Developing Monitoring Techniques for the Invasive Goldspotted Oak Borer (Coleoptera: Buprestidae) in California

Abstract

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.

Acute Oak Decline and Agrilus biguttatus: The Co-Occurrence of Stem Bleeding and D-Shaped Emergence Holes in Great Britain

“…This trend has also been documented for A. planipennis [48] and A. auroguttatus [60], although both of these species also show a preference for green traps [61,62]. In this study A. biguttatus was not caught on any green traps, however, recent studies showed green canopy-based traps did catch A. biguttatus, albeit in very low numbers [63].…”

Impact of the goldspotted oak borer, Agrilus auroguttatus, on the health of coast live oak before and after treatment with two systemic insecticides

“…If aggregation is a key factor in colonization of oaks by A. auroguttatus , effective management of the pest might focus on removal of moderately to severely infested trees and insecticide application to lightly infested trees. This management activity may require more effective early detection techniques than are available presently …”

“…Agrilus auroguttatus holes are uniquely sized and shaped and, with training, can be distinguished from emergence holes produced by other woodborers in California oaks . In contrast, other life stages are impractical to monitor: adults are rarely observed and the currently recommended detection trap is not very effective; eggs are laid in bark crevices and almost impossible to find; larvae developing within the tree cannot be observed without destructive sampling which would have killed trees and jeopardized our long‐term monitoring of insecticide efficacy and tree health. Destructive sampling was also not acceptable at these privately owned sites.…”

“…Early detection and assessment of infestation level are critical tools for focusing management programs. Currently, the primary approach available for managing A. auroguttatus involves preventing infestation of healthy trees by limiting movement of and destroying insects in infested wood through procedures such as debarking, tarping or grinding .…”

Pest survey card on Agrilus auroguttatus

“…According to Coleman and Seybold (2008), purple prism glue-coated traps (developed by Francese et al 2008) on a 3 m pole with an ethanol attractant were found to be effective. In another study, Seybold et al (2010) found that purple traps had higher capture rates at a height of 3 m, while green traps had more captures at a height of 4.5 m. Comparing colours of flight-intercept prism traps (three sides, 35.6 by 59.7 cm, Francese et al, 2008), Coleman et al (2014) found that purple and green were equally effective at catching A. auroguttatus males, while purple traps were more effective for capturing females. In another study, Seybold et al (2010) found that purple traps had higher capture rates at a height of 3 m, while green traps had more captures at a height of 4.5 m. Comparing colours of flight-intercept prism traps (three sides, 35.6 by 59.7 cm, Francese et al, 2008), Coleman et al (2014) found that purple and green were equally effective at catching A. auroguttatus males, while purple traps were more effective for capturing females.…”