Spatial Displacement of a Lure Component Can Reduce Catches of Two Nontarget Species During Spring Monitoring of Southern Pine Beetle

Abstract

Local outbreak risk for the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae), is forecast with a trapping survey conducted every spring throughout the southeastern United States. Traps baited with pine odors and components of the D. frontalis aggregation pheromone are used to obtain abundance estimates of both this species and its clerid predator Thanasimus dubius (F.) (Coleoptera: Cleridae); these data are entered into a predictive model that estimates outbreak risk. An attractant synergist for D. frontalis, endo-brevicomin, has recently been included in the survey lure, but it can have the unintended effect of attracting nontarget species Hylesinus pruinosus Eichhoff (Coleoptera: Curculionidae: Scolytinae) and Enoclerus nigripes (Say) (Coleoptera: Cleridae) which, due to their sometimes large numbers and general similarity in appearance to the target species, could complicate sorting and counting of trap catches. Analysis of bycatch data from a previously-published, 31-mo trapping study in Mississippi indicated that displacement of the endo-brevicomin releaser 6 m from the trap largely eliminated catches of the nontarget species H. pruinosus and E. nigripes while not reducing catches of the target species D. frontalis and T. dubius. Our analysis demonstrates that interspecific differences in spatial responses to attractive semiochemicals can be used to improve insect trap selectivity. Both nontarget beetle species were captured in highest numbers during late winter/early spring, coinciding with the D. frontalis survey.

Effect of Trap Color on Captures of Bark- and Wood-Boring Beetles (Coleoptera; Buprestidae and Scolytinae) and Associated Predators

“…Our results also highlighted that trap color can partially minimize the inadvertent removal of certain checkered beetles (e.g., black traps reduce catches of C. mutillarius) but not others (e.g., T. formicarius). Thus, other strategies must be developed to minimize the bycatch of predators, such as modification of trap design [18] and displacement or selective choice of lures [17,19]. Finally, given that our study was carried out only in 2019 and in a single area located in north-eastern Italy, it would be worth repeating the same trapping trial in other locations and in different years as the response of wood-boring beetles to baited traps has already been shown to potentially change in space and time, e.g., [16].…”

“…Traps baited with pheromones and host volatiles are often used at high-risk sites and nearby natural areas to intercept incoming beetles soon after their arrival and to reduce the chances of their establishment [10][11][12]. The efficacy of this practice depends on several variables such as trap type, trap height, or lure specificity (e.g., [13,14]), which are often combined in order to attract several beetle species simultaneously (e.g., [15,16]) and hopefully minimize the inadvertent removal of associated natural enemies (e.g., [17][18][19]). Recent studies have shown that trap color can affect trap catches of longhorn beetles (Coleoptera: Cerambycidae) [20,21] but its effect on jewel beetles, bark and ambrosia beetles, and their associated beetle predators (e.g., Cleridae) has been investigated so far only for a limited number of species.…”

Semiochemicals for management of the southern pine beetle (Coleoptera: Curculionidae: Scolytinae): successes, failures, and obstacles to progress

“…The beetle produces almost solely the ()-enantiomer of endo-brevicomin and predominantly (-)-frontalin (Payne et al 1982;Sullivan et al 2007b); however, for both compounds, the much less costly racemic blend has activity similar to the predominant enantiomer (Payne et al 1982;Sullivan and Mori 2009;Sullivan et al 2011) and is used in the operational lure. It is recommended that the endo-brevicomin device be placed several metres from the trap to maximise the synergistic effect of the endo-brevicomin on the attractant in the trap (Sullivan and Mori 2009; B.T.S., unpublished data) while reducing unwanted bycatches of endo-brevicomin-attracted species whose presence complicates sample handling (Shepherd and Sullivan 2017). Until recently, the recommended host odour component for the operational lure had been turpentine, a resin distillate, from the host species Pinus taeda Linnaeus (Pinaceae).…”