Seems to me that since around 2010 or so, we (around the Vancouver, WA/Portland, OR area) have seen higher populations of azalea lace bugs on azaleas, rhododendrons and pieris. But in my coaching practice I’m seeing them especially on azaleas. And more so on plants that are in sun and drought stressed. The photo below shows severe lace bug damage to an azalea.
There are lace bugs for several genera of plants, but so far, I’ve only observed them on azaleas and rhodies around here. Though some members of these three genera do (well, used to do) quite nicely in sunnier situations, we’re finding most are no longer surviving lace bug infestation when located in the sun—particularly when drought stressed. Please see my blog post from 2011 when I first noticed lace bugs on my own plants for some background information. Below is a photo of lace bugs where they are most likely seen—on leaf undersides. The little black dots are lace bug poo.
Here in the PNW, we love azaleas and rhodies. We are also learning to love the idea of sustainability—growing plants that can survive with little extra input of resources (including water). Our summers have always been warm and dry, but if this past summer is any indication, it could be they are becoming even drier. Here in Vancouver, WA, we went 90 days this past summer with only 1 day with a paltry 1/2″ of precipitation.
If in our gardens, we’ve provided great soil for our plants, selected them carefully, and watered them appropriately when they were young, then our gardens may have survived such a harsh summer as we had here this summer. But most azaleas, rhodies and pieris (among other plants) aren’t equipped to survive such treatment. And when they begin to struggle, that is when lace bugs move in.
Choices for New Plants
If we are planting a new garden, we can ensure success with these genera by locating them away from summer afternoon sun exposure, and providing adequate water, rich organic soil with plenty of mulch on top, and little competition of other plants in the root zone. Or, if our garden is exposed to late-day sun and/or drought conditions, then we should consider choosing different shrubs.
Most azaleas, rhodies and pieris I know of cannot be considered ‘drought tolerant’. Some do better than others in brief drought situations. I’m not sure why we suddenly have more lace bug activity here in the PNW. It sorta doesn’t matter why—they’re here. We must deal with them.
Choices for Existing Plants
If you have existing azaleas, rhodies or pieris which are under lace bug attack, evaluate their sun exposure, soil moisture retention, and mulch coverage. If you find the plants are in less-than-perfect locations, you can try to move them to better locations. But moving is stressful, and doing it to already-stressed plants can be the final nail in the coffin—particularly if the plants are mature and established.
I don’t like to recommend chemicals to treat most pests. But for plants that are in acceptable locations, light lace bug infestation can be managed with a strong spray of water from the hose (repeated as necessary) to the undersides of the leaves. Start checking your plants shortly after they bloom for tell tale signs of these pests.
If the plants are in questionable habitat and for whatever reason cannot be moved, you might try insecticidal soap (again, repeated as necessary) sprayed directly on the bugs. An application of a good layer of finished compost, and boosting the irrigation will help provide better habitat for the plants. I’m not saying make the soil WET. But instead of letting the soil dry completely between watering, or letting drought conditions arise in the first place, set a watering schedule so as to maintain appropriate moisture for these types of plants.
My recommendation, if your azaleas, rhodies or pieris plants are located among other drought-tolerant plants (which is not their desired habitat) and you are working toward a more sustainable garden, is to remove them and replace with more suitable, drought-tolerant plants.
However, I found a handout from OSU on lace bugs with a list of azaleas that are said to have very good resistance to lace bugs. Yippee! I’ve not seen all of those azalea cultivars available here in Vancouver, so I did as much online research as possible. Unfortunately, most cultivars seem only to be available in Southern states, and there is almost no record online for a couple of the cultivars. But the list is a start. See it and my additional notes below.
Azaleas Resistant to Lace Bug Attack(in order of decreasing resistance)*
- ‘Flame Creeper’ (Macrantha)
2-3′ x 3-4′; scarlet-orange flowers; late-season bloom; good sun tolerance
- ‘Delaware Valley’ (Glenn Dale ?)
3-4′ x 4-6′; white flowers; mid-season; prefers part-shade; Southern cultivar
- ‘Rosebud’ (Gable hybrid)
4′ x 4′; shell pink double flowers; mid-season; prefers part-shade; spreading habit
- ‘Copperman’ (Glenn Dale)
3-4′ x 4-5′; red-orange flowers; late-season; prefers part-shade; Southern cultivar
- ‘Hahn’s Red’ (Kurume)
6-7′ x 6-7′; semi-double rosy-red flowers; mid-season; prefers part-shade
- ‘Boldface’ (Glenn Dale)
size – ?; white throat, red blotch, lavender flowers; mid- season; Southern cultivar
- ‘Mrs. GG Gerbing’ (Indica)
6-8′ x 4-6′; white flowers; Southern cultivar
white flowers; very little data about this cultivar; Southern cultivar
- ‘Salmon Beauty’ (Kurume)
size – ?; salmon-pink flowers;
very little data about this cultivar; Southern cultivar
- ‘Hino Crimson’ (Kurume)
2′ x 3-4′; crimson-red flowers; red foliage in winter; good sun tolerance
*Research by Dr. Peter Schultz, Virginia Beach Experiment
Encore® Azaleas claims that some of their cultivars are lace bug resistant. See their list. But the way I read their study, it was done in Mississippi, which is a humid state (study details are at a link on the page referenced). Here in Vancouver, WA, our summers are dry, and that is one factor which invites lace bugs. So try the Encore® cultivars with my caution.