Systena hudsonias Forster Coleoptera Chrysomelidae

Natural History

Distribution. Redheaded flea beetle is distributed widely in the eastern United States and Canada. Although it has been collected in Montana, it is rarely found west of Manitoba, Kansas, and eastern Texas.

Smartweed flea beetle occupies a similar range. It is distributed widely in the eastern states and provinces, but is found only as far west as South Dakota, Colorado, and New Mexico.

Host Plants. The adults of both redheaded and smartweed flea beetle have been observed to feed on various vegetables, including bean, beet, cabbage, corn, eggplant, lettuce, okra, parsley, potato, and sweet potato. Other crops such as alfalfa, apple, clover, cranberry, currant, gooseberry, grape, horseradish, raspberry, soybean, sugarbeet, sunflower, strawberry, and numerous woody ornamental shrubs are also attacked. As might be expected of insects with such a wide host range, numerous weed hosts have been reported, including smartweed, Polygonum pensylvanicum; lamb-squarters, Chenopodium album; giant ragweed, Ambrosia trifida; plantain, Plantago major; beggartick, Bidens frondosa; redroot pigweed, Amaranthus retroflexus; Canada lettuce, Lactuca canadensis; Canada thistle,

Cirsium arvense; and giant foxtail, Setaria faberii. Of the aforementioned weeds, the first four are thought to be preferred by redheaded flea beetle. Redheaded flea beetle larvae have been observed developing on corn, and both species attack sugarbeet.

Life Cycle and Description. Apparently, there is only a single generation per year. Adults are present from mid-summer until winter. Eggs are present at all times except spring. The biology of smartweed flea beetle is almost unknown. Following is a description of redheaded flea beetle.

  1. The eggs are elliptical, and slightly more rounded at one end. They measure 0.70-0.85 mm long. Eggs are deposited in the soil beneath suitable food plants, usually at a depth of 1.5-5.0 cm. This is the overwintering stage, and eggs must receive a period of chilling before they will hatch.
  2. Larvae are whitish with a brownish head capsule, and bear numerous spines. There is a prominent anal tubercle bearing a tuft of setae. Larvae develop from May to July, feeding on plant roots. Larvae display three instars and reach a length of about 8 mm during development, which requires about 30 days.
  3. Pupation occurs in the soil.
  4. Adults measure 3.5-5.5 mm long. They are dark reddish brown, with an orange-red head. Head color, the basis for the common name, is diagnostic, although related species such as S. elongata (Fabricius) may have a reddish brown head. The hind femora are enlarged. The large size of Systena spp. is a good diagnostic character, and among the common crop-feeding flea beetles only Systena and Disonycha spp. exceed 3.5 mm. The adults are active from June through September or October in the North, and through November in the South, depending on weather. There is a report of adults overwintering in Indiana, but this has not been confirmed. Eggs are deposited beginning in July, but remain in diapause until the following spring.

The adults of smartweed flea beetle are distinguished from redheaded flea beetle only by the lack of an orange-red head. In all other respects, they are virtually identical (Smith, 1970). Further study may demonstrate that smartweed flea beetle is merely a color variant of redheaded flea beetle.

The biology of redheaded flea beetle is not well studied. Hawley (1922), Smith (1970), and Jacques and Peters (1971) provided the most complete information on life history.

Adult redheaded flea beetle.

Adult redheaded flea beetle.

Adult smartweed flea beetle.

Damage

The adults feed on the epidermis of foliage, usually the upper surface. They create elongate holes, often leaving the lower epidermis intact as a transparent membrane. They may aggregate on certain plants, and often prefer weeds to crops. Jacques and Peters (1971) noted that the adults were abundant on corn only in the absence of preferred weeds. Corn silks were observed to be preferred over leaf tissue, and beetles were observed to leave corn ields after silks were mature. Hawley (1922) noted that bean plants usually recovered from defoliation; the exception was during dry weather, when permanent damage or death could occur.

The larvae feed on, and burrow within, plant roots. Jacques and Peters (1971) found redheaded flea beetle larvae interspersed with corn rootworm larvae among corn roots in Iowa, but flea beetle larvae were much less numerous, and less damaging than northern corn rootworm. Riley (1983) documented severe damage to germinating soybean seeds and seedlings by redheaded flea beetle in Mississippi. The larvae scored the seed surface, and burrowed through the seed, stem, and roots.

Management

Weed management is a key to effective management of both redheaded flea beetle and smartweed flea beetle, as these insects consistently are reported as pests only where favored weeds are abundant. Chemical treatments applied for corn rootworm larvae are adequate for redheaded flea beetle larvae, though seldom needed. Adult damage is easily prevented with foliar applications of insecticide if the crop is carefully monitored.

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