Adult tarnished plant bugs, Lygus lineolaris, are about 1/4
inch long, brownish with yellow markings, and generally shiny
or brassy in appearance; a yellow, V-shaped mark is present
on the dorsal surface (the "top" or "back"
of the insect) just behind the head. Adults overwinter in vegetation
that provides protection from extreme cold. In the spring, they
are attracted to flower buds and shoot tips of many plants,
including apple, peach, and strawberry.
on image for larger version
Figure 1. Adult Tarnished Plant Bug. Length is 1/4
inch (6 mm)
2. Tarnished Plant Bug, Adult and Nymph
Several generations of this insect develop each year, and adults
and nymphs are present on many different plants from April or
May until a heavy frost in the fall. Tarnished plant bugs use
piercing/sucking mouthparts to feed on sap from flower buds.
As they feed, they inject a toxin that kills surrounding cells.
This results in berries that remain small, with a concentration
of seeds at the end of each ripening berry. These distorted
"button berries" remain woody and unmarketable.
Controlling weeds in and around strawberry fields reduces in-field
overwintering and removes sources of early-season flowers that attract
adult tarnished plant bugs to fields. However, weeds in and near
strawberry fields should not be mowed when strawberry buds are forming
and flowers are beginning to open, as tarnished plant bugs will
move from weed hosts to strawberries at a time when the crop is
especially vulnerable to damage.
for monitoring tarnished plant bug infestations and determining
whether or not to use an insecticide vary depending on whether adults
or nymphs commonly cause damage in a particular region. Adults that
migrate into fields appear to cause more damage than subsequent
nymphs during most seasons in Illinois. Producers are advised to
control tarnished plant bugs if:
- the field has suffered substantial damage from tarnished plant
bugs in previous years
- tarnished plant bug adults are present in the field and sweep
net samples produce more than 2 tarnished plant bug adults per
10 sweeps as buds begin to form.
if nymphs are present when buds are forming (particularly for later
varieties or day-neutral varieties), shake flower clusters over
a white pan or paper to dislodge the nymphs and count them. If counts
exceed 1 nymph per 4 flower clusters or more than 10 percent of
the flower clusters are infested (regardless of count), application
of an insecticide is warranted. See the most recent edition of the
Illinois Commercial Small Fruit and Grape Spray Guide
for details on the insecticides registered for control of tarnished
palnt bug in strawberries. Where tarnished plant bug control is
needed, insecticides should be applied soon after blossom buds first
become visible and again if reinfestation occurs just before bloom.
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