Geranium × oxonianum · Perennial
Vine weevil: Apply nematodes to the soil in autumn or use a systemic insecticide drench.
Slugs and snails: Use iron phosphate pellets or beer traps to reduce populations around the base of plants.
Powdery mildew: Improve air circulation and spray with a fungicide or milk solution at first sign of infection.
Geranium sawfly: Hand-pick larvae or apply an insecticidal soap spray to infested foliage.
Downy mildew: Remove affected foliage and avoid overhead watering to keep leaves dry.