Black Spot on Roses
It’s likely one of the most common blights of rose gardeners everywhere, black spot is the fungus that just keeps coming back. It loves hot, humid/wet conditions (sound like this year or what?) so it’s beginning to pop up on leaves everywhere. The first phase of this fungal disease is its namesake as black spots begin to show on the surface of the leaves. As the spots get larger yellow emerges on their rim, eventually causing the whole leaf to become yellowed and then fall off. You many even begin to see black or purple spots on the actual stems of the plant. If not treated thoroughly you can bet you’ll be singing the same sad song next season.
First off, get rid of any diseased leaves and canes. Prune diligently and then rake up all fallen leaves. Once you’ve done this spray the entire plant with a fungicide. There are a number of organic options such as Copper, Lime Sulfur, Neem Oil, Potassium or Ammonium Bicarbonate.
Now prevent it from returning, don’t water the leaves and only water in the morning. Ensure plenty of air circulation around cultivars and be sure to space roses properly. Stay wary my friend, or you’ll be seeing spots.