Euschistus conspersus Uhler Hemiptera Pentatomidae

Natural History

Distribution. Consperse stink bug occurs in western North America from British Columbia and Idaho south to California and Nevada. It is a native species.

Host Plants. Consperse stink bug damages vegetable and fruit crops. Known principally as pest of tomato, it also feeds on apple, apricot, blackberry, fig, loganberry, peach, pear, plum, and raspberry. It also is found occasionally in alfalfa, barley, cotton, sorghum, and sugarbeet. Among the numerous weeds known to support consperse stink bug are bracken fern, Pteridium aquilinum; dock, Rumex sp.; horehound, Marrubium sp.; mallow, Malva sp.; mullein, Verbascum sp.; plantain, Plantago sp.; mustard, Brassica sp.; and the thistles Cirsium occidentale and C. mohavense.

Natural Enemies. Stink bug eggs are parasitized by Trissolcus and Telenomus (Hymenoptera: Scelioni-dae). The level of parasitism varies greatly, and the first generation is typically lightly parasitized. Digger wasps, Dryudella sp. (Hymenoptera: Sphecidae), prey on nymphs, and spiders are important predators of adults.

Life Cycle and Description. In California, there are two generations annually, but only one generation is present in cooler areas. The adults overwinter in reproductive diapause and commence production of eggs in March or April. First generation nymphs are found from April to June, and adults from June to

  1. Second generation eggs are present from July to August, nymphs from July to October, and adults until the subsequent spring.
  2. Eggs are deposited in clusters of 7-28 eggs, with most clusters consisting of 13-15 eggs. They normally are arranged in four short rows of 3-4 eggs. Adults are not very discerning in their oviposition habits, selecting dry leaves and plants unsuitable for nymphal growth as well as suitable host plants. Initially pearly white in color, the barrel-shaped eggs bear a fringe of spines around the top. The eggs turn pink as they mature. Duration of the egg stage is about 5-30 days under field conditions, and averaged 6.2 days when reared at 27°C. Females may produce up to 640 eggs during their life span, though mean fecundity is about 225 eggs.
  3. There are five instars. The early instars are black and reddish, but later instars are various shades of yellow and brown. Duration of the nymphal stage ranges from 23-79 days under field conditions. When cultured at 27°C, mean development time was 25.6 days. Mean duration of the instars was 3.1, 5.6, 4.3, 4.9 and 7.7 days, respectively, for instars 1-5. Temperatures of about 27°C seems optimal for development and oviposition. The first instar does not feed, and young nymphs remain clustered around the egg cluster during this instar.
  4. The adult measures 11-12 mm long and 66.5 mm wide. It is grayish-brown or greenish-brown dorsally, but sprinkled with numerous small black spots. The ventral surface is greenish, yellowish, or brownish. The legs are yellowish, though they also bear some black spots. The antennae are yellow or reddish, and darker at the tip. Adults overwinter under weeds and trash in the field. In the spring, overwintered adults feed on weeds and commence oviposition on both weeds and crop plants. Second generation adults commence egg laying after a pre-oviposition period of about 10-32 days.

The biology of consperse stink bug was given by Borden et al. (1952) and Hunter and Leigh (1965). Development was described by Toscano and Stern (1976). Toscano and Stern (1980) described reproductive biology. Alcock (1971) described aggregation and mating behaviors. Aldrich et al. (1991b) provided information on the chemistry of a volatile that attracted nymphs and adults of consperse stink bug and other Euschistus spp., as well as stink bug parasi-toids. A key to distinguish stink bugs commonly affecting vegetables is also found in Appendix A.

Adult consperse stink bug.

Damage

Stink bugs feed on developing fruit, usually green fruit, causing white corky tissue to form beneath the skin at the site of feeding (Michelbacher et al., 1952). However, pink and red fruit also is readily attacked (Zalom et al., 1997). Dimpling or distortion of the fruit is common. Stink bugs seem to favor the stem end of tomato fruit, but they also feed elsewhere. Some fruit drop also occurs and stink bugs are implicated in transmission of pathogenic yeast, though plant disease transmission has not been demonstrated specifically for consperse stink bug. Damage is often localized along the margin of a field because the bugs encounter these plants first as they disperse into a crop from overwintering shelter.

Management

Stink bugs can be sampled with a sweep net or by visual observation, often in association with a beeting sheet or tray. Insecticides are applied to foliage and young fruit to protect susceptible crops from injury, though stink bugs are quite difficult to kill. It is important to obtain good penetration of canopy foliage down to the soil level, because these stink bugs often are found on lower portions of the plant. Border treatments are especially important, because this is the portion of the field injured most severely.

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