| Two of the most damaging insects on perennial
plants are the tarnished plant bug, Lygus lineolaris,
and the four-lined plant bug, Poecilocapsus lineatus.
These two plant bugs can cause serious problems
because they have such a wide variety of host
plants. The four-lined plant bug feeds on 250 plant
species which are mostly herbaceous. The tarnished
plant bug is a problem on a wide variety of
ornamental flowers.
Symptoms and Diagnosis
Damage varies slightly from the two plant bugs. The
four-lined plant bugs cause small (1/16 inch),
discolored areas on leaves where they suck out cell
juices. Injured areas will turn black or become
translucent, and after several weeks, the dead tissue
may drop out, leaving small holes. The adults feed
on the upper surfaces of leaves and are voracious
feeders. The topmost leaves will generally be the first
to be injured.
Damage from the tarnished plant bug is in the form
of distorted foliage or disbudded plants. This damage
is caused by the overwintered adults which attack
swollen and opening buds in the early spring. The
disbudding will cause the plant to be short and
bushy. If the attack takes place after shoot elongation
begins, the tip will often turn black and die, or it
will be so damaged that shoot stunting or distortion
occurs. Stems frequently break at the injured area.
Life Cycle
The four-lined plant bug overwinters as eggs inserted
into a slit near the top of tender shoots. Nymphs
emerge from the eggs in May. Nymphal coloring
varies from bright red to yellow. The species requires
about 30 days to complete nymphal development.
Forewings of adults are yellow, but may turn bright
green. However, the four black stripes that give the
insect its name remain distinct. This species
normally has one generation a year.
Adults of the tarnished plant bug overwinter as
adults in leaf litter. Beginning in the spring, they lay
eggs mainly in the stems and flowers of herbaceous
plants. After hatching, the young nymphs usually
remain to feed on the same plant until they mature.
The nymph is green or pale yellow and grows
rapidly. Adults are capable flyers and readily move
from place to place. There may be two to five
generations per year. In midsummer, a life cycle may
be completed in about 25 days. By late summer,
populations can become very abundant.
Integrated Pest Management Strategies
1. Live with the damage. Since damage is often
cosmetic, some damage can be tolerated.
Often, natural predators will keep the insects
under control.
2. Remove leaf litter. To limit problems in coming
years, clean up leaf litter to avoid overwintering
sites for tarnished plant bugs.
3. Prune out egg masses. Learn to identify the egg
masses of four-lined plant bugs and prune them
out in winter.
4. Use insecticidal soaps. If populations are high
enough, spraying with an insecticidal soap may
be necessary. Because the tarnished plant bug can
go through many generations in a single year and
cause great damage to a plant, it is best to initiate
control when it first appears.
5. If necessary, use chemical insecticides. Plant
bugs can be controlled with malathion,
methoxychlor, and carbaryl (Sevin). | 
