Azalea lace bug (Stephanitis pyrioides)

There is a relatively new pest in Oregon that can damage azaleas, rhododendrons and pieris (Ericaceae): The azalea lace bug (Stephanitis pyrioides) was first confirmed in Oregon in 2009 by Oregon State University (OSU) researchers after it was found in Washington in 2008.

The pest becomes active in mid- to late May and early June, when it starts laying eggs, which are partially embedded in the tissue underneath leaves. Both adult and immature bugs eat the leaves, leaving a yellow dot-like pattern on the surface and black fecal spots underneath. Heavy feeding can kill plants.

Some azaleas are immune to the pest, including Azalea indica ‘Alba Magnifica’, ‘Flame Creeper’ and ‘Delaware Valley White’. However, these and other resistant varieties have not been tested in Oregon’s climate, cautioned entomologist Gail Langellotto, the statewide coordinator of OSU Extension’s Master Gardener program.

Monitoring for the pest and dealing with it early in the season are the best defenses, she said. You can apply insecticidal soaps, horticultural oils and neem-based products regularly to the bottom of the affected leaves to reduce or prevent further damage, but they will not restore the plant to its untouched appearance.

For new plants, choose a partially shaded spot in your yard, and regularly water and fertilize it. Azalea lace bugs are more likely to damage plants in hot, sunny locations or in drought-stressed conditions.