Common Tree Diseases
Diseases are common plant problems in the landscape. Often, it can be difficult to identify diseases because the causing organisms are rarely seen with the naked eye, and they spread by microscopic growth and spores. However, the signs and symptoms on the tree become obvious as the disease takes hold.
Tree diseases can affect any part of the tree, or the entire tree. Named for the type of damage they cause, we have leaf spot, leaf blotch, scab and blister, defoliation, needle cast, and yellowing or chlorosis as named symptoms. Stem canker and galls, trunk and root rot are also very prominent tree disorders.
Before you take corrective action, you have to determine what is causing the problem. A correct diagnosis is the first and most important step in developing and applying a correct treatment, which allows you to address the problem rather than simply treat the symptom. This is when a diagnosis from a professional arborist may prove critical.
Here are some of the most virulent tree diseases that might affect your area:
Phytophthora Root & Crown Rot
Combinations of crown dieback, discolored or loss of foliage and a generally unhealthy appearance.
Trees can suffer phytophthora for years before death, if the decline starts to spread from the root system, as pictured. If the crown or basal stem is attacked, however, the tree may be killed within a single season.
Young trees are especially vulnerable to phytophthora, due to their underdeveloped root systems and crowns. Good soil drainage is recommended to guard against phytophthora, as the disease thrives in warm, moist soil.
Anthracnose refers to a symptom rather than a specific fungus. Many fungi produced these symptoms on specific host plants.
The most common symptom of this group of diseases is irregular dead areas or blotches on the leaves. Sometimes whole leaves are engulfed. Cankers may girdle twigs and small branches causing them to die. The resulting regrowth from lateral buds can give the tree a gnarled or crooked appearance.
Symptoms on most trees are confined to the leaves the disease is considered more lethal if the fungi invades the twigs and branches and can prove fatal as in the flowering dogwood. Note that many plant diseases and adverse weather conditions can cause similar symptoms.
This disease spreads to oak trees in two ways: carried by insects and by root graft infections (when roots of different trees meet each other in the soil and form a connection). Sap feeding beetles spread this fungal disease from infected trees to wounds on healthy trees. Oak wilt disease symptoms progress differently in red oaks, white oaks, and live oak. However, they have one critical symptom in common: leaf drop. This is important because most other oak disorders do NOT cause leaf drop. When leaf drop is combined with one or more other oak wilt symptoms, the disease may be reliably identified.
On red oaks, the symptoms include: leaf drop; partially brown and partially green leaves, starting at the margins and working toward petiole (the leaf’s stem). There is a rapid progression of symptoms from top down and the tree dies quickly, resulting in dark streaking that may appear under bark and spore mats underneath the bark (this appears ONLY in the red oak family). Surrounding red oaks may also wilt and die.
On white oaks the symptoms include: leaf drop; partially brown and partially green leaves that seem to discolor from the tip down in a more solid pattern than red oak group; may be olive drab in color and appear dry. There is a rapid progression of symptoms from tip of branches inwards. The branches die one at a time over a period of time; the tree death may take months or years and dark streaking may appear under bark.
The live oak family (Texas oak) symptoms include: leaf drop and interveinal chlorosis (yellowing between the leaf veins). Symptoms appear throughout the tree, the tree dies within one to six months, dark streaking may appear under bark. Surrounding live oaks may also wilt and die.
Any plant infested with large numbers of sucking insects or growing beneath one of these plants may be affected by sooty mold.
Sooty mold fungus is a general term for several species of fungi or molds that use the honeydew secreted by sucking insects as food to develop and grow.
It generally does not cause damage to the plant, but can be a considerable nuisance to homeowners as it affects anything beneath the trees including hardscape, cars and structures.
Fire blight is a common bacterial infection that results in twig dieback.
The classic symptom of a shepherd’s crook with a burned appearance to the leaves and twig is a sure sign of this destructive disease. The disease can destroy limbs and even entire shrubs or trees.
Phytophthora Root & Crown Rot: Andrej Kunca, National Forest Center (Slovakia)
Anthracnose: R. J. Reynolds Tobacco Company Slide Set, R.J. Reynolds Tobacco Company
Sooty mold: Joseph O’Brien, USDA Forest Service
Oak wilt: William M. Ciesla, Forest Health Management International
Fire blight: John Hartman, University of Kentucky
All images catalogued on www.bugwoord.org.
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23 thoughts on “Common Tree Diseases”
I think one of our cherry trees has black knot. Do you have any recommendations for DIY treatment? Should all affected branches/limbs/etc. be pruned and, if so, when? What can/should I purchase to apply to the tree to stop and prevent future growth? I have read about copper solutions but would like more advice. I hope to hear from someone soon. Thank you.
Some of these pictures are a little startling because I think my trees may have these diseases. The degenerating leaves is something that I thought happened naturally or during colder months. I’ll have to bring out a professional to confirm the issue and see if they can treat it for me. Thanks for the awesome info!
Hi David Hawkins would like to tell you some tree diseases is natural and some is if sometimes we careless about trees and lack of knowledge how to proper care. I was very careless about the trees but when i saw it not seems well and not looking good i got tense, i read some blogs and search from the internet about tree diseases and one of my friend suggest me professional who can help me, now I am relaxed about it. i would love to suggest you just visit a site http://www.arboristtreeondemand.com/ they may be suggest you some tips after see the pic or they can visit also.
This is some great information, and I appreciate your point that dropping leaves is a symptom of oak wilt. I have a red oak tree, and its leaves have been falling, and they’re turning kind of brown as well. I’ll definitely look into having a professional come and see if it’s oak wilt, and to see if it can be treated. Thanks for the great post!
Very informative read thank you. A Lot of the trees around my area are highly susceptible to fire blight.
You mentioned that a symptom of Anthracnose is irregular dead areas and blotches on the leaves. That seems to be the main thing that we have noticed about our old oak in our backyard. We have loved having this tree and want to do what we can to keep it healthy. I think that calling in a tree service will be the way to go. We will have to show them the symptoms in the hope that they can give the right diagnosis. Thank you for sharing!
My tree seems to have the sooty mold that you mentioned. That’s good that it doesn’t pose too much of a threat to my plant. It sure makes it look bad though; I think I’ll call someone to take care of it.
Hi I have a gray-green kind of mold or fungus growing on my trees It completely killes the trr=ee. So far it seems to affect mostly the cedar but it also spread onto regular tree as well. do you know what that is? and what can I do about it?
Hi Nancy Roslyn Rappaport ,
This was a best outstanding informative post you shared on this page about the common Anthracnose diseases from the tree without any wastage of time ,If you want to to remove this kind of disease from a tree and start proper care of trees in a public garden ,Then you must provide a proper tested sterilized water to trees daily according to the period of a time daily and also sprayed a medicine of Anthracnose disease which help you to remove this kind of disease quickly from tree trees and increase the beauty of a garden .
I have a weeping cherry tree that we nust cut a completely dear limb off of it,,now today I see another dead limb right in the same area, also some of the leaves has holes in them like something is eating at my tree.
Can you tell me what this might be and if so let me know how it should be treated.
I appreciate your help
We see a lot of Oak Wilt down here and your description is way better than the way I’ve been explaining it to our customers. I’m going to start referring clients to your site for more in depth info on tree diseases. Thanks for the info.
Fire blight is really bad news. I’ve seen it ruin dozens of trees in the southwest and Texas.
I just wanted to emphasize early detection. Because I have seen some folks take extra precautions to prevent things like fire blight or leaf scorch. Preventative medicine is the best. There are those iron treatments and garden sprays or soaps you can use, but more importantly is proper planting and pruning.
I highly recommend learning about common tree diseases and spotting them early on for your trees.
I have a Lindon tree it has buds coming but then just stop leafing out. Branchs don’t seem to be dead ?
I have a dogwood tree and suddenly the leaves are getting weird dark brown streaks all over them. Is there a way to send a pic of what it looks like so I can get help with this?I don’t want my tree to die.
I appreciate this work amazing post for us I like it.
I have a Calamander Tree that was flourishing; full of leaves and trunk growing thicker and blacker. In the space of two days it is stone dead. All the leaves have fallen off and branches are brown twigs. What has happened? Has someone poisoned it or can this happen naturally?
Honey fungus is one of the biggest problems in this part of the world. Not much to be done except remove the tree and burn it! So easily spreads to other trees and shrubs. I’d be interested to know whether honey fungus is a problem in other parts of the world?
Very informative, thanks! It’s great to have resources out there on these types of tree service topics.
I had a bunch of pine trees I inherited from my aunt last year & the bugs ate them all up… thanks for the info, this would be good to know in case Round 2 happens.
We have seen a spate of live oak issues recently – a problem which is being taken seriously by local government to ensure we keep these beautiful trees healthy.
I’m glad you explained that the most common symptom of Anthracnose is irregular blotches or dead areas on the tree’s leaves. My husband and I were sitting under the tree in our yard last night to enjoy the nice weather, but he noticed some stage dark partches in the leaves that we were unsure about the cause of. Thanks for letting me know that it might be best to discuss Antrhacnose with a professional arborist soon!
We are very thankful for all your ideas and for sharing them to all your readers. Keep it up and we will continue to support your web posts.
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There are so many similarities between tree care and modern medicine. Catching the issue/disease early is important, but preventive care is always best. A lot of great info here. Thanks for sharing.
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