Carpophilus spp.
Taxonomic placing: Insecta, Holometabola, Coleoptera, Nitidulidae.
Common name: Sap beetles.
Geographical distribution: Widespread in tropical, subtropical and temperate regions.
Host plants: Fruits of many trees, especially when ripening, damaged and decomposing, or in fermenting plant material.
Morphology: Carpophilus spp. are minute beetles with short truncate elytra that only partially cover the abdomen. The adults are brown, black-brown, or black, the antennae are 11-segmented and the legs yellow-red. The short elytra are generally yellow-brown and the body is 2-4 mm in length. The larvae are whitish or yellowish with a brown head, final length 5-7 mm. The adults of C. hemipterus (Linnaeus) may be distinguished from other Carpophilus spp. by the presence of two pale spots on the elytra.
Life cycle: These beetles are strong fliers, capable of covering several kilometers in search of food. The eggs are laid in damaged fruit on the trees or when rotting, on the shaded ground under citrus and date palm trees. Mature larvae emerge from the fruit to overwinter as pupae in the soil. Development from egg to adult takes 16-21 days at 27°C and 12-15 days at 32°C.
Ecology: High temperatures and humidities during summer promote the buildup of large sap beetle populations. In date groves the first source of food is provided during June, when many green fruit drop. They are infested by beetles of the first generation, whereas the adults of the second generation infest dates on the tree. These beetles are secondary pests, and as such, almost never attack sound fruit. However, their presence on dates is an exception to the rule. Adults can live 6-12 months and deposit 500-1000 eggs. Adults and larvae occur in all seasons and several generations are produced annually. In Israel, Carpophilus mutilatus Erichson and C. hemipterus are prevalent throughout the autumn, winter and spring, their populations declining in summer. In summer, they are replaced by Carpophilus humeralis (Fabricius) and Haptoncus luteolus (Erichson), the latter being most abundant during the summer and autumn. Most sap beetles damage to ripening fruit is apparently caused by the latter two species.
Economic importance: Carpophilus spp. are worldwide pests of fruits and grains, both before and after harvest, and are a nuisance in canning factories and other food processing establishments. They infest ripening dates on the tree and on the ground. They enter the fruit, usually at the calyx end, feeding on the pulp and thereby causing damage. The drop of green date fruit during the summer, which is mainly caused by infestation of the date stone beetle, Coccotrypes dactyliperda Fabricius, enhances Carpophilus populations and increases the damage. Pest penetration into the fruit facilitates the development of microorganisms, resulting in rot and fruit fermentation that further downgrades the fruit. Damage is thus reflected in reduced yield and quality.
Four species of sap beetles damage dates in Israel: the dried fruit beetle, C. hemipterus, the confused sap beetle, C. mutilatus, the pineapple beetle, C. humeralis and the yellow nitidulid, H. luteolus. The pattern of their specific damage varies between years and in different regions. Infestation by sap beetles in untreated groves may be high, up to 40% in Israel and about 90% in Aswan, Egypt.
Management
Mechanical control: Covering of date bunches with dense plastic nettings (0.8 x 0.5-mm perforations) was very efficient in preventing nitidulid penetration into the bunch and in reducing fruit infestation. However, continuous use of the same nettings for several years increased the damage caused by the greater date moth, Arenipses sabella Hampson, and is not recommended. Exposure of beetle-infested dates to pressure of 100 mm mercury and 2.8% oxygen caused most of the pests to leave the fruits after a 4-hr. Storage at -18°C caused very rapid kill of both species in 2-3 hours.
Chemical control: Sap beetles infesting dates may be controlled with organophosphates, pyrethroids and insect growth regulators (IGRs), applied during the color-changing phase of the fruit, with a second treatment applied 2-3 weeks later.
The chitin synthetase inhibitor triflumuron (alsystin) indirectly affects egg hatch of C. hemipterus and C. humeralis via the adult stage of the beetle and is very effective against larvae of both species.
Attraction to aggregation pheromones and food volatiles. Male-produced pheromones, to which both males and females respond, were identified for nine Carpophilus spp. All contain alkyl-branched, conjugated, triene or tetraene hydrocarbons. Capture is highly synergized by volatiles from fermenting food materials, as captures in traps baited with pheromone-host volatiles combinations were higher than in traps baited with host volatiles alone. There is some cross attraction and pheromones of one species may attract other congeners.
Natural enemies: Thirty-three species of parasitoids of nitidulid beetles are known. Species of Zeteticontus Silvestri, (Encyrtidae) are commonly associated with sap beetles. Zeteticontus utilis Noyes, a solitary endoparasitoid of the larvae of Carpophilus spp., was collected in Israel mainly in spring and early summer. In the laboratory it develops in C. hemipterus and C. mutilatus, but not in C. humeralis or H. luteolus. Zeteticontus utilis is rare in the field, thus not considered an important enemy of sap beetles. Third instar larvae of C. humeralis and C. hemipterus are susceptible to entomopathogenic nematodes, which affect the larvae that enter the soil for pupation and may therefore have potential for controlling these pests.
References
Bartelt, R.J. 1997. Aggregation pheromones of Carpophilus spp. (Coleoptera: Nitidulidae): Review of chemistry and biology. Recent Research and Development in Entomology 1: 115-129.
Blumberg, D., Doron, S. and Bitton, S. 1985. Effect of triflumuron on two species of nitidulid beetles, Carpophilus hemipterus and Urophorus humeralis. Phytoparasitica 13: 9-19.
Blumberg, D., Kehat M., Goldenberg, S., Bartelt, R.J. and Williams, R.N. 1993. Responses to synthetic aggregation pheromones, host-related volatiles, and their combinations by Carpophilus spp. (Coleoptera: Nitidulidae) in laboratory and field tests. Environmental Entomology 22: 837-842.
Carpenter, J.B. and Elmer, H.S. 1978. Pests and diseases of the date palm. Handbook U.S. Department of Agriculture # 527.
Kehat, M., Blumberg, D. and Williams, R. N. 1983. Seasonal abundance of sap beetles (Coleoptera: Nitidulidae) in date plantations in Israel. Phytoparasitica 11: 109-111.
Lindgren, D.L. and Vincent, L.E. 1953. Nitidulid beetles infesting California dates. Hilgardia 22: 97-117.
Navarro, S., Donahaye,E., Rindner, M., Dias, R. and Azrieli, A. 1993. Integration of controlled atmosphere and low temperature for disinfestation and control of dried fruit beetles. In: Navarro, S. and Donahaye, E. (eds) Proceedings International Conference for Controlled Atmosphere and Fumigation in Grain Storages pp. 389-398.
Dr. Daniel Blumberg.
Department of Entomology, Agricultural Research Organization The Volcani Center; P. O. Box 6, Bet Dagan 50250, ISRAEL, Email: dblum@netvision.net.il