United States 

Department o 

Agriculture 

Forest 

Service 

Northern

Region 

200 East Broadway 

P.O. Box 7669 

Missoula, MT 59807 

Report 04-8 March 2004

PROTECTING WHITEBARK PINE TREES FROM 

MOUNTAIN PINE BEETLE ATTACK USING VERBENONE 

Sandy Kegley1 and Ken Gibson2

Abstract 

Efficacy of verbenone in protecting individual 

whitebark pine trees from mountain pine beetle 

attack was tested for a second year. Standard 5-

gram verbenone pouches, replaced at midseason, were tested along with new thicker 

membrane (longer lasting) pouches and untreated 

controls. Treating individual whitebark pine 

trees with either two standard or two thicker 

membrane pouches significantly reduced 

mountain pine beetle attacks compared to 

untreated controls. This test provides additional 

evidence that individual pine trees can be 

protected from mountain pine beetle attack using 

verbenone. 

Introduction

Verbenone, (4,5,5-trimethylbicyclo [3.1.1] hept3-en-2-one), a known anti-aggregation 

pheromone of mountain pine beetle (MPB), 

Dendroctonus ponderosae, has been tested in the 

past with inconsistent results in protecting 

1

Forest Health Protection, Coeur d’Alene Field Office 2

Forest Health Protection, Missoula Field Office 

lodgepole and ponderosa pine stands (Amman 

and others 1991, Amman and Lindgren 1995, 

Bentz and others 1989, Gibson and others 1991, 

Shore and others 1991). Recently, a 5-gram

“pouch” formulation, releasing 10 times as much

verbenone as past releasers has been tested in 

lodgepole, whitebark, and ponderosa pine stands 

with promising results (Bentz and others 2004, 

Borden and others 2003, Progar 2003, Kegley 

and others 2003, Gibson and Kegley 2004). 

Our observations during previous tests of the 5-

gram pouch in whitebark pine stands discovered 

new MPB attacks in treated areas late in the 

season. The verbenone pouch label indicates a 

lifespan of 25-40 days, weather dependent. This 

led us to believe that the standard pouch may not

be eluting verbenone throughout the entire MPB 

flight period, especially during years of extended 

above-normal temperatures. Because of this 

potential problem, we have replaced pouches in 

mid-summer to ensure tree protection throughout 

the season. Our objective for this study was to 

compare the effectiveness of a “new” thicker 

membrane (3 ml) pouch, formulated to elute 

verbenone over a longer time period, with the 

standard pouch (1.5 ml), replaced at mid-season. 
Methods 

The test was conducted near Morrell Peak, 

Seeley Lake Ranger District, Lolo National 

Forest, Montana in an area with an active MPB 

population (fig. 1). Our treatments were (1) 

control, no verbenone; (2) two standard 

verbenone pouches per tree, replaced in late July; 

and 3) 2 new (slow-release) pouches per tree, not 

replaced. There were approximately 50 trees in 

each treatment and treated trees were at least 130 

feet apart. Verbenone pouches were stapled to 

whitebark pine trees as high as we could reach 

on the east and west sides of each tree. In 

addition to verbenone pouches, a MPB-attractant 

pheromone (tree bait) was placed approximately 

10-15 feet from each treated tree to assure equal 

beetle pressure. 

Additional verbenone pouches were placed on 

site, stapled to the north side of a tree, collected 

at 2-week intervals, and placed in plastic bags in 

a freezer. At the end of the test, they were sent 

to Phero Tech, Inc. for analysis of verbenone 

content and actual release rate in the field. 

Statistical Analysis 

Numbers of trees with no beetle attack, 

pitchouts, strip attack, and mass attack were 

summarized by treatment. The Pearson Chisquare test was used to test for significant 

differences in the type of MPB attack between 

treatments. Because we have found a 

relationship between tree diameters (d.b.h.) and 

MPB attack in whitebark pine (Kegley and 

others 2003 & 2004), analysis of variance F test 

was used to test for significant differences in tree 

d.b.h. between treatments. 

Figure 1. Verbenone test site near Morrell Peak. 

Results and Discussion

As in the Selkirk Mountain test in 2002 (Kegley 

and others 2003), verbenone successfully 

protected whitebark pines from MPB on Morrell 

Peak. There were significantly more control 

trees mass attacked than in either of the 

verbenone treatments (p<.000) (fig.2). There 

was no significant difference between the 

standard and new pouches for mass attacks, 

pitchouts, or strip attacks. However, there were 

twice as many pitchouts or strip attacks on trees 

treated with the new pouch as there were with 

the standard pouch (table 1). 

2 
August 18. MPB flight period in whitebark pine 

stands has been found to extend well into 

September (Kegley and others 2004). 

This pouch analysis helped validate the 

need to replace standard pouches midseason. The low elution rate of the new 

pouch at higher elevations may not be 

sufficient to protect trees (John Borden, 

Phero Tech, personal communication). 

Higher elution rates for the new pouch 

were found in low-elevation ponderosa 

pine stands, likely due to temperature 

differences (Gibson & Kegley 2004). 

Figure 2. MPB attack by treatment on Morrell Peak.

0%

20%

40%

60%

80%

100%

Control Standard New

Treatment

% Trees

mass attack

strip attack

pitch out

No attack

Table 2. Elution rate and residual verbenone for standard and

new pouch at Morrell Peak, June 11- Sept. 11, 2003 (data from

PheroTech, Inc.) 

Residual Verbenone 

(gms) Date Elution rate (mg/day) 

(placed 

June 11, 2003) Standard

Pouch 

New

Pouch 

Standard

Pouch 

New

Pouch 

23 June 4.46 4.6 16 4 

7 July 4.07 4.46 28 10 

21 July 3.82 4.29 18 12 

5 August 3.16 4.16 44 10 

18 August 2.7 3.85 35 24 

11 September 2.85 3.79 0* 3 

*pouch had ceased eluting verbenone sometime around August 18

Table 1. Mass attacks, strip attacks, and pitchouts by

treatment 

Treatment MPB 

category Control Standard

Pouch New Pouch 

Ave. d.b.h. 13.9 14.9 14.6 

No attack 26 (54%) 41 (85%) 37 (76%) 

Any attack 22 (46%) 7 (15%) 12 (25%) 

Pitch out 1 ( 2%) 2 ( 4%) 3 ( 6%) 

Strip attack 1 ( 2%) 2 ( 4%) 5 (10%) 

Mass attack 20 (42%) 3 ( 6%) 4 ( 8%) 

Total 48 48 49

Conclusion

Verbenone pouches have shown great promise in 

protecting whitebark pines from MPB attack, 

even when using tree baits to attract beetles. 

Operationally, tree baits would not be used and, 

it seems logical to conclude, attacks on treated 

trees would be even less. This treatment would 

be especially useful in protecting high-value, 

blister-rust-resistant whitebark pine. To date, the 

use of two standard, 5-gram verbenone pouches 

per tree, replaced mid-season, has shown the 

most consistent results in protecting individual 

whitebark pines. 

Average d.b.h. of all whitebark pines in this test 

was 14.5 inches. There were no significant 

differences in average d.b.h. of trees in any 

treatment (p=.223) (table 1). 

Pouch analysis showed differences in residual 

verbenone and elution rates between the two 

pouches (John Borden, Phero Tech, personal 

communication) (table 2). The standard pouch 

released a higher amount of verbenone per day, 

but had a shorter elution period than the new 

pouch. It appeared the standard pouch stopped 

releasing verbenone sometime around 

3 
4 

Acknowledgements 

We thank John Schwandt, Gary Kempton, Tim 

Cudmore, and Sandi Bousquit for assistance in 

locating and treating test trees, and data 

collection. Michael Marsden conducted the 

statistical analysis. 

Literature Cited 

Amman, G.D.; Thier, R.W.; Weatherby, J.C.; 

Rasmussen, L.A.; Munson, A.S. 1991. 

Optimum dosage of verbenone to reduce 

infestation of mountain pine beetle in 

lodgepole pine stands of central Idaho. 

Research Paper INT-446. Ogden, UT: 

USDA Forest Service, Intermountain Forest 

and Range Experiment Station. 5p. 

Amman, G.D.; Lindgren, B.S. 1995. 

Semiochemicals for management of 

mountain pine beetle: status of research and 

application. In: Salom and Hobson (eds.), 

Application of semiochemicals for 

management of bark beetle infestationsProceedings of an informal conference. Gen. 

Tech. Report. INT-GTR-381. Ogden, UT: 

USDA Forest Service, Intermountain Forest 

and Range Experiment Station. p 14-22. 

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S.A.; Rasmussen, L.A.; Haneman, D. 1989. 

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attacks in susceptible stands of ponderosae 

pine. Research Note RM-495. Ft. 

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pine stands of western Montana. Research 

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of mountain pine beetle-attacked trees in 

second-growth ponderosa pine. FHP Rpt. 04-

7, USDA Forest Service, Forest Health 

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Kegley, S.J., Gibson, K.E., Schwandt, J., 

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mountain pine beetle attack. FHP Rpt. 03-9, 

USDA Forest Service, Forest Health 

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northern Idaho 2001. FHP Rpt. 04-5, USDA 

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pine. Western Journal of Applied Forestry 

18 (4) 229-232. 

Shore, T.L.; Safranyik, L., Lindgren, B.S.. 1991. 

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18(4):533-541.