Hemiptera Pentatomidae

Natural History

Distribution. This native insect is found throughout the United States and southern Canada, and extends south into Mexico. Two subspecies are recognized by some authors: E. servus servus (Say) occurs in the southern states, including Virginia, southern Illinois, Texas, Arizona, and southern California; E. servus euschistoides (Vollenhoven) occurs in the northern portions of the continent. They meet in a broad band of intergradation from Maryland to Kansas. E. servus is the most abundant member of the genus in southern states.

Host Plants. This species has a wide host range. Among the vegetables attacked are bean, cabbage, corn, cowpea, okra, pea, pepper, squash, and tomato. Other crops that serve as hosts include such field crops as alfalfa, clover, cotton, lespedeza, oat, soybean, sweet clover, and timothy, and such fruit crops as apple, citrus, peach, pear, raspberry, and tobacco. Some of the weeds fed upon by brown stink bug are cocklebur, Xanthium sp.; curly dock, Rumex sp.; flea-bane, Erigeron annuus; goldenrod, Solidago sp.; horse-weed, Erigeron canadensis; ragweed, Ambrosia sp.; mullein, Verbascum thapsus; pigweed, Amaranthus sp.; prickly lettuce, Lactuca scariola; yellow thistle, Cirsium horridulum; and Canada thistle, Cirsium arvense. Mullein is reported to be especially important as it is present early in the season before many other hosts are available.

Natural Enemies. Brown stink bug is parasitized by Telenomus and Trissolcus spp. (Hymenoptera: Sce-lionidae), Hexacladia smithi Ashmead (Hymenoptera: Encyrtidae) and several flies, including Gymnosoma fuliginosum Robineau-Desvoidy, Trichopoda pennipes (Fabricius), Cylindromyia binotata (Bigot), C. euchenor (Walker), C. fumipennis (Bigot), Gymnoclytia unicolor

(Brooks), G. immaculata (Macquart), Euthera tentatrix Loew (all Diptera: Tachinidae), and Sarcodexia sterno-dontis Townsend (Diptera: Sarcophagidae) (McPher-son, 1982). Yeargan (1979) studied mortality of brown stink bug eggs in Kentucky, and reported that when egg masses were distributed in crops about 50% were parasitized,12% were destroyed by predators, and 20% failed to hatch probably due to undetectable natural enemy feeding. When stink bugs were allowed to oviposit naturally on plants 60% were parasitized, 37% were destroyed by predators, and 2% failed to hatch. Obviously, natural enemies have the potential to destroy a high proportion of stink bug eggs.

Life Cycle and Description. There are two generations annually throughout the range of this species, though in northern locations many late-developing nymphs of the second generation perish with the onset of winter. The adult is the overwintering stage. Overwintered adults usually commence egg laying in early May and continue through mid-June. The adults from the first generation produce eggs beginning in August, and the nymphs from this generation mature, but do not produce eggs, before the onset of winter.

  1. Females deposit eggs in clusters of about 20, but counts of 14 and 28 eggs per mass are especially common, probably reflecting ovariole number. Overwintered adults produce, on average, about 120 eggs per female, with over 500 being produced by an occasional individual. The egg production by first generation adults is lower, usually 40-80 per female. The eggs are yellowish-white, and slightly greenish initially. They are somewhat barrel-shaped, attached one end to a leaf, and with a row of 30-35 small processes ringing the upper end of the egg. During warm weather the incubation period is typically 5-6 days (range about 3-14 days).
  2. There are five instars, the mean durations of which were 3.7, 5.1, 4.9, 6.9, and 6.7 days, respectively, when reared on beans in Arkansas (Rolston and Kendrick, 1961). In contrast, Woodside (1946) reported mean instar durations of 5.3, 9.3, 10.3, 13.0, and 13.6 days when reared on peach in Virginia. The difference in total nymphal development time, 33 vs 51 days, is not likely due solely to food plant effects, because the long egg incubation time of about 9 days in the Virginia study suggests cooler rearing conditions. Nymphal lengths are reported to average 1.5, 2.4, 4.2, 8.5, and 10.4 mm, respectively. The young nymphs are light colored dorsally, with the thorax yellowish-brown and the abdomen white or yellow. The abdomen also bears red markings. The antennae are reddish-brown. The older nymphs have substan tially the same appearance, though the abdomen is always yellow. The wing pads become evident in instar four, and the pads overlap abdominal segments in instar five.
  3. Adults from the first generation do not all go on to produce eggs. Over 90% of insects reaching adulthood after August 1 enter reproductive diapause. Even adults produced in June may enter diapause, but the incidence is much lower. Adults successfully overwinter under plant debris and amongst weeds. In Arkansas, survival of adults sheltering in mullein was especially high. Open habitats, rather than wooded environments, seem to be favored (Jones and Sullivan, 1981). Longevity of overwintered adults in the spring usually is about two months, but some persist for the entire summer before perishing. The adult measures about 11-15 mm long, and is brown or grayish-yellow. The abdominal segments, when viewed from below, bear black spots at the lateral angles. The lateral edges of the pronotum, or "shoulders," are rounded. A key to distinguish stink bugs commonly affecting vegetables is found in Appendix A. (See color figure 144.)

The most complete life-history study was conducted by Rolston and Kendrick (1961), but McPher-son (1982) provided an excellent summary of biology. Munyaneza and McPherson (1994) provided developmental data, description of the nymphal stages, and information on rearing. Aldrich et al. (1991b) provided information on the chemistry of a volatile that attracts nymphs and adults of brown stink bug and other Euschistus spp., as well as stink bug parasitoids.

Damage

Nymphs and adults feed on tender shoot tissues, buds, and fruit. Most damage to vegetables takes the form of deformed fruit, aborted blossoms, or death of young tissue. Sedlacek and Townsend (1988) and Apriyanto et al. (1989a,b) found that young corn plants

Adult brown stink bug.

were damaged by stink bug feeding. Symptoms included chlorotic lesions, tightly rolled leaves, wilting, stunting, increased tillering, delayed silk production, and smaller grain weight. The first instars, however, feed little or not at all—a common condition among stink bugs.

Management

Phillips and Howell (1980) stressed the importance of weeds in stink bug biology, and noted that damage was higher in weedy areas, especially following senescence of the weeds. Reduced tillage practices and presence of cover crops seem to contribute on increases in stink bug abundance, probably because weeds are more abundant. Thus, if stink bugs are prone to be a problem, it is important to monitor weed populations. Pheromones specific to Eustichus spp. can be used to capture and monitor abundance of this stink bug. Foliar insecticides are effective, with special care warranted to protect the blossoms and fruit.

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