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Garden Q&A: How to keep lace bugs from turning your plants yellow

My azaleas and Japanese andromeda get yellow spots. Last year some leaves turned yellow, almost white. There were so many spots! Now it’s starting again. How can I stop this disease?

Your andromeda and azaleas have lace bugs, an insect that inserts its feeding tube into the leaf and sucks out the contents of plant cells. This makes tiny dots known as stippling. Look under the leaves for lace bugs. Their lacey bodies are not easy to distinguish, but you’ll easily see the black spots of their fecal matter. Lace bugs are extremely common on both azaleas and andromeda, shrubs that like moist organic soil and partial shade. The more stressed the shrubs — the sunnier, the dryer — the more they have lace bugs. There are several generations a year. You can spray repeatedly with horticultural oil, coating the undersides of all leaves, but the problem will recur if this is not a good site. You’ll do better to move your shrubs elsewhere where they can grow happily. They still might have a few lace bugs, but they will not ruin the overall appearance. Search “lace bugs” on the HGIC website.

In March, I planted several bare root apple trees. Each is approximately 3-4 inches tall. One has grown leaves at the top of the trunk, but the others have only leaves near the base of the tree. The leaves appear to be above the graft. Should I remove these leaves or allow them to grow? If the trunk stays leafless, should it be pruned down?

Rub off any shoots that start from the base. If the top of the trunk does not leaf out eventually, contact the source of your plants and get new plants.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.


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About Mary Ellen Bellusci

Mary Ellen Bellusci is a longtime resident of Baltimore, Maryland... A foodie, traveler, writer, and pursuer of happiness.