Black spot can be found on numerous plants - including roses, flowers, fruits, and leaves. It is especially problematic when the weather is hot and humid.
Black spot is a fungus that primarily affects roses but can also be found on other ornamental and garden plants. It can be found on flowers, fruits, and leaves and is problematic when the weather is hot and humid. Problems are greatest when leaves stay wet for 6 hours or more.
Black spot produces round, black spots with fringed margins that can be up to 1/2 inch in diameter. The spots form on the upper sides of leaves. The leave tissue surrounding the spots turns yellow. Usually lower leaves are infected first, and infected leaves often fall off the plant early.
Black spot overwinters in fallen leaves and branches. Water splashing on the soil under plants catapults the spores unto the plants above.
What To Do and Helpful Tips
- Regular feedings provide the nutrients your plants need to grow strong and help protect them from disease.
- Remove plant debris from garden beds in the fall to prevent black spot from overwintering in fallen leaves and branches. Throw infected plant material in the trash. Do not compost it to help keep the disease from spreading.
- Wet plant leaves encourage many fungal diseases, including black spot. Apply water directly to the roots, like with a soaker hose, to help prevent the disease.