Key Features
- Small, round sunken spots on leaves
- Leaves curled and distorted
- Black and yellow striped bug
Symptoms
Adults are yellow and black whereas nymphs superficially resemble adults, but are more orange in color. Damaged leaves will have sunken, round spots and be distorted. Spots are dark colored that fade to a lighter color and often fall out after a few weeks leaving holes. This type of damage can be distinguished from leaf spot disease by assessing the shape and size of the spots. Four-lined plant bugs make distinct circular spots each time they feed on the leaf surface.
Biology
Eggs overwinter in clusters on woody stems of plants and hatch in early May when lilacs are in bloom. Both immature nymphs and adults damage leaves when they pierce the leaf surface and suck out the sap from a circular area. Adults appear 3-4 weeks after egg hatch. Adults feed and lay eggs for about a month. There is one generation per year.
Management Recommendations
Reduce plant bug problems in landscape beds by removing stem residue from flower stems in the fall. If damage becomes severe and many bugs are present, pesticide treatment may be warranted. The sooner the treatment is applied, the more damage it will prevent. To help preserve pollinators apply insecticides when plants are not flowering.
Effective Pesticides
Active Ingredients include: Acetamiprid, Bifenthrin, Carbaryl, Cyfluthrin, Insecticidal soap (Potassium salt of fatty acid), Lambda- cyhalothrin, Malathion, Permethrin, Pyrethrin, Resmethrin
Resources
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
