Lace Bug on Azalea

Asked November 18, 2020, 2:21 PM EST

Hi there. What's the latest on control of lace bugs? I have two large azaleas that are critical to my homes front entrance landscaping. It used to be that only one azalea was showing signs of infestation and I could spray twice in spring with hort soap and that would control it well enough. This year there was at least one surge and definitely one in the fall, and the azalea looks worse than ever. The other azalea also started showing signs of infestation. I now understand that there are often two or three generations from spring through October. Spraying those two large azaleas over a six or seven month period is going to be very difficult for me to do. I've heard that a neem oil soil drench is effective? But also heard it wasn't so effective. I'd prefer not to use heavy chemistry to control the lace bugs but would be interested in knowing what is the most effective and the least toxic options for decent control. (PS, I swear I submitted this question back in September but never got an answer and now I can't find the response email from Ask an Expert, so I'm trying again)

Lane County Oregon

1 Response

Here is a link to a thorough response to a similar question regarding azalea lace bug: https://ask.extension.org/expert/questions/195508
Among the keys to successfully battling lace bugs are these:
- Stressed plants appear to be the most common victims. To relieve stress, thin out individual plants to increase aeration, and ease of applying sprays; irrigate every two weeks through our dry months for good health; and decide if the plants are in excess sun – if so, consider rigging temporary shade or moving the shrub in the fall.
- Start spraying the undersides of the leaves when the first generation hatches, usually mid-May. Monitor to determine the appropriate timing. To do so, check the undersides of the leaves every several days as you look for the small dark colored nymphs (youngsters). The most effective time to spray is right after the hatch, when the nymphs are in a rather tight cluster.
- Most insecticide sprays are contact materials; in other words, the spray must thoroughly cover the undersides of the leaves. (See the list below.)
- Repeated sprays of these materials are required during the growing season because the lace bugs have multiple generations. You have the best chance to decrease the population – and damage – when new generations hatch in mid-May and again in June, July, August, with perhaps another in September.
- Don’t spray if the temperature is, or will be, above 80F.

The following contact insecticides will temporarily control lace bugs if the product thoroughly covers the underside of leaves where lace bugs live and feed. Repeat the spray according to label directions:
- Azadirachtin
- Insecticidal soap
- Narrow-range horticultural oil. Use in the fall to coat the undersides of the leaves where the eggs are laid alongside the midrib.
- Neem oil
- Spinosad
- Several options among systemic pesticides are acephate and imidacloprid.

If you decide to replace your azaleas, Encore azaleas have proved themselves to be among those tolerant of lace bugs in other regions. Their performance in the northwest remains to be seen.

You might like to review this recent publication: “Azalea Lace Bug” http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/40424/em9066.pdf