Azalea problem

Asked October 5, 2020, 4:37 PM EDT

Hello, I have 2 azalea bushes that have yellow leaves and don't look healthy. They're on the eastside of my house and get plenty of sun. They did bloom this spring. Please see the attached pictures. Do they need fertilizer? Thanks in advance for your insight. Terry

King County Washington

4 Responses

Do me a favor--go out and look at the back of the leaves. Do they have black stuff all over the back? Please get me closeups of both the front and back of the leaves. Thank you.

I have attached some pictures of the leaves. I recently planted some other azaleas near these and they also look like they have the same issue.

Okay, so your poor azaleas are infested with Azalea Lace Bug. It's an insect that lives on the back of the leaves, and pierces the leaf with its mouth and sucks the juices from the leaves. That's why all the leaves look silvery white. The black stuff you see on the back of the leaves is bug poop, or "frass." If you enlarge the photo, you can see the tiny insects or get a magnifying glass to see them. They are surprisingly beautiful considering the damage they do. So many people in the PNW have problems with this Lace Bug. WSU's Hortsense has suggestions for control, but it can be very difficult. If you look at the underside of the leaves, at the main veins, you may see a corky beige area--that's where the eggs they've laid will overwinter, and are completely protected from any insecticide.

One thing you can do now is to hose off the underside of the bushes with a very strong stream of water to remove the immature forms of the insect. Keep your plants healthy by growing conditions: partial shade, fertilize and irrigate properly. There are insecticides listed in the article, and I would suggest starting with Neem oil, insecticidal soap, or products containing spinosad. The others listed are highly toxic to pollinators. SInce you are seeing live adult Lace Bugs, you can safely use a pesticide now--before they finish laying eggs for the season. I looked into using a soil drench with imidacloprid in the fall, but the toxic effects last into bloom time next spring, and will be dangerous to pollinating insects. In the spring use one or more of the above mentioned organic pesticides at 2 week intervals when the spiky little nymphs (immature forms) appear, usually in mid=April. But please read all label instructions to protect yourself, others, the environment and pollinating insects. Good luck!

Thank you.