An old Mafia adage states, "Hold your friends close and your enemies closer." If you are managing landscapes with perennials, there is an enemy you need to hold close and take a closer look at. The main beetle damaging perennials in August is the Chrysomelidae beetle. Chrysomelid beetles are small, leaf feeding beetles and include flea beetles. Adults are often rounded, shiny and brightly colored. The adults are mainly metallic in appearance. The larvae of the chrysolmelids feed in exposed positions on leaves of host plants. The exception is the flea beetle larva, which feeds in the root zone of plants.
PLANTS CHRYSOMELIDAE BEETLES DAMAGE. Many herbaceous perennials, including heather, Onethera (sundrop), geum and hibiscus are susceptible.
In this family, Chrysomelidae are flea beetles which are shiny beetles that are relatively small in size with enlarged hinds that enable them to leap off foliage when disturbed. Several species of flea beetles attack the leaves of several species of herbaceous plants. The adult beetles feed mostly on foliage and leave tiny pits or small holes in the leaves. When a large number of beetles feed on foliage, the foliage has an unattractive appearance with many pits and ragged holes in the foliage.
The larvae of the beetles usually feed on the roots of the same plant that the adults feed on. The larvae can cause shallow tunneling of roots but rarely then causes significant damage to the plant. Adult beetles overwinter and become active in spring and remain active through the summer. Females lay eggs around the base of plants and the larvae primarily feed on the roots. Pupation occurs in the soil. Flea beetle adults are highly mobile and disperse readily. Adults invade an area in mass and can cause damage to plants very rapidly. One of the common flea beetles in the U.S. is the striped flea beetle, which is black or brown, with two crooked yellow stripes down the back.
Flea beetles usually fly in from weedy areas and damage young seedling plants. The best control is to keep weed populations down in areas surrounding the managed landscape beds. Chemical control can also be used.
The author is from the University of Maryland Cooperative Extension. This article was excerpted from Groundwork, a publication for the Landscape Contractors Association of Maryland, Washington, D.C. and Virginia. Look for the second part to this article on how scale insects affect woody and herbaceous plants next week.