The lygus bug (or tarnished plant bug) is native to North America, and it is especially common across the eastern half of the continent, from northern Canada to southern Mexico. It is one of the most damaging Hemiptera species, known to feed on almost all commercial crops. Lygus lineolaris boasts at least 385 different host species, the majority of which belong to the plant subclasses Rosidae and Asteridae. Producers can help prevent infestations by eliminating weed hosts (butterweed, goldenrod, fleabane, etc.) nearby, cultivating preferred host plants away from the edges of nurseries, and destroying favourable overwintering sites.
Life cycle and appearance of Tarnished plant bug
Adult Lygus lineolaris are true bugs that can grow up to 6.5 mm in length and are variable in colour; generally they are brown with yellow, orange or red accents, but their colouring can range from pale yellow with few dark accents to almost completely black with yellow markings. Adults that have overwintered are typically darker than summer adults. Regardless of colour, all lygus bugs have a light-coloured “V” shape on their dorsum (back).
Lygus bugs overwinter under plant debris, such as dead weeds, leaf litter and tree bark, and become active in early spring. They begin to feed on developing plant buds and shoots immediately, migrating into crops throughout the spring and into summer. As they feed, they lay their eggs on crop stems and, if the weather is warm enough, can produce up to three generations per year.
The eggs of Lygus lineolaris are about 1 mm long, shaped like a thin, slightly-curved flask, truncated with a flat cap from which the nymph emerges. The adults insert their eggs into the host plant tissue with only this cap exposed. Small (1 mm) yellowish-green, wingless nymphs emerge from the eggs 7–10 days later and begin to feed alongside the adults.They go through five nymphal stages, and as they mature they develop dark spots on the thorax and abdomen as well as wingpads. The lygus bug completes its life cycle in three to four weeks.
Lygus bug adults and nymphs attack the seeds, buds and flowers of plants, piercing them with their needle-like mouthparts, injecting enzyme-filled saliva to break down the plant tissue and sucking out the contents. The following symptoms begin to appear a few weeks after feeding injuries are incurred:
- Buds turn white, fail to develop and drop off;
- Leaves developing from damaged buds are ragged and discolored;
- Flowering is delayed, flowers fall without forming fruit or fruit falls without maturing;
- Fruit feeding damage causes cat-facing and dimpling;
- Seeds darken and collapse or shrink;
- Terminal plant growth is yellowed and distorted;
- Plants develop split-stem lesions;
- Nodes swell and internodes become elongated;
- The number of vegetative branches increases and plants develop multiple crowns;
- Transmission of diseases, such as soft rot and ring rot.