Fourlined Plant Bug

The fourlined plant bug, with a host range of over 250 species, is one of the most destructive sap-feeding insects. It injects a powerful digestive enzyme that destroys cells around feeding sites, producing almost instantaneous symptoms (Figure 1). Damaged areas shrink and collapse, producing necrotic areas (Figure 2) that may subsequently drop out, leaving small shot-holes. Feeding injury can cause distortion of expanding leaves.

Figure 1. A small dark spot is usually visible in the center of the feeding lesion, which is usually more uniform than a bacterial leaf spot.(Photo: Lee Townsend, UK)

Figure 1. A small dark spot is usually visible in the center of the feeding lesion, which is usually more uniform than a bacterial leaf spot.(Photo: Lee Townsend, UK)

Figure 2. New (light green) and older (dark) feeding spots caused by the fourlined plant bug (Photo: Lee Townsend, UK)

Figure 2. New (light green) and older (dark) feeding spots caused by the fourlined plant bug (Photo: Lee Townsend, UK)

Insect Development

Fourlined plant bugs pass winter as eggs in host plant tissue. Eggs hatch in early spring and the nymphs begin to feed. Damage is common on perennials (mint, composites, as well as shrubs, such as azalea, forsythia, viburnum, etc.) Feeding damage from their red and black nymphs (Figure 3) is intense during the 4-week developmental period because they do not travel far; their movement is limited to crawling on or between adjacent, touching plants.

The adult fourlined plant bug, which appears in early June, has a yellow-green body with a yellow-orange head. They have four parallel black lines (Figure 4). Winged adults live for several weeks and because they can move easily, their feeding damage is usually spread over many landscape plants. There is one generation each year.

Figure 3. Fourlined plant bug nymph and feeding spots. (Photo: The Ohio State University Plant Bug Fact Sheet)

Figure 3. Fourlined plant bug nymph and feeding spots. (Photo: The Ohio State University Plant Bug Fact Sheet)

Figure 4. Adult fourlined plant bug (Photo: Lee Townsend, UK)

Figure 4. Adult fourlined plant bug (Photo: Lee Townsend, UK)

Management

Insecticidal soap can provide acceptable control of immature stages but is less effective against the mobile adults because the insects must be hit with spray droplets to be killed.  Physical protection of herbs and mint with a cheesecloth covering may be an acceptable alternative for small plantings.

 

By Lee Townsend, Extension Entomologist

 

Posted in Landscape Trees & Shrubs