Sanitation options for managing oak wood infested with the invasive goldspotted oak borer (Coleoptera: Buprestidae) in southern California.

Movement of invasive wood-boring insects in wood products presents a threat to forest health and a management challenge for public and private land managers. The goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), is a new pest in San Diego and Riverside Cos., CA, believed to have been introduced on firewood. This beetle has caused elevated levels of oak mortality since 2002. From 2009-2011, we tested several sanitation methods, applicable to large and small land parcels, to reduce or prevent goldspotted oak borer emergence from infested oak wood. In most experiments, emergence of goldspotted oak borer adults from the positive controls demonstrated that the beetle could complete development in firewood-sized pieces of cut oak wood. In 2009, adult emergence from sun-exposed oak wood began and peaked 2- to 4-wks earlier at a low elevation site than at a high elevation site (late May to late June). However, there were no significant effects of elevation or host species on the emergence response of goldspotted oak borer by solarization treatment in this study. Solarization of infested wood with thick (6 mil) and thin (1 mil) plastic tarpaulins (tarps) did not significantly reduce emergence of adults despite recordings of greater mean and maximum daily temperatures in both tarped treatments and greater relative humidity in the thick-tarped treatment (all compared with nontarped controls). Grinding wood with a 3"-minus screen (< or = 7.6 cm) significantly reduced goldspotted oak borer emergence compared with control treatments, and this was the best method for reducing adult emergence among those tested. In a separate grinding study, no adults emerged when wood was ground to 9"-minus (22.9 cm), 2"-minus (5.1 cm), or 1"-minus (2.5 cm) screen sizes, but a low level of adult emergence from the positive controls limited any inferences from this experiment. Debarking cut wood pieces eliminated goldspotted oak borer emergence from the wood fraction, but adults emerged from the shaved bark and phloem.

Suitability of pines and other conifers as hosts for the invasive Mediterranean pine engraver (Coleoptera: Scolytidae) in North America.

The invasive Mediterranean pine engraver, Orthotomicus erosus (Wollaston) (Coleoptera: Scolytidae), was detected in North America in 2004, and it is currently distributed in the southern Central Valley of California. It originates from the Mediterranean region, the Middle East, and Asia, and it reproduces on pines (Pinus spp.). To identify potentially vulnerable native and adventive hosts in North America, no-choice host range tests were conducted in the laboratory on 22 conifer species. The beetle reproduced on four pines from its native Eurasian range--Aleppo, Canary Island, Italian stone, and Scots pines; 11 native North American pines--eastern white, grey, jack, Jeffrey, loblolly, Monterey, ponderosa, red, Sierra lodgepole, singleleaf pinyon, and sugar pines; and four native nonpines--Douglas-fir, black and white spruce, and tamarack. Among nonpines, fewer progeny developed and they were of smaller size on Douglas-fir and tamarack, but sex ratios of progeny were nearly 1:1 on all hosts. Last, beetles did not develop on white fir, incense cedar, and coast redwood. With loblolly pine, the first new adults emerged 42 d after parental females were introduced into host logs at temperatures of 20-33 degrees C and 523.5 or 334.7 accumulated degree-days based on lower development thresholds of 13.6 or 18 degrees C, respectively.

Densities of Agrilus auroguttatus and Other Borers in California and Arizona Oaks.

We investigated within-tree population density of a new invasive species in southern California, the goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), with respect to host species and the community of other borers present. We measured emergence hole densities of A. auroguttatus and other borers on the lower stem (bole) of naïve oaks at 18 sites in southern California and on co-evolved oaks at seven sites in southeastern Arizona. We sampled recently dead oaks in an effort to quantify the community of primary and secondary borers associated with mortality-species that were likely to interact with A. auroguttatus. Red oaks (Section Lobatae) produced greater densities of A. auroguttatus than white oaks (Section Quercus). On red oaks, A. auroguttatus significantly outnumbered native borers in California (mean ± SE of 9.6 ± 0.7 versus 4.5 ± 0.6 emergence holes per 0.09 m² of bark surface), yet this was not the case in Arizona (0.9 ± 0.2 versus 1.1 ± 0.2 emergence holes per 0.09 m²). In California, a species that is taxonomically intermediate between red and white oaks, Quercus chrysolepis (Section Protobalanus), exhibited similar A. auroguttatus emergence densities compared with a co-occurring red oak, Q. kelloggii. As an invasive species in California, A. auroguttatus may affect the community of native borers (mainly Buprestidae and Cerambycidae) that feed on the lower boles of oaks, although it remains unclear whether its impact will be positive or negative.

Developing monitoring techniques for the invasive goldspotted oak borer (Coleoptera: Buprestidae) in California.

The goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), is an invasive species that has colonized oak woodlands in southern California. To better define its seasonal flight activity, assist with forest and integrated pest management activities, and define the current distribution in California, an effective monitoring technique for A. auroguttatus is necessary. We assessed the efficacy of two colors of flight-intercept prism traps, the placement of these traps at three heights, and several commercially available lures [Manuka oil, Phoebe oil, and a green leaf volatile, (3Z)-hexenol] for monitoring the flight of adult A. auroguttatus. Landing rates and the densities of D-shaped emergence holes of A. auroguttatus adults were assessed on the lower stems of coast live oak, Quercus agrifolia Née, of varying size and crown health classes. Purple flight-intercept prism traps placed at heights of 3 m and 4.5 m caught significantly more female A. auroguttatus than green prism traps. In one experiment, males also responded at a significantly higher level to purple than to green prism traps placed at 3 m height. The addition of commercially available lures significantly enhanced male, but not female, A. auroguttatus trap catch when compared with unbaited control traps. There were no differences among male flight responses to the three lures. A. auroguttatus landing rates and emergence hole densities were significantly greater on the largest-diameter trees (>76.2 cm diameter at breast height) and on trees with severe crown thinning or complete crown collapse. The annual increment in emergence hole densities was also significantly greater on trees with severe crown thinning or complete crown collapse. In three trapping studies over multiple years in southern California, the adult flight period began as early as mid-May, peaked in mid-June to early July, and ended in early- to mid-September. To demonstrate the efficacy of the detection method for A. auroguttatus (unbaited purple traps at 3 m height), a delimitation survey conducted from 2009 to 2012 confirmed that the species was only present in San Diego Co., but that the distribution was expanding northward.