Lace bugs on my Rhodies

Asked June 29, 2020, 5:09 PM EDT

Good afternoon. I have just discovered that my rhododendrons and azaleas are being attacked by lace bugs (Stephanitis pyriodes). Are there systemic insecticides that can be used to control them that will not harm my plants? Thank you. Best regards from Eugene, Larry Hipple

Lane County Oregon

1 Response

Thank you for providing the photo of the lace bugs. Hopefully you can consider using a varied approach that includes cultural controls that include reducing stress on shrubs (stress makes them more susceptible to lace bugs & other problems). These include:
- Pruning shrubs to increase air circulation through branches and ease spray application;
- Irrigate every two weeks in the summer (dry season) - don't use overhead spray;
- Minimize use of high nitrogen fertilizer & lime in vicinity of these shrubs (excess nitrogen isn't needed by rhododendrons and lime can raise pH making the soil less hospitable to roots)
- Try repeat strong water sprays hitting upper & lower surfaces of leaves to try to dislodge bugs ( will need to repeat due to multiple hatchings).

If you feel more action is needed, try sprays with insecticidal soap solution or neem oil solution (always follow label instructions). Ensure spray reaches upper & lower surfaces of leaves. You may need to repeat every month for successive generations hatching.

If this still doesn't work and you have a heavy infestation, there is one systemic insecticide you could consider. This is dinotefuran which is a neonicotinoid (very toxic to pollinators like bees). It should never be applied when the rhododendron or any adjacent plants are in flower or pollinators are present. Apply after blooming completed. This systemic is only active during the year of application. ALWAYS FOLLOW LABEL INSTRUCTIONS. Do NOT use any other systemics like imidacloprid because they may be active for several seasons and pose a long term hazard to pollinators like bees.