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Australian Eucalyptus Snout Weevil

 

Gonipterus scutellatus Gyllenhal -- Coleoptera:  Curculionidae

 

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       Eucalyptus is a ubiquitous landscape, shade, and windbreak tree throughout southern and central California.  The trees are valued for their fast growth and tolerance of poor soils and drought.  Eucalyptus is now threatened by several pest insects accidentally introduced into California from Australia, one of which is the Australian gum tree weevil.

 

       Adults are stout, red-brown beetles, ca/ 7-9 mm in length. Adults live 3-6 months, with females typically laying 600-800 eggs during their lifetime.  Eggs are laid inside dark-colored egg cases, each containing 6-12 eggs.  Egg cases are attached to the upper surfaces of new foliage, where they are readily visible as dark pellets. The larvae are legless, yellow-green, and slug-like, with dark stripes down the sides.  A coating of slime and chains of black fecal pellets, which frequently adhere to the larvae, characterize them.

 

       The weevil entered Ventura County, California in about the spring of 1994.  The beetle has since spread throughout Ventura and Los Angeles counties.Damage and Economic Impact: Both larval and adult snout beetles consume eucalyptus foliage, particularly new shoots and leaves.  Adult feeding damage is characterized by notching of the leaves, giving them a scalloped appearance.  Young larvae score trenches in the leaf surfaces, while older larvae consume the entire leaf.  Trees are rapidly defoliated by feeding weevils and can be killed by repeated defoliation.  Snout beetle populations can build to high levels in a matter of months, so that entire windbreaks and groves can be quickly stripped of foliage and eventually killed.  Area-wide control of the snout beetle with insecticides is not feasible because of the problems associated with pesticide coverage of large trees spread over significant areas.  Pesticide use is especially problematic in residential areas.

 

REFERENCES:

 

Cadahia, D.   1986.  The importance of insect pests in the Mediterranean region.  Bulletin OEPP/EPPO Bulletin 16:  265–283.

 

Cowles, R. S. & J. A. Downer.  1995.  Eucalyptus snout beetle detected in California.  California Agriculture 49:  38, 40.

 

European and Mediterranean Plant Protection Organization.  2017.  Data sheets on quarantine pests: Gonipterus gibberus and Gonipterus scutellatus.  Archived 2017-01-16 at the Wayback Machine.

 

Hanks, L. M.,  J. G. MillarT. D. Paine & C. D. Campbell.  2000.  Classical Biological Control of the Australian Weevil Gonipterus scutellatus (Coleoptera: Curculionidae) in California.  Environmental Entomology  29 (2):  369-375.

 

 Leyva, E.  1969.  Present situation of the pests on Eucalyptus sp. world-wide.  Boletín del Servicio de Plagas Forestales 24:  119–128 (in Spanish).

 

Maltzeff, P. & E.  Colonnelli.  1993.  Gonipterus scutellatus Gyllenhal nel Lazio (Coleoptera: Curculionidae).  Bollettino dell'Assoc. Romana di Entomologia, 48:  103-105.

 

Marelli, C. A.  1927.  The eucalyptus weevil found in Argentina is not the same as the Tasmanian species Gonipterus scutellatus.

   Revista Museo La Plata 30:  257–269. (in Spanish).

 

Richardson, K. F. & R. H. Meakins.  1986.  Inter-and intra-specific variation in the susceptibility of eucalypts to the snout beetle Gonipterus scutellatus Gyll. (Coleoptera: Curculionidae).  South African For. Journal 139:  21-31.

 

Rivera, A. C.,  S. S. Carbone & J. A. Andres.  1999.  Life cycle and biological control of the Eucalyptus snout beetle by Anaphes nitens in north-west Spain.  Agricultural and Forest Entomology 1:  103–109.

 

Tooke, F. G. C.  1955.  The eucalyptus snout-beetle, Gonipterus scutellatus Gyll. A study of its ecology and control by biological means.  Union of South Africa, Department of Agriculture, Entomology Memoirs, vol. 3. The Government Printer, Pretoria.

 

Williams, J. R.,  L. A. Moutia & P. R. Hermelin.  1951.  The biological control of Gonipterus scutellatus in Mauritius.  Bulletin of Entomological Research 42:  23-28.