Carpophilus lugubris Murray Coleoptera Nitidulidae

Natural History

  1. Sap beetles of the genus Carpophilus are found throughout the United States and southern
  2. Dusky sap beetle, a native insect, is the most important species. It is found from the Atlantic to the Pacific, and south into Central and South America, but is most numerous in eastern and midwestern states. Other Carpophilus spp. of occasional concern include antique sap beetle, C. antiquus Melsheimer; corn sap beetle, C. dimidiatus (Fabricius); and dried fruit beetle, C. hemipterus (Linnaeus).

Host Plants. Sap beetles have derived their name from their tendency to feed on sap and other sweet secretions. However, they also feed on fungi, pollen, damaged or rotting fruit, and occasionally on undamaged fruit. Among vegetables, corn is the crop most commonly injured, followed distantly by tomato. Dusky sap beetle is definitely a primary pest that feeds on uninjured corn; the other species are more likely associated with vegetable matter injured by other insects or by physical disruption.

Natural Enemies. Natural enemies of sap beetles seem to be few and their effects generally are unknown. The insidious flower bug, Orius insidiosus (Say), feeds on sap beetle eggs. A wasp, Cryptoserphus abruptus (Say) (Hymenoptera: Proctotrupidae), parasitizes beetle larvae. A nematode tentatively identified as Hexamermis sp. (Nematoda: Mermithidae) was found to infect up to 89% of adult beetles collected at certain sites during the spring in Illinois (Dowd et al., 1995), but it was absent from most sites. Some Carpophilus spp. are known to be affected by Howardula sp. nema-todes (Nematoda: Allantonematidae) and the fungus Beauveria bassiana. When sap beetle larvae occur in corn ears containing larvae of corn earworm, Helicov-erpa zea (Boddie), they are often killed by the caterpillars.

Life History and Description. Overwintering occurs underground in both the pupal and adult stages, usually in association with crop debris. The adults become active early in the spring, and enter corn fields about the time tassels are produced. Several overlapping generations may occur without distinct periods of abundance. In Washington and Maryland, eggs predominate in July, larvae in late July-early August, and adults are most abundant during August and taper off in September. Total generation time requires 1-3 months.

  1. The eggs are milky white, elongate oval, and measure about 1.2 mm long and 0.25 mm wide. Eggs are commonly deposited on corn silk, but they also can be found on the fecal material of boring insects, wet accumulations of pollen, and other food sources. Silks that are turning brown or have dried are particularly attractive to ovipositing beetles. The eggs may be deposited singly or in short chains of 3-5 eggs. Duration of the egg stage is 2-4 days at 21 °C.
  2. The larvae are white, yellowish, or pinkish, but bear a brownish head and caudal plate. The caudal plate, at the tip of the abdomen, is marked by a semicircular notch. The tip of the abdomen also bears a fleshy protuberance ventrally. The body bears sparse but moderately long hairs. Connell (1956) indicated that there are three instars, with a duration of about two, three, and eight days, respectively, followed by a prepupal period of about seven days. However, Tamaki et al. (1982) reported that there are four instars of dusky sap beetle with a mean duration of 4.5, 4.5, 3.5, and 9.6 days, respectively.
  3. After completion of the feeding period, larvae drop to the soil. They dig into a depth of 2.57.5 cm and prepare a small cell for pupation. Duration of the pupal stage averages 9.2 days at 21 °C in warm weather, but some individuals overwinter in the pupal stage.
  4. The adult measures 3.5-4.5 mm long, 1.8 mm wide, and is oval in form. It is dull brownish-black in color. As is common among sap beetles, the elytra are short, exposing the terminal abdominal segments. The antennae are club-shaped. Average adult longevity is reported to vary from about 130300 days, depending on its diet, but this species is obviously a long-lived insect. Adults are active fliers. The adult males produce aggregation pheromones that are synergized by food odors (Bartelt et al., 1991; Lin et al., 1992). Although different sap beetles produce unique pheromones, there is considerable cross attraction (Bartelt et al., 1994). Adults often overwinter either in the soil or above-ground in sheltered locations. Overwintering adults are not in diapause and become active whenever weather allows.

Some elements of dusky sap beetle biology were described by Connell (1956) and Tamaki et al. (1982). Description of several Carpophilus spp., and keys to common adult and larval sap beetles found in eastern states, were given by Connell (1956). Downie and Arnett (1996) also treated the adults of eastern species, and Hatch (1982) treated the western species. Rearing was described by Tamaki et al. (1982). Williams et al. (1983) published a bibliography of Carpophilus.

Damage

Sap beetles differ considerably in their tendency to attack undamaged vegetables. Among the Carpophilus spp., only dusky sap beetle is known to attack uninjured fruit frequently, whereas other species may be occasional contaminants of vegetable matter previously injured by caterpillars, grasshoppers, birds,

Carpophilus Spp Corn
Adult dusky sap beetle.

or other factors. Research in Delaware (Connell, 1956) and North Carolina (Daugherty and Brett, 1966) indicated that the attack in early season on the corn crop by sap beetles was independent of corn earworm damage. However, a positive association of sap beetles was found later in the season with corn ears exhibiting injury by corn earworm.

The presence of young sap beetle larvae in corn kernels is of particular concern because they are hard to detect. Sap beetles are responsible for rejection of considerable quantities of corn at canneries, and also transmit fungi which produce mycotoxins.

Management

  1. Sap beetles can be captured in traps baited with aggregation pheromone, pheromone plus whole wheat bread dough (Bartelt et al., 1994), or whole wheat bread dough alone (Peng and Williams, 1991). Various types of traps can be used with equal success, but they tend to be very efficacious if placed close to the soil surface. Dowd et al. (1992) described a particularly effective trap. Aggregation pheromones sometime concentrate beetles without capturing them, which can lead to localized crop damage.
  2. Insecticides often are applied during the silking stage of corn production to prevent infestation by dusky sap beetle, apparently because fermenting pollen is highly attractive. Sweet corn producers usually treat at this time to prevent infestation by corn earworm and other caterpillar pests, thereby suppressing sap beetles also (Harrison, 1962).

Cultural Techniques. Cultural practices affect dusky sap beetle damage. In North Carolina, early planted corn is more heavily infested than late planted corn. Sweet corn varieties differ in susceptibility to injury, owing primarily to different survival rates among larvae rather than selective oviposition behav ior by adults (Daugherty and Brett, 1966). Connell (1956) attributed increase in sap beetle damage to the loose husk found on some corn varieties, and to short husks that provide little coverage of kernels at the tips of the ears.

Sanitation is an important element of sap beetle management. Corn ears that are left unharvested, particularly those on or in the soil, support survival and overwintering of beetles. In Delaware, decomposing ears support larvae until December, when larvae leave the ears to pupate in the soil. Burying ears at a depth of 10 cm or greater inhibits sap beetle survival. Other decomposing crop debris, including lettuce and tree fruit, favors sap beetles, and they can be attracted to trees that are infected with bacterial wetwood (W. Cransaw, personal communication). Thus, windbreaks and wood lots can be an important source of beetles.

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Responses

  • Cesare
    Are Nitidulidae pests in garden?
    8 years ago
  • Luwam
    What is the natural enemy of the carpophilus beetle?
    8 years ago

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