cultivar they may or may not be hardy. If these were plants you purchased during the fall when the garden centers are filled with these colorful plants, they are probably not a hardy variety. They can potentially come back for a few years but are not a long-lived, reliable perennial. Since you have many different cultivars it may be more of a moisture issue causing them to decline. These plants require a well-drained soil; if they are growing in a space that does not drain well and you have had as much rainfall as we have had here in Kentucky, this could certainly be a possibility. You can always take a sample to your County Cooperative Extension Service for analysis. You can visit their Web site at http://ag.udel.edu/extension/directory/sussexcounty.htm. The horticulture agent will be able to give you a more definitive answer after looking at your sample. |
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| Are you aware of a serious disease that is moving southward that will kill all Knock Out roses? Ricky, Franklin |
| Hello, Ricky in Kentucky: As far as roses go, the Knock Out roses and other shrub roses are pretty disease-resistant. I am not sure if you are referring to a disease known as Rose Rosette or not, but this is the only serious issue associated with Knock Out roses. It not only affects shrub roses but also multiflora roses. This disease originally thought to be a virus was first detected in the 1930s. It was found out west on wild roses. It is spread by an microscopic, wooly mite as well as grafting. Initial symptoms include abnormal growth that is distinctively red in color with abundant thorns that are usually more rubbery than prickly. It resembles what is known in the plant world as a "witch’s broom." It usually starts on the new growth of one cane but can quickly spread to the rest of the rose. Unfortunately, miticides are not effective against this insect. If you suspect that your roses are infected you can take a sample to your County Cooperative Extension so the horticulture agent can have it sent off to the University of Kentucky for a proper diagnosis. If you want to read more about this disease, the following link is to the July 2011 issue of the inspector findings in Kentucky: www.uky.edu/Ag/NurseryInspection/newsletter/11news/June2011.pdf
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| Can I treat my river birch on my own for iron deficiency? Tammy, Omaha |
| Hi, Tammy: Iron deficiency, also known as iron chlorosis, is typically a problem where soils are highly alkaline. Symptoms include yellowing on the tips of the foliage, and in severe cases all the foliage will yellow. This can also be an indication of nitrogen deficiency, so it is important to be certain what the real issue is. In most cases, it is not that the soil does not contain sufficient iron levels, it is more likely the case where the soil pH does not allow the plant to take it up. Have you had your soil tested recently? I would suggest this before applying any product such at tree-tone that contains iron or any foliar spray since it will not get to the root of the problem if indeed it is your soil pH and not the lack of iron. Your County Cooperative Extension Service is a reliable source to contact for having your soil tested. It typically costs a small fee but your results will indicate the soil pH as well as nutrient levels. There are two Extension offices in Douglas and Sarpy counties. The central offices are located at 8015 West Center Road in Omaha. The phone number is (404) 444-7804. The south offices are located at 1261 Golden Gate Drive Suite 4E in Papillion. The phone number is (402) 444-7804. The horticulture/agriculture agent(s) will be able to give you specific instructions for having your soil tested. Let them know why you are having it tested so your results will specify iron levels. |
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| Do you know a natural or herbal preventive fungicide for phytophthora in peonies? Anne, Princeton |
| Hello, Anne: Phytophthora cactorum is a fungus that is actually commonly found in our soil. When we introduce certain plants such as peonies into this soil, they can become diseased. Of course, there are other factors that make the peonies more susceptible to this fungus. Peonies should be planted in full sun, with good air circulation and well-drained soil, which is key to protecting these flowering shrubs. The drainage can be improved by adding a product such as Permatill to your existing soil. Permatill is an expanded slate material and will help to break up clay and improve drainage as well as air circulation within the soil. The best natural defense is planting in an optimal environment. Phytophthora is spread by rain when it splashes from the soil onto the plant; this is especially true during cool springtime weather. This is why we water from the base of the plant and avoid watering the foliage. It is also a good idea to avoid watering mid-day into the evening before the sun goes down since there is not enough sunlight to allow the foliage to dry out. Morning watering is best. The fungus can also be spread through contaminated tools, so it is important to clean your gardening tools frequently. If the roots are infected on your peonies, you should remove the plants as well as the soil surrounding the roots. If the roots are still healthy, make sure to remove and dispose of all contaminated foliage/stems. They will be dark brown or black in color with a leathery texture. Fungicides will only be effective as a preventive measure if the plants are not yet diseased or to parts of the plant that are not yet affected. Neem oil is a natural product that can be used as a fungicide. As with any fungicide, natural or not, it will only be useful when used as a preventive treatment. |
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| I have a 17 foot white pine; about 6 feet on the top is mostly dead. Can I just cut that off to save the tree? Wayne, Philadelphia |
| Hello, Wayne in Pennsylvania: I am going to assume by the size of your pine that it is an established planting. When we see a bit of die-back on the top branches coming out of the winter months, it is usually associated with winter damage caused by lack of moisture going into the winter months. If this is the case then these needles will drop and the pine should put on new growth to replace them. Unfortunately, your case seems a bit more severe than this and there may be something more serious going on since such a large portion of the tree is affected. White pines (Pinus strobus) are susceptible to white pine blister rust and white pine weevil. Both are pests that can be detrimental to the evergreen. Tip blight is also a possibility: you would see tiny fungal spores at the base of each individual needle. This is a more serious problem and should be positively identified. You really have to get up close to identify any insect or disease problems on any plant. Without seeing a sample of your tree I can only speculate, and the only way to find out for sure what is going on is to have someone take a closer look. You can contact a certified arborist in your area to have them come out and give you a positive diagnosis and treatment options. If you need local recommendations you can contact your County Extension Office.
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| I have a Cleveland select that has a bark issue. It is on its second season and I just saw this. It looks like the bark is bubbling up, and then wants to peel off off the main trunk. I have a picture if that would help. Daniel, Louisville |
| Hi Daniel: Pyrus calleryana 'Cleveland Select' is also known as 'Chanticleer,' 'Select,' 'Glen's Form,' and 'Stonehill.' The common name for this tree is Callery pear, much less confusing than all the different cultivar names. This ornamental tree is native to China and can have structural issues but as for the bark oozing you really should have a certified arborist take a look. In the Louisville area, Limbwalker and Greenhaven Tree Care are both reputable companies with certified arborists. Fireblight is serious issue with fruiting pears and when seed was brought to the U.S. from China in the early 1900s the hope was that they could breed pear trees to be resistant to this disease, but the bubbling ooze is a good indication that this is the problem. As this pathogen spreads it will cause foliage, stems, and flowers to shrivel. It can be detrimental to the tree and a lifelong maintenance issue. Disease spread depends on environmental conditions and each season will differ. The sooner you can have someone look at your tree the better. Louisville, KY |
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| I have a couple of evergreens (I think some sort of yew and maybe a blue spruce) that look like they're dying but I don't know why. They were well-established on my property when I bought my home (several years ago) but I believe this has gradually happened over the last year for some reason. I have pictures if that would help. I am afraid it may be too late to save them but I want to do what I can to try.
A., Fort Knox |
| Hello, A. in Kentucky: Some browning and inner foliage drop is normal on evergreens but if the damage is more widespread then something else is going on. Insect and disease issues are specific to plant species so it is unlikely that they are suffering from the same issues. Spruces are subject to a number of different problems but fungal issues are the most common. Damage normally begins on the lower branches and over time works its way up. Yews (Taxus) are also susceptible to fungal issues, especially in poorly drained sites. At this time you can remove the damaged foliage and take a sample to your County Cooperative Extension Service or a local garden center for a horticulturist to look at. The problem needs to be positively identified before treatment options can be discussed. For now, you will want to keep the area under the plants free of plant debris because this is a wonderful environment for insects and disease to live. Plants that are already stressed are more susceptible to insect and disease problems. These are established plants but at this point you want to avoid fertilizing, and if Mother Nature does not provide moisture you will want to make sure they get watered during the summer heat. Unfortunately, once evergreen foliage begins to turn it is usually too late to prevent further damage and in most cases they do not put on new growth to replace the lost. |
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| I have a half dozen Knockout roses that have been destroyed. I have seen no beetles (this being my first thought) and the leaves do not seem to look quite as if they had been eaten; some sections do look so but just as many areas have dried out patches throughout the leaf. Within a short time the entire plant was defoliated.
I do not know if a photo would help in identifying the issue but I have several on my PC I could send if this is possible?
I have another half dozen that are look extremely healthy; these are separated from the dead ones by a 2-foot concrete patio, but next year I fear they will fall victim to this malady if it is not treated correctly.
William, Beachwood |
| Hi William in New Jersey: Knockout roses are more disease-resistant than some of the old-fashioned roses, but certainly not pest-free. As with all plant material, they are going to be more susceptible to insect and disease issues if they are not growing in ideal conditions. Roses demand a minimum of six hours of direct sun and nutrient-rich soil. That being said, it is difficult to give you a specific answer not being able to see your roses but your first thought is certainly a possibility. At this time of year, the beetles are not going to be on your roses but the damage they could have done earlier in the season is still evident on the foliage. After they are done eating, the foliage looks clear, kind of lacy, and when it rains it pushes the remaining foliage through, leaving you with holes. Rose slug is another possibility. For a positive diagnosis you can take a sample to your County Cooperative Extension Service or to a reputable garden center. For now, be sure to remove all fallen foliage and other plant debris since this provides a great place for insects to over-winter. Good sanitation practices are important in terms of a healthy garden.
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| I have a Knock Out rose that has a disease called witch's broom I think. I have done some research on this disease and it says that there is nothing to do but destroy the rose, but this research was about five years old. Has there been any additional information on this? This is such a beautiful bush and I hate to dig it up. We also tried spraying it, but it didn't seem to do any good. Can you help me please? Bettie, Greensburg |
| Hello, Bettie: Knock Out roses for the most part are quite disease-resistant. In horticulture, witch's broom is a term used to describe a specific type of growth habit. Described as small clumps of short twigs, these witch's brooms develop when a bud is injured, and as a result the plant produces many weak shoots as opposed to one healthy shoot as a survival technique. In some cases witch's broom is a secondary response to the real problem. Spraying will not be effective if we are not sure what we are spraying for. Witch's broom is not common with roses and I would not suspect that this is what is going on with your rose. Of course without seeing it I cannot say for certain. Finding out the real reason why your rose is unhappy is essential to nurturing it back to health. It is difficult to say what the problem is without having any details. If you could give me more specific information about what is going on with your rose I can be of more help. You are welcome to send a picture to angiemcmanus@hotmail.com or you can always take a sample of your rose to your county Extension office. The Green County offices are located at 106 South Public Square. You can reach them at (270) 932-5311 or visit their Web site at http://ces.ca.uky.edu/green. The horticulture/agriculture agents will be able to help you and they can send it off to the University of Kentucky for diagnosis if necessary. |
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| I have a red maple tree and the leaves are dying. I put MiracleGro on it three days ago: what's wrong with it? Matt, French Lick |
| Hi, Matt: Not having any specific details about your red maple (Acer rubrum) I cannot say for sure what is happening. Is this a new planting or an established tree? Did the tree put on new growth earlier this spring and now the foliage is dying back? There are less susceptible Acer rubrum cultivars but the species is subject to a few different insect and disease problems. This large shade tree is also associated with fungi and rot problems. For a proper diagnosis you can take a sample of the foliage to your County Cooperative Extension Service. You can visit the Orange County Web site at www.ag.purdue.edu/counties/orange/pages/default.aspx or reach them at (812) 723-7107. The horticulture agent will be able to give you more insight. You can also have a certified arborist come out and take a look at your tree. The Extension service and/or your local garden center/nursery should be able to give you local recommendations. As far as the fertilizer it received, this should not hurt your tree. As with all plant food, it is important to only apply the amount recommended on the product label. Too much food can be detrimental to any plant. I would not suspect this to be the case with your tree since it looked bad before you fertilized. In order to help your tree it is essential to find out what is really going on, and then take steps to help prevent any further decline. Treating for a problem that may or may not exist does not benefit the tree. |
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| I have a weeping mulberry tree and it was beautiful a few days ago. I looked at it today and the leaves were all curled up and very brittle and had little tiny holes all over the leaves. Is the tree dying or does it have some kind of disease? What can be done? Melissa, Olmstead |
| Hello, Melissa: I cannot be certain what is going on with your weeping mulberry (Morus alba) without actually seeing it or knowing any specific details of your tree. How long has this tree been planted in its current location? Does it receive a good amount of sunlight? All plant material is more susceptible to problems when they are not planted in ideal situations. There are a few different insect and disease problems associated with mulberries, including scale, mites, mildew, and bacterial blight. For a more definitive answer you should take a sample to your County Cooperative Extension Service. The Logan County offices are located at 255 John Paul Road in Russellville. The telephone number is (270) 726-6323. The horticulture/agriculture agent will be able to identify the problem and give you solution options. For now make sure to keep the area around your tree free of any fallen plant debris. This will prevent further disease spread. |
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| I have a weeping mulberry tree and last year it got some kind of white stuff on it: can you tell me what this is and how to get rid of it? Ernestine, Vine Grove |
| Hello, Ernestine: The common mulberry tree (Morus alba) is very susceptible to a fungal disease commonly known as powdery mildew. I suspect this is what your tree is suffering from. In most cases it is not fatal, but it should be controlled for a healthier tree. In general, plants are more likely to become diseased when they are not living in optimal conditions. If your weeping mulberry is growing in a shady location with poor drainage and/or poor air circulation, this fungi will continue to be a problem. Good sanitation practices throughout the growing season are important for reducing spores as well as from over-wintering and re-infecting the tree the following year. Make sure to remove and dispose of all dead foliage on and around the tree. You want to avoid overhead watering, there is no benefit to watering the foliage; in fact it can make the mildew worse. This fungus thrives in hot humid weather and for those of us gardening in Kentucky, it is hard to avoid these conditions. Spraying with a fungicide is an option of last resort in my opinion. Good cultural practices will be very effective in terms of keeping the fungi under control. Some plants are more likely to become infected with powdery mildew than others, and mulberries are very susceptible. It is always a good idea to plant disease-resistant cultivars. |
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| I have a willow tree more than a year old that is losing its bark, and the limbs on the upper have of tree are dead. Can you help me with these problems?
Stanley, Arlington |
| Hello, Stanley: There are many disease and insect problems associated with willows. I cannot say for certain what is happening with your tree not being able to see it. It sounds like there may be a couple of different things going on. When you peel back the loose bark, are there any insects? If so, this is not a good sign, it means there is decaying organic matter and the tree is rotting. The best thing to do would be have a certified arborist come out to take a look at your willow or if possible you could take a sample to your County Cooperative Extension Service. The branches that are no longer living will need to be pruned out to prevent further insect and/or disease spread. Willows are pretty durable trees but the fate of the tree will depend on the extent of the damage. A certified arborist will be able to give you professional, reliable advice. |
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| I have China Girl holly shrubs that have an infestation of scale and sooty mold. Can you advise how to treat this condition? Paul, Prospect |
| Hello, Paul: Scale and sooty mold are a common problem among hollies. This is the time of year we notice the white insects on the underneath part of the foliage. At this stage these sap-sucking insects have hatched and are beginning to feed on our evergreens. There is only one generation per year, so controlling them now while they are active is essential in reducing the population for next season. A granular insecticidal systemic is effective; it works internally through the root system of the plant so it does take a bit longer to work than a foliar application. Spraying the holly with a horticultural oil is another option; the oil is used for hard-bodied scale and a soap can be effective on a soft-bodied scale although we typically see the hard scale species here in Kentucky. With a severe infestation it may be a good idea to use a combination of systemic and oil. The problem with the oil is that it is difficult to spray the underside of the foliage. As far as the sooty mold, this is caused from the scale; as they feed they secrete this sugary substance known as honeydew. It drops on the lower foliage and this is where the sooty mold grows. Aesthetically it is not very pleasing but it will not harm your plant. It can actually be wiped off if you have the patience to do so. Controlling the scale will control this fungus. As with any product always follow recommended application rates. |
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| I have Easy Does It roses that try to grow and bloom, but the leaves and buds grow in wads. My other rose is doing fine. Could it be the grafting? Ann, Wallingford |
| Hi, Ann in Kentucky: Easy Does It roses are a newer introduction that were developed for their showy flowers and for their disease resistance. I am not exactly sure what you mean by “wad” like flowers and foliage but these floribunda roses do flower in clusters. Do the roses actually bloom or do they form and drop? Do you see any unusual features on the foliage? Clearly, they do not look like the one healthy rose and so I am wondering if they are planted in the same space? Is it possible that the other two roses are not getting as much sun as the happy one? These roses are considered disease resistant but just like any other plant if they are not growing in ideal conditions, they are a lot more susceptible to insect and disease issues. Roses demand a minimum of six hours of direct sun, nutrient-rich, well-drained soil, and good air circulation. In general, there are a number of different viruses and fungus problems associated with roses and a positive identification is necessary before treatment options can be discussed. Without seeing your roses I can’t be more specific so you should take a sample of your roses to a horticulturist at a local garden center or your County Cooperative Extension Service. You can visit the Fleming County Web site at http://fleming.ca.uky.edu. For now, make sure that the area around your roses is free of fallen plant debris; this is a great environment for disease spread. If the roses are grafted and the understock is taking over it would not give your roses the characteristics that you described. |
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| I have several Mohawk viburnums that are sick; one has already lost a great deal of its growth. What can I do to protect the remaining shrubs? I did not find any insect or fungus grwoth, the leaves just die and then the branches. Patricia, Nicholasville |
| Hello, Patricia: Mohawk viburnums are known for their brilliant red flower buds that open to white blossoms with a spicy fragrance. This viburnum is a hybrid between burkwoodii and carlesii, which makes this cultivar resistant to bacterial leaf spot as well as powdery mildew. How old are your shrubs and have you used any sulfur sprays on your plants? Making sure they are planted in ideal growing conditions is important for the health of your shrubs. In general, viburnums are quite adaptable to most soil conditions, but prefer soil that is acidic and well-drained but moist. These deciduous shrubs should be planted in full to part sun, meaning they should receive at least four hours of sunlight each day. Good air circulation is important in preventing disease, as well as avoiding overhead watering. All plants are susceptible to insect/disease problems when they are not planted in an ideal location. From what you have described, it sounds like your shrubs may have shoot blight, which is a fungus (Botrytis cinerea) that first affects the foliage and eventually can cause twig dieback. It is difficult to say for sure not being able to see your viburnums, so for a positive diagnosis you should take a sample to your Cooperative Extension service or to a local garden center with a knowledgeable staff. For now, remove and destroy all infected parts and keep the area around your shrubs free of plant debris. |
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| I have three of same kind of Bradford pear trees: two are in excellent shape, but one barely puts out leaves and they turn brown. Is this tree lacking something? Jerry, Hopkinsville |
| Jerry, hello again: The most common problem with these trees is more structural than insect or disease related. They are fast-growing trees and tend to be short-lived, usually due to splitting during wind/ice storms. Brown foliage can be a symptom of root injury or stress related to uneven moisture levels. Too much moisture or not enough have the same physical appearance. Fireblight can also be a problem with these ornamental pear trees. This is a bacterial disease that is more common during periods of high temperature and excessive rainfall. The foliage turns black on the new growth and does not drop. The best thing to do would be to take a sample to your County Extension Service for them to diagnose. That way you know what exactly you are dealing with and they will give you treatment options as well. The Christian County offices are located at 2850 Pembroke Road. The phone number is (270) 886-6328.
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| I have two huge rhododendrons that appear to be dying. The leaves are brown and even the new sprouts wilt and die. Can I add something to my soil to help or did the ice storm permanently damage them? Rebecca, Bardstown |
| Hi, Rebecca: Since your rhododendrons are putting on new growth I do not think we can blame the problem entirely on the ice storm. I am not saying that your plants were not damaged by the storms, but the wilting of the new growth may be a secondary ailment. It is difficult to say for sure but from what you have mentioned it sounds like they may be suffering from root damage. Most cultivars of rhododendrons are susceptible to the fungus phytophthora, which can cause root rot. This is especially true when they are planted in poorly drained soil and the clay we have here in Kentucky is not the best in terms of drainage. Unfortunately it is often too late to save the plants after these symptoms appear. You can check the base of the plant by peeling back the bark to see if there is any brown discoloration of the tissue. If this is the case there is little you can do, but if it looks green and healthy then this is not the problem and you should take a sample of the foliage to your County Extension Service for the horticulture/agriculture agent(s) for them to look at.
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| I just noticed my Gerbera daisy has a gray fungus on all the leaves. Can it be saved? I cannot find any information on what to do. Kathy, Arlingto |
| Hello, Kathy: It sounds like your Gerbera daisies are suffering from a fungus commonly known as powdery mildew. The symptoms are exactly what you have described. Powdery mildew thrives when temperatures range between 68-82 degrees with high humidity. We cannot control Mother Nature but there are a few things we can do to help reduce the spores from spreading. We know that this fungus is spread by both wind and water. As with any plant, it is important that we place them in a location where they will grow and thrive. Each plant has different growing requirements and Gerbera daisies are no different. They prefer to grow in full sun, which means they should receive six hours of sunlight each day. They should not be overcrowded because good air circulation is important for disease control. Over-fertilizing can also contribute to an unhealthy plant. It is best to water early in the morning and only to water the soil, not the actual foliage, since this can contribute to additional spore development. These practices will help reduce the problem but you will also want to remove all infected foliage. Safer brand fungicide and Neem Oil are both organic options for control. |
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| I live in central Italy and two years ago planted a hedge of laurels; they have not done well as the leaves have turned yellow, red, and brown. Margaret, San Ginesio |
| Hi Margaret, Given where you are gardening I assume the laurel you are growing is the culinary, Laurus nobilis, commonly known as bay laurel. This broadleaf evergreen is native to the southern Mediterranean region and where it is hardy, it can reach 30 feet tall and 20 feet wide. They are happiest growing in full to part sun and nutrient-rich, well-drained soils. Since yours were new additions to the garden a couple of years ago they should have had time to establish their roots, but may be subject to drought if not given sufficeint moisture. As for the discoloration of your plants, have you noticed any insect activity on the foliage? Scale, mealybugs, and spider mites can be a attracted to an already stressed plant but this would be a secondary issue and not cause the actual discoloration of the foliage. Have you noticed any distortion of the the leaves? Are they wilted or curled? When not grown in ideal conditions, these evergreens can be subject to anthracnose and some other fungal issues, but you really should have a local horticulturist take a look and give you a positive diagnosis before control options can be discussed. Some cultivars actually have foliage that is yellow as it first emerges. For now you should remove the dead foliage and keep the area around the plant free of any plant debris. This will help reduce potential disease spread. San Ginesio, Italy |
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| My hydrangea plants get black spots on the leaves. Some are in full sun and others in the shade. What can I do to prevent this? Charles, Florence |
| Hi, Charlie in Kentucky: Black spot on hydrangeas is caused from a fungus. There are a couple of different possibilities and without seeing your plants I can’t say for certain which one you are dealing with, but the good news is that it rarely kills the plant. It certainly does not look pretty and if left alone can spread throughout the plant so sanitation is important in terms of control. You will want to watch new growth as it emerges this spring and take a sample to your county Extension service or a local garden center to have the fungus identified for control purposes. Be sure to clean up all plant debris around your hydrangeas as the spores can spread if left alone. Avoid overhead watering since moisture left on plant foliage can lead to disease issues. If you do need to water it is always best to do so in the morning. This way if moisture does get on the foliage it will have time to dry before nightfall. Good sanitation practices usually keep fungus problems in check but if your hydrangeas are suffering from a severe outbreak then a fungicide may be applied. Removing all infected foliage and keeping the space around your shrubs clean will help prevent future spread. Make sure your plants have enough nitrogen to maintain steady growth, and a layer of mulch helps keep the moisture in, the weeds down, and in your case will help prevent spores from bouncing back up onto your plant when it rains. |
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| My question is two-fold: I have a willow tree with some sort of fungus on the trunk and branches. Is there a cure?
Next, I have a sassafras tree growing about 55 feet from the willow. Each year it gets in full bloom but the tips of several branches are bare of any foliage. Could the same fungus be attacking both trees? Ron, Monticello |
| Hi, Ron in Kentucky: As a general rule insect and disease issues are specific to individual plants, so it is highly unlikely that the issue with your willow is the same as your sassafras. Depending on the species of willow (Salix) you are growing, they are susceptible to many insects and fungal problems. Scab, blight, and canker are all possibilities and all of these can potentially be devastating to your tree, so it is important to prune out all infected branches now and dispose of them. As the leaves drop in the fall be sure to rake and dispose of them so the spores can’t over-winter and cause further spread. Fungicides may be an option but it is necessary to have the fungus properly identified first. Sassafras is a native tree that does not typically have a lot of issues. Like all plants, if they are stressed and not growing in ideal conditions they are more susceptible to disease. Is it just at the tip of the branches and does it put on new growth throughout the growing season? This does not sound too alarming but it is best to have a certified arborist come out and take a look at your trees. You could also take a sample of your trees to your County Cooperative Extension Office to have the horticulture agent take a look. You can visit the Wayne County Web site at http://wayne.ca.uky.edu. They may also be able to give you recommendations for certified arborists in your area. |
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| My squash was looking so pretty; now it has some kind of fugus. What can I do to save them? Katie, Shepherdsville |
| Hi, Katie: It sounds like your squash has powdery mildew, a common problem among many plants. There are many different species of this fungi and each one is specific to a host plant. The species that attacks squash is caused by the fungus Erysiphe cichoracearum, which makes the foliage look like it has been covered with a white powdery substance. Severe cases cause the foliage to turn yellow and wither. This disease is more common during hot, dry conditions, which we have certainly had recently. Fortunately it does not affect the fruit. Control can be difficult after the plant has been infected. Good cultural practices are essential to prevent further spread. Making sure the squash is planted in full sun with good air circulation and planting resistant varieties is important. Fungicide applications are only a preventive measure. Once the plant is infected the fungicides will not help with the existing problem but will help prevent new infections and further spread. You should avoid using any chemicals on vegetable crops but there are organic fungicides available and horticultural oils can be effective in mild cases. Oils need to be applied at lower temperatures and, as with any product, make sure to read and follow all instructions. For now make sure to remove all foliage that is severely infected. Keep the space around your crop free of infected plant debris. A thin layer of mulch can also help prevent the spores from spreading.
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| My tomato plants are healthy looking and a good size but the lower 20% of the plant has yellow leaves that turn brown. Can you suggest anything as to cause and cure? Hoyt, Stanford |
| Hello, Hoyt: When tomatoes have the symptoms you have described, such as the lower foliage on plants turning yellow then brown, the most common problem is a fungal disease known as either early or late blight. This disease starts on the lower leaves and then works its way up the plant. You would first notice dark spots on the foliage. Severe cases can destroy plants but if noticed early you can prevent future spread by removing the affected foliage and mulching around the plants to help stop the spores from splashing up. This problem is common during periods of excessive rainfall. Maintaining proper fertility is also important in controlling this problem. Nitrogen deficiency has similar symptoms without the dark rings. Solving this problem is as easy as spraying the foliage with a general purpose fertilizer such as fish emulsion. Then apply a granular slow-release fertilizer to maintain a healthy nutrient level. Good drainage is important as well. |
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| My willow tree has turned brown. Where can I find pictures of willow trees with bacterial blight? Willa, Clarksville |
| Hello, Willa: Willows (Salix) can be susceptible to bacterial twig blight. The good news is that in most cases it is not detrimental to the tree. This fungal problem is more common on trees that are stressed and on the decline. It is also more prevalent during wet seasons, which we have had so far this year. You will first notice defoliation or scorched looking foliage on new growth and then the actual twig becomes infected. These twigs should be pruned out and destroyed. Make sure to clean your pruners before and after use to prevent disease spread. It is always best to have the problem identified so you know what you are dealing with and the best way to prevent or treat the problem. Online the most reliable sites to look at are universities or Extension Web sites. For a positive identification take a sample to your County Extension Service. The Montgomery Extension Service is located at 1030 Cumberland Heights Road in Clarksville. The phone number is (931) 648-5725. The following like is a Web site that has pictures of
bacterial blight on willow trees plant-disease.ippc.orst.edu/disease.cfm?RecordID=1154
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| Our Knock Out roses are blooming in clumps and the thorns are huge, they look like small weapons.We cut the roses back, but there are no buds coming back.
Julia, Bardstown |
| Hello Julia: The characteristics you have described sound similar to that of roses that are suffering from as disease known as Rose Rosette. Do the stems have a reddish color? If so, you should remove all parts of the plant that are infected and dispose of them. Rose Rosette is the only serious issue associated with Knock Out roses. It not only affects shrub roses but also multiflora roses. This disease, originally thought to be a virus, was first detected in the 1930s on wild roses out west. It is spread by a microscopic, wooly mite as well as by grafting. Initial symptoms include abnormal growth that is distinctively red in color with abundant thorns that are usually more rubbery than prickly. It resembles what is known in the plant world as a "witch’s broom." It usually starts on the new growth of one cane but can quickly spread to the rest of the rose. Unfortunately, miticides are not effective against this insect, so catching the problem early is key to saving your rose. You can take a sample to the Nelson County Cooperative Extension so the horticulture agent can have it sent off to the University of Kentucky for a proper diagnosis. The Nelson County Web site is http://nelson.ca.uky.edu. Bardstown, KY
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| Our river birch has leaves that are turning yellow and falling off. Is this a diseaase or drought issue?
Gillian, Prospect |
| Hello, Gillian in Kentucky: There are a few different reasons why the foliage on your river birch (Betula nigra) is turning yellow. The most common reason is a result of heat and lack of moisture. Is your tree a new planting or has it been part of the landscape for many years and has an established root system? Either way, this tree is a water lover, and this growing season has been so hot and dry that if your tree did not receive supplemental moisture, this is likely the reason for the yellow foliage. As a result of this type of stress the tree will drop some of its foliage. Chlorosis is another possibility; this iron deficiency occurs when the soil is too alkaline for the plant to take up the iron or it might just not be available at all. If the yellow leaves have green veins then chlorosis is a possibility. Thankfully, river birch does not have many insects or disease problems, but birch leaf blight is a fungal issue that can cause the foliage to develop black spots with yellow rings around them. Infected foliage will eventually turn pale yellow and fall from the tree. It is important to have the problem diagnosed so you know what treatment options you have. You can take a sample of the foliage to the Jefferson County Extension office to have the horticulture agent take a look and give you a positive diagnosis, or you can take a sample to one of the local garden centers as well. This way you will know exactly what you are dealing with and how to treat for it.
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| The leaves at the bottom of my tomato plants are turning yellow and seem to be moving up the plants. What is the problem? Lillian, London |
| Hello, Lillian: This seems to be a common problem with many gardeners this year. The amount of rainfall we have had this year has a direct effect on the potential problem. The most likely cause of the foliage turning yellow is a type of fungal disease such as early or late blight. Good sanitation and fertilization will help prevent spread. Remove and dispose of all foliage that is not healthy. This disease starts on the lower leaves and then works its way up the plant. The fungal spores can be splashed up onto the foliage during rainfall or hand watering, so adding a thin layer of mulch around the plants will help prevent the fungus from spreading. Maintaining proper fertility and good drainage is also important in terms of growing a healthy crop. Nitrogen deficiency is a common problem with tomatoes and has some of the same symptoms. Solving this problem is as easy as spraying the foliage with a general purpose fertilizer such as fish emulsion; this will give your plants instant nutrients. Then apply a slow-release granular fertilizer to maintain a healthy nutrient level. Make sure your tomatoes are planted in full sun and have good air circulation. They are more susceptible to disease when they do not receive sufficient sunlight or are over-crowded.
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| The leaves on my austrees are turning yellow and falling off in June. Why would this happen? Gladys, Russell Springs |
| Hello, Gladys: Austrees are a hybrid willow. They are a cross between a hankow willow (Salix matsudana) and a white willow (Salix alba). Like all members of this genus they are very fast growers, up to 15 feet in one year, and have extensive root systems that require a lot of moisture. Because these trees are such rapid growers their wood is weaker than a slower growing tree and are damaged easily during wind and ice storms. Unfortunately, these trees are not ideal for the home landscape unless they are needed to control soil erosion. Willows are susceptible to a wide range of insect and disease problems so it is difficult to say for certain why the foliage is turning yellow. It may be chlorosis, which is a lack of chlorophyll and can be caused from a few different possibilities such as lack of nutrients, high pH (alkaline soil), and poor drainage. For a positive diagnosis you can take a sample to your County Cooperative Extension Service.
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| The March issue of Kentucky Living talked about David Bunch, who treats his soil with a fungicide before planting tomatoes. What fungicide would one use for this purpose? Sharon, Lewisburg |
| Hi, Sharon: Tomatoes are susceptible to several fungal problems, the most common being early and late-season blight. These soil-borne pathogens over-winter in the soil or on plant debris, so if your tomatoes have been infected by any fungal problems in the past it is important to take preventive measures. Good cultural practice is the most effective means of avoiding future problems. Crop rotation is especially important when it comes to soil-borne pathogens. It is best to move your tomatoes (and any other plant in this family) to a different space in the garden every two to three years. If there are pathogens in the soil, not planting host crops in that space will essentially starve the pathogen and allow you to plant tomatoes there in the future. Mulching is another way to protect fruit from these pathogens and will help stop spore dispersal. Spraying a fungicide or using a soil drench before planting would be a preventive measure, but there are many harmful fungicides out there that are not recommended for use on any edibles. If you do use a fungicide on your tomatoes, make sure you use a product that is organic and labeled for use on vegetables. If there is an established population of pathogens, cultural practices will be safer and more effective than any fungicide. |
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| There is a white substance all over the branches and leaves of one of our bushes: what could it be? Jean, Louisville |
| Hello, Jean: There are a few different possibilities of what this white substance could be. Scale, mealy bugs, and powdery mildew are all potential culprits. I cannot say for sure without knowing what the plants are or seeing a sample. Do you know what the actual shrubs are? Different plants are more subject to certain insects and/or fungal problems. For example, if you told me that your Euonymus had a white substance on it, I would not hesitate to tell you that your plant has scale, but the best thing to do is have the problem positively identified. That way you know how to treat the problem and know what to look for in the future. Is it possible to bring samples of your plants into the Plant Kingdom? We are located on Westport Road in St. Matthews. That way we can look at them and tell you what is going on and give you treatment options. The Cooperative Extension Service is also a great source of information, and you can also take your samples to the offices on Barrett if that is closer for you. I am sorry I cannot give more definitive answers at this time. |
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| Two Bradford pear trees have leaves that haven't looked normal all year. The bark was opening up so I sprayed for bores a few weeks ago. Friday, I pulled some of the loose bark from the tree thinking I would see where the bores had been, but it isn't bores. There are long tunnel-looking places up and down the tree. It doesn't look like an insect has been there, but I have no idea what is happening. Can you give me any advice? Bonnie, Bowling Green |
| Hello, Bonnie: Ornamental pear trees are delightful when they bloom in the spring. The most common problem with Bradford pear (Pyrus calleryana ‘Bradford’) is normally more structural than insect or disease related. They are fast-growing trees and tend to be short-lived, usually due to splitting during wind/ice storms because of their growth habit. They are, however, susceptible to a few different insect and disease problems. Brown foliage can be a symptom of root injury or stress related to uneven moisture levels. Too much moisture or not enough has the same physical appearance. Fireblight can also be a problem with these ornamental pear trees. This is a bacterial disease that is more common during periods of high temperature and excessive rainfall. The foliage turns black on the new growth and does not cause die back. A good indication of this is a shepherd's hook appearance at the end of the tip. From what you have described it does sound like your ornamental pear has either a borer or beetle problem, and depending on the stage of their life cycle you may not see the actual culprit. The tunnels were certainly made by an insect but without being able to see your tree, I cannot say for certain exactly what caused this damage. It really would be best to have a certified arborist come out and take a look at your tree. Typically when we see insect damage on plants it is a direct correlation with the plant, or tree in your case, not being healthy to begin with. Insects are drawn to plant material that is stressed. This is another good reason to have someone come out to look at your tree to see if it is worth treating. You can contact your Cooperative Extension Service for local recommendations on certified arborists in your area. |
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| We have three maple trees in the back of the house and have a problem with one that's about 10 years old. Its leaves are as dense as the others, but for the last three years the leaves curl, turn brown, and fall off. The tree is growing with new shoots,but get a certain size and start browning. Any thoughts? Jerry & Mary, Shelby County |
| Hello, Jerry & Mary: Depending on the species of maple, they can be susceptible to a number of different insect and disease problems. Without being able to see it I can only speculate, but here are some thoughts. If the foliage is turning brown, curling up, and falling off only on certain branches, it could be Verticillium wilt, a fungal problem. It usually does not affect the entire tree. It can also be related to drought stress: even though the other two maples are not showing the same effects, it could be a matter of where the trees are growing or if they are closer to downspouts or a slope in the landscape. It seems to be more of a cultural issue than a disease problem, especially if the maple is growing at the same rate as the other two. We cannot be certain until the foliage returns and it can be properly diagnosed. The Cooperative Extension Service is a valuable resource for this purpose. The Shelby County office is located at 1117 Frankfort Road in Shelbyville. Their phone number is (502) 633-4593. |
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| We planted tomatoes in pots on the deck. The plants are very full and there are tons of green tomatoes. We have had a lot of rain this season and the four ripe tomatoes so far have been rotten through. Do you think it's because of the rain or what else do you suggest?
G., West Haven |
| Hello: It sounds like the actual plants are thriving but the problem is with the fruit itself. It is difficult to say what is going on with your tomatoes not being able to see them. Does the foliage have any discoloration? If so, late blight could be a possibility. It appears during periods of wet, cool weather. This disease affects the foliage, and if conditions persist a secondary rot can destroy the actual fruit. Blossom end rot is another possiblity, which is a calcium deficiency usually caused from uneven moisture levels. There are a number of rots and wilts that can affect tomatoes. For a positive identification, you should take a sample to your Cooperative Extension Service or to a local garden center with a knowledgeable staff. When growing tomatoes in containers, it is important to make sure they are planted in a loose, nutrient-rich, well-drained soil. The container must have drainage and the soil should be consistently moist but never sopping wet. A thin layer of mulch will help retain moisture. Avoid watering during the evening hours and avoid watering the foliage altogether. For now, remove all foliage that is not healthy, as well as any damaged fruit. This will prevent further spread of possible disease. Soil-borne fungus can splash up onto foliage/fruit during rainfall, so it is a good idea to strip the lower foliage of the plants to help reduce this possibility. |
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| What can I do about mold and mildew on my phlox? Teresa, Manchester |
| Hello, Teresa: Phlox and powdery mildew go hand in hand. There are a few cultivars that are more mildew-resistant than others. ‘David’ is probably the most available cultivar. After the very wet and humid spring we have had mildew is going to be abundant on our garden phlox. In terms of control it is always a good idea to clean up around our plants with any fallen plant debris. This is especially true in the fall so that the fungal spores do not over-winter. Spraying with a fungicide is an option but it is only preventive, not curative, so it will need to be continuously sprayed throughout the growing season. If you decide to go this route check with your local garden center to see what they carry and be sure to follow label instructions. Good air circulation is important in preventing further mildew development. It will begin on the lower foliage and eventually work its way up the plant. Removing infected foliage will help prevent further spread. This fungus can make our phlox look unsightly and in severe cases it can weaken the plant. When watering be sure to only water the soil and not the plant. Ideally we want to water in the morning or early afternoon, never at night because the foliage will not have a chance to dry before nightfall and this creates a great environment for fungus to thrive. Phlox should be planted in full sun. |
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| What can I do to get rid of rust on my hollyhocks? Joyce, E. Bernstadt |
| Hello, Joyce: Hollyhocks are spectacular while in bloom, but the same can not be said for their foliage during most of the growing season. The most common problem with these perennials is rust caused by the fungus puccinia malvacearum. This fungus causes the foliage to look unsightly and in severe cases can cause plant failure; it does not affect the flowers. Rust can spread rapidly, especially during a wet spring like we have had in Kentucky. Good sanitation is essential in controlling the spread of this unmistakable fungus. It overwinters on plant debris, so it is important to clean up all remnants that have fallen. Removing infected foliage as soon as you see it in the spring will also help prevent further infection. Fungicides can be effective but they are only preventive, not curative. They must be sprayed at the first sign of infection and continuously during regular intervals throughout the growing season. As with any chemical, always follow application recommendations on the product label. |
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| What is the rust colored powdery substance coming on the base or lower branches of our Knockout roses? Bill, Morganton |
| Hello, Bill in North Carolina: As far as roses go, Knockout roses are quite disease-resistant. Like all other plant material, if these shrubs are not given ideal growing conditions they are more susceptible to insect and disease problems. They are sun lovers and should receive a minimum of six hours of direct sunlight each day. They prefer to grow in well-drained nutrient-rich soil. Good air circulation is important as well. If your rose is not growing in these conditions, you might consider moving it to a location where it will be happier. From what you have described, it sounds like your rose is suffering from rose rust caused by a specific fungus (phragmidium). What appears as a rust color powder is actually a cluster of fungal spores. It typically first appears on the foliage and then spreads to the canes. All infected parts should be pruned out and disposed of. Be sure to clean your pruners after you have finished to prevent disease spread. Avoid overhead watering and only water early in the day so the foliage that does get wet has time to dry before nightfall. Depending on how severe the infection is you can use a fungicide to control further spread. You can always take a sample to your County Cooperative Extension Service for the horticulture agent to look at. They will be able to give you a positive diagnosis and control options.
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| What would cause the tips of a yucca plant to appear braided? Dee Ann, Omaha |
| Hi Dee Ann: Yucca is a large genus of plants and, depending on the species you are growing, you may be referring to a hardy species for your zone or one you are growing as a house plant. There are species (Yucca rupicola) that have a twisted-looking growth habit but if this were the case all the foliage would have this characteristic. Certain species of yucca are susceptible to mites, which can cause distorted growth like you have described. These pests are hard to see without a magnifying glass but with severe infestations you may see some webbing. As with all plants, when they are not grown in ideal conditions they are more likely to have insect and/or disease issues. Yucca plants should be grown in full to part sun and well-drained soil. For now, all infected growth should be removed and you might want to have a horticulturist at your county Extension office take a look at it to give you a positive diagnosis. Omaha, NE |
