Q. I have a rhododendron that is infested with rhododendron lace bug. Last year I bought an insecticide to rid my infested rhododendron of lace bug. Unfortunately it didn’t work. I realize that I need to spray beneath ALL the leaves to truly be effective-, which is the problem. Should I remove most of the leaves and then spray? Whatever I use, I will need to cover the rhodie with netting to keep the birds out. I’m assuming any “good killing” spray will be harmful to birds. Thanks, Anni Watkins – Tacoma, WA
A. This is a good candidate for an insect alert so for those of you with rhododendrons that want to inspect for signs of lacebug look for a yellow to brown speckling on the surface of the leaves. But as you have alluded to all the activity is below the leaves where the lacebugs and their juvenile nymphs are feeding. So any spray does not necessarily need to be beneath all the leaves, but rather beneath all the leaves that have lacebugs on them. They feed like aphids with piercing sucking mouthparts extracting sap. The “lace” of the adult insect’s wings can only be seen under a microscope since the adults are only about 1/8 of an inch long. What are usually most visible on the underside of the leaves are the insect’s excrement and the nymph’s shed exoskeletons, which are shed at each stage of growth. Often a large infestation of Rhododendron Lace Bug is a sign that the rhododendron may be under stress. Sometimes infestations are exacerbated by drought, high a pH soil (they prefer to be somewhere between 4.5 to 6.0) or too much direct sun. Since you have not mentioned any beneficial insects present feeding on the Lace Bugs like Ladybugs then a spray is an effective alternative. But your assumption that any “good killing” spray will be harmful to birds “ain’t necessarily so”. Both insecticidal soap and neem oil will control Lace Bugs. Or you can use the best of both worlds and use a new neem soap, which is derived from the neem oil, and works like a souped-up insecticidal soap since it also has neem’s insecticidal properties (anti-feeding, growth regulator). Humans have been using neem on their own bodies (especially in India) and I have even seen neem toothpaste recently at the supermarket. You won’t have to net off your rhododendrons to protect the birds when using neem-based garden products.