Software
Houzz Logo Print
psk8er

Black spot

13 years ago

I vowed to stay ahead of black spot this year and started spraying every 2 weeks as soon as they started to leaf. I ordered Bayer Advanced Disease Control for Roses Flowers and Shrubs and have been using that. I have black spot :( When I saw the first signs I started spraying once a week and each morning I take a basket and pick every leaf that shows any sign of bs. It seems to be getting better but the weather is also getting warmer and my bushes have reached the point it is very difficult and painful to reach in there and remove affected leaves. Can I spray more often without harming the bushes? If I don't get this taken care of before the heat and humidity hits I'm afraid I will lose the battle again. I have also read that I should spray the ground as well as the bushes and use cornmeal. Plan on doing this as soon as I get home. Thanks for any help you can offer. I guess you can tell I'm new to this.

Comments (20)

  • 13 years ago

    Trust me--you are probably discovering infections that began before you started spraying. If you spray thoroughly according to directions, you will not have further problems. You don't have to pick off the sick leaves where it is inconvenient. Having sprayed a couple of weeks at 7-day intervals, you can go back to the 14-day interval.

    The other possibility is that you have some disease other than the common ones, black spot and cercospora. If so, it will probably stop as soon as the weather warms. Please try to post a sharply focused closeup of spotted leaves.

  • 13 years ago

    I will post one in the morning. One thing I didn't mention is I don't find it very often on older/larger leaves. It is mostly on tiny new leaves that couldn't be more than a day or two old. I have planted several new bushes this year and just don't want them having to battle this before they are even established. I will google and read what I can find about cercospora. Thank you!

  • 13 years ago

    Bayer DC completely controls cercospora as well as blackspot. I was thinking your roses could have spot anthracnose (which only attacks a fraction of rose varieties) or downy mildew (which is rare in home gardens outside coastal California). These diseases develop only in cool, drippy weather and will go away when the weather warms.

  • 13 years ago

    How long since you started spraying? I was delayed from spraying due to too rainy/cold/windy weather. I had some spots, I think they were athracnose, not BS. It was too cool for black spot.

    I sprayed the weekend of the 6th. I did have some leaves spotted after I sprayed, but they were likely infected before I sprayed. Most of the roses look ok. I'd wait it out.

  • 13 years ago

    Instead of spraying more often, I'd suggest rotating fungicides. If you spray the same fungicide all the time, a strain of BS resistant to it may survive. Bayer Advanced Disease control contains Tebuconazole, a systemic--I'd suggest occasionally spraying a contact fungicide like Daconil or Mancozeb.

  • 13 years ago

    Thanks to everyone! I really thought I was in trouble but I feel much better now. I has been unseasonably cold here but being new to this thought things would get worse when the hot/humid weather hit. In Alabama the humidity is very high.

  • 13 years ago

    Do yourself a favor. Buy a 3 lb bag of Mancozeb (Manzate) and add it to you're spray routine every 2nd or 3rd spray. This will keep your bush's super clean and nothing can get immune to the Bayers ADC.

  • 13 years ago

    Michaelg has the right of it. Once you have it and spray other leaves that were already infected but not showing symptoms yet will continue to spot. Only the new and previously uninfected leaves will remain clean. The spray does not "cure" already infected leaves. It protects the new and uninfected leaves from getting it. Just keep to a regular program and it will prevent new outbreaks.

  • 13 years ago

    here is the photo. These leaves are tiny. Entire group is only 3/4" long. Thought things were better but this morning it was as bad as ever. Guess I will be buying Mancozeb on my lunch break.

  • 13 years ago

    It's very unlikely that you have tebuconazole-resistant black spot. I wouldn't bother with the mancozeb myself, but if you do get it, you must adjust the pH of the tank water to acid pH 4-5, or the mancozeb will lose its potency.

    Black spot doesn't normally attack leaves until they have fully expanded. Downy mildew does attack the new growth. Can't tell in the photo, but a diagnostic is that DM spots often stop when they run into a vein, creating straight edges or angles on one or two sides of the spot. No commonly available chemical controls downy mildew well. I think ag extension would tell you that DM has never been a chronic problem in home gardens in Alabama. However, episodes could occur in cool weather.

  • 13 years ago

    If one is considering using Mancozeb, please read the following thread:

    http://forums2.gardenweb.com/forums/load/roses/msg0300394823674.html

    Here is a link that might be useful: suggested thread

  • 13 years ago

    OK then. I guess I will get to eat lunch after all. I looked at the leaves and the spots do cross the veins. So it is black spot? I don't know how this happened. I had terrible black spot last year so I started spraying as soon as I saw a leaf. I didn't get to spread cornmeal or spray the ground last night because of rain. Does spraying the ground help? Did this carry over from last year? My bushes have had a few leaves removed but aren't that bad. It is the rose tree that
    is going to be in trouble if I don't get this stopped.

  • 13 years ago

    Spraying the ground probably does not help.

    What is the variety of climbing rose that has the problem? It might be one that is susceptible to spot anthracnose. If you let a leaf grow out and post a picture of a mature spot, we might be able to identify the disease.

    If I were you, I would not be worrying so much. The only inexorable spot disease in Alabama is blackspot. I doubt this is blackspot. If it is, tebuconazole will control it.

  • 13 years ago

    The one that is having the most trouble is Weeks Cinco de Mayo rose tree. I will let a leaf grow out and post if It is still a problem. Thanks

  • 13 years ago

    If it is black spot there is probably nothing you could have done to prevent it. The spores are everywhere, in the air, the soil, the plants, and, yes, it does winter over. If the weather conditions are right it shows up.

    Black spot, while ugly, is not going to kill your rose. Relax and wait for the weather to get warmer and dryer and it will probably just go away on it's own.

  • 13 years ago

    We usually say "tree rose" or "standard" for a rose grafted on a trunk. "Rose tree" is an old-fashioned term for a large shrub or climbing rose.

  • 13 years ago

    One more picture and then I will stop obsessing and just do the best I can. I removed everything I saw that was yellow or spotted yesterday before I came to work. This is what I had when I got home. It was also worse on a couple of bushes. I am trying to let a leaf mature as suggested but since they fall off if you touch them after they turn yellow I'm not sure any of them will make it. I know BS isn't supposed to kill them but if the leaves continue to go like they have this week I don't see how it can survive. I did sprinkle the cornmeal around them last night. It might not help but most of us in the south believe a little cornmeal never hurts anything! :) Thanks to everyone

  • 13 years ago

    Oh-- I think those leaves are on short, abortive shoots that tried to grow out in the winter and were damaged. They are so much smaller than the normal foliage. Just snap off the shoots that are producing these leaves. Over-wintering leaves always get a lot of blackspot because they are damaged or senile or the spots incubated before you started spraying.

  • 13 years ago

    I will continue to remove them. I hope you are right because this one was a gift from my daughter and I would really hate to lose it. I wasn't sure if it was rose tree or tree rose so thanks for letting me know. I am here to learn everything I can. I have a question about plant markers but guess I should post that separately. I'll let you know how she does. Thank you again for your help

  • 13 years ago

    I have a lot of roses that have those little yellow leaves. The weather has been so crazy, my roses tried leafing out a few times and were frozen back. We are having some nice windy/rainy weather, so I'm hoping that gets rid of all those ugly leaves.