Plant, Grow, And Prune Roses - The Old Farmer's Almanac

Good gardening practices, such as removing dead leaves and canes, will help reduce pests. If problems develop, horticultural oil and insecticidal soap can help control insects and mildews. Possible rose pests and problems:

• Japanese Beetles: See many tips for deterring these pests, including great companion plants for roses which will help prevent Japanese Beetles.
• Aphids: All plants deal with aphids which are easy to manage with a spray of water or insecticidal soap; just stay on top of your plants and check consistently.
• Black Spot: Rose plant leaves with black spots that eventually turn yellow have black spot. This is often caused by water splashing on leaves, especially in rainy weather. Leaves may require a protective fungicide coating, which would start in the summer before leaf spots started until first frost. Thoroughly clean up debris in the fall, and prune out all diseased canes.
• Powdery Mildew: Leaves, buds, and stems will be covered with a white powdery coating. Mildew develops rapidly during warm, humid weather. Prevent mildew by pruning out all dead or diseased canes in the spring.
• Botrytis Blight: This gray fungus will cause the flower buds to droop, stay closed, or turn brown. Prune off all infected blossoms and remove any dead material. Fungicide application may be necessary.
• Spider Mites
• Thrips
• Rust
• Stem Borers
• Deer: Roses are a delectable tidbit, so try planting lavender near your roses. Not only will you have the makings of a nice potpourri, but the scent of lavender will discourage browsers. You can also spread human or dog hair around the garden area or check our list of deer-resistant plants to protect your roses.

In general, avoid rose issues by buying disease-resistant varieties and cleaning up debris, weeds, fallen leaves, and any diseased plant material as soon as possible.

Also, speak to your local Cooperative Extension or trusted nursery about a spray program with products approved in your state.