Tarnished Plant Bug,
Lygus lineolaris (Palisot de Beauvois)

I. Introduction: The tarnished plant bug (TPB) is a general feeder found on many wild and cultivated plants throughout the U.S. In peach orchards TPB attacks buds, flowers, and fruit, making it an important direct pest present throughout the growing season.

II. Hosts: Adults and nymphs may be found on many herbaceous plants, especially legumes. Adults will often prefer mullein, alfalfa, clover, vetch, chickweed, and dandelion. Depending on the time of year, TPB may also be found on pigweed, lambsquarters, plantain, goldenrod, and aster. Only adults are found on peaches. Because of the intimate connection with alternate hosts in the ground cover, fruit injury and populations within the tree are often influenced by ground cover management.

III. Description: Adults (picture above) are about 1/4 inch (6 mm) long and 1/8 inch (3 mm) wide, flattened and oval in shape. Wings are folded flat over the body, and are mottled brown with some yellow. On the back side of each wing there is a distinct yellowish triangle with a brown to black spot on the posterior tip. The head is small, with a long beak that projects back under the body when at rest. Nymphs are pale yellow-green insects about the same size as aphids, but may be distinguished by the segmented abdomen and the presence of wing pads.

IV. Biology: Adults overwinter under bark and leaves, and around alfalfa and other legumes, or around a number of other weeds that seeded late in the summer or early fall. There are three to three and a half generations per year in the mid-Atlantic area. The insects feed with piercing, sucking mouthparts, sucking plant juices from the feeding site. Adults become active in the spring as buds begin to swell. Overwintering adults primarily feed on weed hosts unless disturbed in the ground cover by mowing, discing or similar operations which force them to move into the tree canopy. In the orchard, they first feed on expanding buds, and to a minor degree on terminal shoots. Adults continue to feed during bloom and after fruit set. First brood nymphs are present from late April through mid June. First generation adults may be found in the orchard from late May through late June. With the exception of the overwintering adults, this is often the largest of the summer generations, and often causes the most damage as adults disperse from weed hosts to peach trees. Later generations may continue to disperse from weeds to fruit throughout the season.

V. Injury: The insect feeds by piercing the plant and sucking out sap. Small droplets of sap may be present around the injury point on buds and fruit. Prior to shuck split, feeding injury causes bud, flower or fruit drop. Very little fruit drop is seen after shuck split to shuck fall. (See MSU link to peach growth stages).  Prior to pit hardening young fruit becomes deeply injured (see picture below). This early season "catfacing" injury results from tissue death at the feeding site, while the fruit continues to grow around the site, resulting in deformity. Injured areas may be fuzzless, corky, and depressed, and may have a small amount of dried gum in the center. As fruit matures, additional injury can appear as scarring, which is similar to typical catfacing, but without deformed fruit, gummosis or bleeding, and shallow-water soaked areas at the feeding site.

Catfacing examples 2, 3.

Injury may appear as either old or fresh. Recent feeding is not calloused over, and is often represented by gumming, either in small lumps or in a single strand exuding from the fruit. There may be a number of injury marks on the same fruit, caused from the probing around of a single insect. Water-soaked areas may also appear in multiple spots on the same fruit.

VI. Monitoring: Monitoring for TPB can be done by direct tree examinations, jarring or beating tray counts, sticky traps, orchard floor sweep sampling, and fruit damage counts; the most critical time is between petal fall and shuck fall. Visual examination of trees for adults is both tedious and time consuming, and may often give irregular results, since much depends on the temperature and time of day. Beating tray sampling may be done with a framed white sheet placed on the ground beneath the tree, or with a hand held square yard canvas beating tray, made for this purpose. One or 2 branches 3/4 -1 inch (1.9-2.5 cm) in diameter are beaten with a rubber mallet or heavy stick wrapped with rubber hose 3 to 4 times, or shaken abruptly. Insects that land on the cloth must be counted immediately.

Sweep sampling gives a good indication of the catfacing insects present in the ground cover. This method picks up nymphs as well as adults, and therefore can be used to help predict population growth. Because sweep sampling does not include those insects in the trees, it must be used as an indicator for a pest population that can move into the trees if the ground cover is disturbed. Sampling should be done with a heavy duty sweep net, taking at least 50 sweeps encompassing 180° per sample site, or per block. Sampling should be biased towards the thicker ground cover and weeds that are blooming or have seeded.

Fruit may be monitored by sampling 200 fruit per block. Direct fruit sampling is a must for any pest monitoring program, and will help identify other plant bug activity, leafroller and fruit moth injury, as well as diseases. Both old and new plant bug feeding should be recorded. If insects are feeding on the fruit, the detection of fresh injury is critical. Since injury points out a weakness in the spray program, changes can be made immediately.

White sticky boards have been used for TPB monitoring in apple orchards, but their use has not been very successful in peach orchards. If they are used, they should be in the outer one or two rows. Traps mimic bloom color, and should be placed from one and a half to two feet (0.5 m) above ground on the tree or on stakes near weeds. Ground cover should be cleared around the traps. Traps should be monitored and replaced on a weekly basis, or cleaned and adhesive renewed if needed. These are only useful for detecting relative abundance of the population, and should not be relied upon as the only sampling method.

There are no action thresholds based on tarnished plant bug monitoring. Ground cover sampling usually yields higher populations where flowering weeds are most abundant. Therefore good weed control accompanied by mowed grass or clean cultivated aisles aides in overall catfacing insect management. Since it is a direct pest, no more than one or two percent fruit injury should be tolerated at any one time. Sprays should be applied during times of adult activity, since this is the damaging stage in orchards.

Fact sheets: Virginia Tech, Michigan State University, Cornell University
This is taken primarily from a chapter by D. F. Polk, H. W. Hogmire and C. M. Felland on peach direct pests, reprinted with permission from Mid-Atlantic Orchard Monitoring Guide, published by NRAES, 152 Riley-Robb Hall, Ithaca, New York 14853-5701. (607) 255-7654.
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