Feeding by the four-lined plant bug causes brown to translucent spots on young foliage of many herbaceous and woody plants. Injured leaves become distorted, curled and, if damage is severe; may fall off.
Because the spots are small, somewhat circular and fairly uniform, many gardeners think they have a disease on their plants. Also contributing to the illusion of disease is the fact that these insects are fast moving, frequently dropping to the ground, hiding under foliage or flying away when disturbed, so are rarely seen. A third reason people might think this is a disease is that dead plant tissue may drop out, leaving a shot hole. Many leaf spot diseases have this symptom.
As the common name suggests, adults of this true bug have four black longitudinal stripes surrounded by yellow to yellow-green on the leathery part of the wing covers. Beyond this, the membranous part of the wings is black. The head and body are a golden yellow with yellow-green legs that have black markings. Antennae are black. Adults are one-quarter inch in length. Nymphs are smaller, wingless, brightly-colored yellow to red, with black spots in rows on the segments of the abdomen. Mouthparts are piercing-sucking.
This insect overwinters as eggs laid in linear slits near branch tips of woody plants. Eggs hatch in late spring after most foliage has emerged. The nymphs feed on the upper sides of leaves, withdrawing chlorophyll with their piercing-sucking mouthparts. Approximately 30 days and five molts later, the adults appear. Adults feed for about a month, then mate and the female lays eggs. There is only one generation each year.
Pirone lists eight herbaceous perennials, three annuals and three woody shrubs as hosts for this insect. Johnson and Lyon say it feeds on 250 plant species. Azalea, dogwood, forsythia, honeysuckle, hydrangea, viburnum and weigela are some of the more common shrubs attacked. Shasta daisy, coreopsis, dahlia, morning glory, lavender, lupine, geranium and zinnia are some annuals and perennials that are attacked. Vegetables, small fruits and some herbs, such as basil and mints, also serve as hosts.
On ornamentals and leafy vegetables, where tolerance for injury is low, monitoring should begin mid-spring. At the first sign of injury, control measures should be taken. These insects are heavy feeders, and a few can cause much discoloration, so it's best to treat early.
Least toxic methods of control for ornamentals and edibles would include insecticidal soap, the dormant and summer weight oils and where feasible, removal of egg masses by selective pruning. Johnson and Lyon say egg-laying sites are easily visible after leaves drop in autumn.
When needed, malathion, acephate (Orthene) or carbaryl (Seven) can be used on ornamentals. Methoxychlor and malathion are each registered for certain edible crops. Read the label carefully to be sure you are using the insecticide properly. Also, follow the days-to-harvest recommendations for the safety of those who eat the produce.
Whenever using insecticides, be sure the insect you want to control and the plant you are using it on are both listed on the label.
Johnson, W. T. and H.H. Lyon.1994.Insects
that Feed on Trees and Shrubs.Cornell University.p.396-397
Davidson, R.H. and L.M. Peairs.1966.Insect Pests of Farm, Garden and Orchard.John Wiley & Sons, Inc. p. 531
Pirone, P.O. 1978.Diseases and Pests of Ornamental Plants.John Wiley & Sons, Inc. pp.61, 199, 203, 210, 228,
247, 265, 310, 315, 339, 353, 354, 397, 538
University of Massachusetts Extension System.1994.1994 New England Management Recommendations for Insects,
Disease and Weeds of Shade Trees and Woody Ornamentals. Edited by Robert D. Childs. p. 117
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