WWETAC Projects

Project Title: Improved early detection for the Mediterranean pine engraver, Orthotomicus erosus, an invasive bark beetle

STDP ID: R4-2008-01

Status: Ongoing

Principal Investigators and Affiliations: Steven J. Seybold, Pacific Southwest Research Station (PSW), Davis, CA; Robert C. Venette, Northern Research Station (NRS), St. Paul, MN

Collaborators and Affiliations: Mary Louise Flint, Deguang Liu, both UC Davis (UCD), Davis, CA; Beverly M. Bulaon, Forest Health Protection, Sonora, CA; Carl Jørgensen, FHP, Boise, ID; Steve Munson, FHP, Ogden, UT

E-mail Contact: Steve Seybold, sseybold[at]fs.fed.us; Steve Munson, smunson[at]fs.fed.us

Key Issues/Problems Addressed: The Mediterranean pine engraver, Orthotomicus erosus, was first discovered in California in 2004. The situation with O. erosus is urgent but highly uncertain. This insect has the potential to cause mortality in healthy trees within the Pinaceae, but to date, infestations in the United States seem to have been restricted to stressed trees. The bark beetle does not yet occupy its full potential geographic range. The effects of the insect could be more severe as the insect spreads and encounters new host species, genotypes, and environments. Given that O. erosus is still in the early stages of the invasion, forest pest managers have a unique opportunity to closely monitor the situation and make a rapid response to new finds.

The project uses O. erosus as a highly relevant case to answer important questions in early detection of invasive species. The project formally integrates our improvements in detection technology with the Forest Health Technology Enterprise Team’s (FHTET) advances in risk mapping to produce a clear set of detection guidelines. The statistical foundation underlying this integration becomes especially important when traps are placed, but no beetles are captured. Is it the case that the beetle is really not present locally or would the placement of a few more traps have revealed the presence of the beetle, but at a very low density? The resulting tools from this project will allow managers to formally describe the likelihood that the beetle was present, but simply was not detected.

Study Objectives and Goals:

The study is aimed to answer the following questions:
• Are infestations of O. erosus more widespread than currently estimated?
• How quickly are populations spreading in the United States?
• Has O. erosus established populations outside California?
• How effective are commercial baits at detecting O. erosus when populations are small?
• Can alternative deployment strategies further enhance the effectiveness of an improved attractant for O. erosus?

Answers to these questions will complement the Invasive Species Risk Map for O. erosus being produced by FHTET. Collectively this information will be used to produce guidelines for the early detection in areas of high risk for O. erosus establishment and subsequent pine mortality.

General Description: Despite warnings that O. erosus was an extreme risk to urban, managed, and natural forests (Eglitis 2000) and was being intercepted regularly at ports-of-entry (Haack 2001), existing safeguards failed, and the beetle was detected and confirmed as established in the California Central Valley in 2004 (Penrose et al., in prep). Research conducted in rapid response to its introduction has focused on the identification and chemical optimization of a semiochemically derived bait, now ready for widespread deployment (Seybold et al. 2006, Lee et al. 2007, see preliminary data). Trap captures with the improved bait [(±)-α-pinene at approx. 300 mg/d release rate; (–)-ipsdienol at approx. 150 μg/d; and methyl butenol at approx. 40 mg/d] can be 10 times these with the commercial bait, particularly for the relevant low-density populations (i.e., at distances >500 m from a mark-recapture release point, fig. 1). The improved bait costs about 5 times as much, but at low population densities, the detection cost of the bait alone was $1.29/beetle for the improved bait and $1.94/beetle for the commercial bait. Although the cost-effectiveness of detection at low population densities is favorable for the improved bait, indiscriminant placement of baited traps will still be costly and may not achieve a desired probability of detection.

At PSW, Seybold and UCD cooperators, Drs. M.L. Flint, J.C. Lee, and D.-G. Liu, have investigated many aspects of the biology of O. erosus in California. In no-choice tests on cut logs in the laboratory, the insect fed and reproduced on all pines (Pinus spp.), black spruce (Picea mariana (Mill.) B. S.P.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), tamarack, and white spruce (Picea glauca (Moench) Voss), although the extent of reproduction varied. In mark-release-recapture studies, the beetle was capable of dispersing at least 1 km in several hours, although most insects did not move that far. In the laboratory, Venette and colleagues have found that the beetle is freeze intolerant, but may withstand temperatures as low as –15°C.

Venette and Seybold are collaborating with FHTET (Marla Downing) on the development of an Invasive Species Risk map for O. erosus. Initial analyses confirm our assumption that Intermountain Region is in the center of the potential Western United States range for O. erosus. Because Layton, UT, (suburb of Ogden) has a major distribution center located in the Business Depot, the potential for introduction in this area is quite high. The detection of the banded elm bark beetle (Scolytus schevyrewi Semenov) (Lee et al. 2006) in the area supports our conjecture that the area is a likely site for the introduction of invasive bark beetles. The Business Depot in Layton also has ornamentally planted susceptible hosts (Pinus nigra and P. sylvestris L.) that contribute to a relatively high establishment potential.

The new project will integrate a new tool for the detection of the invasive O. erosus with results from FHTET’s national risk map for O. erosus to produce an efficient, statistically-based protocol for the early detection of this highly threatening species. By (year), we will:

(2008): Evaluate the efficiency of an optimized attractant to detect O. erosus at low beetle density (needed to estimate the sensitivity of the trap) by conducting a large-scale (10-km radius) mark-recapture experiment; measure the effective trapping range of the optimized lure (needed to determine the “effective area” sampled by a trap) following methods described in Turchin and Odendaal (1996) and Turchin (1998).

(2009): Continue evaluations initiated in 2008 with adjustments based on year 1 results. Develop preliminary sampling protocols (e.g., No. of traps in high-risk areas vs. moderate-risk areas). Initiate test of early detection in California, Utah, and Idaho.

(2010): Revise detection protocols and repeat test of early detection in California, Utah, and Idaho.

We expect to produce a series of scientifically defensible sampling guidelines that will specify the number and general placement of baited traps in geographic zones with a similar probability for O. erosus introduction, establishment, and impact. The number of traps will depend on the desired probability of detection, the sensitivity of the trap, and the extent of the infestation. Knowing the effective radius of the trap will allow us to estimate the statistical probability that O. erosus might be present in a region but at a density that is too low to be detected.

Status: From 1 to 18 June 2008, three large-scale, mark-recapture studies were conducted with the Mediterranean pine engraver, O. erosus, in the Tulare Lake area near Kettleman City, California (Kings Co.).  Project partners Bulaon, Munson, and Venette provided on-site assistance to Liu and Seybold with this work.  Data are being analyzed, but preliminary observations of the results suggest that beetles were captured primarily in the southern and eastern traps, reflecting the prevailing winds from the northwest.  Recapture rates ranged from 9 to 40% of the approx. 6,000 beetles released in each trial.  Most recaptured beetles were trapped at distances 100 and 500 m from the release point; beetles moved to these locations within 20 to 60 minutes of release.  A few individuals (0.2 to 0.7%) were recaptured between 2 and 10 km from the release point.  Greater percentages of the population can likely disperse long distances (2 to 10 km from the release point), but the low density of traps located at these distances probably resulted in a minor underestimate of these percentages.
      The improved bait performed 6 to 15 times better than the commercial bait in recapturing the released beetles.  Trapping previous to the trials and the absence of unmarked beetles during the trials suggests that there is no evidence of a wild population of O. erosus at this site.  Furthermore, there is no host material was available within a 20 km radius of the release site.  In a survival study of unreleased, marked beetles in cages, about 85% were dead after 48 hrs of outdoor exposure (June 16-18).
      In late July and early September, 2008, two additional mark-recapture studies were conducted to evaluate effective trapping range of the pheromone trap baited with the improved attractant.  In both studies 2,800 beetles (1,400 of each sex) were released and lured to one trap.  Both studies showed that beetle flight activity occurred primarily in the first morning of release during the two-hour period between 8 and 10 AM when the temperature was warm enough and the winds were not so strong to inhibit attempts by beetles to disperse.

Preliminary results from the second study suggest that a single trap with the improved attractant recaptured about 60, 50, 48, 41, 35, 27, and 21% of the beetles released from 2.5, 5, 10, 20, 40, 60 and 80 m, respectively.  A single trap recaptured 50% of the females released between 10 and 20 m, and 50% of males released between 2.5 and 5 m.  Therefore, the effective trapping range of a single trap may be greater for females than males.  The effective trapping range of the trap with the improved attractant could be greater than 0.07 ha for females.   

Products: We envision reporting the results in (1) a peer-reviewed publication on trap efficiency at low density incorporating both 2007 preliminary data and data from 2008 and 2009 (e.g., Journal of Economic Entomology or Ecological Entomology); (2) a peer-reviewed publication on effective trapping range (Journal of Economic Entomology); and (3) a Forest Service General Technical Report summarizing the sampling guidelines with the California, Utah, and Idaho survey data as the proof of concept.

Our project team plans to continue to give oral and poster presentations at various meetings of pest management specialists, land managers, arborists, and scientists, and to continue to prepare extension literature as the need arises. Our linkage to Mary Louise Flint’s program is especially important, as she is the Director of IPM Education and Publications for the UC Statewide IPM Program. Their program has Web-based offerings, which would insure that the guidelines that we develop will have longevity and will be readily and widely available.

Background Citations:

Eglitis, A. 2000. Orthotomicus erosus Available on-line http://spfnic.fs.fed.us/exfor/data/pestreports.cfm?pestidval=9&langdisplay=english . In USDA Forest Service, Exotic Forest Pest Information System.

Haack, R.A. 2001. Intercepted Scolytidae (Coleoptera) at U.S. ports of entry: 1985-2000. Integrated Pest Management Reviews 6: 253–282.

Lee, J.C., Negrón, J.F., McElwey, S.J., Witcosky, J.J., and Seybold, S.J. 2006. Banded elm bark beetle–Scolytus schevyrewi. USDA Forest Service Pest Alert Series R2-PR-0-06.

Lee, J.C, Jiroš, P., Liu, D.-G., Hamud, S.M., Flint, M.L., and Seybold, S.J. 2007. Pheromone Production and Flight Response of the Mediterranean Pine Engraver, a Recently Invasive Bark Beetle in California. J. Chem. Ecol. (in preparation).

Penrose, R.L., Lee, J.C., Liu, D.-G., and Seybold, S.J. 2007. California: A Hotbed for Invasive Scolytidae including the First Established North American Population of the Mediterranean Pine Engraver, Orthotomicus (Ips) erosus. Manuscript for American Entomologist (in preparation).

Seybold, S.J., Huber, D.P.W., Lee, J.C. , Graves, A.D., and Bohlmann, J. 2006. Pine monoterpenes and pine bark beetles: a marriage of convenience for defense and chemical communication. Phytochemistry Reviews 5: 143–178.

Turchin, P. 1998. Quantitative analysis of movement: measuring and modeling population redistribution in animals and plants. Sinauer, Sunderland, Mass.

Turchin, P. and Odendall, F. J. 1996. Measuring the effective sampling area of a pheromone trap for monitoring population density of southern pine beetle (Coleoptera: Scolytidae). Environmental Entomology 25: 582–588.

Project ID: FY08TS56