Does anyone know what these orange bumpy spots are on my hollyhock leaves, and how to get rid of them? Many of the leaves on the plant look like this. I have tried removing the affected leaves but new ones keep getting infected as well. The plant keeps growing--it's gotten a lot bushier over the summer (no blossoms)--but I am concerned about these orange bumpy spots that keep appearing on the leaves.
I believe that is rust, but I don't know how to treat it- hopefully someone will help you.
thanks, Jo. Yes, I think you are right. I'm hoping DrOBarr will have some suggestions for treatment?
This is rust. There are some specific strains of rust that are host specific. The one that likes Hollyhock will also attack other closely related plants like Mallow (the weed and the nice flowers).
Control of most fungi (rust is a fungus) is to get the spray on the plant before you see the rust. Keep the new leaves protected. That way, when the spores land on the leaves they cannot grow.
Also, clean up the old leaves, even pull off the green leaves that are heavily infested.
Remove related plants that are also hosts (the weedy mallow, for sure!)
Do not overhead water. Keep the leaves dry as much as possible.
If I remember, rust can be controlled with pretty much any garden spray that is a fungicide.
Here is some more info about rusts.
http://www.ipm.ucdavis.edu/PMG/r280101211.html
thanks, Diana.
Thats definetly rust. And Diana_k is right on the money. Very few products can cure any of the Puccinia's very well.
If you are organic only you can use Serenade or copper or sulfur, though the copper and sulfur may cause some leaf burning. Neem oil or Serenade or any other biological is not likely to be very helpful at this point with the disease so far along.
Fungicides like (Daconil) clorothalonil or difenaconazole or really almost any broad spectrum product would work. I would apply on a 7 day schedule until symptoms go away.And of course removing the most diseased leafs without affecting the overall plant too much is always good to reduce rust innoculum from infecting the new growth.
Thanks DrOBarr I appreciate the recommendation! I'll do that!
