Question
I have a large Knockout Rose bush in my front yard (2 yrs old), gets morning to noon sun, shade rest of the day. We're in Zone 8. It has been extremely full and beautiful, about 4 ft tall now. In the past 3 wks, it has rapidly been losing leaves, so much so that only the top foot of the plant has leaves. I've noticed a lot of the leaves are yellowing and have dark spots. Also noticing only a fraction of the number of blooms, as compared to the past few months (I trimmed one day in July and I stopped counting at 200, and had only done 1/2 the bush!). I'd say I have max 50 blooms right now. Please tell me there's something I can do for my rose! Thanks so much,
Brandy

Answer
The spores of the Black Spot fungus float around in the air and when conditions are right, such as wind and rain, they are pushed to the ground. When they land on rose leaves they start their life cycle. First they sink their roots into the leaf and use up it's nutrients. Then they bloom or become a black mound. If enough of these spores live on a rose it dies, turns yellow and drops off. As you can see, you can't get rid of it permanently only control it. Certain rose colours are more prone to this disease because they contain the genes of a rose that likes a dry climate in their background. Yellows, oranges, scarlet reds and whites are more prone. That is not to say that all roses with these colours are prone but many of the older ones are. You can use a fungicide on your roses now and that will keep it under control. Just ask at a garden center for a fungicide spray for Black Spot. This is the time of year that conditions are usually right for Black Spot to spread. Good success has been had by giving roses a sulfur and dormant oil spray before they leaf out in the early spring. It is the same spray that is used on fruit trees. The instructions for roses are on the back. Again depending on your weather, if it has been a hot summer this will put roses under stress and they will be winding down now. The Black Spot disease will also weaken them a little. Spray them now with a rose fungicide, water well and deeply past 8 inches because that is where the feeder roots are, the rest of the roots are anchors. Many people are having unusually hot spells in their summer and roses do not like hot spells and will re-act to them by slowing down to save their energy. Your rose will come back just fine next spring. Hope this helps.