Flowers
Senior Member
Posts: 116
Joined: Thu Jan 08, 2015 2:30 pm
Location: Fort Collins, CO, USA Zone 5b, sometimes 6

Rust on my miniature roses?

My miniature rose plant has had a powdery mildew problem for a while, but today I noticed some brown spots has it developed into something worse?

Flowers
Senior Member
Posts: 116
Joined: Thu Jan 08, 2015 2:30 pm
Location: Fort Collins, CO, USA Zone 5b, sometimes 6

Forgot the pics.
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imafan26
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Posts: 13961
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

I would get rid of the infested leaves and treat it with a fungicide. Myclobutanil is for eradication. Copper sulfate, neem, and dithane are better for protection.

https://www.domyownpestcontrol.com/myclo ... 4_468.html

Flowers
Senior Member
Posts: 116
Joined: Thu Jan 08, 2015 2:30 pm
Location: Fort Collins, CO, USA Zone 5b, sometimes 6

Do you know of any organic fungicides?

imafan26
Mod
Posts: 13961
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

Copper sulfate and neem I believe are acceptable for organic. But are only useful for prevention. Once you have a fungal problem and especially rust, you need to go systemic. You may not have rust just yet, the underside would have orange spots and I cannot tell. Sometimes powdery mildew can turn leaves a reddish color. You can try cutting back all of the diseased leaves, improve the environment, which may mean changing the location if it is in a pot because spores will be hanging in the air. You will need to continue spraying to prevent reinfection of the new leaves.

Fungal disease is something you really need to be proactive about, it is much easier to prevent than to treat.
https://www.rhs.org.uk/advice/profile?PID=748
https://www.extension.purdue.edu/extmed ... p-69-w.pdf

Flowers
Senior Member
Posts: 116
Joined: Thu Jan 08, 2015 2:30 pm
Location: Fort Collins, CO, USA Zone 5b, sometimes 6

I read somewhere on here that potassium bicarbonate is a good method for preventing and sometimes eliminating powdery mildew and other fungal issues, so I just sprayed it with some. I'll also try changing the location to lessen crowding and increase light. Hopefully that will cure the issue, if not maybe I can try something less organic. What do you think?

imafan26
Mod
Posts: 13961
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

Spores are in the air so you need to improve air circulation as well, more light probably won't hurt. I have heard of potassium bicarbonate. It is supposed to be used by the food industry, but I could never find it.

I have used baking soda to try to keep the leaves drier and milk has antifungal properties as well. Use milk that has some fat in it, the oil will help wick off water. I have tried these things before and with improved air circulation and lowering humidity, they have stemmed the tide of minor infections. I have pruned and used a systemic fungicide for the best results at cure especially with black spot.

Flowers
Senior Member
Posts: 116
Joined: Thu Jan 08, 2015 2:30 pm
Location: Fort Collins, CO, USA Zone 5b, sometimes 6

I tried the milk and it didn't really work. I bought my potassium bicarbonate from a wine making website, it's supposed to be very similar to baking soda, but a little stronger. I'll try opening the window on warm days for increased circulation.



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