Red turpentine beetle primary attraction increases linearly with (−)‐β‐pinene+ethanol dose regardless of component ratios, and no change in response with addition of high‐release frontalin

Abstract

Lure efficacy for primary attraction of red turpentine beetle, Dendroctonus valens (Coleoptera: Curculionidae: Scolytinae) observed previously in US Pacific Northwest ponderosa pine forests is (−)‐β‐pinene+ethanol > (+)‐3‐carene+ethanol > (+)‐α‐pinene+ethanol. Influence of (−)‐β‐pinene+ethanol release rates was tested with nine lures representing all combinations of three release levels for each compound in a 3 × 3 factorial design field test in Oregon. Beetle catch had a positive, linear relationship with the combined (−)‐β‐pinene+ethanol total release (or dose), resulting from higher release of either one or both compounds. Reversing component ratios, that is, 1 : 2 versus 2 : 1 with similar total doses, produced minimal changes in beetle response. Females produce frontalin with dual aggregation and sex‐pheromone functions. In another test, high‐release frontalin, defined as >1.0 mg/day release, was tested at 1.4 to 1.5 mg/day in combination with each monoterpene+ethanol lure above and their trap catch compared with (−)‐β‐pinene+ethanol lures. Presence of high‐release frontalin produced minimal changes in beetle responses.

Red turpentine beetle primary attraction to β‐pinene or 3‐carene (with and without ethanol) varies in western US pine forests

“…The D. valens trap catch increases as β-pinene release rates rise (Hobson et al, 1993), or the combined release rates of β-pinene+ethanol increase by changing either one or both components (Kelsey & Westlind, 2022).…”

“…(+)‐3‐Carene (>90.0%), and (−)‐β‐pinene (≥97%) were purchased from Sigma Aldrich (St. Louis, MO) and dispensed from low‐density polyethylene (LDPE) bottles (15 mL, The Cary Company, Addison, IL) similar to those used in previous tests (Erbilgin et al, 2007; Kelsey & Westlind, 2020, 2021, 2022; Liu et al, 2013; Sun et al, 2004). They were filled in advance to the threaded neck with a small air bubble under the cap, then grouped by lure type in sealed plastic bags and stored at 5°C.…”

“…(+)-3-Carene (>90.0%), and (À)-β-pinene (≥97%) were purchased from Sigma Aldrich (St. Louis, MO) and dispensed from low-density polyethylene (LDPE) bottles (15 mL, The Cary Company, Addison, IL) similar to those used in previous tests (Erbilgin et al, 2007;Kelsey & Westlind, 2020, 2022Liu et al, 2013;Sun et al, 2004). They were filled in advance to the threaded neck with a small air bubble under the cap, then grouped by lure type in sealed plastic bags and stored at 5 C. Before initial weighing they were held 5 days at room temperature to saturate the LDPE bottles (Kelsey & Westlind, 2020), then refilled, weighed and immediately returned to the cold room for a few hours until further processing.…”

“…valens response was linearly related to the total dose of (À)-β-pinene+ethanol released and changing their release ratios had minimal impact on attraction (Kelsey & Westlind, 2022).…”

“…Additional tests found the D . valens response was linearly related to the total dose of (−)‐β‐pinene+ethanol released and changing their release ratios had minimal impact on attraction (Kelsey & Westlind, 2022). (−)‐β‐Pinene+ethanol and (+)‐3‐carene+ethanol lures have not been tested outside Pacific Northwest pine forests.…”