J. Sweeney, P. de Groot, L. MacDonald, J. Gutowski
Natural Resources Canada, Canadian Forest Service, Fredericton
SERG Project #2002/01
Year of Project: 2003
Report Received: 2004
The brown spruce longhorn beetle (BSLB), Tetropium fuscum (F.) (Coleoptera: Cerambycidae), has been the focus of an eradication program in Halifax, Nova Scotia, since 2000. In 2001 and 2002, we developed a synthetic host volatile (spruce blend) lure and found it was significantly attractive to T. fuscum. Addition of an ethanol lure to the spruce blend lure synergized attraction of both T. fuscum and a related exotic species, T. castaneum. Our objectives for 2003 were to 1) test the effect of the release rate of spruce blend and ethanol on attraction of T. fuscum and T. castaneum; 2) compare the composition of cortical volatiles in stressed vs. healthy spruce and determine their relative attraction to T. fuscum; and 3) test the efficacy of wet vs. dry collecting buckets in Colossus and IPM Intercept traps.
Traps baited with high release rate lures of spruce blend + ethanol caught significantly more T. fuscum and T. castaneum than any other treatment, a 2- to 7-fold increase in catch over traps baited with low release rate lures of spruce blend + ethanol. Baiting traps with high release rate lures of spruce blend and ethanol will significantly increase the probability of detecting T. fuscum where it is present. Material costs will also be reduced because only two high release rate lures (one spruce blend and one ethanol) are required per season compared to five (four spruce blend and one ethanol) low release rate lures.
Red spruce trees that had been girdled in May the previous year were significantly moisture-stressed compared to ungirdled control red spruce, whereas similarly treated Norway spruce trees were not. The cortical volatiles of stressed red spruce contained significantly lower mean concentrations of (+/-) α-pinene and greater concentrations of 3-carene than did those of unstressed red spruce. Synthetic lures were made to simulate the monoterpene composition of both stressed and unstressed red spruce and were tested with or without ethanol lures for attraction of T. fuscum in trapping bioassays. Contrary to expectations, the "unstressed" lures were more attractive than "stressed" or standard spruce blend lures; only traps baited with unstressed lures or unstressed lures + ethanol lures caught significantly more T. fuscum than unbaited controls.
Trap design and type of preservative (wet vs dry) significantly affected mean catch of T. fuscum. Colossus traps caught about twice as many beetles as the IPM traps, and "wet" traps (with 50% propylene glycol in the collecting bucket) caught more beetles than "dry" traps (with a dichlorvos strip). The effect of trap design remained significant even when catch was expressed per unit of cross-sectional trap surface area, which suggests the greater catch in the Colossus traps was partially due to visual attraction, i.e., a larger "tree" silhouette, and not due simply to greater interception of beetles attracted by host volatiles. Type of preservative affected mean catch more so in IPM traps than in Colossus traps, possibly because the latter’s deeper, straight-sided collecting cup may have allowed fewer beetles to escape from dry traps.
We recommend that trapping surveys for detection of BSLB in 2004 use Colossus traps baited with ultra-high release rate lures of spruce blend and ethanol.