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Black Spot and Powdery Mildew

Posted: Mon Apr 14, 2008 3:40 pm
by Hobbit
Last year nearly all my roses (HT/Floribunda?Climbing) suffered from Black Spot and Mildew.
Currently all are clear with lots of new growth.
Should I be spraying now, and adopting the motto `Prevention is better than cure`.
Thanks in advance for any advice.

Posted: Mon Apr 14, 2008 7:54 pm
by doccat5
What do you want to spray them with?

Black Spot. This fungus disease is most common in humid and rainy conditions; the fungus spores germinate in water. Once a plant is infected, the fungus will remain in the canes through the winter and reappear on the next season's growth. Many of the HT's have poor resistance to it, but it is controllable with good sanitation in and around your bed. Same with powdery mildew. If you live in a humid area, it goes with the turf.

Normally, it's suggested to use fungicides to control. I don't use chemicals, I do however, use sanitation practice, pick roses that are highly resistant, and work on improving the health of the soil in my beds. I only have 3 HT's left, they were all Mother's Day gifts many moon ago and are about 25 years old. Which is the only reason they are still here. I have gone almost exclusively to rugosas and antique roses. They are just a lot easier to care for and I love the fragrance and the hips. I do use a cup of corn meal around the base of my roses first thing in the spring. That does seem to help, how it works, I have no clue, but the worms love it, I also periodically dig in a banana peel around the bushes. The worms love those too, so the soil is very rich and friable.

Hope that helps.

Black Spot & Mildew

Posted: Tue Apr 15, 2008 5:39 am
by Hobbit
Thanks Doccat5. I have been using Dithane 945 as a fungicidal agent and Liquid Derris to combat Black Spot/Greenfly/Red Spider Mite. I will have to do a little research to see what else is on the market, and basically get in there before the problems arise.

Posted: Tue Apr 15, 2008 5:48 pm
by doccat5
Man, you are using heavy hitters up front. You must really have a very bad problem. The ingredient in Dithane 945 is listed as practically nontoxic. Is that like being practically pregnant? Yucky, buddy.
Liquid Derris contains rotenone, which is not quite nuclear, but close.

Posted: Tue Apr 15, 2008 6:48 pm
by imagardener2
We used dusting wettable sulphur powder in our yard last week for a bad flea infestation. As my husband was spraying the grass he asked if I wanted him to spray my roses as well as the bag was also labeled for black spot and powdery mildew.


Neither of us had any idea it was good for that, but that's what I'll be using in the future - should we ever get enough rain again to have to worry about such maladies. :(

Posted: Fri Apr 18, 2008 10:53 pm
by doccat5
Yes, using sulfur is one organic way to get black spot under control. You just need to make sure you are applying it when the wind isn't blowing and you dress accordingly and follow the directions. It's potent stuff, but not the nuke it variety of fungicide. LOL