Azalea Lace Bugs

Blue Danube azalea

Queen of early-blooming shrubs, nothing says spring quite like azaleas. And, in case you haven’t been paying attention, azaleas can also say summer and fall, too, with the introduction of the popular reblooming Encore brand of azaleas. And while East Texas provides ideal climate and soil for growing these charming plants, azaleas can also have their share of problems.

Azaleas prefer an evenly moist soil during the growing season. A well-drained soil, high in organic matter provided by compost and peat moss, are ideal conditions for growing azaleas. Unfortunately, summer rainfall is rarely regular, so supplemental irrigation is typically required to provide the moisture to keep azaleas growing and happy.

If azalea plants regularly wilt between waterings, you need to take steps to correct that condition or you may damage or even lose some of your plants. Analyze your irrigation system to make sure it is putting out enough water from each head, and that the spray pattern is reaching all the plants. Older plantings may need a top dressing of compost which can filter into the soil to help increase water holding capacity. And, check the depth of the layer of mulch on the surface of the soil. Mulch really cuts down on evaporation and keeps the soil cooler.

White stippling on the upper surface of azalea leaves typical of a heavy infestation of azalea lace bugs.

One of the most damaging pests of azaleas is the azalea lace bug. These sap-sucking insects seem to preferentially attack azaleas under stress, often being worse in sunnier sections. Azalea lace bugs can be difficult to see, but their damage is unmistakable. When damage is severe, the leaves can almost be bleached from their feeding damage.

Azalea lace bugs feed on the under sides of the leaves, piercing into the interior of the leaf and feeding on the cells containing the green chlorophyll pigments. This creates a white dot on the top of the leaf. Leaves can have so many white dots that leaves almost turn grey or ashen appearance. Even after lace bugs are gone, the damage will remain until the leaves fall off.

Azalea lace bug damage on underside of the leaves, showing their tell-tale black droppings.

Another sure sign of the presence of lace bugs are the black, varnish-like droppings they deposit on the undersides of the leaves.

Adult lace bugs have transparent wings and have a very lacy, delicate look. The immature stages have a dark, spiny appearance. There can be at least 2 generations per year, and possibly up to 4. They overwinter in the egg stage on the underside of leaves, hatching out in early spring. Since numbers can build up rather quickly, early detection and treatment is the best approach to avoid heavy damage.

An adult azalea lace bug.

They are rather easy to kill, but any contact-type insecticide needs to be applied in a manner that the spray reaches the under sides of the leaves. Knocking them off with a sharp stream of water is a cultural control, but may not give great control if there are large numbers. Insecticidal soap and horticultural oils are low-toxicity insecticides, but again, the spray needs to reach all the undersides of the foliage. Oils should not be used when temperatures are in the 90’s. There are also several systemic insecticides that can do a good job of controlling them, plus give longer control.

Since their feeding damage remains after the bugs are dead, you might wonder if you really got them under control. Monitor the newest growth, looking for the tell-tale signs of their droppings on the undersides of the leaves. You will need to continue to monitor the newest growth the following growing season since azalea lace bugs overwinter as eggs on the leaves. A late winter application of a horticultural oil spray can help suppress future infestations.

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