California Fivespined Ips
Key Wildlife Value:Pine engraver and California fivespined ips create dead tops in large trees when they colonize the upper crowns of large pines, which results in formation of unique woody structures and provides entry courts for stem decay fungi. These beetles also create small diameter pine snags. Trees killed by I. paraconfusus and I. pini eventually contribute to levels of down wood when they break or fall over. Colonized trees and treetops provide foraging habitat for woodpeckers. When small diameter trees are killed in a grouped pattern, canopy gaps are formed, increasing structural diversity and sometimes resulting in increased compositional diversity of developing stands.
Distribution in Oregon and Washington:California fivespined ips occurs in Oregon west of the Cascade Mountains crest, and pine engraver occurs throughout Oregon and Washington.
Hosts:Most commonly found in ponderosa, lodgepole, sugar, and Jeffrey pines, but may occur on almost any species of pine
Diagnosis:Other than scattered individual, small-size, stressed tree mortality, two mortality patterns are typical. In small-diameter pine stands, outbreaks are associated with abundant fresh windfall or logging slash. In these situations, mortality tends to be randomly clustered rather than diffusely scattered. Activity in larger trees causes death of the upper 1/2 to 1/3 of the crown, usually in scattered individuals. Reddish-orange boring dust in small mounds around entrance holes, in bark crevices, and on the ground around infested trees can indicates attack by I. pini or I. paraconfusus. Colonizing beetles do not produce pitch tubes. Foliage usually begins to fade within a few weeks of attack during summer months, but may not fade until the following spring when trees are attacked in the fall.
Diagnostic gallery patterns will be found under the bark of infested tree boles. Galleries etch the sapwood surface, are free of frass and usually longitudinal, with total lengths of 10 to 25 cm (4 to 10 in). The overall pattern may be somewhat variable, appearing as Y-, H-, or star-shaped, and with a centrally located nuptial chamber. Larval galleries are packed with frass and extend laterally 2.5 to 5.0 cm (1 to 2 in) from the egg galleries. Mazelike feeding galleries lightly etched onto the sapwood surface also may be evident, sometimes obscuring the egg gallery patterns.
Larvae are white legless grubs with brown heads. Pupae are white and soft, with body forms somewhat resembling adults. Adult beetles are cylindrical with clubbed antennae, dark red-brown to black, and about 4 mm long. A dish-shaped depression with four (I. pini) or five (I. paraconfusus) spines along each side is located on the posterior end of the wing covers.
Life History:Pine engraver and California fivespined ips have two to four generations per year in Oregon and Washington. Two generations per year are normal east of the Cascades crest, while in the milder climate of southwest Oregon, up to four generations per year may occur. There are four life stages: egg, larva, pupa, and adult.
Beetles emerge from their overwintering sites in spring when daily maximum temperatures reach 15 to 21° C (59 - 70o F). Males bore through the bark of fresh down material or severely weakened trees to construct nuptial chambers. They emit a pheromone that attracts females and other males, and usually mate with three to four females. Each mated female constructs an egg gallery beginning in the nuptial chamber, excavating outward parallel with the grain of the wood and depositing her eggs in niches along the sides. Frass is pushed out the original entrance holes to keep the galleries clear for movement, and accumulates on the boles and at the bases of the trees until scattered by wind or rain. After hatching, larvae bore away from the egg galleries, feeding in the phloem until they complete their development. Pupation occurs in oval pupal cells, and adults emerge about 1½ to 2 months after initial attack. This cycle is repeated 1 to 3 more times through the remainder of the season. If additional suitable material is not available in midsummer when the progeny of the first brood emerges, beetles will attack standing trees. Broods develop most successfully in shaded slash and on the undersides of cut logs, where bark moisture remains favorable throughout development. Pine engraver adults sometimes congregate in large groups under the bark of standing trees in late summer, where they feed on inner bark, nearly obliterating any egg gallery patterns. The winter is spent under the bark of trees and slash or under duff and litter on the forest floor. Pine engravers overwinter mostly as adults, and California fivespined ips spend the winter as mature larvae, pupae and adults. Populations emerging in the spring are usually small, because overwintering populations usually experience high levels of mortality.
Like the mountain pine beetle, California fivespined ips introduces a blue-stain fungus that helps it overcome tree defenses. Other bark beetles, including mountain pine beetle, Jeffrey pine beetle, and western pine beetle, often attack and kill large pine trees with tops colonized or killed by I. pini or I. paraconfusus.
Important habitats and outbreak dynamics:Pine engraver is most active in locations east of the Cascades crest in Oregon and Washington. Pine trees and down material in western Oregon are more frequently colonized by California fivespined ips than by pine engraver. Fresh down pine material and trees under stress from overcrowding, injury, drought, or disease provide important habitat. Fresh down material greater than 7.6 cm (3 in), in particular, provides optimum habitat for colonization and brood production, and is especially important habitat in the spring and early summer when standing trees tend to still have adequate moisture and are more resistant to beetle attack. Both beetle species are limited to thin-barked (0.3 to 2.5 cm, or 1/8 to 1 in, thickness), small diameter portions of live stems, or recently cut or weather-damaged host material. They commonly colonize green slash of any diameter, small trees 5 to 25 cm (2 to 10 in) in diameter, and the thin-barked tops of larger trees. Entire large trees are sometimes successfully colonized during outbreaks.
When populations are low, scattered individuals and groups of usually 10 trees or less are colonized. Attacked trees frequently are injured, diseased, or suppressed. Outbreaks can be initiated by human activities (most commonly by thinning operations in sapling and pole-size pine stands) or by drought. Outbreaks usually last no more than one year, due to high mortality of overwintering beetles, and are seldom detected until after most mortality has already occurred. Outbreaks usually occur when precipitation during the months of April through July is 75 percent of normal or less. During such years, overstocked stands of sapling and pole-size ponderosa pine are especially susceptible to attack, and the tops of large ponderosa pine trees are frequently killed. Old records indicate that about 50 percent of recently top-killed ponderosa pine are attacked on the main bole by the western pine beetle within a few years. The remaining 50 percent may survive for long periods as stag-topped trees. Trees in overstocked young stands are often killed in large clumps of 50 to 500 individuals. Due to their sporadic nature and short duration, the effects I. pini or I. paraconfusus outbreaks on stands over time usually is not one of thinning, but of sporadic aggregated mortality. Outbreaks in thinned stands of sapling and pole-size ponderosa and lodgepole pine may occur when fresh slash is available to adults emerging from their overwintering locations during spring and early summer. Populations increase rapidly in the down material, then later generations move into nearby healthy standing trees in midsummer as the trees begin experiencing moisture stress. Such outbreaks are especially likely to occur during warm, dry years.
Opportunities for Manipulation to Increase Wildlife Habitat:It may be possible to create small diameter snags in even-age, sapling and pole-size ponderosa or lodgepole pine stands deficient in dead wood by creating or retaining limited numbers of slash piles having green material larger than 7.6 cm (3 in), and piling them around the bases of trees in areas selected for snag creation. Habitat for animals that utilize concentrations of dead wood would be increased as well. However, use of this method would be largely experimental, and it is unknown to what degree it could reliably achieve desired outcomes.
Potential Adverse Effects:Outbreaks during droughty years may cause extensive mortality having an undesired distribution in overstocked sapling and pole-size ponderosa pine stands. Outbreaks associated with thinning slash may result in the death of large numbers of residual trees, requiring additional expenditures to meet management objectives for stocking and cover.
How to Minimize the Risk of Adverse Effects:
Vigorous, fast growing stands are the most effective deterrent to mitigate
the effects of drought-induced outbreaks of pine engraver and California fivespined
ips. Keeping sapling and pole-size stand thinned so trees maintain optimum
growth will help to minimize any adverse effects of such outbreaks. Stands
thinned to basal areas of 80 to 100 square feet per acre have been found to
be less susceptible to beetle attack.
Tree mortality may be avoided following thinning operations by adhering to the following guidelines:
- Do not create green slash with diameters greater than 7.6 cm (3 in) during January through July. Down material less than 7.6 cm (3 in) may be created at any time because it dries out rapidly, and these beetles avoid breeding in partially dried or dried slash.
- Scatter slash in openings away from shade to encourage rapid drying. Slash piles result in shading that slows the drying process and maintains favorable habitat.
- Keep slash at least several
yards away from the boles of standing trees. If enough beetles are attracted
to slash near trees, adjacent trees may be killed.
When larger slash is created during January through July, the following techniques may be used to prevent excessive tree mortality:
- Reduce the amount of suitable breeding material before August by chipping fresh slash, or by trampling slash with heavy machinery to break it into small pieces and then scattering it in open areas. The use of heavy equipment in this manner, however, should be carefully prescribed to prevent adverse effects upon soil structure and future stand health.
- When thinning large areas, a technique called the “green-chain” may be employed. Thinning, which may begin as early as January, is timed so that new slash is being either continuously created or created at 2-week intervals during July and August. Because fresh slash is more attractive to I. pini or I. paraconfusus than standing trees, this continuous supply of slash absorbs beetles as they emerge from slash created during January through June.
- Another technique that may be employed when thinning large areas is to create very large piles of slash, at least 3.3 m (10 ft) high and 3.3 m (10 ft) long, spaced in thinning units at distances no more than 0.4 km (1/4 mi) apart. The slash in the interiors of these piles is plentiful and remains shaded and attractive to I. pini or I. paraconfusus during the summer months, preventing attacks upon residual trees.
ReferencesGoheen, E.M., and E.A. Willhite. In prep. Field guide to the common diseases and insect pests of Oregon and Washington conifers. USDA Forest Service, Pacific Northwest Region, Forest Health Protection.
Furniss, R.L., and V.M. Carolin. 1977. Western forest insects. USDA Forest Service. Misc. Publ. 1339. 654 pp.
Kegley, S.J., R.L. Livingston, and K.E. Gibson. 1997. Pine engraver, Ips pini (Say), in the western United States. USDA Forest Service, Pest Leaflet 122. 5 pp.
Miller, J.M., and F.P. Keen. 1960. Biology and control of the western pine beetle. USDA Forest Service Misc. Publ. No. 800. 381 pp.
Overhulser, D.L. 1999. Pine engraver beetle (Ips pini), Oregon Dept. of Forestry Forest Health Note. 4 pp. Available on-line: http://egov.oregon.gov/ODF/PRIVATE_FORESTS/docs/fh/PineEngrvr.pdf
Overhulser, D.L. 2000. California fivespined ips (Ips paraconfusus), Oregon Dept. of Forestry Forest Health Note. 3 pp. Available on-line: http://egov.oregon.gov/ODF/PRIVATE_FORESTS/docs/fh/calif5spine.pdf
Schultz, D.E., and W.D. Bedard. 1987. California fivespined ips. USDA Forest Service, Forest Insect and Disease Leaflet 102. 8 pp.
Website linksPine engraver links, An Online Catalog of Western Forest Insects and Diseases
not yet available: Field Guide to the Common Diseases and Insect Pests of Oregon and Washington Conifers