Tarnished Plant Bugs

Tarnished plant bugs feed on more than half of our garden crops, using their piercing mouthparts to suck the life from beans, stone fruits, strawberries, and other edibles. While these pests were once only found east of the Rocky Mountains, they now occur throughout North America.

Close-up of tarnished plant bug face (USGS Bee Inventory and Monitoring Lab) Public Domain

Tarnished plant bug damage

Tarnished plant bugs (Lygus lineolaris) eat all aboveground parts of a plant. They feed by injecting saliva into host plants. This saliva breaks down the pectin and plant tissues, making it possible to suck up their meal. As they feed, they cause distorted and discolored fruit and pod lesions. You may also see growing tips that are distorted, have lesions, or are dying back. Affected flowers tend to be distorted, discolored, or have signs of blight. These pests are responsible for blossom drop of tomatoes and peppers. Seeds may be distorted or shriveled. And the entire plant may show signs of dwarfing or rosetting due to tarnished plant bugs

Tarnished plant bug (Rylee Isitt) CC BY-SA 2.0

​Tarnished plant bug identification

Tarnished plant bugs are nearly identical to their western siblings, the Lygus bugs. Like their other relations, the capsid bugs and four-lined plant bugs, they all have a distinctive triangular or V-shape just behind the head and what I call the shoulder area (pronotum). This triangular area is called the scutellum. Their wing tips often form a diamond-shaped area at the rear end. Tarnished plant bugs are small, usually ¼” long. They are brown with yellow, orange, or red markings.

Tarnished plant bug anatomy (Kate Russell)

Tarnished plant bug nymph (Scott Bauer) Public Domain

Tarnished plant bug lifecycle

Tarnished plant bugs overwinter as adults in weeds and fruit trees. Females prefer laying their eggs in cotton plants, but they will make do with what’s available. These eggs are laid in mid-spring and hatch in early summer. Populations tend to peak when eggs hatch and again in mid-autumn.

Tarnished plant bug management

These pests like to hide in nearby weeds, so lose the weeds and mulch those areas with free wood chips from your local arborist. Tarnished plant bugs have several natural enemies. One nursery web spider, Pisaurina mira, loves to feed on tarnished plant bugs, so avoid those broad-spectrum pesticides.

While pesticides are commonly used against juvenile tarnished plant bugs in commercially grown crops, the effectiveness of those chemicals is decreasing. Pesticides don’t work well on adult tarnished plant bugs, to begin with. Research has shown that these pests are attracted to pink sticky paper, so that’s an easy organic control method. Certain parasitic wasps also play a role in controlling tarnished plant bug populations. A strong spray from the hose can dislodge juveniles, who are often unable to find their way back to a host plant.

Be on the lookout for these pests the next time you’re weeding around your fruit trees or garden plants.