Tarnished Plant Bug
Beginner
Scientific Name
Lygus lineolaris
Identification
- Adult tarnished plant bugs (TPB) are small, oval, brownish-black (6- 6.5 mm or 1/4 in.) with yellow triangular area on each wing
- Nymphs are green, resembling aphids
- They cause a broad range of damage on vegetable crops including necrotic spots on the florets and curd of broccoli and cauliflower
- Ethnic crucifers, such as Chinese broccoli, can also suffer damage to the flower stalk
Often Confused With
Aphids
Squash bugs
Period of Activity
The TPB is a sporadic pest, present in Ontario throughout the growing season. Overwintered adults become active around mid-to-late April and populations continue through to late September. Adults are highly mobile, moving readily from adjacent crops when disturbed by harvest activities.
Scouting Notes
Monitoring for plant bug can be done during the 5 x 5 monitoring for other insects. Take special notice of the presence of preferred host weeds (mint family, chickweed, pigweed and alfalfa) and check these areas for nymphs.
Thresholds
None established
Advanced
Scientific Name
Lygus lineolaris
Tarnished plant bugs have a large host range. They are known to attack over 270 different plant species. Certain weeds are a preferred habitat for this insect. It can be commonly found on members of the mint family, chickweed, pigweed and alfalfa.
Identification
The adult tarnished plant bug is a small, oval, brownish-black insect about 6- 6.5 mm (1/4 in.) in length. It has a characteristic yellow triangular area on each wing. Nymphs are green in colour and resemble aphids. They progress through five instars before moulting to adults. The final three instars have wing pads.
Tarnished plant bugs damage cauliflower curds and broccoli beads. On cauliflower, feeding damage results in brown streaking along the surface of the curd. As it wanders over the curd surface, it pierces the plant tissue with its mouth parts, sucking out plant juices causing affected plant area to become a tan colour. Damage such as this to the curd leaves the plant vulnerable to attack by soft rot bacteria and renders the head unmarketable.
On broccoli, feeding damage as a result of the sucking activity of the plant bug is indicated by dry, shrivelled, greyish-brown beads scattered across the head. Bacterial rots may invade this damaged tissue.
Ethnic crucifers such as gai lahn (Chinese broccoli) can suffer damage to the flower stalk. Tarnished plant bug damage can include flower abortion and deformities to the growing point.
Often Confused With
Aphids
Squash bugs
Biology
The insect overwinters as an adult in hedgerows, weedy areas and woods. In the spring it migrates to preferred hosts to lay eggs. Nymphs develop on these hosts until their wings develop and they become adults. The insect is most susceptible to control at the nymph stage. Because of their relative immobility, cutting alfalfa that has a high population of young nymphs will cause them to starve.
Adult plant bugs migrate on warm summer breezes. They are opportunistic feeders and will infest fields for short periods of time during these migrations. If preferred hosts, such as pigweed, are not present, they will soon leave the field.
There are three to five generations of tarnished plant bug per year.
Period of Activity
The TPB is a sporadic pest, present in Ontario throughout the growing season. Overwintered adults become active mid-to-late April. First generation adults appear about 2 months after the emergence of the overwintered adults, which corresponds to about 214 degree days above 9.3°C (48.7°F) in Ontario. Remaining generations continue emergence until late September. Adults are highly mobile, moving readily from adjacent crops when disturbed by harvest activities.
Scouting Notes
Monitoring for TPB can be done during the 5 x 5 monitoring for other insects. Take special notice of the presence of preferred host weeds and check these areas for nymphs. This insect is most threatening after head formation in cauliflower and broccoli and resident populations should be controlled.
Thresholds
None established.
Management Notes
- Tarnished plant bugs breed on many common weed species, including chickweed, dandelion, lamb’s-quarters, ragweed and fleabane.
- Control weed species that are attractive to tarnished plant bug.
Weed control in and around vegetable plantings will help reduce potential infestations. - Monitor neighbouring alfalfa fields for the presence of nymphs, and if possible, arrange to cut before adults have developed.
