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Flowers, Fruits, and Frass

Local and statewide information on a variety of current topics for home gardeners and market growers.
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Lace Bugs on Sunflowers

Posted by Kelly Allsup - Bugs

Lace Bugs on Sunflowers

By Kelly Allsup

Horticulture Extension Educator

It was the frass (insect excrement) on a sunflower leaf that caused me to stop and take a closer look. Upon further inspection, the frass was lined along the veins of the leaf and looked like black tar. The leaf was covered in stippling (feeding injury) and neucrotic spots (dead tissue). Then the culprits moved when I poked at them. They were chrysanthemum lacebugs (Corythuca marmorata). Chrysanthemum lacebugs are about a 1/4th of an inch, brown-gray or tan in color have delicate wings held flat with markings giving it the appearance a miniature cut square of lace.

Chrysanthemum lacebugs prefer feeding on asters, sunflowers and goldenrods. The feeding injury is caused from the piercing and sucking mouth parts. The excrement is strategically placed along the vein and secures the eggs to the leaf. They prefer the underside of the leaf but one of the plants I saw had colonies on the upperside because the population was high. Nymphs are small shiny brown and suck sap. They congregate while they are young nymphs on the underside of the leaves. Damage from high populations is more severe in dry weather.

Hover fly larvae, lady beetles and lace wing larvae will prey on these garden pests. Daily water sprays until population is reduced can be highly effective. The University of Illinois suggests treating with horticulture oil, insecticidal soap, neem oil or imidacloprid. If you have chrysanthemum lacebugs this year, look out for stippling when plants are young and population is low. This garden pest is an excellent example of how a gardener's weekly notes can be a valuable management tool when dealing with garden pests in the next season.



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