A Gardeners Forum Forums Gardening Reference Gardening in 2006 Brown Spots

On my gernaniums that eventually kill the leaves. Anyone have any idea? They aren't bugs, I don't think. The leaves just look like they have the chicken pox on the undersides. I've never seen this before.

I've broken off the affected leaves and even trimmed off a whole branch, but they keep coming back. They're really bad now.

Thanks for any help I can get!

are they seed germaniums or scented geraniums ?

Any of these??

Geranium Diseases ???????

Buglady, they must be seed geraniums because they just stink like geraniums. No, they're not scented.

Weezie, from the pictures, it looks more like this The only difference is that the spots don't have the little circles around them. I'm willing to bet it's rust. What do you think? OH! And my fiddle leaf has it, too!

I second rust. Can you email me a larger image of it so i can see closer? suzanne@bugladyconsulting.com

Its definitely a fungal pathogen by the markings, round and crosses over veins.

if this is just one plant, i would just throw it out so it does not spread. If you want to try and save it you need to remove all infected leaves to the garbage asap. You don't want the fungal spores spreading, the come out the bottom side of the leaves, thus the rust like powder you get with "rusts".

be sure to wash your hands after handling, so you do not spread the disease. Also CLEAN YOUR CLIPPERS, they will spread the disease too.

oh wait.. you didnt take that photo... just realized that. blond moment.....

AAAH! Suzanne! I can't throw out my babies! There's two of them with those spots. Both plants are pretty big and just beginning to bloom. What I think I'm going to do is pull all of the affected leaves and if I need to trim the plants as far back as I can then I'm going to use that fungicide that the instructions on that web page that Weezie sent me said.

LOL Yeah... I didn't take that picture but I'll explain it better to you. On the underside of the leaves are a bunch of brown dots but they don't have the circles around them that the picture does. However, they do cross over on some veins. Some leaves are just covered with them and some have just a few. There are some leaves that have actually died and are just barely hanging on to the larger stem.

Thanks for reminding me to disinfect my clippers! I rarely think of that!

well you need to make sure you have a fungicide that will kill fungal spores. Not many do, but the hydrogen peroxide products will.

I have used this product for a few years now, it works wonders on many plant diseases, and it is safe to use. It is organic. http://www.gardensalive.com/article.asp?ai=682

Buglady, do I just look on the label and see if it's a peroxide fungicide or is there a specific brand name?

Ironside, it sounds like a great product worth looking into! Thanks!

here is an aricle with some information. hydrogen peroxide

Baking soda is also very useful in killing fungus of many types on plants and is very safe. Also Neem oil products are very multipurpose and fast acting. I have had wonderful luck with both.

WOW, Suzanne! That's some article! Great to know and thank you!

My kind of math!
LOL Good ole pop bottles!

I'm learning all kinds of good things here! Can't ask for anything simpler than baking soda.

I trimmed my babies way back today. There sure isn't much left of them but I'm sure they'll do much better... maybe! One of them had a bunch of dead wood that was black and wet on the inside. Never seen this before so I don't know if it will survive or not. Could it be rot from all the rain we've had??

Fungi yes, rust no,
That is a fungi called anthracnose. It can effect pretty much everything from lawns to giant oaks! Pick off the infected leaves and discard them. This is one of the hardest fungal diseases to deal with. I have never used that fungi soap myself so I can not say if it will work. If it does not do the trick, I would suggest using a fungicide with either a manganese and zinc or a daconil base.

Just so you know rust is a fungus.

Anthracnose is just a general term to describe several fungal pathogens that leave black circular sunken spots. Anthracnose can be host specific, so just because its infects one plant does not mean it will infect other different species around it.

Back to rust, they reason it get its name is because when you rub the bottom sides of leaves infected with the fungus you can get a red powder on you. What this is, is the fungal spores that have pushed though the leaf and are dispersing. This happens later in the rust life cycle, so early symptoms will not include the this.

I went back and checked some of my pathology texts and production manuals and could not find mention of Anthracnose on geraniums, this does not mean it can not happen, just not one of the more common problems.

Also what homeowner fungicides have manganese in them? I know the commercial ones, but don't know all the homeowner brand names these days.

whohoo spring is here!!!

Bug Lady I know rust is a fungi, like I said Fungi "yes" rust no.

Anthracnose is just a general term to describe several fungal pathogens

Actually you are right and wrong, it is not just a general term, but yes it does cover a host of pathogens. When one or more of the pathogens attacks a plant in a certain way it is called anthracnose. Much the same way that the same germ which can cause a chest cold in one or a head cold in another will develop in someone else spine and be called meningitis. They are caused from the same pathogen, but have totally different cures.
Yes it can be host specific. It can leave some plants along and trash others, while having different symptoms on each plant.
To a lawn, it is usually a death sentence, to a hardwood, it may just develope a few black spots or the tree can loose all of its leaves and recover the next year.

I believe MancoZeb is available to the home owner under various labels, or at least in this state it is, I don't know the regulations in each state so I could not say.


By the way, the early symptoms of rust are yellow to orange to red lesions on the leaf. The powder is the last thing to develop. Also rust prefers shade and plants that have a nitrogen deficiency. Rust is one of the easiest diseases to control, all you have to do is fertilize and it will go away on its own, with no fungicides.

Oh I forgot to mention that the break down of the word actually means "anthra" (black)"nose" (hairs).
While most anthracnose infections usually show some black spots, the hairs are less frequent and sometimes only visible under a microscope, not all black spot diseases are anthracnose. Leaf spot is a common disease that mimics anthracnose, and has other identifying characteristics.