Historic, Archive Document

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United States Department of Agriculture

Forest Service

Intermountain Region

Ogden, Utah





Forest Insect and

Disease Conditions

Intermountain Region 1984

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Intermountain Region 1984 Compiled by Andrew Knapp

Forest Pest Management State and Private Forestry USDA Forest Service Intermountain Region 324 25th Street Ogden, Utah 84401

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K. Andrew Knapp


Group Leader Program Manager/ Pesticide Coordinator

Ogden Field Representative

Plant Pathologist Biological Technician

Boise Field Representative Entomologist Entomologist

Plant Pathologist Plant Pathologist Biological Technician

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Subject Page Resume of Conditions................. ee, enon Je MONE (ORS QOCUPE D! 1 ENTOMOLOGY Sere ER CSCC LO ter eon etree eM i ce Geos fe lS ey. sas ahha bo asala a leud wns Woe Fa MES ewes 1 Douglas-fir beetle.............. cna. oReeatteraggn cok eapppermsliees! dct Sree thre Bely ainan aia Semtpal ates es th 2 IC AG SCO oe ae. Weems irr hg oe als oGns 6 50s ee ke a Kl POY OES 2 Shisha. bili ele nalts Gemcytyh gamete) opectonat edeiedaie whee 4 bead ete elegant Sos 6 lee Ele CUCOLLCWOLIN fame SMe eV cS ERIS ce ee ln ne ee Oe 6 Con 2h RETR Ree Gg OE a Se ee rere 12 ee EY are ee eee cick as Slate as es ee BS CE ee ete 12 BRU S ce CLES SSCS TETI OCT Pcs ne RO eR SN a so 7 cae hah a ale es re 12 Ome OMmsecucOnditionS.cetree in aie. amin aac im the Mmetio. Nahe Fowmet, ert - 15 PATHOLOGY Ly Ualacie (Ladi tate SWE ih re Mey a acanarar ih cabherii weer diy denier neta ols. Ear ae Aiur ie ar ae ara rt 17 BOR OL argISC ASC) hen ne yah ea SRE EIA ayes EES ote ek net 17 POROUS IIE ICCUIG CASL ene le ee i ae ee te ee ee eels wl lz Seca nicemaes wmline. (marine Mruietat, Bins PARSONS HOMIE. 6k ee ress 17 Sea ar ES ee me ee Si Gig gd Nh ee we ae nek NO Raa A Shyer eine ee ee ese. ae 17 (onja dalSge. a. hy SE EA a eee eee er 18 ee eect let Cieas Menten Mr tetT tare en Cre re Ee ee ee ee ke a 18 GEN REYSTE! ... BS oe Este bey leone ei acne cir erga gece ect se a ge 18 AanOsussoot disase.s. cmecuay 14 Ine: Waetnmaontha- Mahi Monet be Smee Sia a 18 PPIIATTOMTOOLRCISCASE TNE ee hn ie ne gue ve eke Bo tense aie els ne gee a 19 Beitr re Stat Olea git Miran eh lem eritrecty Wh cee hteee Hie ti fe.V fata erm. OS Acie up - 19 ET MMGMEGISCASG MEST TE a a a tee es ee ee oa 19 Summary of disease conditions ... ee beeen eee tees 20

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Tree mortality caused by mountain pine beetle increased two-fold over 1983 levels, with ap- proximately 3.3 million dying trees recorded. Increases in beetle-killed trees occurred on most forests.

Spruce beetle populations remained at a low level with only scattered pockets of mortality on the Payette, Uinta, Bridger-Teton, Fishlake, and Manti-LaSal National Forests.

Western spruce budworm activity decreased in extent and intensity throughout southern Idaho and Wyoming, but increased in Utah. Approximately 2.3 million acres were infested this year.

Pine butterfly defoliated ponderosa pine on approximately 2,800 acres on the Boise National Forest, a significant decline from 1983 levels.

Conifer defoliation by Douglas-fir tussock moth during 1984 was not observed. However, small pockets of Douglas-fir mortality, resulting from previous defoliation by this insect in the Owyhee Mountains in southern Idaho, were noted.

Incidence of needle casts intensified in localized areas on Douglas-fir, ponderosa pine, and lodgepole pine.

The occurrence of two stem rust fungi on ponderosa pine was notable. Comandra rust was identified on seedlings and saplings in one small area on the Payette National Forest, and limb rust was found on 60- to 70-year-old pines on the Dixie National Forest.

Dwarf mistletoe suppression projects were conducted on 4,637 acres in 1984. Presuppression Surveys were conducted on 192,594 acres to identify incidence and infection severity of this pest.

A severe summer hailstorm caused extensive branch flagging of subalpine fir and lodgepole pine on 7,300 acres near the town of Salmon, Idaho.

Several root diseases and apparent root disease complexes were detected in most conifer species throughout the Region. Among the root disease organisms detected were Fomes an- nosus, Armillaria mellea, Inonotus tomentosus, and Phaeolus schweinitzii.


Mountain Pine Beetle, Dendroctonus ponderosae Hopkins

The Ashley and Wasatch-Cache National Forests in northeastern Utah continued to sustain the largest amount of tree mortality in the Intermountain Region. Mountain pine beetle killed ap- proximately 2.9 million lodgepole and ponderosa pines on the Ashley National Forest and 327,000 lodgepole pines on the Wasatch-Cache National Forest. The infestation on the Wasatch-Cache National Forest will continue to expand into uninfested areas of lodgepole pine. The infestation on the Ashley National Forest is predicted to continue, but most of the susceptible host type is currently infested, and expansion into new areas will not be signifi- cant. Elsewhere in Utah, mountain pine beetle populations in ponderosa pine on the Dixie, Fishlake, and Manti-LaSal National Forests remained relatively inactive. A reduction in moun- tain pine beetle activity in lodgepole pine was noted on the Uinta National Forest.

Mountain pine beetle activity increased in southern Idaho, where approximately 47,000 lodgepole and ponderosa pines were killed. Significant infestations are located near Dead- wood Reservoir and along Clear Creek on the Boise National Forest, along Goose Creek on the Payette National Forest, throughout the Big Wood River drainage on the Sawtooth National Forest, and throughout Caribou Basin on the Caribou National Forest. The Targhee National Forest experienced localized reductions in beetle activity throughout the Centennial Moun- tains; elsewhere on the Targhee National Forest beetle activity increased. On the Challis and Salmon National Forests, small centers of beetle activity are located along the Salmon River between Sunbeam and Clayton and in the Camas Creek drainage respectively.

In Wyoming approximately 30,000 lodgepole pines, a three-fold increase from 1983, were kill- ed on the Bridger-Teton National Forest. The greatest amount of tree mortality is located along the Greys River and throughout the Gros Ventre River drainage.

Specific mortality figures, summarized from aerial detection surveys, are displayed in table 1, and the status of infestations is found in table 2. Locations of major infestations throughout the Region are shown in figure 1.

Douglas-fir Beetle, Dendroctonus pseudotsugae Hopkins

Significant Douglas-fir mortality attributed to the Douglas-fir beetle continued on the Bridger- Teton National Forest in western Wyoming; some 3,100 fading trees on 7,000 acres were iden- tified. Mortality is concentrated along Horse Creek and Little Horse Creek, near Hoback Junc- tion, and along the Buffalo Fork near Blackrock Guard Station.

Douglas-fir beetle activity decreased throughout southern Idaho and Utah. Specific mortality figures, as noted by aerial detection surveys, are found in table 1.

Pine Engraver Beetle, Ips pini (Say)

Pine engraver beetle activity increased slightly over 1983 levels. Fewer than 900 trees were killed Region-wide. Mortality was concentrated in the Boise Basin and Trinity Creek areas of the Boise National Forest and on adjacent state and private lands. Small, localized infestations were also located in Colson Creek, Owl Creek, and near Granite Mountain Lookout on the Salmon National Forest. Specific mortality figures, as noted by aerial detection surveys, are displayed in table 1.

TABLE 1. Number of Trees Killed by Bark Beetles in Region 4 During 1983-84.

Forest Ashley

Boise Bridger- Teton Caribou* Challis* Dixie Fishlake Manti- LaSal Payette Salmon Sawtooth Targhee


Wasatch- Cache”


Mountain Pine

Year Beetle

1984 2894484 1983 1,265,514 1984 14,016 1983 6,442 1984 30,245 1983 11,707 1984 13,200 1983 14,703 1984 1,115 1983 1,190 1984 160 1983 1,228 1984 1983 1984 175 1983 239 1984 2,868 1983 5,880 1984 788 1983 232 1984 2,934 1983 2,260 1984 11,803 1983 6,749 1984 139 1983 1,240 1984 327,539 1983 80,317

1984 3,299,466



Trend Up













Douglas- Fir Beetle


183 351


224 20

257 574

3,720 1,321

Trend Down










603 371

301 354

904 725




Engelmann Spruce Beetle

28 63

328 63

*Only portions of Forest flown; actual mortality figures are probably considerably higher.






TABLE 2. Status of mountain pine beetle infestations by state during 1984.

Land Ownership Class

National Forest Other Federal

State and Private


National Forest Other Federal

State and Private


National Forest Other Federal

State and Private



Outbreak Area (Thousand Acres)

443 0.50



UTAH 470.3 28 6.8


WYOMING 20 2.6



Number of Trees (Thousands)

41.6 0.47



3,158.0 22.2



25.7 3.3



FIGURE 1. Areas infested by mountain pine beetle in Region 4 during 1984.


Spruce Beetle, Dendroctonus rufipennis (Kirby)

Regionwide spruce beetle activity remained at a low level. Infestations declined on the Uinta and Manti-LaSal National Forests, but increased slightly on the Bridger-Teton, Payette, and Fishlake National Forests (table 1).

Western Spruce Budworm, Choristoneura occidentalis Freeman

Western spruce budworm defoliated Douglas-fir, grand fir, and subalpine fir on approximately 2.3. million acres in the Intermountain Region during 1984 (figures 2 and 3). Generally, defolia- tion decreased in extent and intensity in Idaho and Wyoming and increased in extent and in- tensity in Utah. Reductions in defoliation intensity often occurred in areas which have been in- fested for substantial periods. Increases in defoliation intensity and extent usually occurred in areas only recently infested. Infestations increased in size by expanding into contiguous areas; few new isolated infestations were observed.

In southern Idaho reductions in defoliation occurred in older infestations on the Boise, Caribou, Payette, and Targhee National Forests. Acreage of defoliation was dramatically reduc- ed on the Salmon and Challis National Forests, possibly due to adverse climatic conditions. New areas of defoliation were observed on the Sawtooth National Forest and adjacent state land southeast of Burley.

In Utah minor infestation expansions were noted on the Dixie, Fishlake, and Manti-LaSal Na- tional Forests. A small decline in infested acreage was identified on the Wasatch-Cache Na- tional Forest.

Significant decreases in infestation size and intensity occurred on the Bridger-Teton National Forest in western Wyoming.

Acreage infested by forest is displayed in table 3, and the status of infestations is shown in table 4. Locations of major infestations throughout the Region are identified in figure 4.

Defoliation Defoliation Defoliation WML ae WG


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Heavy Moderate Light Defoliation Defoliation Defoliation


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TABLE 3. Areas of defoliation by western Spruce budworm in Region 4 during 1983-1984 as determined by aerial detection surveys.

Defoliation Intensity ae

Forest (and Adjacent Land) Year Light Moderate Heavy Total Change

Boise 1984 290,942 308,422 186,933 786,357 24,655 1983 140,277 290,313 380,421 811,012

Bridger-Teton 1984 149,718 26,746 694 177,158 137,460 1983 188,782 101,910 23,926 314,618

Caribou* 1984 8,875 108,119 28,112 145,106 + 64,946 1983 2,868 27,556 49,736 80,160

Challis* 1984 615 - - 615 87,765 1983 79,262 7,613 1,505 88,380

Dixie 1984 26,124 9,779 9,422 45,325 + 29,524 1983 10,027 5,448 326 15,801

Fishlake 1984 23,108 6,659 2,262 32,029 + 10,478 1983 17,197 3,125 1,229 21,051

Manti-LaSal 1984 38,580 13,569 0 52,149 + 25,062 1983 22,855 4,232 0 27,087

Payette 1984 271,627 133,557 58,592 463,776 5,226 1983 69,684 132,875 266,444 469,002

Salmon 1984 3,768 9,753 1,849 15,370 —262,297 1983 235,040 37,117 5,510 277,667

Sawtooth 1984 102,779 31,042 10,688 144,509 + 55,830 1983 49,191 36,545 2,942 88,679

Targhee 1984 173,444 212,113 91,409 476,966 83,613 1983 64,896 312,858 182,825 560,579

Wasatch-Cache 1984 5,850 2,025 0 7,875 6,255 1983 10,525 3,606 0 14,130

Grand Teton 1984-2, a ce Ed ele ea Not Flown

National Park 1983 3,576 3,687 8,763 16,026

R-4 TOTALS 1984 1,095,430 861,784 390,021 2,347,235 437,454 1983 894,180 966,885 923,627 2,784,692

*Only portions of Forest flown; actual acreage figures are probably considerably higher.

Land Ownership Class

National Forest Other Federal

State and Private


National Forest Other Federal

State and Private


National Forest Other Federal

State and Private


TABLE 4. Status of western spruce budworm by State during 1984.


Outbreak Area (Thousand Acres)

1,910.7 0.3







WYOMING 164.7 125 0.01

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FIGURE 4. Areas defoliated by western spruce budworm in Region 4 during 1984.


Sugar Pine Tortrix, Choristoneura lambertiana (Busck) and Pine Needle Sheathminer, Zelleria haimbachi Busck

On the Targhee National Forest in southeastern Idaho these insects defoliated lodgepole pine on approximately 60,000 acres. Activity was concentrated along the west slope of the Teton Mountains (figure 5). Naturally occurring parasites were actively attacking the two defoliators and should contribute to population collapse. Scattered pockets of defoliation by these pests also occurred on the Boise, Payette, Sawtooth, and Caribou National Forests.

Pine Butterfly, Neophasia menapia (Felder & Felder)

While numerous white butterflies were again conspicuous on the Boise, Payette, and Salmon National Forests, defoliation declined dramatically. Serious ponderosa pine defoliation was identified on 2,800 acres this year compared to 16,000 acres last year. Defoliation occurred near Crown Point on the Boise National Forest (figure 6). Preliminary evaluations conducted in the fall of 1984 indicate population collapse is due to regulatory pressure from predators and parasites.

Douglas-fir Tussock Moth, Orgyia pseudotsugata (McDunnough)

As predicted by evaluations conducted during the fall of 1983, the four-year-old Douglas-fir . tussock moth infestation in the Owyhee Mountains in southwestern Idaho collapsed with no current year defoliation being recorded during aerial surveys. Single tree and group mortality of Douglas-fir apparently resulting from previous activity by the defoliator were identified in | areas which had been moderately to heavily defoliated for at least three consecutive years. Defoliation by this insect was not noted elsewhere in the Region.

Pheromone detection traps were placed on the Boise, Payette, Salmon, and Sawtooth National Forests and State lands around Bellevue, Idaho. Preliminary trap analysis indicates decreased Douglas-fir tussock moth activity throughout southern Idaho.


FIGURE 5. Areas of defoliation by sugar pine tortrix and pine needle sheathminer on the Targhee National Forest during 1984.


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FIGURE 6. Areas defoliated by pine butterfly on the Boise National Forest during 1984.

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Forest insect and Disease Conditions

Intermountain Region

Insect Host Location Remarks

Douglas-fir beetle Douglas-fir Idaho, Group killing of Douglas-fir occurred

Dendroctonus Utah, on the Bridger-Teton, Boise, and

pseudotsugae Hopk. Wyoming Payette NF’s. Activity generally increased with 3,720 trees being killed in 1984.

Douglas-fir tussock Douglas-fir Idaho No current defoliation observed, but

moth Orgyia tree mortality resulting from previous

pseudotsugata defoliation noted.


Larch casebearer Western larch Idaho Infrequent observations noted in

Coleophora laricella 1984.


Mountain pine beetle Lodgepole, Idaho, Mountain pine beetle killed

Dendroctonus ponderosa, Utah, approximately 3.3 million trees in

ponderosae Hopk. and other pines Wyoming 1984. Populations increased on the Boise, Bridger-Teton, Sawtooth, and Targhee NF’s. A major epidemic continues to cause extensive mortality on the Ashley and Wasatch NF’s in northeastern Utah.

Pine butterfly Ponderosa pine Idaho Light to moderate defoliation occurred

Neophasia menapia over 2,800 acres on the Boise NF.

(Felder & Felder) Populations are declining.

Pine engraver Pines Idaho A slight decrease in activity was

beetle /ps pini (Say) noted. Fewer than 1,000 trees were killed on the Boise, Payette, and Salmon NF’s.

Pine needle Lodgepole pine Idaho New infestations of this insect along

sheathminer Zelleria with the sugar pine tortrix were noted

haimbachi Busck defoliating lodgepole pine on over 60,000 acres of the Targhee NF in southeastern Idaho.

Spruce beetle Engelmann Idaho, Localized infestations continue to

cause minimal mortality on the Bridger-Teton, Fishlake, Manti-LaSal, Payette, and Uinta NF’s where 328 trees were killed.

Dendroctonus spruce Utah rufipennis (Kby.)


SUMMARY (Cont.) Forest Insect and Disease Conditions Intermountain Region

Insect Host Location Remarks

Sugar pine tortrix Pines Idaho This insect along with the pine

Choristoneura needle sheathminer defoliated

lambertiana (Busck) lodgepole pine on 60,000 acres of the Targhee NF in southeastern Idaho.

Western pine beetle Ponderosa pine Idaho, Very few trees were killed by this

Dendroctonus Nevada insect.

brevicomis LeConte

Western pineshoot Ponderosa pine Idaho Scattered infestations were noted borer Eucosma throughout southern Idaho. sonomana Kearfott

Western spruce True firs, Idaho, Confiers on approximately 2.3 million budworm, Douglas-fir, Utah, acres were defoliated in 1984. Choristoneura western larch, Wyoming Infestations expanded on the Dixie, occidentalis Free. spruce Fishlake, Manti-LaSal, and Sawtooth

NF’s. Reductions in defoliation occurred on the Boise, Bridger-Teton, Challis, Payette, Salmon, Targhee, and Wasatch-Cache NF’s.

Western tussock Willows, Idaho Activity was insignificant in 1984.

moth, Orgyia vetusta Ceanothus gulosa Hy. Edwards


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Douglas-fir needle cast, Rhabdocline pseudotsugae Syd.

Endemic levels of Doulgas-fir needle cast occurred in Douglas-fir stands throughout southern Idaho. Infection severity increased to moderate levels most noticeably on three Ranger Districts in southern Idaho this year; the Weiser, New Meadows, and McCall Ranger Districts, Payette National Forest.

Elytroderma disease, Elytroderma deformans (Weir) Darker

Ponderosa pine across southwestern Idaho has experienced light to moderate Elytroderma in- fection throughout the 1980’s. Each year, however, infection appears to intensify in a few areas. In 1984 severe infection was noted on the Boise National Forest; east of the Crawford Guard Station, Cascade Ranger District, and along Manhattan Creek, Idaho City Ranger District.

Lodgepole pine needie cast, Lophodermella concolor (Dearn.) Darker

Areas of noticeable infection develop each year throughout southern Idaho forests. In 1984 severe needle discoloration caused by this pest occurred in contiguous, densely stocked lodgepole pine stands around the Stanley area of the Sawtooth National Recreation Area. Moderate amounts of infected foliage were noted on the adjacent Yankee Fork Ranger District, Challis National Forest.

Salt damage

Magnesium chloride, applied to roadways to reduce dust, damaged single leaf pinyon pine and juniper on the Humboldt National Forest. Affected trees showed crown dieback and foliar tip burning. Foliar chloride analysis revealed significantly higher concentrations of this ion in discolored foliage than in undiscolored foliage.

Comandra blister rust, Cronartium comandrae Pk.

This stem rust is often found infecting lodgepole pine of all sizes in southcentral and southeastern Idaho, northern Utah, and western Wyoming forests. It was identified in 1984 on ponderosa pine seedlings and saplings in the Seid Creek area of the Weiser Ranger District, Payette National Forest. Infections resulted in top, branch, and entire-tree mortality.

Dutch elm disease, Ceratocystis ulmi (Buisman) C. Moreau

Forty-two disease-infected trees were identified in Boise, Idaho. This is a significant increase over the annual average of 6 trees. The increase is attributed to a build-up of the fungus vec- tor, elm bark beetle, in elm wood debris created during severe summer windstorms.


Limb rust, Peridermium filamentosum Pk.

Concentrations of limb rust infections on ponderosa pine were identified in a 60- to 70-year-old stand on the Aquarius Plateau, Dixie National Forest. Foresters are concerned about the im- pact of this disease in immature stands. Studies and surveys are being initiated to determine the rust’s distribution and impact.

Dwarf mistletoes, Arceuthobium spp.

More Ranger Districts each year are developing long range plans for dwarf mistletoe suppres- sion. Primary interest is in protecting partially or fully regenerated stands which are threatened by the parasitic plants. Information gathering for presuppression surveys, suppression projects, and post-suppression reviews was conducted on eleven National Forests. Accomplishments are reported in table 5.

TABLE 5. Acres of presuppression surveys and suppression projects conducted in 1984.

Presuppression Suppression Post-Suppression National Forest Survey Acres Project Acres Review Acres Ashley 596 160 386 Boise 60,200 1,402 54 Bridger-Teton 1,540 270 0 Caribou 6,300 170 170 Dixie 92 500 362 Payette 19,912 279 ) 177 Salmon 35,300 29 40 Sawtooth 0 27 27 Targhee 54,824 1,540 0 Toiyabe 130 260 82 Wasatch 13,700 0 100 TOTAL 192,594 4,637 1,398

Hail damage

Hailstones caused extensive branch wounding and flagging to sapling- and pole-sized subalpine fir and lodgepole pine over 7,300 acres in the Fenster Creek area northwest of Salmon, Idaho. Field evaluations revealed no mortality due to the storm.

Annosus root disease, Fomes annosus (Fr.) Cke.

This fungus frequently becomes established in new areas by invading freshly exposed stumps. This year, FE annosus was found killing ponderosa pine, lodgepole pine, Douglas-fir, white fir, grand fir, and subalpine fir in several new locations. Ponderosa pine seedling and sapling mor- tality was found near Ola Summit on the Emmett Ranger District, and Pine Gulch on the Mountain Home Ranger District, Boise National Forest; and in the East Branch Weiser River drainage on the New Meadows Ranger District, Payette National Forest. Mortality of lodgepole pine saplings and subalpine fir saplings and poles was also found within the East Branch


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Weiser River drainage on the New Meadows Ranger District. Douglas-fir sapling mortality was found near Moorehead Flat on the New Meadows Ranger District; white fir mortality was detected in a campground on the Spanish Fork Ranger District, Uinta National Forest; and grand fir sapling and pole mortality was found along the Round-up Creek road on the New Meadows Ranger District.

Armillaria root disease, Armillaria mellea (Vahi. ex Fr.) Quel.

Armillaria mellea appears to be a weak parasite in southern Idaho forests where it is occa- sionally associated with small areas of mortality in various conifer species. One small ponderosa pine mortality center involving five-to-ten dwarf mistletoe-infected saplings and poles was detected near Ola Summit on the Emmett Ranger District, Boise National Forest. In Utah this fungus was found associated with mountain pine beetle activity in lodgepole pine.

Red-brown butt rot, Phaeolus schweinitzii (Fr.) Pat.

Old growth Douglas-fir in southern Idaho is commonly infected by the red-brown butt rot fungus. The fungus is often associated with other root pathogens, primarily Inonotus tomen- tosus. Detection is based primarily on occurrence of the dark-brown sporophores found at the base of infected trees; occasionally, decay is detected in windthrown trees or in stumps re- maining after harvest.

Extensive amounts of decay were found throughout mature to overmature Douglas-fir stands in the Beaver Creek drainage on the Cobalt Ranger District, Salmon National Forest. Douglas-fir beetle was frequently associated with mortality of severely decayed trees. Decay incidence was also noted in the Round-up Creek drainage on the New Meadows Ranger District, Payette National Forest; and in McGarry Canyon and Picnic Hollow areas on the Dubois Ranger District, Targhee National Forest. .

Tomentosus root disease, Inonotus tomentosus (Fr.) Gilb.

Windthrow and mortality caused by this fungus was found with increasing frequency in Engelmann and blue spruce stands on the Dixie National Forest. The disease appears to be widespread in spruce stands on the Aquarius Plateau which regenerated following a spruce beetle epidemic 60 to 70 years ago. Infection may also be affecting growth and predisposing spruce to bark beetle attack. A demonstration area was established in Peterson Grove on the Dixie National Forest to show effects of different treatments on spread of the disease.

The fungus is frequently detected in roots of windthrown or dozer uprooted Douglas-fir in southern Idaho and occasionally in subalpine fir in southwestern Idaho.



Annosus root disease Fomes annosus (Fr.) Cke.

Armillaria root disease

Armillaria mellea (Vahl. ex Fr.) Quel.

Aspen trunk rot Phellinus tremulae (Bond) Bond & Boriss

Comandra rust Cronartium comanarae Pk.

Cytospora canker Cytospora chrysosperma Pers. ex Fr.

Dasyscypha canker Dasyscypha sp.

Dothistroma needle blight Dothistroma pini Hulb.

Douglas-fir needle cast Rhabdocline pseudotsugae Syd.

Dutch elm disease Ceratocystis ulmi (Buism.) C. Mor.


Forest Insect and Disease Conditions

Intermountain Region


Ponderosa pine, lodgepole pine, Douglas-fir, true firs

Douglas-fir, grand fir, ponderosa pine, lodgepole pine


Lodgepole pine, ponderosa pine


Ponderosa pine, lodgepole pine

Ponderosa pine


American elm


Idaho, Utah, Wyoming

Idaho, Utah, Wyoming

Idaho, Utah, Wyoming, Nevada

Idaho, Utah, Wyoming

Idaho, Utah, Wyoming




Idaho, Utah



Detection of F annosus infections in- creased throughout the Region. Infec- tion often results in mortality of young pines and Douglas-fir and in butt rot of true firs.

Identified killing five to ten ponderosa pine saplings on the Boise NF. Also found on roots of mountain pine beetle-killed lodgepole pine on the Wasatch and Bridger-Teton NF’s.

Decay is prevalent on the Sawtooth NF; also detected in most aspen stands throughout the Region.

Causes topkill of lodgepole pine in southeastern Idaho, northern Utah, and western Wyoming. Infections on ponderosa pine regeneration on the Payette NF were detected.

Common on aspen throughout its range. Causes mortality of branches, main stems and entire trees, par- ticularly those previously infected with Marssonina blight.

Scattered incidence in southern Idaho on sapling-sized pine, par- ticularly those being damaged by snow.

Noted in only one area in southern Idaho: the confluence of the Middle Fork Weiser River and Lightning Creek.

Moderate to severe infection levels on the Weiser, New Meadows, and

~ McCall RD’s, Payette NF. Endemic in-

fection levels elsewhere in southern Idaho.

Increased infection and subsequent mortality detected in and around Boise, Idaho. Forty-two infected trees died.

eae eee


Dwarf mistletoes

Arceuthobium spp.

Elylroderma disease

Elytroderma deformans (Weir) Darker

Fir broom rust Melampsorella




Lophodermium spp.

Hail damage

Indian paint fungus


tinctorium (E. & E.)

ee =,

Lodg2pole pine needle cast Lophodermella

concolor (Dearn.)


Limb rust Peridermium filamentosum Pk.

Marssonina blight Marssonina populi

(Lib.) Magn.

Meria needle

disease Meria laricis



Douglas fir, ponderosa pine, lodgepole pine, western larch, Jeffrey pine

Ponderosa pine

Subalpine fir

Ponderosa pine

Subailpine fir, lodgepole pine

Grand fir, white fir

Lodgepole pine

Ponderosa pine


Western larch


Idaho, Utah, Wyoming, Nevada







Idaho, Nevada



Idaho, Utah, Wyoming




Continued to be the most widespread and frequently observed pests in the Intermountain Region. Suppression projects removed infected overstory trees from 4,637 acres on ten National Forests.

Occurrence is coextensive with host distribution in southwestern Idaho. High levels of infection were noted east of Crawford Guard Station on the Cascade RD, and along Manhattan Creek on the Idaho City RD, Boise NF.

Infections occur scattered throughout the host type; but very high infection levels occur in some areas including the Cassia Division of the Sawtooth NF.

Scattered incidence on pole-sized and larger ponderosa pine on the Boise and Payette NF’s.

Over 7,300 acres of branch flagging resulted from an early August hail storm in the Fenster Creek area northwest of Salmon, Idaho.

Common in old growth stands of true fir.

Moderate to heavy infection was noted around the Stanley, Idaho, area of the Sawtooth Nat. Rec. Area and on the Challis NF. Infection was of incidental occurrence elsewhere.

High infection frequency was noted in stands on the Dixie NF.

Scattered incidence of light to moderate infection intensity was noted throughout host type, with the exception of heavy defoliation of some clones in Utah.

Incidence and severity of infection on the Boise and Payette NF’s appear to be increasing after several years of very low incidence. The most notable occur- rence was in pole-sized stands on the east face of West Mtn. (Cascade RD, Boise NF) where a combination of fac- tors including frost, budworm, and Meria laricis caused severe foliage discoloration.


Needle rust of fir Pucciniastrum spp.

Needle rust of pinyon pine Coleosporium crowellii Cumm.

Red-brown butt rot Phaeolus schweinitzii

(Fr.) Pat.

Red ring rot Phellinus pini (Thore:

Fr.) Pilat.

Salt damage

Spruce broom rust Chrysomyxa arcostaphyli Diet.

Stalactiform rust


coleosporioides Arth. f. coleosporioides

Subalpine fir needle cast Lirula sp.

Tomentosus root disease /nonotus tomentosus (Fr.) Gilb.

Western gall rust Endocronartium harknessii (J. P. Moore) Hirat.

Western pine aster rust Coleosporium asierum (Diet.) Syd.


True firs

Pinyon pine

Douglas-fir, ponderosa pine

True firs, pines, spruce, Douglas-fir, western larch

Pinyon pine, juniper

Engelmann spruce

Lodgepole pine

Subalpine fir

Subalpine fir, Douglas-fir, spruce

Lodgepole pine, ponderosa pine

Lodgepole pine





Idaho, Utah, Wyoming


Idaho, Utah, Wyoming

Idaho, Utah, Wyoming


Idaho, Utah

Idaho, Utah, Wyoming




Infection remained at light levels on firs in southwestern Idaho.

Severe infection of pinyon pine by this pest was observed in House Canyon on the Toiyabe NF.

Decay is common throughout forests of southern Idaho, especially in trees over 200 years old. This fungus is often found associated with other root pathogens and bark beetles.

Usually found in butts and stems of infected hosts in Idaho. Found on spruce in southern Utah and lodgepole pine in western Wyoming.

Use of dust abatement salt, magnesium chloride, caused foliar tip burn and crown dieback on the Humboldt NF.

Scattered throughout host type.

Occasional! localized occurrence throughout the host type in southern Idaho, northern Utah, and western Wyoming.

Pockets of infected trees scattered along the North Fork of the Payette River, Payette NF.

Decay is often found in southern Idaho, frequently in conjunction with Phaeolus schweinitzii in windthrown Douglas-fir. It was associated with decline and windthrow of subalpine fir on the Dubois RD, Targhee NF. Infection of blue and Engelmann spruce on the Dixie NF results in group mortality and windthrow.

Occurs throughout host types where infection incidence varies from very light to very heavy.

Occasional infections were noted throughout the host type.


Beveridge, R. L., and D. B. Cahill. 1984. Western spruce budworm feeding effects on conifers located on the Boise and Payette National Forests. USDA Forest Service, INT Region, FPM Report 84-7, 25 p.

Beveridge, R. L., and K. A. Knapp. 1984. Detection and dissemination of forest pest data in the Intermountain Region utilizing aerial detection surveys and computer mapping systems. USDA Forest Service, INT Region, FPM Report 84-8, 19 p.

Cahill, D. B., K. A. Knapp, and R. L. Livingston. 1984. Western spruce budworm activity during 1983 and predicted activity for 1984 on the Boise and Payette National Forests and adja- cent forest lands. USDA Forest Service, INT Region, FPM Report 84-5, 10 p.

Holland, David G. 1984. Biological evaluation to assess mountain pine beetle activity in Stand 16, Compartment 44 on the Flaming Gorge Ranger District, Ashley NF—1983. USDA Forest Service, INT Region, FPM Report 84-1, 5 p.

Hoffman, J. T., and Hobbs, E. L. 1984. Lodgepole pine dwarf mistletoe in the Intermountain Region. USDA Forest Service, INT Region. Plant Disease 69: In press.

Marshall, J. P. 1984. Evaluation of vegetation damage along Nevada highways in the lake Tahoe Basin. USDA Forest Service, INT Region, FPM Report 84-3, 15 p.

Reardon, R., D. B. Cahill, and R. W. Thier. 1984. Implication and injection of systemic chemical insecticides in Douglas-fir in Idaho to increase seed yield. USDA Forest Service, INT Region, FPM Report 84-6, 9 p.

Thier, R. W., and P. J. Mocettini. 1984. Douglas-fir tussock moth monitoring in