I have lots of Arisaema triphyllums on my property. Not all of them are the same.
I've started looking at stable variations that I have. One really looks strange to me.
It has water marks on the leaves that come through on new plants too.
Any idea what's that?
I think, I got the answer. It looks like systemic rust pathogen, Uromyces ari-triphylli. At least it's localized and seem to be host specific. I'll talk to some people at the Univ. about it and start erradication process once confirmed.
Ouch, had to go look that one up and then run outside to check mine to see if I had any leaves that had what you described as water marks. I don't and I checked a couple hundred.
http://www.suite101.com/article.cfm/shade_gardening/98802/3
Native populations of A. triphyllum are sometimes infected with a rust fungus, Uromyces ari-triphylli that shows up as orange spots on the undersides of the leaves, eventually covering the spathe and stem. There is no known cure for this. I have removed affected parts (to the trash - wash your hands afterward before touching any other plants) in hopes that the tuber would have enough reserves to return. Sometimes it does and is free of rust; sometimes not. But the recommended treatment is to discard the entire plant in the trash (not the compost), tuber and all, to prevent the fungus from spreading to other populations of any Arisaema species in the area.
These are the exact links I came upon. I am glad that I have it localized to two plants with babies. Got those out in a trash bag. Now I am keeping a watch on the rest of the Jack population I have.
I wish I took the photos before I bagged the plants but I did not. When I examined the undersides, they had yellow-orange spots that matched the pictures. It did not occur to me to turn the leaves when I took the photographs above to turn the leaves. I read that the plant is poisonous, so I try to handle it always in gloves. Nothing new from the folks at the Univ.
Extension on the ID.
Boy has this been the year for fungus! Everybody seems to have something or other. Talk about fungus amung us! And native plants are definitely stressed with all the invasive species popping up here there and every where combined with unseasonably warm weather.
My thoughts are that you hit the id on the head with the existence of the yellow-orange spots on the undersides of the leaves. Great detective work. I swear I went out and checked every plant of mine that I could find for water marks like yours a second time and came up empty handed. I did also flip over leaves looking for the fungus.
You need to submit those photos to the University because they don't have any showing anything but the actual fungus. That patterning on the leaves might end up being a tell tale sign of the presence of the fungus. Those photos of yours could help somebody know to look on the underside of leaves! You've got something there that isn't too common! A great tool!
