Although there are many species of sap beetles, only several species are known agricultural pests of field and stored products. These include the dusky sap beetle Carpophilus lugubris Murray on field and sweet corn; the corn sap beetle, C. dimidiatus on field corn; the complex C. dimidiatus (F.), C. freemani Dobson and C. mutilatus Erichson on stored maize (Arbogast and Throne 1997); the driedfruit beetle C. hemipterus (L.); the pineapple beetle, Urophorus humeralis; a picnic beetle, Glischrochilus quadrisignatus (Say); the strawberry sap beetle, Stelidota geminata (Say); and the yellowbrown sap beetle, Epuraea (Haptoncus) luteolus (Erichson) a pest of dried fruit. Sap beetles are often considered minor pests but the presence of large numbers of sap beetles on a host plant can prove economic in terms of crop damage caused by the feeding beetles, but impact on crop value is primarily due to the contamination of products ready for sale by adults and larvae. In addition to damage caused by feeding, sap beetles have also been recognized as vectors of fungi (Dowd 1991).
Abdominal segment VIII of males is heavily sclerotized, well raised and large. In females it is usually reduced and submembranous.
The dusky sap beetle adult, C. lugubris, is about 2.8 mm long with short elytra. The adult is uniform dull black in color.
Picnic beetles, G. quadrisignatus and G. fasciatus, are about 6.4 mm long black with four orange spots on the wing covers or elytra.
The strawberry sap beetles adult, S. geminata, is less than 2.8 mm, light to dark brown oval and somewhat flattened.
Eggs: Eggs are milky white and sausage shaped, and 0.8 mm long and 0.23 mm wide.
Larvae: Larvae of all three genera are white (pale yellow when mature) with a light brown head, opposing external mouthparts and three pairs of small true thoracic legs. The larval body is elongate, sub-cylindrical, somewhat dorsoventrally flattened, slightly sclerotized except for hard sclerotized epicranium. The body of the larvae bears few hairs, and is equipped with hardened projections from the end of the abdomen that are species specific.
Pupae: Pupae are white, turning cream colored and later tan before adult emergence. The pupa is typical exarate (furrowed) averaging 4.4 mm in length and 2.0 mm in width (Parsons 1943).
The different species of Carpophilus are similar with respect to their biology. However, most work has been focused on the biology of C. lugubris. Investigations carried out by Sanford and Luckman (1963), showed that in Illinois, C. lugubris is very active in fall and overwinters as adults in soil or debris near the bases of trees or stumps. They become active around April or early May and are attracted to decomposing plant material or wounds in trees. The newly emerged females of the over-wintering generation deposit eggs on or near decomposing plant material such as corn ears on or in the soil. Larvae feed on whatever is available when they emerge and eventually pupate in the soil. Adults of this first generation and those of the over-wintering generation migrate in June to early sweet corn plantings shortly before or soon after it silks. Adults feed on the silk and fallen pollen from tassels. Wherever wet pollen collects on the plant such as the leaf whorls and axils they will feed and deposit eggs. The adults are also attracted to insect and plant volatiles produced by ear-wounding damage of the corn earworm Helicoverpa zea. It was observed that adults preferred to deposit eggs on earworm frass, earworm damaged corn ears, and even smut galls when compared with undamaged ears.
The dusky sap beetle is the predominant species on sweet corn. Larvae hatch within two to five days at 75°F (24°C). They pass through three instars in 14 days, drop to the ground where pupal cells are formed a few inches below the soil surface. In summer, 28 to 30 days elapse between egg deposition and adult emergence. From July to November all stages of the insect can be found in the fields of sweet and field corn and in some decomposing fruits and vegetables especially melons. Heaviest infestation occurred during the four days preceding harvest. If population densities are high adults are likely to oviposit in any corn ears that are available regardless of maturity or in the absence of damage.
The longevity and fecundity of C. lugubris adults varies. Male longevity was reported by Sanford (1963) to be 115.2 days on average. In the same study the life span of females was 101.3 days (range: 74 to 147 days). The average number of eggs laid per female was 99.5 (33 to 304 eggs).
Three to four generations have been reported in the latitude of Illinois and two in Ohio (Dowd and Nelson 1994). The number of generations encountered in the literature was found to vary and may be as result of differences in latitude, temperature, availability of suitable food sources, position of monitoring traps and some confusion with overlapping generations.
G. quadrisignatus, commonly known as a picnic beetle, overwinters as an adult in Illinois. Hibernation sites are similar to that of C. lugubris. Picnic beetles become active on warm days in late winter or early spring. Most eggs are deposited in May. Females can oviposit up to 400 eggs in their lifetime. Females reproduce primarily near decomposing plant material. Eggs are deposited at random near decomposing plant material rather than on the material itself. To be suitable for oviposition and larval development, food material must be either buried in the soil or be in contact with the soil and it must be moist. Active adults of the new generation begin leaving the soil in June. They fly to fields of ripening or damaged berries, tree wounds and corn. Adults live a long time and in late June various life stages including both the new and overwintering generation can be found together in soil. In Illinois picnic beetles have been observed feeding on the silk and pollen of undamaged corn causing primary damage and allowing subsequent entry and oviposition by the dusky sap beetle. They also invaded fields that had corn stalks damaged by the European corn borer. They were secondary invaders in fields where ears were damaged by the Japanese beetle. Two generations were noted in Ohio the second occurring on field corn left in the field after harvest (Dowd and Nelson 1994).
S. geminata, the strawberry sap beetle, migrates each spring from overwintering sites. Temperature plays a key role in regulating spring migration of S. geminata (Gertz 1968, Weiss 1979). First generation beetles develop in the strawberry fields. Dowd and Nelson 1994) reported early migration peaks in both raspberry and corn at the end of the strawberry season which may indicate that these sites are utilized by the beetle for over-wintering. S. geminata was not found to overwinter in strawberry plantings. However, Lobiopa insularis (Cast.) is the most frequently observed sap beetle in Florida strawberries (Price 2004), although several other smaller species inhabit the fields.
Okumura and Savage (Potter 1995) found that E. luteolus has a more rapid development and mature larval development is attained after 11 days when placed in culture.
These pest species generally feed on fruits and other plant parts that are ripening or decomposing. Their host range may include tree and small fruits such as peaches, figs, blueberries, raspberries and strawberries, pineapples, melons, field and sweet corn, stored corn and dried fruit products. The species mentioned above are characterized by their affiliation with a specific host or group of related hosts. However, the beetles are not restricted in their host range.
Sap beetles can also vector mycotoxin producing fungi to corn and strawberries (Dowd and Nelson 1994). Maize sap beetles appear to be well adapted for vectoring mycotoxigenic fungi, including species in the genera Aspergillus, Penicillium and Fusarium. The adults feed on corn plant residues left in the field after harvest. These residues usually contain spores of Aspergillus or Fusarium which not only damage crops but produce toxins harmful to humans and animals. They have also been implicated as vectors of forest pathogens causing wood rots (Peng and Williams 1991).
Some species, such as the dusky sap beetle, C. lugubris, and the beetles in the genus Glischrochilus, are implicated as vectors of tree diseases such as oak wilt, Ceratocystis fagacearum.
Sanitation. Field sanitation appears to be an important means of control. It's best to harvest sweet corn, tomatoes, melons, berries and other produce immediately they ripen. Damaged, diseased and overripe fruits and vegetables should be removed from the area at regular intervals. Such material should be destroyed, or, if buried, should be buried deep below the soil.
Chemicals. Chemical treatment is recommended for the control of sap beetles in Florida. Previously, chemical control of corn earworm usually indirectly controlled sap beetle. However, in recent years chemicals suitable for corn earworm and fall armyworm control has not been effective for sap beetle control. With the advent of Bt corn to control corn earworm, one study has indicated that direct feeding damage of sap beetles on Bt corn is possible in the absence of corn earworm (Dowd 2000) hence warranting chemical intervention or a suitable management protocol for these pests. Several products are registered for use on corn and strawberries for the control of sap beetles. These pesticides can be incorporated in baits to trap incoming sap beetles.
Insect Management Guide for fruit
and nuts
Insect Management Guide for field corn
Insect Management Guide for strawberry
Insect Management Guide for sweet corn
Baits. Research has shown that sap beetles are strongly attracted to certain volatile plant compounds in ripening or decaying fruits, and themselves produce pheromones/kairomones that elicit an aggregating behavior. Baits using such material can be effective in trapping and monitoring sap beetle populations, and hence determine when treatment is necessary.
Varietal selection. Tight, long-husked corn varieties have been recommended for corn. These varieties are more resistant to corn earworms and the beetle itself and therefore are less likely to be infested by sap beetles. Varieties shown to be resistant to sap beetles include Country Gentleman, Golden security, Tender Joy, Trucker's Favorite, Stowell's Evergreen and Victory Golden. Though these varieties sustain less injury than susceptible varieties they are not immune to attack.
Biological control. Research continues in the area of biological control. A nematode, Psammomeris nitiduesis, was found in living sap beetles collected near Illinois corn fields. Scientists believe that the nematode enters the body of the beetle in late summer when they are pupating in the soil. Scientists are studying ways to move infected sap beetles into areas where the nematode does no exist so the nematode can be used as a biological control agent. Researchers at Ohio State University evaluated a tiny parasitic wasp Brachyserphus abruptus for the control of the strawberry sap beetle. They are mass rearing the parasite for release at the time of strawberry fruit set. The parasite keeps the larva from maturing into an adult beetle, thereby eliminating reproduction and reducing subsequent sap beetle populations.
Author: Lisa Myers, University of Florida
Photographs: Ken Gray, Oregon
State University; Greg S.
Nuessly, James F. Price and Lyle Buss, University of Florida; and Keith Weller, USDA
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-256
Publication Date: December 2001. Latest revision: September 2004.
Copyright 2001-2004 University of Florida
Featured Creatures
Department of Entomology and Nematology
Division of Plant Industry
Electronic Data Information Source
G. quadrisignatus adult
C. lugubris adult
E. luteolus adult
C. fumatus adult
C. lugubris adult
C. lugubris larva
C. lugubris pupa
adults and larvae on corn
larvae on corn
L. insularis adult and larva
L. insularis adult
L. insularis larva
damage
damage to strawberry