The Tropical Fruit Forum
Citrus => Citrus General Discussion => Topic started by: matt_citrus on August 24, 2021, 07:23:05 PM
-
30 or so trees in very close proximity and the only one experiencing this is a Shiranui. New growth flushes are browning and dying off. Is this one of the common fungal infections?
(https://i.postimg.cc/5X7cQ7qL/IMG-20210824-184743210-2.jpg) (https://postimg.cc/5X7cQ7qL) (https://i.postimg.cc/KkTCVZXD/IMG-20210824-184802504-2.jpg) (https://postimg.cc/KkTCVZXD)
-
Perhaps have answered my own question but offer it to the experienced growers for confirmation.
Looks very much like the Alternaria Brown Spot symptoms on young growth in this recent research paper:
Alternaria brown spot on new clones of sweet orange and lemon in Italy (https://www.researchgate.net/publication/339230035_Alternaria_brown_spot_on_new_clones_of_sweet_orange_and_lemon_in_Italy)
(https://i.postimg.cc/qhxnL5BM/Symptoms-caused-by-artificial-inoculation-of-Alternaria-alternata-on-detached-leaves-of.jpg) (https://postimg.cc/qhxnL5BM)
And in this UF publication: Alternaria Brown Spot (https://crec.ifas.ufl.edu/extension/canker/pdf/CH01700.pdf)
-
It looks as if the damage is confined to only the tenderest part of the new leaves; it may be a reaction to an environmental stress, rather than fungal invasion. Did you spray the citrus recently? Sometimes insecticidal soap burns tender young growth while mature growth shows no damage. Other types of horticultural sprays/fertilizers can also burn young shoots. Certain varieties are more sensitive than others. Bright sunlight on water or oil spray droplets can also cause burning on tender growth. Perhaps to be safe, isolate the plant, but don't give up hope.
-
It does not look like Alternaria Brown Spot.
-
I had brown die back on new growth on my Santa Teresa lemon last year, potted, after almost daily rains all year. I brought it out of the rain, snipped off the infected leaves, and sprayed it with copper fungicide. It has not had a problem since, and is back outside in the rain like all my other in ground and potted citrus. I think it was just more sensitive to too much rain and I wonder if it didn’t get a fungus from being too close to some rhododendron that also have been suffering from a brown leaf disease. No problem this year, but not as much rain this year either.
-
It does not look like Alternaria Brown Spot.
The mystery continues then.
-
Does anyone have suggestions for treatment? New growth continues to be affected.
-
I have the same issue with a few potted trees, not citrus. I tried sprays, replanting in different soil, fertilizers, macros, part shade, full sun... Nothing works.
-
Matt, how cold does your night temperature get now? Maybe it's just cold damage to young leaves.
I would just cut off the branches with the black leaves that look damaged. Doesn't look like a big deal but you never know.
-
Coming back to this, I'm fairly certain now that it's Alternaria Brown Spot.
Don't have a good mechanism for control yet given how often it rains.
-
Fungicides ae usually needed for adequate control. Maneb, mancozeb, chlorothalonil, metiram, strobilurins, and copper fungicides are the most widely used products. Where the disease is severe and environmental conditions are favorable for he pathogen, several applications are usually required to produce acceptable control. In humid climates, applications begin when the spring flush is one-fourth expanded Where humid conditions exist, follow-up sprays could be required. Good Luck with your tree. We would appreciate hearing out how your tree is doing. (Taken from the Compendium of Citrus Diseases.)