I am not familiar with anthracnose, anybody can tell? If not, any hints on what it could be? This 'Akane' had the same problem last year but I did not do anything and the plant has been strong and healthy this spring. The spots appear in summer with hot weather. Affected leaves drop from the plant. There are other maples nearby but are not affected, just this one. Gomero
Thanks but I'm pretty sure it is not sunburn, plant is in shade. I'm quite familiar with sunburn. Gomero
hello gomero, i'm not familiar with anthracnose or the cultivar 'akane', but the seemingly random pattern of drying on your leaves, reminds me of what happened to the leaves on an abnormally long shoot of my 'higasayama' last year. i actually had three new shoots that exceeded three feet, but the leaves that were affected received no direct sunlight, which is what confused me. no other branch on the entire tree exhibited this type of drying. the two differences i see between mine and yours is mine were afflicted sometime in september, as my leaves were starting their fall colors, and your dried leaves appear brown whereas mine seem much darker, almost black. furthermore, as you can see, the petioles remained very healthy despite the demise of the leaves. so far, this year, everything looks good. sincerely n. musume
Neko, Thanks for your tip. I've seen similar behaviour in some cultivars where only one branch is affected. In the case of my Akane all branches are affected. Gomero
hi gomero, it seems taht i got the same problem with one of my acer pamatum it is quite different from sunburn the leaves have some burnt point, then they become reddish and die at the end i will send you an email so we can talk about it in french
here is a good pic of my poor acer palmatum please help me! it is the firts time it happens can it be overfertilization? it is really hot here for the last month but the acer is watered carefully and is in part shade the main problem is that it is near some others acers (less than 2 meters) and i fear for verticilium wilt what should i do? thanks again
Reading the description of Anthracnose in the books, it is written that it appears mainly during wet, cool conditions. Well, if this is the case then my Akane's problem may not be anthracnose since it appeared during hot, dry conditions. Then, what it is?, When I take out leaf scorch (plant is in the ground, in shade, not fertilized, mulched and regularly watered at night; and also leaf scorch normally spread from the tip and margins inwards) I run out of possibilities. Gomero
According to notes here and in the Photo Gallery, this ‘Akane’ is planted under other shrubs, gets only three hours of sun, powdery mildew, and potentially has had anthracnose for two consecutive seasons. Just from the diagnosis of powdery mildew alone, which I understand does not generally affect many Japanese maples, I would move this tree to a spot with better air circulation in the fall after it is dormant. I would water from below the leaves, and if in a rainy climate, a spot with a few more hours of sun to dry the leaves might be beneficial as well, at least until this problem is cleared up. Both powdery mildew and anthracnose overwinter on the tree and in the leaves, debris, and mulch on the ground, and are splashed up onto the plant again with rain and watering, and blown by the wind onto other susceptible plants. For chemical treatment of the fungus, which I wound not recommend for anthracnose without a definitive diagnosis, I would recommend mancozeb treatment over the other more toxic alternatives described in some of the links, and definitely remove and destroy all of the leaves and debris in the area, and move the mulch somewhere else. A lengthy review of some reading on issues related to this question follows, so proceed with patience. It sure would be nice if we could find some close-up photographs of anthracnose on Japanese maples; a google image search yields photographs of only leaves of other maple species. Some publications note that anthracnose is not yet well understood. Others note that differentiating between symptoms of leaf scorch and anthracnose can be difficult, with some, but not all, noting that leaf scorch usually occurs between the veins, while anthracnose occurs along the veins, with both typically being described as various tones of brown, although some note that it can be black as well. Anthracnose “nfections are usually initiated in the spring when new growth is emerging, but can occur throughout the entire season when the weather is favorable … includ[ing] periods of extended cool, moist, or wet weather. … Anthracnose symptoms are apparent from late spring to early summer, but additional cycles can result in damage that is visible later in the growing season.” http://www.caes.state.ct.us/FactSheetFiles/PlantPathology/fspp066f.htm. The symptoms of anthracnose “vary from small, circular to irregular spots … to larger blotches that are usually associated with the midribs and veins. Veinal necrosis [browning] is common on … maples. When immature leaves are infected ... these leaves may become severely distorted. Young leaves may die and fall soon after a heavy infection.” http://web.aces.uiuc.edu/vista/pdf_pubs/621.pdf, Physiological leaf scorch, which is the most common, indicates one or more of several factors are affecting the tree. “It is caused by dry weather, combined with wind and high temperatures. When trees do not get enough water they will scorch. The symptoms are on all parts of the tree or only on the side exposed to sun and wind. Scorching due to dry soil may be overcome by proper watering. A response to an undesirable soil contaminant, such as salt (applied to roads for wintertime ice control), accumulation of fluorides in containerized soil mixes with perlite, or high levels of phosphate fertilizers. A reaction to a vascular pathogen, either fungal or bacterial.” http://hgic.clemson.edu/factsheets/HGIC2005.htm. Note that the symptoms described above do not match those described elsewhere for bacterial leaf spot. “If scorching is due to an inadequate or diseased root system, watering may have no effect.” http://hort.ufl.edu/trees/ACEPALC.pdf. Disease also weakens the plant, which would make it more susceptible to other fungal infections. Leaf blight may co-occur with anthracnose. “The causal fungi of anthracnose on maple are found in the genera Discella, Discula, Monostichella, and Kabatiella. … Leaf blight, caused by the fungus Kabatiella, often results in early defoliation of … Japanese maple. Fruiting bodies (acervuli) of the causal fungi may appear on either the upper or lower surface of the leaves.” http://www.aces.edu/pubs/docs/A/ANR-1049/ANR-1049.pdf. If an extension lab is not readily available, a 20X lens is recommended for observations of leaves, if one is interested in looking for things such as fungal fruiting bodies, which are telltale signs. Several publications describe mature leaves as being more resistant to anthracnose, and many describe the brown areas as eventually curling, as we see in both sets of photographs. What is also interesting in Gomero’s first photograph (which file is large enough to zoom in on, whereas Neko’s set is, unfortunately, not) are the clear areas of bordered darker green, which if monitored, are likely to be the first stages of this problem. In Neko’s, there are also areas of lighter brown, which if monitored are likely to be moving toward the necrotic stages seen elsewhere on the same leaves.
anthracnose hello laurie, thank you for your very informative, detailed post. i see that i shall have to do quite a bit of reading on anthracnose. i changed the size of the images in my previous post to a higher quality, to facilitate a detailed look at my affected leaves. my 'higasayama' had a rough first year at my place as it came straight from the nursery packed with aphids, and lots of osmocote. it also developed quite a bit of powdery mildew as it was in shade for most of late spring and early summer. i do remember that the discoloration began to exhibit itself late in the season after a period of hot, dry weather. i repotted it and moved it this winter to a location which has plenty of air circulation in a yard that receives direct sunlight for a couple of hours before noon, and then again from about 2 pm - 4 pm. there is no chance of too moist a climate where it is now, and the only water it receives is straight from a hose. as i wrote to gomero, everything seems fine so far. the only note of interest is there were only a handful of sets of leaves that had any appreciable variegation. thank you again. ^_^ n. musume
Laurie, Great article on anthracnose, thanks for the effort. I fully support what you say: C'mon, with all the pros reading this forum, there must be confirmed cases of this disease and a few pictures could help. In one of the references that you give it is written Which explains some of the comments made in this thread. I still vote for anthracnose and I will try to catch and burn as many fallen leaves as I can. Next spring I will treat preventively and trust the maple will make it through. Gomero
