I don’t know what kind of tree it is. But it looks like the same brown spots are on both the tree and the hydrangea bush, plus also on an adjacent peach tree. What IS it? And what do we do to treat it?
Looks to me like septoria leaf spot. It is a fungal infection. Difficult to get rid of. It usually affects the lower leaves first. Copper Sulfate spray is a good preventative.
In Nashville, it is probably Cercospora Leaf Spot but both cercospora and septoria are basically a generic problem called "leaf spots". Cercospora symptoms: scattered, small, circular-ish, brown or purple spots first appear on leaves near the base of the plant. On the Big Leaf/French/Hortensia Hydrangeas, the centers of these spots eventually turn from tan to light gray in color and are surrounded by a brown or purple halo. A hole may develop in the center sometimes. The spots are "usually" about one-eighth to one-fourth inch in diameter but I have seen larger ones too. This combination of a pale center and dark margin is usually called a frogeye leaf-spot pattern. In contrast, the Cercospora leaf spots on oakleaf hydrangeas appear somewhat angular in shape and are dark brown to purple in color. Often, heavily spotted leaves turn yellow-green and may fall to the ground (if they do, discard them in the trash). Typically, the spotting begins on the leaves at the base of the plant when they touch soil containing the fungi and then the problem gradually spreads upward through the canopy. Spotting of the leaves can be seen with a magnifying lens in spring if you look hard enough but, it usually is more visible after June 20th... the Summer Solstice... when chlorophyll production is reduced with each passing day. By mid to late summer, the spots slowly become more visible as the amount of green in the leaves is slowly reduced. Also, heavy fall rains may make the leaf spots more noticeable in some years. Cercospora is typically an aesthetic problem but if allowed to spread, premature leaf loss is unsightly and the lack of foliage will steal plant vigor (healthy, green leaves produce food for the roots and very, very infected leaves produce no or less food for the roots), causing the plant -in extreme cases- to succumb to other problems/pests. The fungi is almost all over the world in the soil. Fallen diseased leaves are the primary source of spores of the causal fungus Cercospora hydrangeae. These spores are spread to the healthy lower leaves by splashing water on the bottom of the plant. The problem then “moves upwards”. Once C. hydrangeae is introduced into a planting of hydrangea, yearly outbreaks of this disease are likely to occur. Frequent late summer rain showers will not only greatly increase the rate of disease spread, but also intensify the level of leaf spotting and defoliation. Somewhat ironically, extended periods of drought in the late summer/fall will usually suppress disease development and spread. Removing dead diseased leaves, increasing air flow between plants, applying just enough nitrogen to maintain a moderate growth rate and watering only the soil and never the leaves will help slow the development and spread of Cercospora leaf spot. Since the appearance of symptoms is usually delayed until late summer to early fall, protective fungicide sprays are rarely needed for the control of this disease on hydrangea in the landscape or nursery. For effective control of Cercospora leaf spot with a fungicide, begin applications when spotting of the leaves is first seen and continue applying that treatment as needed. Typically, protective fungicide treatments are suggested only on highly valued plants that suffer noticeable damage every year. Because the problem happens at the end of the growing season, many people do not want to spend money on the problem. Some fungicides listed next may be expensive, especially to treat just one plant but, that being said, I think I saw a Bonide fungicide for sale in spring 2021 at Lowes for $6-10. Fungicides registered for the control (not cure) of Cercospora leaf spot are listed next, with the active ingredient first and the commercial product name in parenthesis: azoxystrobin (Heritage; this one has the smallest application rate and largest repeat interval); chlorothalonil (Bonide, Daconil); mancozeb (Dithane; Protect; others); myclobutanil (Immunox); thiophanate-methyl (Cleary's 3336); some copper fungicides containing copper hydroxide (Kocide) Examples of clean sanitation practices that can help control the problem greatly since nothing available cures it: Remove plant debris (leaves, blooms, stems and in extreme cases, also remove/replace the mulch); discard the debris in the trash, not in a compost pile. Destroy severely afflicted plants but, if you do not want to do this for sentimental reasons, consider cutting all hydrangea stems once the plant goes dormant and all plant parts turn brown & then replace the old mulch with new mulch. Do not water over-headwith a sprinkler system or with a hose. Instead, water using soaker hoses or drip irrigation. If you only have a sprinkler system, consider activating the station that waters the hydrangea from 6-8am... and also consider if the area may be getting too much water. I have a hydrangea by the house entrance that has Cercospora but with drip irrigation and clean sanitation practices, the problem has been controlled (some foliage still remains affected but not like it once was). In years with a lot of rain in the fall, the problems are worse than on drier years. However, the problem has not migrated to other very closely planted mophead hydrangeas, Pee Gee Hydrangeas and Oakleaf Hydrangeas (or other plants/trees). The problem in your third picture does not appear to be the same as the one in the hydrangea leaves but, if those leaves from the tree also somehow get a lot of water from the sprinkler, I would try to address that. Do remember that, at least in our areas, dormancy is starting. Thus, some tree leaves are starting to look past their prime and they will soon yellow/brown out & drop as fall 2021 officially arrives on Wednesday.
Has anyone used Agri-Fos for control with success? You may recall mine getting hit but I won"t know until next spring If I have control. I used Clearys 3336 flowable systemic early. The potassium salts of phosporous acid are twitchy about doses. Too much burns. I have started small. Since it too is systemic I am hoping to impact dormancy to some degree such that spring renewal finds the plant protected internally.
There is a lot of risk with that product. I could not find references that said potassium salts of phosphoric acid were successfully used to control cercospora leaf spot... except in the label of that product. It only referred to the product being used/tested in crops, not in specific plants like hydrangeas. Since the product did not mention that it has been tested on hydrangeas, it is difficult to say if the product may cause harm to hydrangeas. Be careful to read all of the information, including dosage, frequency use/intervals. Click here to see the PDF document: https://r.search.yahoo.com/_ylt=Awr...abel.pdf/RK=2/RS=0xD_zOoLJt94AVQjWCE0vxs5yu8-
I originally became interested in Agri-fos because of sudden oak death. That disease is more related to leaf spots than I knew. The more I read the label, the happier I became. I have used it several times in this wet summer with really good, fast observable results both in the garden and out.
Once a plant, especially the foliage displays unwanted markings. Alarm bells start. Simple rule here. If you are aware that your plant can be open to viral, bacterial attacks. DON'T wait untill you see the signs. All the chemicals under the sun, will not cure it. Where possible, live with it and defoliate. Where possible. Spray etc against getting the infection.
