McGregor, Mark D.

United States. Forest Service. Northern Region. State & Private Forestry

Undetermined

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USDA FOREST SERVICE/NORTHERN REGIONDIVISION OF STATE & PRIVEWReport No. 73-9		5200April 1973••STATUS OF MOUNTAIN PINE BEETLE, GALLATIN DISTRICT,GALLATIN NATIONAL FOREST, 1973byMark D. McGregor, EntomologistEnvironmental ServicesINTRODUCTION An epidemic infestation of the mountain pine beetle, Dendroctonusponderosae Hopk., was detected by aerial observers during August 1970on the Gallatin Ranger District, Gallatin National Forest (fig. 1).At that time, about 3,800 trees were infested on approximately 2,000acres of mixed ownership which included Burlington Northern Railway,State of Montana, private, and National Forest.A survey by Gallatin National Forest personnel in 1971 showed the numberof infested trees had doubled in 1 year's time.11 This prompted ameeting of resource managers of the intermingled ownerships within theoutbreak area and included Big Sky, Inc., Burlington Northern, MontanaDivision of Forestry, and U.S. Forest Service. At that meeting, controlstrategy was discussed for drainages with major infestation. Alterna-tives for suppression were (1) direct control with ethylene dibromide,(2) fell and burn infested trees, (3) salvage logging, and (4) donothing. Direct control by felling and burning of infested trees wasinitiated on National Forest land during spring 1971. Felling andburning was done in Hellroaring and Logger Creek drainages. Removalof infested trees by logging was done in the Swan Creek campground.Examination of treatment areas in October 1971 (McGregor and Dewey 1971)showed direct control apparently did little to reduce the potentialfor increase in either Hellroaring or Logger Creek drainages.a•1/ 5240 letter dated April 21, 1971, from Maynard T. Rost, TimberStaffman, Gallatin NF, to the Gallatin Forest Supervisor.••4041		 A variable plot cruise (BA = 10) was conducted in four areas. Plotswere located at 5-chain intervals on lines 5 chains apart. A Spiegel-Relaskop was used to determine trees to be tallied in each plot. Each• tree 5 inches d.b.h. and larger occurring in the variable plot wasrecorded by species, measured for diameter at breast height and totalheight. Then trees were classified into one of the following fiveclasses:0 - Green, uninfested.•	 1 - Attacked in 1972; green foliage, brood in cambium.2 - Attacked in 1971; red foliage, brood emerged.3 - Snags; attacked in 1970 or prior, majority of needles dropped.4 - Pitchout; green foliage, pitchtubes, no brood.A 100 percent cruise was conducted in six other infested areas. A total40	 of 558 acres were surveyed. Data were analyzed by a modified salecruise program.RESULTS The coniferous stand surveyed is composed of 68.3 percent lodgepole pine,41		 17.8 percent Douglas-fir, 12.5 percent Engelmann spruce, and 1.2 percentsubalpine fir. Habitat type of the areas sampled is Abies lasiocarpa/Vaccinium scoparium; that of areas 100 percent cruised is Pseudotsugaemenziesii/Symphoricarpos albus. Elevation within the infested arearanges from 5,350 to about 7,000 feet. A breakdown of residual greenstems is shown in table 1.Table 1.--Green stems/acre before and during mountain pine beetle out-break, Gallatin Ranger District, Gallatin National Forest, 1973 Diameter classYear 6 8 10 12 14 16 18+ Total1970 35.6 65.9 100.0 72.5 49.6 25.9 45.5 395.01971 34.9 63.9 92.2 56.8 34.7 19.3 36.2 338.01972 32.7 56.8 80.6 47.6 26.5 14.1 29.7 288.0Tree mortality and volume loss data are shown in tables 2 and 3. Theestimated number of trees killed during 1970-72 was 10,845, with anestimated volume loss of 797,802 board feet of merchantable timber.Approximately 4 percent of the lodgepole pine stand was killed in 1970,5 percent in 1971, and 7 percent in 1972. Average d.b.h. of infestedtrees was 10.7 inches in 1970 and increased to 12.5 inches in 1971-72.Residual green lodgepole pine averaged 8 inches d.b.h. A breakdown ofdead stems/acre by d.b.h. size class is shown in table 4.••-3-cti0 C•1CV inOHulr-I4J0HCO CA tor•-• -4- in H r-1ONH0CA 0)0)b0 C'1 0\ i-i•ri T-:•4 .1' H lin0r-ia)r--I;4 0011a 0 0 in -I-z ON0 4tt	 • 0 0 0 0•W ..p ref m en inZ	 • A-I r.-1 Hc-.4	 -4	 --a	 mr-	 .ON	 H	 e,.1CllisC)0 4 0 0 0Ca	 •aj JD C4 en -a-Z'•H H I--1Cl-0 r-• . •c:en 1-1 H14-100 .0 0 0 0CO	 •0J •O•0 r-0cr,0 0%cr,ID	 4-1OVlevO CIl CflW	 CO N -4- C'..1C..1	 4-1rCO\ in r-r-I CV Cr)	 CV -4"H CV VD CO	 Vj CO•C4- VI	 H 0in %.0 •••7 I--	 0.1' -4' inCr) ON	 ONr,	 CV ‘.0VDI-1 RIN.0ena..4"CV0N.en	 v:,%ID	 0I--r-I.. ^Cr)00 1*--C') 0 n	 H CV(.1 Cr)	 C•)ao•,-1o•oo..-1o	 0,..,1	 u•o	 0	 CVH H H H	 1-4e-i in c0	 .1- 0 a \. • • .H ,-•i tv) CD	 VD 1/40 COCV H H0 0 0• • •0 en el0	 0 I inr-I	 H	 CNIHONHenCOHCV•H	 H•	co IHHcr% ocsiO	 O o o r-• •co	 o• O+ o0-'	 en	 '.00 in VD in cho O	 c0	 O	 Lf-1F-▪ 	 lin	 VDS••••••-4-•••Table 3.--Estimated lodgepole pine volume loss due to mountain pine beetle, Gallatin Ranger District, Gallatin National Forest, • 1970-72 Unit surveyedAcresinfestedVolume loss/acre(board feet)Total volume loss(board feet)1970 1971 1972 1970 1971 1972Upper Portal Cr. 35 54.0 174.0 189.0 1,888 6,102 6,604Cascade Cr. 20 164.0 139.0 408.0 3,289 2,784 8,168Squaw Cr. 45 148.0 193.0 43.0 6,664 8,704 1,949Swan CreekCampground 25 26.0 646Tamphery 40 42.0 66.0 92.0 1,665 2,659 3,698Greek Cr. 30 1,011.0 95.0 30,319 2,855Indian Ridge 58 1,251.0 118.0 1,837.0 72,549 6,860 106,532Hellroaring Cr. 260 302.0 545.0 816.0 78,573 141,719 212,087Logger Cr. 45 564.0 531.0 441.0 25,390 46,178 19,857Total or average 360.7 347.1 438.5 190,018 245,325 362,396Table 4.--Dead stems/acre, Gallatin Ranger District •	 Gallatin National Forest, 1970-72 Diameter classYear 6 8 10 12 14 16 18 Total1970 0.1 0.4 1.4 1.4 1.3 0.6 0.5 5.71971 -- .1 1.0 1.5 1.4 .6 .9 5.51972 .2 7.1 1.1 9.1 8.2 5.1 .6 31.4Total .3 7.6 3.5 12.0 10.9 6.3 2.0 42.6•••••• -5-•• ••••DISCUSSIONLodgepole pine comprises nearly 70 percent of the stand within theareas surveyed. Amman and Baker (1972) found that survival of lodgepolepine to attack by mountain pine beetle was only 37 percent in the lowerelevational zones (5,000 to 7,000 feet). This was because a generationof beetles could be produced in 1 year, while at elevational zones of8,900 feet or higher, more than 1 year was required to complete ageneration and survival of lodgepole pine to attack by the mountainpine beetle was higher. A similar relationship holds for basal areawhich ranged from 32 percent in elevational zones of 5,000 to 7,000feet and 71 percent in elevational zones averaging 8,900 feet (Ammanand Baker 1972). Roe and Amman (1970) stated that stands above the8,000 foot elevation zone could be relatively safe from mountain pinebeetle; also, the risk of losing lodgepole pine to the beetle waslowest in the Abies lasiocarpa/Vaccinium scoparium associations (highelevations), and intermediate in the Pseudotsuga menziesii/Calamagrostisrubescens (low elevations). These survey data show our heaviest infes-tation to be in the Abies lasiocarpa/Vaccinium scoparium habitat type.The number of trees killed by the mountain pine beetle has increasedsteadily since 1970. Ratio of new to old attacks was 1:1 from 1970-71,and 1.4:1 from 1971-72. Approximately 73 percent of the mortalityoccurred in trees 12 inches d.b.h. and larger. It has been shown thatmountain pine beetle strongly favors trees of larger diameters eachyear, as well as over the life of the infestation (Gibson 1943;Hopping and Beall 1948; Cole and Amman 1969), and that trees 12 inchesd.b.h. and larger produce more beetles than they absorb (Cole and Amman1969). This probably accounts for the increase in number of treesattacked from 1970-72.Greatest tree mortality occurred in Hellroaring, Indian Ridge, andLogger Creek areas respectively. A decrease in the number of infestedtrees occurred in Logger Creek from 1971 to 1972, but the number oftrees killed increased significantly in Hellroaring and Indian Ridgeareas.Additional heavy infestation exists on State and private ownershipdirectly north of Logger Creek drainage. Size of area infested andnumber of trees killed is expected to increase on private ownership in1973.All indications point toward an increasing trend during 1973. Numberof infested trees will probably increase, and new infestation can beexpected in uninfested stands.Salvage logging for removal of infested trees would do much to slow theimpetus of the outbreak. A decrease in the number of trees killed isnot expected as long as stands contain significant numbers of lodgepolepine above the 10-inch d.b.h. size class; and as long as stands are over-stocked which results in competition between trees and reduces growth,thus reducing tree vigor and resistance to beetle attack.•-6-REFERENCES CITEDAmman, Gene D., and B. H. Baker, 1972. Mountain pine beetle influenceon lodgepole pine stand structure. Jour. Forestry 70(4).Cole, W. E., and Gene D. Amman, 1969. Mountain pine beetle infestationsin relation to lodgepole pine diameters. USDA Forest Serv., Inter-mountain Forest & Range Exp. Sta., Ogden, Utah, research noteINT-95, 7 pp.III	Gibson, A. L., 1943. Status and effect of a mountain pine beetle infes-tation on lodgepole pine stands. Forest Insect Lab., USDA ForestService, Coeur d'Alene, Idaho, 34 pp.Hopping, G. R., and G. Beall, 1948. The relation of diameter of lodge-pole pine to incidence of attack by the bark beetle, Dendroctonas0	 monticolae Hopk. Forest Chron. 24: 141-145.McGregor, M. D., and J. E. Dewey, 1971. Evaluation of mountain pine411	 beetle infestations on the Gallatin Ranger District, Gallatin NF,Montana. USDA Forest Serv., Division of State and Priv. Forestry,Missoula, Montana, report 71-14.10Roe, A. L., and G. D. Amman, 1970. The mountain pine beetle in lodge-pole pine forests. USDA Forest Serv., Intermountain Forest & RangeExp. Sta., Ogden, Utah, research paper INT-71, 23 pp.••••	 -7-

Status of mountain pine beetle, Gallatin District, Gallatin National Forest, 1973

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Status of mountain pine beetle, Gallatin District, Gallatin National Forest, 1973

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