Intrinsic dispersal capacity of the Mediterranean pine engraver, Orthotomicus erosus, an invasive bark beetle

Mediterranean pine engraver, Orthotomicus erosus (Wollaston), is a nonnative species that was first detected in North America in 2004. The dispersal characteristics of this insect are not known, but they are needed to accurately predict how quickly populations might spread. To estimate its intrinsic dispersal capacity, three mark-recapture trials were conducted in the Tulare Lake area near Kettleman City, California (Kings Co.), a homogenous agricultural landscape with no hosts and very few trees or shrubs. About 6000 marked beetles were released for each trial. Traps were placed in pairs with one trap baited with a commercially available bait for O. erosus, and the other baited with an improved pheromone bait. Pairs of traps were placed in the cardinal directions at 0.1, 0.5, 1, 2, 4, 6, 8, and 10 km radii. Preliminary assessment of the results suggests that O. erosus was captured primarily in the southern and eastern traps, reflecting the prevailing winds from the northwest. Recapture rates were approximately 10%. Most recaptured beetles were trapped at distances 100 and 500 m from the release point, and these moved to these locations within 20 to 60 minutes of release. A few individuals were recaptured between 4 and 10 km from the release point. There was no evidence of a wild population of O. erosus at this site. In a companion survival study of unreleased, marked beetles in cages, about 85% died after 48 hrs of outdoor exposure in the windy, hot, and dry weather of California Central Valley.