Tarnished Plant Bug
Egg - The tiny, elongate egg is slightly curved.
Nymph - The wingless nymph is yellow-green in color with several black spots on its back. Length varies from 1.5 mm to slightly less than adult size. The fourth instar nymph has wing pads.
Host plants - Tarnished plant bugs infest over 50 economic plants including many field, forage, fruit, and vegetable crops. Also, weeds such as butterweed, fleabane, goldenrod, aster, vetch, dock, and dogfennel commonly harbor these insects in southern states.
Damage - Shiny, circular spots of excrement on various plant parts indicate the presence of tarnished plant bugs. These bugs pierce the terminal growth, squares, flowers and bolls with their needle-like mouthparts and extract plant juices. The most conspicuous result is the appearance of warty growths on flower petals and inside the bolls. The more economically important damage, however, is not as noticeable. Injured pinhead squares and terminals drop from the plant. The anthers of larger squares may turn black resulting in poor pollination and reduced boll set. Larger bolls, opening prematurely, expose lint which becomes discolored, clings inside the warty boll, and is difficult to harvest. Finally, cotton seed harvested from heavily infested fields germinates poorly.
Indirect losses due to this pest greatly enhance its economic importance. Early season chemical treatments eliminate predators and parasites, sometimes resulting in a resurgence of other economically important pests, particularly bollworms.
Life history - In the more southern areas of the Cotton Belt, tarnished plant bugs may remain active year round. In North Carolina, however, adults hibernate in plant debris and resume activity in the spring. At this time females insert eggs into succulent host plant tissue with their sword-like ovipositor. Eggs hatch 1-1/2 to 3 weeks later. The nymphs develop through 5 instars over a 3 week period as they feed on plant sap. Mature nymphs molt and emerge as adults. The first few generations develop on preferred hosts such as small grains, alfalfa, wild grasses, vetch, dock, and fleabane. As hay is cut or as other plants dry out, tarnished plant bugs migrate in large numbers to succulent cotton. During the summer, the life cycle from egg hatch to adult emergence is completed in 4 weeks. The number of generations produced each year depends upon geographic location and weather conditions.
Should infestations occur, estimate populations. Chemical control is recommended in some southeastern states when 15 or more tarnished plant bugs are found per 100 terminals. For specific information on insecticides and rates, consult current North Carolina Agricultural Chemicals Manual.