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.
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.
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