Identification of fungus(?) on Japanese Maple tree and on garden plants - Ask Extension
Hi,
I live in Summit County and we have a fairly old Japanese Maple tree that has had spots on the leaves for the past couple years. We thought thi...
Knowledgebase
Identification of fungus(?) on Japanese Maple tree and on garden plants #797486
Asked June 23, 2022, 3:59 PM EDT
Hi,
I live in Summit County and we have a fairly old Japanese Maple tree that has had spots on the leaves for the past couple years. We thought this may have been transferring to plants in our hydroponic garden, too, so we're wanting to identify it and see if there's something to treat it with.
Summit County Ohio
Expert Response
There are a number of diseases of maple trees, including Japanese Maples that result in spotted leaves. Some are caused by bacteria and others by fungi. Following are a few diseases that cause leaf spots:
1. Tar Spot - this usually starts as small light green or yellowish-green spots that enlarge over the summer and turn black and look like the leaf has been splashed with tar. Tar Spot is usually a cosmetic problem not requiring treatment. If you have had spots in previous years and they did not turn black as the summer progressed, it is not likely to be Tar Spot.
2. Leaf Scorch - Scorch symptoms are light tan or brown areas between the leaf veins or along the leaf margins or edges. Leaf scorch is caused by dry weather combined with wind and high temps. When the tree does not get enough water, the leaf will scorch. From your pictures, it did not appear there was any spotting along the margins or edges.
3. Leaf Spot - Symptoms of Phyllosticta leaf spot on many maple species include the development of small (approximately 1/5 inch), roughly circular, brown spots with dark reddish or purplish borders. Japanese maples develop yellowish or tan
spots, which sometimes have transparent centers. A circular pattern of black fungal fruiting bodies may be seen in the dead areas on infected leaves. On some maples, the diseased center portions of the leaf spots may fall out, giving a shothole appearance to the leaves. Infection occurs on wet leaves by water-splashed spores. Wet weather in spring and
early summer favors disease development. The fungus probably
overwinters on fallen leaves or on buds and twigs of host trees. This disease is not considered a serious landscape problem.
Based on your photos, I am leaning toward Leaf Spot, but to be sure, you can send a sample to the OSU C. Wayne Ellet Plant & Diagnostic Clinic https://ppdc.osu.edu/submit-sample
Following are a few links to Univ Extension websites with more info about Maple diseases that may be helpful:
https://hort.extension.wisc.edu/articles/purple-bordered-leaf-spot/
https://hgic.clemson.edu/factsheet/maple-diseases-insect-pests/
https://www.canr.msu.edu/news/why_do_my_maple_leaves_have_spots
Bacteria and fungus that cause diseases usually impact a single family like Acer (Maples), so your other plants may have a different problem.
1. Tar Spot - this usually starts as small light green or yellowish-green spots that enlarge over the summer and turn black and look like the leaf has been splashed with tar. Tar Spot is usually a cosmetic problem not requiring treatment. If you have had spots in previous years and they did not turn black as the summer progressed, it is not likely to be Tar Spot.
2. Leaf Scorch - Scorch symptoms are light tan or brown areas between the leaf veins or along the leaf margins or edges. Leaf scorch is caused by dry weather combined with wind and high temps. When the tree does not get enough water, the leaf will scorch. From your pictures, it did not appear there was any spotting along the margins or edges.
3. Leaf Spot - Symptoms of Phyllosticta leaf spot on many maple species include the development of small (approximately 1/5 inch), roughly circular, brown spots with dark reddish or purplish borders. Japanese maples develop yellowish or tan
spots, which sometimes have transparent centers. A circular pattern of black fungal fruiting bodies may be seen in the dead areas on infected leaves. On some maples, the diseased center portions of the leaf spots may fall out, giving a shothole appearance to the leaves. Infection occurs on wet leaves by water-splashed spores. Wet weather in spring and
early summer favors disease development. The fungus probably
overwinters on fallen leaves or on buds and twigs of host trees. This disease is not considered a serious landscape problem.
Based on your photos, I am leaning toward Leaf Spot, but to be sure, you can send a sample to the OSU C. Wayne Ellet Plant & Diagnostic Clinic https://ppdc.osu.edu/submit-sample
Following are a few links to Univ Extension websites with more info about Maple diseases that may be helpful:
https://hort.extension.wisc.edu/articles/purple-bordered-leaf-spot/
https://hgic.clemson.edu/factsheet/maple-diseases-insect-pests/
https://www.canr.msu.edu/news/why_do_my_maple_leaves_have_spots
Bacteria and fungus that cause diseases usually impact a single family like Acer (Maples), so your other plants may have a different problem.
