What Could Be Causing Yellow Spots on the Leaves of My Rose Bush?

Black Spot

• Black spot is a fungal infection. It appears at first on leaves as black spots and progresses to black spots surrounded by yellow circles on both sides of the leaves. As the disease spreads, leaves turn from green to yellow and eventually drop to the ground. This disease is very common in humid and rainy conditions. The rose bush may become completely defoliated. Fungicide should be applied as soon as new leaves appear in early spring.

Rust

• Rust on roses is caused by a fungus. It first appears as a rusty powdery substance on the underside of leaves. Eventually yellow or brown spots appear on the top of the leaf, and the leaf may curl or wilt. Infected leaves should be removed and destroyed. Leaves on the ground should be raked. Avoid watering plants from above because excess moisture can cause the fungus to spread.

Insect Pests

• Sometimes insect pests can cause leaves of rose bushes to wilt, turn yellow, appear unhealthy or fall off. Spider mites may infest rose bushes, and infestation can lead to dry leaves with a bronze sheen. Rose scales are small insects with crusty shells. An infestation with this type of insect can cause foliage to turn yellow, wilt and fall from the plant. Spraying bushes with non-toxic insecticidal soap can help control pest problems.

Rose Mosaic

• Bright yellow patterns made up of wavy lines on the leaves of rose bushes may be a sign of rose mosaic. Yellowing may also occur in circles. Rose mosaic is caused by a virus. Infection by a virus causes the plant to be weakened, making it more susceptible to other diseases. Aphids may help spread the virus, so control of aphid infestation may protect nearby plants.

Prevention/Solution

• Prevention of rose diseases begins with selecting hardy roses that are suited to your location. A local nursery can help you choose the right roses for your area. To help prevent fungal infections, roses should be planted in well-drained soil and full sunlight. Diseased leaves should be raked and discarded. Avoid wetting leaves while watering rose bushes.