The characteristic leaf damage produced by Lace Bugs (order Hemiptera; family Tingidae) is becoming evident in southwest Ohio. Lace bugs are tiny insects with the adults measuring no more than 3/16" long. They are so-named because of the lace-like pattern of veins and membranes in their wings. The nymphs are even tinier and appear to be covered in small spikes.
Most of the common lace bugs found in Ohio live on the underside of leaves where both the adults and nymphs use their piercing/sucking mouthparts to suck juices from the leaves. Their feeding damage produces characteristic tiny yellow or whitish leaf spots commonly called "stippling" on the upper leaf surface. The stippling may first appear as distinct 1/4 - 1/2" diameter spots on the upper leaf surface created by 1st instar nymphs feeding near the cluster of eggs from which they hatched.
Heavy stippling may coalesce to produce large, white patches that may eventually become yellow-to-copper colored. Both the adults and nymphs produce black tar-like fecal deposits that also add to the unsightly appearance of heavily infested leaves. High lace bug populations can produce enough leaf damage to cause early leaf drop, branch dieback, and even the death of small trees and shrubs.
Two General Groups of Lace Bugs
Lace bugs can be divided into two general groups: those that feed on deciduous trees and shrubs and those that feed on evergreen shrubs. This is important because lace bugs that feed on evergreen shrubs overwinter as eggs. The nymphs immediately begin to feed once the eggs hatch in early spring meaning that leaf damage occurs early in the season. Lace bugs that feed on deciduous hosts spend the winter as adults under the bark. The time required for egg laying and egg hatch in the spring means damage does not usually appear until late spring.
The two most common lace bugs that feed on evergreen shrubs in Ohio are the azalea lace bug (Stephanitis pyrioides) and rhododendron lace bug (S. rhododendri). Both confine their feeding to their namesake hosts.
Several species of lace bugs are found in our state that feed on deciduous trees and shrubs. Some confine their feeding to their namesake hosts such as the oak lace bug (Corythucha arcuata), walnut lace bug (C. juglandis), and Buckeye lace bug (C. aesculi). Others have multiple hosts such as linden-basswood lace bug (Gargaphia tiliae) which is found on all members of the Tilia genus, and sycamore lace bug (C. incurvata) which feeds on sycamores and occasionally London Planetree. The hawthorn lace bug (C. cydoniae) has the most cosmopolitan palate feasting on a wide variety of rosaceous plants as well as a few plants outside of the rose family. However, they are commonly observed on hawthorn as well as Cotoneaster sp. and Amelanchier sp.
Chrysanthemum lace bugs (C. marmorata) are unusual in two ways. They are found on both the lower and upper leaf surfaces and they may feed on a wide range of herbaceous perennials in the Asteraceae family including asters, black-eyed Susans, goldenrods, and sunflowers. These lace bugs may greenhouses as well as landscapes. Indeed, some infestations I've come across in landscapes in recent years originated in greenhouses.
Lace Bug Management
There are numerous approaches for effectively managing lace bugs; however, early detection is essential to avoiding significant damage. Several of these species have multiple generations per season; their damage builds with each succeeding crop of new bugs.
Effective suppression includes simply applying a heavy jet of water to the lower leaf surfaces to blast away the nymphs. After their water ride, the displaced and disoriented nymphs never find their way back to their hosts. The "whoopee" then splat is followed by an "oh no!" At least, I'd like to think so.
Insecticidal soaps and horticultural oils are also effective against the nymphs; however, direct contact is required. The same is true for pyrethroid insecticides; they are stomach poisons but lace bugs are sucking insects. Systemic insecticides are effective but some, such as imidacloprid (e.g. Merit), must be applied with enough lead-time to allow the active ingredient to migrate to the leaves in a high enough concentration to kill the lace bugs. Of course, before using any insecticide, you must read and follow label directions paying particular attention to avoiding impacts on pollinators (e.g. "Bee Friendly" label restrictions). This is a particular concern with controlling chrysanthemum lace bugs. The lace bug water ride may be the best option!