Sugar Pine Cone Beetle Biological Control

Conophthorus lambertianae (Hopkins)

From: Bellows, Thomas S. ,Carol Meisenbacher, and Richard C. Reardon, 1998, Biological Control of Arthropod Forest Pests of the Western United States: A Review and Recommendations, USDA, FS, FHTET-96-21.

Origin: North America.

Range in North America: California, Nevada, Oregon.

Plant hosts and damage: Pinus lambertiana, Pinus monticola. Several pine cone beetles are known from the West, many fairly specific to particular Pinus hosts (Furniss and Carolin 1977). The sugar pine cone beetle, Conophthorus lambertianae Hopkins, attacks primarily P. lambertiana. The adult beetle bores into the base or supporting stem of immature pine cones in spring. A small tunnel is projected along the axis of the cone in which the female deposits eggs. The larvae feed on the scales, seeds, and tissue of the withered cone. Development to the adult stage takes place in the dead cone during summer, and the adults usually overwinter in the cone.

Natural Enemies: The only natural enemies found reported from C. lambertianae were the predator Enoclerus lecontei Wolcott and the two parasitoids Cephalonomia utahensis Brues and Tomicobia tibialis Ashmead (Bedard 1968).

Pest Status: Among the Western pine cone beetles, C. lambertianae is the most destructive (Keen 1958). Cone crops of various pines periodically are severly damaged by Conophthorus spp. In some years, 25-50% of the sugar pine cones have been killed by C. lambertianae over large areas, increasing the difficulty and cost of collecting seeds for reforestation. In local areas, destruction often exceeds 90% (Bedard 1968). There is an increasing need to protect seed orchards and seed collecting areas from damage by Conophthorus spp., but practical measures have not yet been developed (Furniss and Carolin 1977).

Biological Control: Little is known of the natural enemies of Conophthorus spp. In the case of C. lambertianae (Bedard 1968), the wasp Cephalonomia utahensis parasitizes larvae in cones. The clerid E. lecontei may feed on beetle adults, which are also parasitized by T. tibialis. Significant mortality to the new broods of the cone beetle, attributed to the work of an undetermined entomophagous fungus, was recorded by Miller (1915). Miller reported mortality of up to 79% of broods in Oregon caused by this pathogen in 1914.

Recommendations: Too little is known to make immediate recommendations for the increased efficacy of natural enemies of this or other cone beetles. The report by Miller (1915) of a pathogenic fungus is worth pursuing, although it has not been mentioned in more recent literature. Region-wide application of natural enemies (including pathogens) would be expensive and probably not a viable option, particularly considering the annually variable nature of the cone crop set by sugar pines. Conservation of natural enemies of this species is probably already taking place, as there are no known silvicultural or harvesting practices that would destroy or remove major portions of the natural enemy population.

This pest species may be, as are other native pest species, a candidate for introduction of natural enemies from related species of beetles, in the "new association" paradigm of Pimentel and Hokkanen (1989). Studies of the natural enemies of cone beetles in the Old World may provide candidates for consideration.

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