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Tarnished Plant Bug
Classification and Description: — The tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae), belongs to a group of insects collectively known as plant bugs. Other plant bugs occasionally found in Tennessee include the clouded plant bug and cotton fleahopper. These cotton pests belong to a larger group of insects known as “true bugs,” which include stink bugs and a number of important predatory species (e.g., big-eyed bugs, insidious flower bug). All true bugs have a piercing-sucking mouthpart (i.e., beak).
Adult tarnished plant bugs are about ¼-inch long with a general brown color mottled by patches of white, yellow, reddish-brown or black. A light-colored “V” on the scutellum (behind the head) and two light-colored patches further back on the wings are characteristic. Eggs are about 1 mm long and are almost always embedded into plant tissue, and thus not easily found. Immature tarnished plant bugs (nymphs) typically vary from yellowish-green to dark green or brownish. Later nymphal instars have four dark-colored spots on their thorax and one spot in the middle of the abdomen.
Hosts, Life History and Distribution: — Tarnished plant bugs have a very wide host range including many cultivated and wild plant hosts. They are widely distributed and common across the eastern United States. Important wild hosts include vetch, fleabane, horseweed (marestail), curly dock and pigweed. Winter is passed as an adult, hidden in protected areas such as under leaf litter. Adults become active in early spring. Each female will lay between 50-150 eggs. Eggs hatch in 7-12 days, and it takes about 15-25 days for nymphs to develop into adults during the summertime. Reproduction begins when adults are about 1 week old. Multiple, overlapping generations of tarnished plant bugs occur each year.
Pest Status and Injury: — The tarnished plant bug is the most important pest of Tennessee cotton from the time of first squaring to the initiation of bloom. This insect has become a more common mid-season problem in recent years because of a reduction in insecticides previously used to control boll weevil, bollworm and tobacco budworm. Tarnished plant bugs prefer to feed on squares. Small squares that have been fed upon will usually shed from the plant. Excessive early-season square loss can directly reduce yields or delay crop maturity. Larger squares may remain on the plant, but evidence of plant bug feeding is evident by discoloration and anther damage on “dirty blooms.” Although less common, feeding damage to terminals can also delay maturity by causing plants to lose apical dominance, resulting in “crazy cotton.” After first bloom, injury to bolls from both adults and nymphs may cause cat-facing and boll injury very similar to stink bug injury. Bolls more than 14 days old are typically not preferred feeding sites and are relatively immune to injury.
Management Considerations and Thresholds: — Cotton is most susceptible to plant bug injury during the early squaring period. Sweep-net sampling and monitoring square retention are recommended prior to bloom to determine the level of plant bug infestation. Later in the season, a drop cloth or visual sampling is more commonly done because these techniques are better at detecting nymphs. Currently recommended insecticides and thresholds can be found in the Insect Control Recommendations for Field Crops (PB1768).
Print-Ready PDF Publication (Tarnished Plant Bug W025)