What Is Wrong With My Rabbitbrush?

Are the leaves pale on their upper side and are there any dusty blisters on the undersides?

Are the leaves covered with white powder?

Do the leaves have holes, snail-like cases are present on the leaves?

Are there any cottony balls or green flowerlike swellings on stems?

Likely cause for these symptoms is a fungal disease - Rust. Provide good air circulation around plants by thining them. Avoid making leaves wet when watering. All infected leaves should be removed. Spray leaves with sulfur early in the season to prevent rust or to treat mild infections.

White, powdery patches on the leaves are caused by a fungal disease Powdery mildew. Powdery mildew usually appears in damp places. Encourage good air circulation around the affected plants by thining them and any surrounding plants. Water plants from below to keep foliage dry. Any affected leaves should be cut off and removed. The appropriate fungicidal spray will protect your plant from further infections.

All stages of snailcase bagworm (Apterona helix) take place within a coiled, snail-like case that looks like it is made out of the dirt. Larvae become active in mid-spring and feed on leaves. Control is very difficult since the insect is inside a protective case. Fortunately, this pest does little damage.

Gall flies (Aciurina bigeloviae) cause cottony balls or green flowerlike swellings on stems of rabbitbrush. Controls have not been developed nor are needed. If galls are considered unattractive, they may easily be pruned out. In native stands of rabbitbrush, these gall makers are heavily parasitized by several species of wasps.

Spittlebugs will sometimes attack rabbitbrush. The insect produces a protective foam that looks like spit. The foam helps protect the insect from ultraviolet light, predators, and insecticides. Use a strong spray of water to wash the foam away. The resulting exposure to UV light will kill the insect and expose it to predators. A stronger spray of water may also remove the insect from the plant.