My azaleas are infected by lace bugs. 1. What can I do? 2. Will the infected plants survive? 3. What is the proper disposal method for the infected plants?
Multnomah County Oregon
The plant will survive, in spite of being re-infested every year. It will also bloom profusely every year. If you want to dispose of it, it can be added to the green bin for collection by your regular hauler.
To verify if your azalea lace bugs, please compare your shrub’s leaves with the images in this publication: “Azalea Lace Bug” http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/40424/em9066.pdf.
If we assume your shrub has azalea lace bugs, your best chances to decrease the population is to kill new hatchlings which will occur in spring. (New generations tend to hatch in mid-May, June, July, August, with perhaps another in September.) In the meantime, collect and discard any fallen leaves.
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; and if the plant is in excess sun, consider rigging temporary shade or transplanting to a different site in the fall.
To accurately time the first spray, monitor (check) the undersides of the leaves regularly, beginning in April. Every several days, look for the small dark colored nymphs (the youngsters) as are shown in the above publication. The most effective time to spray is right after the hatch, when the nymphs are still in a rather tight cluster on the undersides of the leaves, before they disperse. If you prefer to avoid pesticides, a harsh water spray to the undersides of the leaves can be very effective at this early stage. Adults are challenging to kill. If you use insecticides, they must also be applied to the undersides of the leaves. (See the list below.)
These contact insecticides will temporarily control lace bugs if the product thoroughly covers the underside of leaves where lace bugs live and feed. Choose from these active ingredients: Azadirachtin; insecticidal soap; narrow-range horticultural oil; neem oil; or spinosad. Follow label directions for use and for repeat application. Don’t spray any pesticide if the temperature is, or will be, above 80F.