I have 2 15-year old Black Oak trees. Brought them from northern IL as acorns.
This year have rust spots appearing on leaves. As damage progresses le...
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Oak tree leaf rust? #806420
Asked August 15, 2022, 5:13 PM EDT
I have 2 15-year old Black Oak trees. Brought them from northern IL as acorns.
This year have rust spots appearing on leaves. As damage progresses leaves curl and whole branches appear to be dying. No leaf fall, yet. Worst damage on a few of the very top branches. Notice tiny white flies on tree. Will send photo in separate email.
Last summer I had no irrigation water, so watered these two trees with City Water. This summer I have limited irrigation. So far these trees have gotten full watering.
Live in urban area, right beside A Canal, just north of Kieger Stadium.
Klamath CountyOregon
Expert Response
Photos.
-----Original Message----- From: Ask Extension <<personal data hidden>> To: David Steiner <<personal data hidden>> Sent: Mon, Aug 15, 2022 2:13 pm Subject: Thank you for your Ask Extension question (#0076351)
Dear David,
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YOUR QUESTION #0076351:
Oak tree leaf rust?
I have 2 15-year old Black Oak trees. Brought them from northern IL as acorns. This year have rust spots appearing on leaves. As damage progresses leaves curl and whole branches appear to be dying. No leaf fall, yet. Worst damage on a few of the very top branches. Notice tiny white flies on tree. Will send photo in separate email. Last summer I had no irrigation water, so watered these two trees with City Water. This summer I have limited irrigation. So far these trees have gotten full watering. Live in urban area, right beside A Canal, just north of Kieger Stadium.
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From my research, and comparison of your leaves with pictures I am finding, it appears this is more likely Tubakia or Actinopelte leaf spot. I attach descriptions and link below with more information.
As for the white flies, they appear aphid like to me and most likely not related to the leaf spots.
Tubakia(formerly Actinopelte)
In mid- to late summer, irregular, dark-brown spots form between the leaf veins and enlarge up to 3/8 inch in diameter and become reddish brown, often with a yellow halo. Trees with iron chlorosis and those under other stresses are most severely affected.
Little damage results from this disease, which does not cause defoliation. No control action is recommended for landscape situations. Apply a fungicide in the nursery beginning at bud break. https://extension.psu.edu/oak-diseases
Actinopelte Leaf Spot: This fungal disease may be a serious problem in wet weather. It is caused by the fungus Tubakia dryina (formerly called Actinopelte dryina). The symptoms are circular, dark to reddish-brown leaf spots with a diameter of ¼ to ½ inch. Spots may run together to form irregular blotches. Tiny black specks in rings are visible in the spots and blotches. Severe infections cause the trees to lose their leaves prematurely. Trees of low vigor that are repeatedly defoliated may die.
Prevention & Treatment: Destruction of all infected plant material will reduce the spread of the fungus. Rake up and dispose of fallen leaves. Small trees defoliated several years in a row may need spraying. Apply mancozeb, chlorothalonil, thiophanate-methyl, or a copper fungicide according to the instructions on the labels. Complete coverage is necessary for control. See Table 1 for examples of specific products.
