Has anyone heard of a petiole borer in oaks? I have a case of white oaks (Q alba) dropping leaves, near the base of the blade. Not chewed by birds or squirrels, no sign of leaf feeding insects.
Any diseases that cause this type of symmptom?
Russ Carlson, RCA
From Scott's post it sounds like you may have been experiencing a wet spring. Have you ruled out Anthracnose?
Also is there one or more plants affected?
Magnesium defficency? or Toxic mulch?
Are there any twig gall formations near petioles?
Stephen, you mention "toxic mulch," Do you have any experience with Clopyralid contaminated mulch and the sypmtoms it might produce on large woody plants? I notice a lot of the literature on this problem comes from the PNW.
I was not particuarly referring to Clopyralid, rather an anaerobic conditions resulting in vascular cell damage or diruption.
No, I have yet to have any experience with Clopyralid contamination.
Most of the mulch around trees used here is bark mulch. Vary seldom have I seen grass clippings or bed hay/feed placed as mulch around trees.
No tests have been performed on larger trees specifically. Susceptibility projections are based upon plant family taxonomy: legumes, solanaceous.
In addition to Oregon and Washington, California preceeded Oregon in adopting handling and restrictions of contaminated compost materials.
Have their been recent drought conditions?
I don't know if it helps, the city of Brantford is located in Southern Ontario. We had a very wet cold spring up here also. We have had leaf drop in Oaks both Red and White, Norway maples and Sycamores. We are seeing both Anthracnose and Verticilium Wilt. Also we are looking at possible Oak Wilt Disease. I hope this might help. We are also having to deal with the Emerald Ash Borer.
I finally got a few leaf samples of the oak leaves. The arborist had thought that he saw girdling, like a twig girdler on a tiny scale, when using a hand lens. Under the dissecting microscope, it appears that the âgirdlingâ is just shrinkage and breaking of tissues where the infection first occurred, girdling the petiole at the surface. Rather odd.
My suspicions have turned to anthracnose or similar disease. Does not appear to be life threatening, Max of about 25 percent foliage loss. No signs of infection on the blades, only the petiole.
Drought- yes, about 20 months, ended (officially) last fall. Winter was about normal, slightly high on rainfall. Spring was very wet, cooler than normal, prime for fungal infections. This is probably not drought related, except as the trees may be somewhat more susceptible or less able to recover.
Bear, DE USA
That sounds consistent with our white oak observations.
The pathologist on our team mentioned he saw some "spots" on petioles that might be anthracnose. We had no "girdling and collapse" as you describe and we were concerned with these symptoms only as part of a broader assessment. So we did not pursue with any disscetion or cukturing.
I am not clear if our pathologist would have looked for or anticipated a different organism on petioles and leaves.
Checked back on one of our white oaks today. No evidence of dropped leaves though some are a little droopy. That could be due to last week's high 90's F temps and the underlying damge we are investigating.
Russ, speaking of your dissecting microscope, did you ever take the digital-video add-on step?
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