Fungus?

Question: Hello,
I have two big pine trees affected by something that google identify as fungus. These are large trees, and next to them is a oak tree with some leaves with spots of a black colony. I also have pics of a lilac and a cherry tree also with affected leaves.
This is at Sudbrook Park, our neighborhood has very old and large trees that make it very relaxing and I would like to preserve.
I work at U Maryland Baltimore, School of Medicine. I'll appreciate your advise.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied November 01, 2024, 10:58 AM EDT
response: The needle yellowing and shedding on the spruce (the evergreen pictured) is normal. (Even though it's a spruce and not a pine, this phenomenon happens with pines as well, sometimes even more prominently.) Many types of evergreens drop leaves in the autumn, just to a lesser extent than deciduous plants (which is why they are still considered evergreen). Some evergreens, like holly and azalea, tend to do this shedding in spring instead of autumn.  During years of higher stress, such as this summer's prolonged drought (still present in most of the state; see linked map), the amount of foliage shed might be exacerbated. While there are "needle cast" fungal diseases of spruce that can be commonplace in our region (particularly on blue Colorado spruce, which is not the type of spruce pictured), the symptoms in the images do not align with those of the disease. Spruces are not very heat-tolerant and can struggle in Maryland conditions, even though they remain popular in area landscaping, so that vulnerability might be a factor contributing to more needle loss than usual (presumably) this autumn. Going forward, in prolonged dry weather, occasional watering can help to reduce their stress. Our Watering Trees and Shrubs page provides guidance. Even though watering as-needed from this point forward won't reverse any needle shed in-progress, it will help to keep the roots healthy, which in turn will keep buds for next year's foliage healthy as well.  Most trees, shrubs, and perennials can contract various leaf spot diseases by late summer and autumn. Very few are serious, and instead are just a cosmetic eyesore, if noticed at all. Most leaf spots are fungal, though some are bacterial, and neither requires intervention at this point. Their spread and severity from year to year can be very dependent on weather. Years with wet stretches of weather (like the repeated rains we had back in spring) can increase the risk of leaf infections, since spores tend to have an easier time infecting foliage when its surface remains wet for a while. While plenty of other factors can affect mature tree health and longevity, leaf spots fortunately aren't among them, though it's possible a struggling tree has a leaf spot infection that has nothing to do with its decline. If a tree is suspected to be in decline, have it evaluated by a certified arborist or licensed tree expert. Although they cannot treat or cure every ailment, they can help make a diagnosis as well as look for sources of tree stress that might be able to be alleviated.  Lilac are routinely affected by both fungal and bacterial leaf infections. They prefer cooler summers (and probably lower humidity too) than Maryland experiences, so sometimes they are stressed and more vulnerable to disease. Powdery mildew is very common, but leaf spots can be too. Our lilac diagnostic page presents the typical issues.  Ornamental (flowering) and edible cherry trees also are vulnerable to an array of issues, whether disease or insect damage, plus environmental stress from drought or over-watering (or poor drainage and soil compaction...anything that keeps their roots too wet or too oxygen-deprived). The ornamental cherry diagnostic page presents those issues, the most common of which is Cherry Shot Hole disease, where leaf spot infections eventually cause holes in the foliage and premature leaf shed (on top of drought stress also contributing to early leaf drop).  With deciduous plants like oak, lilac, and cherry losing leaves now (or soon) for winter, nothing needs to be done because any infections will not affect their long-term health. If the lilac (being the smallest of the three and easier to manage) had leaf infections this year, then raking-up its fallen leaves and disposing of them (don't compost) might help to reduce the spore abundance capable of causing infections next year. However, it's not a foolproof solution, since windblown spores could always arrive again from elsewhere and begin new infections. Use of a fungicide in these situations is both not practical and generally not recommended. This is in part because they will require repeated application to the entire canopy (spray coverage must be thorough) to maintain a barrier to infection, and rains or other uncooperative weather can interrupt that regimen, allowing infection to take place; fungicides don't always work well, for that or other reasons; and because fungicides may cause harm to pollinators or other organisms. Fungicides are also not curative, so they won't be effective after symptoms have manifested.  For now, other than checking plants like the lilac for watering needs, nothing needs to be done, and the needle shedding on the spruces will likely wrap-up within the next few weeks.  Miri

responder: The Question Asker Replied November 01, 2024, 12:20 PM EDT
response: Thank you!!

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied November 01, 2024, 12:32 PM EDT
response: You're welcome!