Q: I have a mature butterfly bush. This year it is looking really bad. The leaves are curling up, like they are not getting enough water, but all my other butterfly bushes are doing fine. Any ideas?
A: My first guess is spider mites. Butterfly bush is commonly afflicted with these pests. Swat a branch on a sheet of white paper and look for small, orange, moving specks. Spider mite control is difficult. Most insecticides are not effective because a spider mite is not an insect.
There are three avenues for control:
1. Wash them off. Spray plants forcefully with a water hose daily, trying to aim the spray at the undersides of leaves. Do this before late afternoon so the foliage can dry quickly and not be attacked by fungal diseases.
2. “Organic” control. Use insecticidal soap or horticultural oil. The soap kills mites on contact. The oil suffocates them. Again, pay attention to the underside of leaves, where the mites are most numerous.
3. Miticides. The following homeowner products are labeled for mite control:
Green Light Red Spider Spray
Ortho Isotox Insect Killer Formula IV
Ortho Rose and Flower Insect Control
Ortho Houseplant and Garden Insecticide