Alternative Formulations of Trap Lures for Operational Detection, Population Monitoring, and Outbreak Forecasting of Southern Pine Beetle in the United States

Abstract

The southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) is a major destructive pest of Pinus L. In the southeastern United States, numbers of this species and a major predator, Thanasimus dubius (Fabricius) (Coleoptera: Cleridae), captured during an annual springtime trapping survey are used to make forecasts of the likelihood and severity of an outbreak during the following summer. We investigated responses by both species to six lure formulations to evaluate their suitability for the survey and allow integration of historical data sets produced with differing lure compositions. Trapping trials were performed at four locations across three states (Louisiana, Mississippi, and Alabama) during spring, and at these and one additional location (North Carolina) in fall 2016. All lures included the pheromone component frontalin. Southern pine beetle preferred lures that additionally included the pheromone component endo-brevicomin and turpentine as a source of host odors (rather than a 7:3 mixture of monoterpenes alpha- and beta-pinene). Thanasimus dubius displayed little discrimination among lure compositions. Lure preferences by southern pine beetle did not differ significantly among locations in spring but were influenced by season. Gas chromatography (GC)-electroantennographic detection analyses with southern pine beetle and GC-mass spectrometry identified numerous known and potential semiochemicals that distinguished volatiles released by the tested host odor devices. The lure combination that included endo-brevicomin and alpha/beta-pinene is recommended for the trapping survey because of its high sensitivity for southern pine beetle and potential for greater data integrity resulting from its reproducible composition.

4‐allylanisole as a lure adjuvant for Dendroctonus frontalis (Coleoptera: Curculionidae: Scolytinae) and two associated beetles

“…The substantial increase in catches caused by combining the 4‐allylanisole and terpene lures (experiment 3) indicates that 4‐allylanisole does not duplicate the attractive effects of alpha ‐ or beta ‐pinene and that the respective signals could have different ecological significance for the beetles. However, the failure of 4‐allylanisole to enhance the attractiveness of the turpentine‐amended lure appears inconsistent with this conclusion, as the turpentine was dominated by alpha ‐pinene (Sullivan et al, 2021). The turpentine contained additional D. frontalis semiochemicals that could have influenced the effects of 4‐allylanisole (Sullivan et al, 2021).…”

“…Experiment 3 assessed whether 4‐allylanisole, when released at a rate found synergistic in experiments 1 and 2 and in a previous study (Munro et al, 2020), could enhance attractiveness of the D. frontalis monitoring lure either in its current formulation or with an earlier host odour component. The current, operational lure consists of frontalin, endo ‐brevicomin, and a blend of alpha ‐ and beta ‐pinene (hereafter ‘pinene lure’) (Sullivan et al, 2021). A prior monitoring lure used turpentine from a host species for D. frontalis instead of alpha/beta ‐pinene as the host odour component, and the turpentine was released from a wick‐and‐reservoir device (Billings & Upton, 2010).…”

“…Trap catch collections and treatment re‐randomizations among traps within lines occurred at 6–8 day intervals. All traps were baited with frontalin (centre of trap) and endo ‐brevicomin (4–6 m away from trap) devices according to standard protocol for the D. frontalis monitoring lure (Sullivan et al, 2021). The endo ‐brevicomin device was attached to the top of a 1.5‐m plastic pole inserted in the ground, and the host odour lure was attached below the top of the trap.…”

“…Populations of D. frontalis are currently monitored across the southeastern USA with uniformly‐baited Lindgren‐type funnel traps (Lindgren, 1983) deployed each spring (Billings & Upton, 2010; Sullivan et al, 2021). Catches of both D. frontalis and its predator Thanasimus dubius (Fabricius) (Coleoptera: Cleridae) are used along with other data to forecast the numbers of D. frontalis infestations during the forthcoming summer at the spatial scale of individual counties (https://www.spbpredict.com).…”

“…The lure used operationally for D. frontalis monitoring is the aggregation pheromone of D. frontalis (i.e. frontalin and endo ‐brevicomin) with a 7:3 mixture of alpha ‐ and beta ‐pinene (Sullivan et al, 2021). To maintain trap captures at manageable numbers for sample processing, the lure is formulated to limit its attractiveness.…”