My azaleas have an infestation of what looks like lace bugs. They are on the underneath side of the leaves and the leaves have turned silver. A gardening company suggested a product from Bayer to pour on the roots, but it's pretty expensive. I have also heard of a product called Confidor tablets that can be buried at the roots. I have about 20 azaleas and 15 rhododendrons. What would you recommend.
“Azalea Lace Bug” contains the currently known details about azalea lace bug, its damage and management. (http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/40424/em9066.pdf )
Management must combine multiple tactics: Cultural (perhaps even replacement with resistant azaleas) and chemical. The following is excerpted from our official disease management resource; I added the bracketed text for clarification:
“Management-cultural control Maintain plant health by providing proper water and nutrition. Stressed plants are more susceptible to insect damage. Grow azaleas in shady areas to minimize damage. Remove leaves with brown patches of eggs along the midrib [on the underside of the leaves]. Hosing plants with a strong stream of water directed at the underside of leaves will help to remove them, and wingless nymphs will not return. Encore Azalea resistant cultivars include: 'Autumn Amethyst', 'Autumn Twist', 'Autumn Royalty', 'Autumn Sangria', 'Autumn Cheer', and 'Autumn Rouge' He also showed that some cultivars were moderately resistant: 'Autumn Embers', 'Autumn Bravo', 'Autumn Starlite', 'Autumn Ruby', and 'Autumn Princess'.”
“Management – chemical [Our resource lists insecticide choices alphabetically by active ingredient rather than by product name.]
- azadirachtin (neem oil)
- horticultural oils
- insecticidal soap
- spinosad A & D “
The two products you asked about both have the same active ingredient: Imidacloprid, a systemic insecticide. I wasn’t able to locate any information comparing the effectiveness of a liquid formulation versus tablets. In a document discussing management for scale insects in trees, the University of California stated “Imidacloprid can be effective when applied to soil during late winter to early spring or before rainfall or irrigation are expected to facilitate root absorption of the insecticide. Summer application to stressed, heavily infested trees is less likely to be effective and is not recommended.”
Thank you for using Ask an Expert,
Thank you so much for your answer about lace bugs on azaleas. It's good to know my options. I especially appreciate the names of the bug resistant azaleas.