Over 10,000 acres of aerially visible western hemlock looper defoliation on grand fir was detected on State and Federal forests of central Idaho in 1972. This is the first report of this insect building up
in Region 1 since a widespread outbreak in 1937-39.
The western hemlock looper has the potential of being one of the most destructive forest insects in North America. It can cause tree mortality in 1 or 2 years of feeding. Extensive tree mortality has
been associated with nearly all past outbreaks.
Outbreaks usually persist for about 3 years at epidemic levels prior to collapsing from natural control agents. Insecticides have been effective in protecting large stands during some looper infestations

Ciesla, William M.

Dewey, Jerald E.

Lood, Rudolph C.

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

Undetermined

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• REPORT NO. 72-10 NOVEMBER 1972•SD144• .M9A3no. 72-10•STATUS OF THEstern Hemlock LooperIN THE NORTHERN REGION 1972 \(A Potentially Devastating Forest Pest)• •U. S. DEPARTMENT OF AGRICULTUREDIVISION OF STATE AND PRIVATE FORESTRY/FOREST SERVICENORTHERN REGION•	 MISSOULA, MONTANA 59801•0•••••Cover photo: Western hemlock looper defoliated tree with subsequentlarval webbing. (Photo taken from Evenden 1938.)•400•• •STATUS OF THE WESTERN HEMLOCK LOOPERIN THE NORTHERN REGION--1971byJerald E. Dewey, William M. Ciesla,-1-/and Rudolph C. LoodForest Insect and Disease BranchABSTRACT Over 10,000 acres of aerially visible western hemlock looper defoliationon grand fir was detected on State and Federal forests of centralIdaho in 1972. This is the first report of this insect building upin Region 1 since a widespread outbreak in 1937-39.The western hemlock looper has the potential of being one of themost destructive forest insects in North America. It can cause treemortality in 1 or 2 years of feeding. Extensive tree mortality hasbeen associated with nearly all past outbreaks.Outbreaks usually persist for about 3 years at epidemic levels priorto collapsing from natural control agents. Insecticides have beeneffective in protecting large stands during some looper infestations.INTRODUCTION The western hemlock looper, Lambdina fiscellaria Zugubrosa Hulst, wasdetected defoliating true firs at several locations in the Clearwaterand St. Joe National Forests in 1972. A total of 10,140 acres ofaerially visible defoliation was mapped in late August (Fig. 1).This is the first report of this insect causing noticeable defoliationin Region 1 since 1938.The western hemlock looper has the potential to be one of the mostdamaging of the forest insect pests in North America, having thereputation of a "real tree killer." Infestations have been reportedin the Pacific Northwest since the late 1800's. An infestation inOregon from 1919 to 1921 is reported to have killed 500 million boardfeet of fir and hemlock on 22,000 acres (Keen 1930).Another infestation on 50,000 acres in Washington killed 200 millionboard feet of timber from 1929 to 1932. Certain portions of thisinfestation were aerially treated with a calcium arsenate dust. Thiscontrol measure was attributed to have saved an additional 90 millionboard feet from destruction (Furniss 1945).1/ Entomologists411	 2/ Biological Technician (Insects)aloC0.1-CO.,-1--04-a)"0S-O) vlo_i-o V)o w, ceO...1L U.-U0 CCr--• LUE 1—(1) •:4C..0 3CeC cr5- UJal _14-wNCU CIZQ4-O w0(/) c'DCOC1)	 •L I–1 w• .01-- 4-)0) CS- 0=0)•r-Li-••0The last hemlock looper infestation reported in Region 1 lasted for3 years, 1937 through 1939. Fifty-six centers of severe defoliationwere identified on eight National Forests in northern Idaho andwestern Montana, plus another in Glacier National Park. Greatestdamage was done on the St. Joe, Coeur d'Alene, and Clearwater NationalForests. Though precise acreages were not determined, it was said tohave covered several hundred thousand acres. Losses were reportedto be up to 60 percent of the stems in the more severely defoliatedstands (Evenden 1944). Evenden (1938) reported that in many forestedareas of northern Idaho and western Montana, the "fir and inter-mingled tree species began to turn brown as though scorched by fire."In the fall of 1937 the moths were so numerous on portions of theSt. Joe National Forest that "in some areas the ground was actuallywhite with their dead bodies, and small streams were even cloggedand dammed (Fig. 2). A very disagreeable odor from the decayingbodies prevailed along the creek bottoms." All but spring water wasrendered unfit to drink.•0Figure 2.--Small stream dammedwith dead adult moths,St. Joe National Forest, 1937.(Photo taken from Evenden1938)In 1944, an infestation in Oregon killed approximately 40 millionboard feet outright and affected a great deal more by partialdefoliation (Furniss 1945).•	 The last major western hemlock looper infestation in the United Stateswas from 1961 to 1964 in Oregon and Washington. It covered an area of••or0-3-•S	 about 70,000 acres. Chemical control was applied to 55,000 acres.Tree recovery was good in areas of good control, but tree mortality1	 existed in areas where looper control was poor (Buffam 1964).LIFE HISTORY AND HABITS Eggs.--The eggs are smaller than the head of a pin and laid individu-ally on the needles, branches, trunks, and in the moss on the trees(Fig. 3). They are of a gray-green iridescent color (Keen 1931).The eggs are deposited in the fall and remain unhatched throughoutthe winter. Hatching occurs in May and June.SSFigure 3.--Western hemlock looper egg.(Photo courtesy of Region 6, USFS,Portland, Oregon.)Larvae.--Mature larvae are about 111 inches long and of the typicalinch worm appearance (Fig. 4). They are green to brown in color withdiamond-shaped markings on their backs. Larval development is com-pleted near the end of August. They then spin from the tree upon asilken web to a sheltered location near the base of the tree on theground to pupate. In areas of looper epidemics "these silken websmay become so abundant that the whole forest looks and feels like onebig cobweb" (Keen 1952).-4-••Figure 4.--Western hemlock looper larva. (Photocourtesy of Region 6, USFS, Portland, Oregon.)Pupae.--The pupae are a mottled tan in color and about one-half inchlong (Fig. 5). Favorite pupation sites include crevises in the bark,411	 cracks in stumps and logs, and in the litter layer. The pupal periodlasts for about 2 weeks.Adults.--The moths emerge from early September to October. Keen(1952) states that moths "during an epidemic are so abundant as togive the impression of a snowstorm in the woods." They are tancolored with two dark wavy lines on the forewing and one on the hindwing (Fig. 6). The wingspread is about 11  inches. The sexes arequite similar with the male having bipectinate (comblike) antennaewhile the female's are filiform (threadlike).Some moths may be observed as late as November, but most egg layingoccurs from mid-September to mid-October. The adults of the westernhemlock looper do not overwinter, so any similar appearing mothsobserved in spring or early summer are of a different species(Furniss 1945).S•-5-••4•Figure 5.--Western hemlocklooper pupa.le• Figure 6.--Adult westernhemlock looper (male).0JO• -6-•IPr• HOSTS AND DAMAGE The true firs (grand and subalpine) are the preferred hosts of thewestern hemlock looper in Region 1, but during epidemics associatedspecies (Douglas-fir, Engelmann spruce, hemlock, white pine, andlarch) are also attacked (Evenden 1938). The young larvae feedconsiderably on such shrubs as huckleberry, salmonberry, and devilsclub defoliating them quite severely before migrating to coniferousspecies (Furniss 1945).Most larval feeding is at the base of the needle, so the needle is.cut off and falls to the ground. This destroys much more foliagethan is actually eaten. Both old and new foliage is fed upon. Asthe caterpillar grows, it feeds on buds and tender shoots. Thisexplains why defoliation by this insect can cause such extensivetree mortality in such a short period of time (Keen 1930). Carolinet al. (1964) reported that "one year's heavy feeding by the western•	 hemlock looper can cause tree mortality on western hemlock."The most severe damage usually occurs in extensive stands of old-growth trees. Stands under 50 to 60 years of age are relatively41		 unsusceptible to looper damage (Anon. 1968). Heavy damage usuallyoccurs for about 3 years before the outbreak is controlled by natural•	 agents.NATURAL CONTROL Natural control of an insect outbreak is a result of such things as:•	 1. Predators2. Parasites3. Disease4. Competition5. Climatic conditionsPredators and parasites have been found associated with all past infes-tations, but never credited entirely with the collapse of the outbreak.At least four parasitic insects have been reared from looper pupaecollected in 1972. These are unidentified to date. Evenden (1938)indicated that large numbers of a dipterous parasite (Phyrnalydellan. sp.) and a hymenopterous parasite (Itoplectis montana Cush.) were•	involved in the 1937-39 infestation.Buffam (1964) states that a virus disease is mainly responsible forcontrolling outbreaks. Generally, it takes several years for naturalagents (predators, parasites, and diseases) to build up to a sufficientlevel to control an outbreak.High larval mortality often exists from a shortage of food, especiallyin areas severely defoliated the preceding season.•• -7-•ve•Unfavorable climatic conditions can strongly influence survival ofthe western hamlock looper. Keen (1952) says heavy rains during theflight period (September and October) reduce egg laying and hastenthe decline of the epidemic.There are no known proven silvicultural control methods for preventingor controlling outbreaks.CHEMICAL CONTROL Past looper infestations have been considered successfully controlledwith the use of such materials as lead arsenate, calcium arsenate,and DDT. All of these insecticides are no longer available forlooper control because of the undesirable side effects experiencedwith their use.The only currently registered insecticide for western hemlock loopercontrol is malathion applied as an ultra-low volume concentration(95 percent ULV), undiluted, at the rate of 8 fluid ounces per acre.This formulation is applied aerially. Chemical spraying must coincidewith the larval stage (late June to early August) to be effective.DISCUSSION AND RECOMMENDATIONS With so little history of this insect's activity in Region 1, it isdifficult to predict its future. However, from the records of the1937-39 infestation and others in Oregon and Washington, it appearslikely that we are in the early stages of an outbreak. Carolinet al. (1964) indicated that "by the time hemlock looper damage isvisible from the air, an outbreak is usually well underway."Looper infestations have been evaluated by using the overwinteringegg populations to predict the following season's defoliation. Thisis a very laborious evaluation that is not always reliable.From the information currently available, it is premature to plan forsuppression at this time. However, because of the potential destruc-tiveness of this insect, it is recommended that it be given closeconsideration. Men on the ground should be alert to abnormal numbersof the moths in forested areas from September through November. Alsoareas with firs showing defoliation away from centers of spruce bud-worm activity should be reported. These areas will probably alsoshow defoliation on the brush species, especially huckleberry, ifexamined prior to leaf fall.•4S10•-8-REFERENCES CITED Anonymous, 1968. The western hemlock looper, Lambdina fiscellariaZugubrosa Hulst. USDA, Forest Service, Region 6, Portland,Oregon 97208, unpublished report.Buffam, Paul E., 1964. Results of the entomological aspects of the1963 western hemlock looper control project in southwestWashington. USDA, Forest Service, Division of Timber Management,Region 6, Portland, Oregon 97208, unpublished report.41	 Carolin, V. M., N. E. Johnson, P. E. Buffam, and D. McComb, 1964.Sampling egg populations of the western hemlock looper in coastalforests. USDA, Forest Service, Pacific Northwest Forest andRange Experiment Station, Portland, Oregon 97208, research paperPNW-14.41	 Evenden, James C., 1938. EZZopia infestations within the InlandEmpire, 1937. USDA, Forest Service, Forest Insect Laboratory,Coeur d'Alene, Idaho 83814, unpublished report.416,	 Evenden, James C., 1944. Letter from Evenden to Dr. P. N. Ammand.Furniss, R. L., 1945. The western hemlock looper in Clatsop County,Oregon, in 1944. USDA, Forest Service, Forest Insect Laboratory,Portland, Oregon 97208, unpublished report.Keen, F. P., 1930. Report of an outbreak of the hemlock looper inPacific County, Washington, 1930. USDA, Forest Service, Bureauof Entomology, Portland, Oregon 97208.Keen, F. P., 1931. Report of the hemlock looper outbreak in SouthwestWashington and its control through airplane dusting. USDA,Bureau of Entomology, Portland, Oregon 97208, unpublished report.41	 Keen, F. P., 1952. Insect enemies of western forests. USDA Miscel-laneous Publication 273, p. 99.•• -9-•PESTICIDES PRECAUTION STATEMENTPesticides used improperly can be injurious to man, animals, andplants. Follow the directions and heed all precautions on the labels.Store pesticides in original containers under lock and key -- outof the reach of children and animals -- and away from food and feed.Apply pesticides so that they do not endanger humans, livestock,lb	 crops, beneficial insects, fish, and wildlife. Do not apply pesti-cides when there is danger of drift, when honey bees or otherpollinating insects are visiting plants, or in ways that may contam-inate water or leave illegal residues.Avoid prolonged inhalation of pesticide sprays or dusts; wear protec-tive clothing and equipment if specified on the container.If your hands become contaminated with a pesticide, do not eat ordrink until you have washed. In case a pesticide is swallowed or4	 gets in the eyes, follow the first aid treatment given on the label,and get prompt medical attention. If a pesticide is spilled on your• skin or clothing, remove clothing immediately and wash skin thoroughly.Do not clean spray equipment or dump excess spray material nearponds, streams, or wells. Because it is difficult to remove alltraces of herbicides from equipment, do not use the same equipmentfor insecticides or fungicides that you use for herbicides.Dispose of empty pesticide containers promptly. Have them buried ata sanitary land-fill dump, or crush and bury them in a level, isolatedplace.NOTE: Some States have restrictions on the use of certain pesticides.Check your , State and local regulations. Also, because registrationsof pesticides are under constant review by the U.S. Department ofAgriculture, consult your county agricultural agent or State Extensionspecialist to be sure the intended use is still registered.•KPLLOw not LASEL.111, ..... MAINFI.WWM

Status of the western hemlock looper in the northern region, 1972

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Status of the western hemlock looper in the northern region, 1972

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