Lace leaf infestation
How to treat lace leaf infestation in rhododendrons?
Lane County Oregon
Azalea lace bug, Stephanitis pyrioides, has been confirmed recently (summer 2009) in Oregon and was confirmed in 2008 in the state of Washington. Damage from this new introduction was noticed first on evergreen azalea plants in landscapes which turn nearly white from feeding damage. This lace bug is also causing damage on rhododendrons, the damage appears to be more severe than damage reported from rhododendron lace bug which has been in the PNW for some time and is reported to have only one generation per year compared to multiple generations reported for azalea lacebug.
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. Hosing plants with a strong stream of water directed at the underside of leaves will help to remove some adults and wingless nymphs. Resistant azalea cultivars include: 'Autumn Amethyst', 'Autumn Twist', 'Autumn Royalty', 'Autumn Sangria', 'Autumn Cheer', and 'Autumn Rouge'. In addition, some cultivars are moderately resistant: 'Autumn Embers', 'Autumn Bravo', 'Autumn Starlite', 'Autumn Ruby', and 'Autumn Princess'.
Select insecticides to preserve populations of beneficial predators which will help control lace bugs. Lacewing larvae like to eat lace bugs.
What insecticide do you recommend?
Chemical control. Spring is the best time to control the first or second generation of lace bugs. Insecticidal soap, horticultural oil, neem oil. Be sure to cover the underside of the leaves.