Identifying and Controlling Common Rose Pests and Diseases

Thrips: Tiny (1/16 inch), dark, fringed wings. Attack tender leaves and buds. Spray acephate (Orthene, Isotox) on young foliage, buds, and soil.

Cane borer: Maggot of sawfly or carpenter bee eggs in freshly cut canes. Sign: neat hole at cane top. Cut down several inches until no maggot/pith damage. Seal cuts with pruning sealer.

Japanese beetle / Fuller rose beetle: Eat foliage and flowers. Hand-pick or spray acephate.

Leaf miner: White chain-like blisters on leaves. Remove and discard affected foliage.

Spittle bug: Greenish-yellow nymph in white foam on new stems in spring. Blast off with strong water jet.

Rose viruses: Yellow/cream veining (variegated look). Vein banding mosaic is minor; line pattern mosaic can kill. Remove and destroy infected plants.

Roseslug: Skeletonized new leaves. Remove foliage or spray acephate/diazinon.

Rust: Red clusters on leaf undersides in high moisture. Spray triforine or chlorothalonil.

Leaf cutter bee: Cuts leaf pieces, leaves white skins. Can defoliate. Spray acephate to prevent colonies.

Rose scale: Gray scales on old canes, suck sap. Scrape off locally or spray acephate/diazinon.

Spider mite: Salt-and-pepper colonies under leaves. Spray acephate on leaf undersides, or mist with water to wash mites to ground (they can't fly).

Blackspot: Circular black spots on leaves in warm, wet, humid weather. Spray triforine or chlorothalonil. Practice sanitation: remove fallen leaves, don't compost.

Rose aphid (greenfly): #1 rose pest. Green, 1/16 inch, colonies on spring growth. Wash off with water or spray acephate, diazinon, or malathion.

Plant bugs (lygus, stink bug): Suck sap from buds, inject toxin causing distortion and bud death. Systemic insecticide (RosePride) prevents attacks.

Downy mildew: Serious fungus defoliating bushes, survives on canes. Preventive fungicide; sanitation (remove leaves/prunings to trash).