Naupactus cervinus (Boheman)
(Also known as Asynonychus cervinus Bohema, Pantomorus cervinus (Boheman) and Naupactus godmani (Crotch)).
Common name: Fuller’s rose beetle.
Taxonomic placing: Insecta, Holometabola, Coleoptera, Curculionidae.
Geographical distribution: Cosmopolitan, CAB International map #214.
Morphology: The adult beetles are 8-9 mm in length. The head, antennae, thorax and fused elytra are grey-brown, the bulging eyes are blackish. Larvae (grubs) are 10-12 mm in length, initially yellow, later whitish, apodous.
Host plants: Polyphagus.
Life history: The parthenogenetic females produce about 150 or more eggs/insect, being more fecund on legumes. The egg masses, which are imbedded in a white sticky material, are deposited at various sites, such as under the calyx of Citrus fruits, in bark crevices and cracks. The eggs hatch within 3-4 weeks and the emerging larvae gnaw on the leaf margins, then drop to the soil, feeding on the host’s roots. Development requires about 6-10 months, and the calculated threshold of development is around 10.00°C. Pupation is near the soil surface and the adults, which cannot fly, emerge in summer. They move up on their hosts to feed and lay eggs. This species is univoltine. Males occur in some populations.
Economic importance: The feeding of the adult on citrus leaves results in a “saw-toothed”, notched appearance, and in partial to almost total leaf consumption (except for the mid-rib). The larvae feed on the roots, sometimes girdling them. Such damage may cause stunting, promote citrus vulnerability to other damaging factors and increase tree mortality. The root-feeding larvae are also serious pests of many economic plants, especially roses. This beetle is a serious quarantine (zero tolerance) problem for citrus-exporting countries.
Management
Monitoring: Previous damage to low-lying, notched citrus leaves indicates past or present beetle infestation. Their current presence on citrus trees can be established by beating branches of 20 or more trees over a tray or plastic sheet. Eggs on citrus fruits can be monitored by examining the underside of the button.
Horticultural control: Preventing the beetles from the citrus canopy by removing lower branches (“skirt-pruning”) and placing sticky bands around tree trunks. Dipping oranges in water at 50°C for 10 minutes and at 52°C for 7 minutes reduced egg hatch by up to 66%, with no damage to the fruits.
Irradiation: Irradiation of exported lemons could be an effective quarantine treatment against the beetle’s eggs.
Chemical control: Granular systemic pesticides can be used against larvae feeding on the roots of roses, and may later control the females. Repeated sprays with a pyrethroid along with skirt-pruning reduces pest numbers.
Biological control: The parasitoid Fidiobia citri Nixon Platygasteridae attacks N. cervinus in the Caribbean, North America and in Australia. Applications of the entomopathogenic nematode Steinernema carpocapsae (Weiser) resulted, after one year, in an average 45% reduction in the number of emerging beetles, rising to a 80% reduction in the following year. Entomopathogenic fungi also infect the beetle, but their overall effect is uncertain.
References
Jessup, A.J., Hood, C.W. and Sloggett, R.F. 1993. The effects of hot-water dipping, methyl bromide with or without cold storage and gamma irradiation on egg hatch of Asynonychus cervinus Boheman (Coleoptera: Curculionidae). Journal of the Australian Entomological Society 32: 99-101.
Johnson, J.A., Soderstrom, E.L., Brandl, D.G., Houck, L.G. and Wofford, P.L. 1990. Gamma radiation as a quarantine treatment for Fuller rose beetle eggs (Coleoptera: Curculionidae) on citrus fruit. Journal of Economic Entomology 83: 905-909.
Lanteri, A. A., Guedes, J.C. and Parra, J.R. 2002. Weevils injurious for roots of citrus in São Paulo State, Brazil. Neotropical Entomology 31: 561-569.
Lodos, N. 1990. Pantomorus cervinus (Boh.) an important pest species of weevil recently detected in Turkey (Coleoptera, Curculionidae). Türkiye Entomoloji Dergisi 14: 245-250.
Masaki, M., Kadoi, M. and Yoneda, M. 1996. Effects of temperature on development of Fuller’s rose weevil, Pantomorus cervinus (Boheman) (Coleoptera: Curculionidae). Research Bulletin of the Plant Protection Service, Japan 32: 7-13 (In Japanese with an English Abstract).
Morse, J. and Grafton-Cardwell, B. 2013. Bifenthrin trunk sprays as a strategy for Fuller rose beetle (FRB) field control in 2013. Citrograph 33 (March-April): 26-33.
Morse, J.G. and Lindegren, J.E. 1996. Suppression of Fuller rose beetle [Coleoptera: Curculionidae] on citrus with Steinernema carpocapsae [Rhabditida: Steinernematidae]. The Florida Entomologist 79: 373-384.
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