Adelphocoris superbus Uhler Hemiptera Miridae

Natural History

Distribution. Rapid plant bug occurs in the United States and Canada principally east of the Great Plains. In western North America it is replaced by superb plant bug, but the two species overlap in the Rocky Mountain region and Great Plains. Both species are native, and there is some thought that they are variants of the same species (Slater and Baranowski, 1978).

Host Plants. These insects are known principally as pests of alfalfa and sweet clover, where they can attain high levels of abundance. Sometimes they move to vegetables, including bean, carrot, celery, and potato. They are also known from field crops such as cotton and sugarbeet, and such weeds as Canada thistle, Cirsium arvense; dock, Rumex sp.; and yarrow, Achillea sp.

Natural Enemies. The little is known about the natural enemies of these insects. In Ontario, the parasitoid Peristenus pallipes (Curtis) (Hymenoptera: Braconidae) was recovered from up to 60% of first generation rapid plant bug nymphs but none from the second generation (Loan, 1965). Some general predators such as the assassin bug Sinea diadema (Fabricius) and the ambush bug, Phymata fasciata (Grey) were thought to affect rapid plant bug in Alberta (Lilly and Hobbs, 1956).

Description and Life Cycle. There are two generations per year in northern areas of the United States. In Canada, there are two generations in southern regions, but only one further north. Overwintering occurs in the egg stage. In Minnesota, eggs of rapid plant bug hatch in May, and by mid-June first generation adults are numerous. Nymphs of the second generation are present in early July, and adults by early August. The second generation adults were observed to deposit eggs in August and September which overwintered. In Utah, superb plant bug exhibits a very similar phenology (Sorenson and Cutler, 1954). In contrast, in a single generation per year population in Alberta, first instars were most abundant in late May, instars 2-3 in mid-June, instars 4-5 in July, and adults from late July-September. Any surviving nymphs and adults die with the onset of winter. The time required for a complete generation is estimated about 55 days under warm conditions.

  1. The eggs are deposited singly in stems of vegetation. The eggs are greenish white or yellow, tend to become reddish near maturity, and measure about 1.2-1.4 mm long, and about 0.3 mm wide. The cylindrical, slightly curved eggs greatly resemble eggs of Eygus spp. (see section on tarnished plant bugs and pale legume bug), but in rapid plant bug the portion of the egg that reaches the surface of the plant, or cap, bears a distinct extension or spine. In superb plant bug, authors who have described eggs (Sorenson and Cutler, 1954; Lilly and Hobbs, 1956) failed to note or illustrate the egg spine or extension; perhaps this indicates that these insects were indeed separate species. Tarnished plant bug and pale legume bug also lack the spine. Incubation of the eggs stage requires about 15-20 days during the summer. Sorenson and Cutler (1954) reported fecundity averaging about 35 and sometimes attaining a level of 100 eggs per female. The larger number is likely more typical in nature.
  2. There are five instars, the mean duration (range) of which is 3.8 (2-6), 2.4 (1-5), 1.8 (1-3), 3.0 (2-4), and 4.3 (3-5) days, for a total nymphal development time of about 15.4 days. The nymphs are brightly colored. They are principally yellow during instar one, but in later instars they are mostly red, with green on the ventral surfaces. In mature nymphs the head is dark. The abdomen bears a broad reddish-brown band near the tip. The antennae bear alternating light and dark bands, usually of red and yellow. The thorax and abdomen lack the dark spots found dorsally on the Lygus spp.
  3. The adult measures 6.8-7.4 mm long. The head, legs, and prothorax of the adult plant bugs are yellow to red. In rapid plant bug the pronotum is yellow or yellowish-brown, though usually there are two large black spots near the hind margin of the prono-tum. In superb plant bug, the pronotum is red, and this structure is seldom marked with dark spots. The heme-lytra are brown except for the lateral edges, which are bordered narrowly with yellow in rapid plant bug, and red in superb plant bug. The antennae are black, and broadly ringed with yellowish-white. The adults are active and fly readily when disturbed. However, they rarely fly far or high, so dispersal is not rapid.

The biology of rapid plant bug was described by Hughes (1943), and nymphal morphology was provided by Webster and Stoner (1914). The biology of superb plant bug was given by Sorenson and Cutler (1954) and Lilly and Hobbs (1956).

Adult rapid plant bug.
Adult superb plant bug.

Damage

These plant bugs are rarely considered to be significant pests, as they do not normally colonize vegetable crop plants. Damage usually occurs when the bugs disperse from a favored crop or weeds, often due to senescence or harvest. Adelphocoris plant bugs inflict damage on seeds and young tissue in much the same manner as Lygus spp. (see section on tarnished plant bugs and pale legume bug).

Management

Because these plant bugs are not often a pest, insec-ticidal control is rarely warranted. Foliar sprays are effective, if necessary. Effective management of alfalfa can do much to alleviate problems with these plant bugs. As they overwinter in alfalfa stems, close cropping of alfalfa in the autumn and feeding the hay to livestock reduces the overwintering population. Burning of stubble in the spring is sometimes recommended, but this practice also destroys predator populations (Lilly and Hobbs, 1962).

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