Fruit IPM Factsheet Fruit IPM Factsheet
Tarnished Plant Bug
Scientific Name-Modified from NCR-63:Common Tree Fruit Pests,
by Angus H. Howitt, Michigan State University
This pest was first described in 1746 by Linnaeus in Sweden. In America, the species was first described by Thomas Say in 1831, though there are indications that it was collected and described here as early as 1781.
Life Stages
Egg: The egg is elongated and slightly curved. The outer end is cut off squarely, and the lid that covers this end is usually flush with the stem. The egg is 0.95 to 1 mm long and 0.25 mm wide.
Nymphal stages: The newly hatched tarnished plant bug is a small, greenish creature less than 1 mm long. It goes through five instars, with wing pads beginning to show in the third instar.
Adult: The adult varies from 4.9 to 5.7 mm long and 2.4 to 2.8 mm wide. Generally, it is brownish mottled with various shades of yellowish and reddish brown. The bug is a flattened oval, with the small head projecting in front.
Host Range
This species feeds and
breeds on a great variety of plants. It attacks apple, apricot, cherry, pear, peach, plum
and quince. It also feeds on small fruits,such as strawberry and raspberry as well as
flowers, vegetables and field crops.
Injury or Damage
Overwintered adults begin feeding on apple, peach
and strawberry buds soon after growth begins. They are most abundant during the prebloom
and blossom periods. Egg laying in the blossom buds begins as soon as the stems in the
clusters start to separate and continues in the fruit until the fruit are about 12.5 mm in
diameter. The plant bugs then migrate to the weeds and become scarce in fruit trees.
Common mustard weed is the preferred host.
Affected fruits may exhibit both feeding and egg-laying injuries. Feeding punctures are usually small and superficial injuries, but the oviposition punctures cause deep depressions and distortion of the fruit. Most of the injuries are inflicted in the calyx tube near the base of the sepals and petals, so the blemishes on the mature fruits appear at the calyx end. Some injuries, however, particularly those made after bloom, may occur elsewhere on the fruit surface.
Apple varieties react differently to tarnished plant
bug oviposition wounds. In Red Delicious and Cortland, very deep depressions usually
result. In Duchess and Greening, the depressions are less pronounced, though these
blemishes may result in a lower grading for the fruit. The degree of injury depends not
only on the number of insects, but also on the weather.
Factors Affecting Abundance
Warm weather in the early season before alfalfa and other ground crops have developed will cause movement into and damage in the fruit trees. Cold, rainy or windy weather at this time will reduce or prevent feeding. Fruit trees near hedgegrows, ditch banks and other hibernation locations are more seriously injured. Droughty conditions that dry up vegetation may cause plant bugs to move into trees.
Life History
The adult bugs hibernation under leaf mold, stones and tree bark, among the leaves of such plants as clover, alfalfa and mullein, and in many other protected places. They become active very early in spring, when they attack the buds of fruit trees, seriously injuring the terminal shoots and fruits. They do not appear to lay their eggs on these plants to any great extent, but rather migrate to various herbaceous weeds, vegetables and flowers, where the eggs are either inserted full length into the stems, petioles or midribs of leaves or into buds, or are tucked in among the florets of the flower heads.
In about 10 days, a small nymph emerges from the egg
and begins feeding on the sap. It grows rapidly, molting five times. The larger nymphs
gradually take on the appearance of the adult. The life cycle is completed in three or
four weeks, so three to five generations probably occur each season. By late summer, the
bugs can be numerous, but because of their obscure and protective coloration and shy
hiding habits, they are not often noticed.
Monitoring
Make regular observations from tight cluster stage to first cover, particularly in orchard areas adjacent to weedy places or locations where alfalfa or other hay crops grow. Unbaited glossy, rectangular, non-reflective, white, sticky boards, hung low in the tree, are effective monitoring traps for plant bugs. Place the traps per block, or about one trap for every 3 to 5 acres. If you find more than three plant bugs per trap by the fruits tight cluster stage, or four bugs per trap by the fruit’s pink stage, apply a prebloom pesticide. For oak and hickory bugs, hang traps in the tops of trees near the edge of the orchard when the orchard is bordered by woods.
Control
Crop cover management is important in preventing the tarnished plant bugs from moving into fruit trees. Plant bugs are difficult to control. Spraying weedy hedgerows and weeds areas adjacent to orchards can reduce the migration of plant bugs into the orchards. On apples, this pest should be controlled at the pink stage. Other plant bugs, such as oak and hickory bugs (Lygocoris spp.), can cause similar injury in orchards bordered by woods. Green stink bugs (Acrosternum hilare) and other stink bugs (Pentatomidae) can also cause injury, especially late in the season.
