J. Entomol. Soc. Brit.Columbia 101,December2004 117 Evaluation oftwo repellent semiochemicals for disruption of attack by the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae) JOHN H. BORDEN* ^ DEEPA S. PURESWARAN* ^ and LISA M. POIRIER^ ABSTRACT When released from attractant-baited multiple-funnel traps, 3-methyl-2-cyclohexen-l- one (MCH) reduced catches of male and female mountain pine beetles, Dendroctonus ponderosae Hopkins, by 67.4% and 71.8%, respectively. 2-Phenyl ethanol reduced the respective catches by 96.6% and 95.1%, but only verbenone and all three compounds together reduced catches to levels no different from those in unbaited control traps. In another experiment, all three binary combinations of the above compounds, plus the ternary combination, reduced catches ofboth sexes by >96%. In comparable tree protec- tion experiments near Princeton BC, MCH and 2-phenyl ethanol alone and together significantly reduced the percentages of pheromone-baited lodgepole pines that were attacked by 16.0%, 33.3% and 40.0%, respectively, but verbenone alone totally pro- tected baited trees, and many trees within 5 m ofthem, from attack. In identical experi- ments near Prince George BC, where mountain pine beetle populations were much higher, adding MCH, 2-phenyl ethanol or both together to verbenone did not cause at- tack to be reduced significantly beyond that achieved by verbenone alone. Our results confirm that 2-phenyl ethanol is an antiaggregation pheromone for the mountain pine MCH beetle, and that is an interspecific synomone. However, because neither was as effective as verbenone in protecting pheromone-baited trees from attack, and adding either or both to verbenone did not improve protection, neither compound warrants fur- therconsideration as apotential tool foroperational disruption ofattack. Key Words: Dendroctonus ponderosae, semiochemicals, pheromones, verbenone, 2- phenyl ethanol, 3-methyl-2-cyclohexen-l-one, attackdisruption INTRODUCTION Although the antiaggregation phero- cacy may be that verbenone is transformed mone verbenone has long been known to to the inactive compound chrysanthenone disrupt attack by the mountain pine beetle when exposed to ultraviolet radiation (MPB), Dendroctonus ponderosae Hop- (Kostyk etal. 1993). Adding repellent non- kins (Amman et al. 1989; Lindgren et al. host volatiles from angiosperm tree bark to 1989a), its efficacy has been inconsistent verbenone has been shown to increase the between years, target species oftrees, and efficacy of protecting lodgepole pines, geographic areas (Bentz et al. 1989; Lister Pinus contorta var. latifoUa Engelmann, et al. 1990; Gibson et al. 1991; Shea et al. from attack (Huber and Borden 2001), and 1992). Part ofthe reason for variable effi- combining a seven-component nonhost 'Department ofBiological Sciences, Simon FraserUniversity, 8888 University Drive, Bumaby BC V5A 1S6 ^Currentaddress: PheroTechInc., 7572 ProgressWay,DeltaBC V4G 1E9 ^Currentaddress: DepartmentofBiological Sciences, DartmouthCollege, HanoverNH 03755 USA ^Ecosystem Science and Management, University ofNorthern BC, 3333 University Way, Prince George BC V2N4Z9 A 5 118 J.Entomol. Soc.Brit.Columbia 101,December2004 volatile blend with an increased release pheromone ofDouglas-fir and spruce bee- rate of verbenone has raised the efficacy tles, Dendroctonns pseudotsugae Hopkins even higher (Borden et al 2003). How- and D. rufipennis (Kirby), respectively ever, at an effective 10 x 10m spacing, the (Rudinsky et al. 1972; Lindgren et al. latter treatment would cost $1,250 per ha, 1989b) that was recently shown to be a excluding labor, limiting itspotential use. repellent synomone for the mountain pine One means ofreducing the cost would beetle (Pureswaran and Borden 2004). Our be to replace the repellent nonhost volatile objectives were to confirm the bioactivity blend with cheaper materials. Two such of 2-phenyl ethanol and MCH, and to de- semiochemicals are the antiaggregation termine in trapping and tree protection pheromone 2-phenyl ethanol (Pureswaran experiments whether they are potential et al 2000) and 3-methyl-2-cyclohexen-l- adjuvants that could increase the efficacy MCH one (MCH). is an antiaggregation ofverbenone. MATERIALS AND METHODS Two randomized complete block, 12- were purchased from Phero Tech Inc., replicate, field trapping experiments (Exp. Delta BC. The attractive trap bait consisted 1 and 2) were set up on 31 July and 13 of the host kairomone myrcene released August 2002, respectively, near the East from a 20 mL polyethylene bottle at 95 Gate ofManning Park BC (49° 19' N, 120° mg/24 h, determined at 23 °C, and the ag- 35' W). Tree protection experiments (Exp. gregation pheromones 82% {-)-trans- 3A and 4A) with treatments identical to verbenol and (±)-exo-brevicomin respec- those in the trapping experiments were set tively released from bubble caps and poly- up on 5-7 July 2002 in the valley ofWhip- urethane flexlures at 1.2 and 0.3 mg/24 h, saw Creek near Princeton BC (49° 9' N, determined at 20 °C. The attractive tree 120° 41' W), and two additional identical bait was identical to the trap bait, but with experiments (Exp. 3B and 4B) were set up myrcene deleted (Borden et al. 1993). on 24-27 July 2002 on the 1400 Road MCH, 2-phenyl ethanol and 80% (-)- south of Prince George BC (53° 21' N, verbenone were released from bubble caps 123° 10' W). at 4.0, 4.2 and 1.8 mg/24 h, determined at For trapping experiments, 12-unit mul- 20, 25, and 20 °C, respectively. Devices tiple-funnel traps were deployed at least 1 were hung in the central funnel of traps m apart along logging roads that passed and affixed to the north face of trees at near infested stands. For the tree protection maximum reach from the ground. The dbh experiments, lodgepole pines with a mini- of all baited trees was measured, and var- mum diameter at breast height (dbh = 1.3 ied among experiments (mean ± SE) as m) of 20 cm were selected at least 25 m follows: 30.9 ± 1.3 cm to 35.1 ± 1.2 cm in apart in rows at least 50 m apart through Exp. 3A and4A near Princeton, and 23.0 ± cutblocks designated for harvest in the fall 0.5 cm to 25.3 ± 0.9 cm in Exp. 3B and4B of2002. nearPrince George. Treatments (Tables 1, 2) in Exp. 1, 3 Captured beetles in Exp. 1 and 2 were and 3B were an unbaited trap or tree collected on 13 and 26 August, respec- (negative control), and an attractive bait tively. Beetles were held at ca. -5 °C in alone (positive control) or with MCH, 2- plastic bags until sexed and counted. phenyl ethanol, verbenone, or all three Tree protection experiments were together. In Exp. 2, 4A and 4B, the control evaluated on 25-27 September (Exp. 3B treatments were the same, but the three and 4B) and 3-4 October (Exp. 3A and disruptants were deployed in all three pos- 4A). The attack density was counted at eye sible binary blends and the ternary blend. level in two 20 x 40 cm panels on the east All semiochemicals and release devices and west faces ofbaited trees and all trees 1 J. Entomol. Soc. Brit.Columbia 101,December2004 119 Table 1. Effect ofMCH, 2 phenyl ethanol and verbenone alone or in binary orternary combinations, on catches ofmountain pine beetles in attractant-baited multiple-funnel traps. Eastgate Road near Manning Park, B.C., 31 July - 13 August 2002 for Experiment 1 and 13-26 August for Ex- periment 2. Mean numberofbeetles captured (±SE)" Exp. No. Treatment' No. reps Males Females 1 MPB bait 12 137.8 ±47.4 a 86.5 ±38.8 a Bait+ MCH 12 44.9± 8.9b 24.4± 8.2 b Bait+z rb 12 4.7± 1.1 c 4.3 ± 1.2 c rSait+ V 1Iz 3.5 ± 1.2 cd 2.3 ± 1.5 cd Rait 4- V+ MPH + 9PF 11z9 1.8±0.5cd 1.1 ±0.8d Unbailed 12 0.8 ± 0.4 d 0.8 ± 0.3 d 2 MPB bait 12 76.1 ±29.8 a 41.3 ± 16.0 a Bait+ MCH + 2PE 10 1.7 ± 0.7 b 1.6 ± 0.7 b Bait+ V + MCH 12 2.2 ± 1.5 b 1.1 ±0.6b Bait+ V + 2PE 12 0.5 ±0.2 b 0.2 ± 0.2 b Bait+ V + MCH +2PE 12 0.4± 0.2 b 0.6 + 0.2 b Unbailed 12 0.1 ±0.1 b 0.3 ±0.1 b 'Treatments as follows: MPB bait = mountain pine beetle bait including /raw5-verbenol, exo- brevicomin and myrcene; MCH= 3-methyl-2-cyclohexen-l-one; 2PE= 2-phenyl ethanol; V=verbonene. ^Means followed by the same letter are not significantly different, REGW test, P<0.05 ANOVA resuhs: Exp. 1., males, F=53.87, df=5,66, P<0.0001; Exp. 1, females, F=34.89, df=5,66, P<0.0001; Exp. 2, males, F=14.45, df-16,52, P<0.0001; Exp. 2, females, F=9.84, df=16,52,P<0.0001. with at least five attacks in the total 0.16 Data for numbers of beetles captured area (31.25/mO were classed as mass- and attack density on baited trees were log- ANOVA attacked. All surrounding lodgepole pines transformed and analyzed by and at least 17.5 cm dbh within 5 m ofbaited the REGW test (Day and Quinn 1989). trees were evaluated as unattacked, at- Data on proportions of baited and sur- tacked, or mass-attacked, the latter being rounding trees that were mass-attacked determined qualitatively by visual estima- were analyzed by chi-square tests for com- tion ofattack density and copious amounts parison between multiple proportions of frass in bark crevices and around the (Jones 1984). In all cases a= 0.05. root collar. RESULTS In the first trapping experiment (Exp. traps (Table 1). 2-Phenyl ethanol reduced 1), MCH, 2-phenyl ethanol and verbenone catches to levels no different from those reduced the catches of male and female achieved by verbenone (both sexes) or the mountain pine beetles in attractant-baited ternary blend (males only), but only the traps by 67.4%, 71.8% and 96.6%, and lattertwo treatments resuhed in catches not 95.1%, and 97.5% and 97.3%, respec- significantly different from those in un- tively, relative to catches in baited control bailed control traps. In Exp. 2, all binary 120 J.Entomol. Soc.Brit.Columbia 101,December2004 Table 2. Effect oftreatment with MCH, 2-phenyl ethanol and verbenone alone, or in binary or ternary combinations, on ranked percentages of pheromone-baited lodgepole pines that were mass- attacked, and on the pooled percentages ofall surrounding trees > 17.5 cm dbh within 5 m of thebaitedtree that were mass-attacked. rercciii Surroundingtrees Exp. no. (no. reps) Location Treatment' baitedtrees N Percent mass-attacked^ mass-attacked^ 3A(25) Princeton MPBbait 100.00 a 103 15.5 ab Bait+MCH 84.0b 119 23.5 a Bait+2PE 66.7 b 104 4.8 b Bait+V+MCH+2PE 0.0 c 127 0.0 c Unbailed 0.0 c 100 0.0 c Bait+V 0.0 c 117 0.0 c 3B(20) PrinceGeorge MPBbait 95.0 a 69 47.8 ab Bait+MCH 80.0 ab 83 31.3 ab Bait+2PE 75.0 abc 62 24.2b Unbaited 40.0be 65 49.2 a Bait+V+MCH+2PE 40.0be 75 18.7b Bait+V 35.0 c 70 27.1 ab 4A(20) Princeton MPB bait 100.0 a 96 26.0a Bait+MCH+ 2PE 60.0b 93 15.1 a Bait+V+MCH 5.3 c 87 1.1 b Bait+V+2PE 0.0 c 89 O.Ob Unbaited 0.0c 103 O.Ob Bait+V+MCH+2PE 0.0c 105 O.Ob 4B(17) PrinceGeorge MPB bait 94.1 a 52 44.2 a Bait+V+MCH+2PE 47.1 b 47 25.5 ab Bait+V+2PE 35.3 b 61 23.0 ab Unbaited 29.4b 67 17.9b Bait+MCH+2PE 23.5 b 52 36.5 ab Bait+V+MCH 17.6b 51 25.5 ab Treatments as inTable 1, Footnote 1, except thatmyrcene is notpresent in MPB bait. ^Percents within a column and experiment followed the same letter are not significantly differ- ent, chi-squaretest formultipleproportions,P<0.05. combinations and the ternary combination and 33.3%, respectively, but verbenone of disruptants reduced catches by more and the ternary blend completely protected than 96%, and in all cases catches in traps pheromone-baited trees and all trees within with disruptive treatments were no greater 5 m ofthem from attack. In Exp. 3B near than in unbaited control traps. Prince George, only verbenone and the In the first tree protection experiment ternary blend significantly reduced the near Princeton (Exp. 3A), all pheromone- percentage ofbaited trees that were mass- baited control trees were mass-attacked attacked, and the lowest percentages of MCH (Table 2). and 2-phenyl ethanol surrounding trees that were mass-attacked alone reduced the proportion of baited occurred in the 2-phenyl ethanol and ter- trees that were mass-attacked by 16.0% naryblend treatments. J. Entomol. Soc. Brit.Columbia 101,Dechmbhr2004 121 In the second tree protection experi- centage of baited trees that were mass- ment near Princeton (Exp. 4A), the binary attacked, but no treatment had a significant MCH combination of and 2-phenyl ethanol effect on attack on surrounding trees. reduced the percentage ofbaited trees that In all cases except Exp. 3B (Bait + V + were mass-attacked by 40%, but did not MCH + 2 PE), disruptant treatments in- cause a reduction in the proportion ofsur- cluding verbenone caused a reduction in rounding trees that were mass-attacked attack density on mass-attacked trees rela- MPB (Table 2). All treatments containing verbe- tive to the bait alone, but in the ab- none reduced attack to zero or to a level sence ofverbenone, only MCH + 2-phenyl not significantly different from zero. In ethanol in Exp. 4B caused a similar reduc- Exp. 4B near Prince George, all treatments tion (Table 3). significantly and equally reduced the per- Table3. Effect oftreatment with MCH, 2-phenyl ethanol and verbenone alone, or in binary or ternary combinations, on ranked densities ofattack by the mountain pine beetle on pheromone-baited lodgepolepines. No. Mean attack density/ Exp. no. . 1ICaCIltiTlYilCInllt^ alldCJvCU 111 ^ UIl dlldLlvCU (no. reps) trees trees'^ 3A (25) Princeton MPB bait 25 125.5 ± 10.1 a Bait+ 2PE 16 112.5± 13.8a Bait+ MCH 23 108.1 ±7.6 a Bait+ V + MCH + 2PE 3 6.3 ±O.Ob Bait+ V 0 no attack Unbailed 0 no attack 3B (20) Prince George Bait + MCH 15 105.4± 10.5 a MPB bait 19 91.4±8.5 ab Bait+ 2PE 14 77.3 ± 10.4 ab Unbailed 10 62.5 ± 13.8 be Bait+ V + MCH + 2PE 8 60.9± 7.6 be Bait + V 13 52.9± 10.2 c 4A (20) Princeton MPB bait 20 129.1 ±8.4 a Bait+ MCH + 2PE 14 98.7± 14.8 a Bait+ V + MCH 6 25.0± 11.9 b Bait+ V+ 2PE 5 8.8 ±4.3 b Bait+ V + MCH +2PE 6 8.3 ± 3.5 b Unbailed 1 no attack 43(17) Prince George MPB bait 15 116.3±9.1 a Bait+ V+ MCH + 2PE 11 64.2±40.1 b Bait+ V + 2PE 9 58.3 ± 11.3 b Unbailed 9 43.8± 10.8 b Bait+ MCH + 2PE 12 40.6± 13.9b Bait + V + MCH 7 40.2 ± 14.8 b ^Treatments as in Table 1, Footnote 1, exceptthat myrcene wasnotpresent in MPB baits. ^Percents within a column and experiment followed the same letterare not significantly differ- ent, chi-square test formultipleproportions,/'<0.05. 122 J.Entomol. Soc.Brit.Columbia 101,December2004 DISCUSSION Ourresults confirm the bioactivity of2- tially greater protection ofbaited and sur- phenyl ethanol as an antiaggregation rounding trees than was found with verbe- pheromone of the mountain pine beetle none alone (Huber and Borden 2001). MCH (Pureswaran et aJ. 2000), and as a However, in a small plot experiment the repellant synomone (Pureswaran and Bor- same nonhost volatile blend caused a den 2004). greater reduction of attack than verbenone Unlike MCH, 2-phenyl ethanol ap- alone when added to high-dose verbenone peared to have some potential as a pest pouches, but not when added to the same MCH management tool. caused only mar- low-dose bubble caps used in our experi- ginal reductions in trap catches, and af- ments (Borden etal. 2003). forded little protection oftrees. In contrast, Our resuhs show that when tested 2-phenyl ethanol caused large reductions alone, 2-phenyl ethanol was more effective MCH in trap catches and greater protection of than in reducing catches in attrac- pheromone-baited and surrounding trees. tant-baited traps (Table 1), as well as the In Exp. 1, 2, 3A and 3B in the southern percentage ofbaited and surrounding trees part of the province, verbenone was so that were mass-attacked (Table 2, Exp. MCH effective alone that there was no opportu- 3A). However, neither nor 2-phenyl nity to observe any potential interaction ethanol alone reduced the attack density of between MCH, 2-phenyl ethanol and ver- trees that were mass-attacked (Table 3), benone. However, near Prince George, and there was no apparent additive or syn- where beetle pressure was much higher ergistic effect of combining the two com- than near Princeton, adding MCH, 2- pounds or ofadding them alone ortogether phenyl ethanol or both together to verbe- to verbenone to protect trees from attack. none did not cause any greater protection Therefore, we conclude that neither com- of pheromone-baited or surrounding trees pound has compelling potential for use as than was achieved by verbenone alone. In an adjuvant to verbenone in operational a similar experiment nonhost volatiles attack disruptionprograms. added to verbenone resuUed in substan- ACKNOWLEDGEMENTS We thank L.J. Chong, P. Dodds and M. Bros. Ltd., International Forest Products Poirier for assistance and Weyerhaeuser Ltd., Lignum Ltd., Manning Diversified Canada Ltd. and Canadian Forest Products Forest Products Ltd., Millar-Western For- Ltd. for access to field sites. 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