Yellowing plants may not need fertilizer

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Check the underside of leaves for evidence of the azalea lace bug.
Check the underside of leaves for evidence of the azalea lace bug.
Contributed Photo

Lace bugs are active now on landscape plants. So now is the time to start checking your plants.

There are more than a dozen species of lace bugs in North Carolina. The most common is the azalea lace bug. This is the most damaging pest of azaleas. Lace bugs overwinter as eggs and start hatching late April into May. As temperatures get warmer, more lace bugs emerge.

You can tell your azaleas have lace bugs if the top of the leaf has yellow flecking. This yellowing is called stippling damage and looks like hundreds of tiny discolored specks on leaves. This is caused when lace bugs poke in their needle-like mouth parts and suck out the plant juices, including chlorophyll. Without chlorophyll that spot turns yellow or white and eventually brown.

Many gardeners believe yellowing azaleas are showing a nutrient deficiency. This may not be the case, so check for lace bugs first. Adding fertilizer to a stressed insect-infested plant only causes more issues.

Lace bugs also make a lot of fecal spots on the undersides of leaves. By checking the underside of the leaf for black fecal spots you can guarantee the issue is not related to fertilizer. Lace bugs feed on many common plants including hawthorn, oak, cotoneaster, pyracantha, crab apple, serviceberry (Amelanchier) and others.

Lace bugs are hard to manage with foliar insecticides because they live on the bottom or underside of leaves. So be sure to direct your spray to cover these plant parts. Horticultural oil or soap and other products are labeled for lace bugs. Lace bugs can also be managed with systemic products. However, many of the lace bugs’ favorite plants also flower, so be conscious of the labels and restrictions regarding pollinators. 

If you have questions about lace bugs or other gardening insects call the trained Wilson Master Gardeners at 252-237-0113. You can also take in plant samples to the office Monday through Friday from 8 a.m. to 5 p.m. or send pictures and email anytime at wilsonemgv@hotmail.com.

Cyndi Lauderdale is a local horticulture extension agent.