Sugden, B. A.

English

Journal of the Entomological Society of British Columbia

E N TOMOLOG ICAL SOCIETY Of BRITISH COL UMBIA, PROC. (1 957), VOL. 54, DEC. 16, 1957 37 A BRIEF HISTORY OF OUTBREAKS OF THE DOUGLAS-FIR TUSSOCK MOTH, HEMEROCAMPA PSEUDOTSUGATA McD., IN BRITISH COLUMBIA! B. A. S UGDEN2 The Doug la s-fir t ussock moth \\'a s fir s t r eport ed defoliatin g Doug la s fir , Psel/(!o/silga lIIe!lziesii PIi rb .) Fra nco, near Cha se in 1916. In 1921 th e type :-;pecimens " 'ere obtained f rom thi s loca li ty and described by l\I cDunn01.l g h a s a new species, H emerocalllpa pselldot -sllga/a. Prior to this th e species wa s r eferred to a s Helllerocampa veINs/a fo rm gll/osa Hy. Ed \\". Since 1916 out breaks have rec urred at inte rval s in Briti sh Columbi a, usually in se mi -arid Doug las fir o r Doug la s -fir - ponderosa-pine fores ts. SeYe re infesta tion ha s r e-sulted in top killing o r comple te tree mo rta lity. The foll ow ing note s on o utbrea k s of Dougla s-fir tu ssock m oth w ere compiled from th e fil es of the F o rest Biology Labol-ato ry at Vernon. HISTORY OF OUTBREAKS 1916-The Douglas-fir tus sock moth was ca using some damage to Dougla s fir g rowing in and near Cha se3. 1917- A small bllt senre infestation occurred at Hedley. The tussock mo th contin-used to kill Douglas fir and some pond e rosa pi ne trees in the vicinity of Ch"se3. 191 5- The Dougla s-fir tu ssoc k mo th r emain-ed ac tive near Chase and H ed ley; a lso minor outbreaks were r epor ted at Salmon Arm and Armstrong. 1919- Infestation s continued at Chase and Armstrong with new outbr l!aks at Vernon and Kamloo ps. D efoliation of Douglas fir was seve re; th '! pond erosa pine fo liage was damaged where the preferred L~ost, fir, had been complete-ly defoliated. 1920-The in sect r emained active between Vernon and K elowna and in the marg-inal fir stands in the vicinity of K am -loops. A population declin e occurred in th e other infestations. I. Contribution Ko. 401, Fores t Biology Division, Science Service, Department of Agriculture, Ottawa, Can ada. 2. Forest Biology Laboratory, Vernon, n.c. 3. The Agricultural Gazette of Canada, Vol. 6, No. 2, February, 19/9. Notes on the Tussock Moth, Hemerocampa vetus t a gulosa Ity Edw., by ,V. B. Anderson. 1921- InieQat ions re lllained ac t ive froll1 Chase II-es t to Kamloo ps and frolll Y em on south t.) Kelmnla. E ntirely defolia ted trees had d ied; reprod uction, sapl ings, and pole-sized Dougla s n.r trees suffered t he hi ghes t mortality. H ea"y defc liation o f the mature o r semi-m ature fil oft en r es ulted in th e death o f th e upp er third of the crmnl. 1922- A Iarg-e POl:ulation ha tched in th e spring, but th e la rvae died b :: fo re ma-turing, thu s bringin g the i:.1festati oll t o a n abrupt end . 1928-No furth er act i\'ity was de scribed until 1928 wh en (\\ -0 in f es tations developed, one nea r h amloo ps a nd the other nea r \ ·e rn o n. These outbreaks \\'e re in Douglas fi r g ro\\'in g adjacent to ranch buildings . 1929- 0uthreaks \\'e re r epo rted from Chase, Little Shus\\-ap L ake, Cascade, and K eltle Valley district s. Greatest dam-age occurred in Sullivan Valley wh ere youn g Dougla s fi r and ponderosa pine tre es on 100 ac res \\'ere ki ll ed. 1930-The Douglas -fir tu ssoc k moth out -breaks relna in ed active. They ranged in size from less than an ~.c r e to 1,000 acres. Report s indicated thelt there was damage near Chase. Grand F ork s, h e tti e Vall ey, south from Ad ams Lake to Squilax, between H ay-wood 's Corn e r and Deep Creek, North Thompso n Valley in th e vicinity of l\·kLure and Sullivan Creek, a long Paul Lake road bord ering Niskonlith Fores t Rese rve, in the marginal Doug-las n I' south of the South Thompso n River a li(I in the nx District north-eas t o f Vern on. 193 1- The in festa ti ons reported durin g 1930 persisted an([ man y increased in size. Also, la rvae were noted defoli a ting Dougla s fir nea r Okanagan Landing. 1932-The po pulati on subsided throughout th e areas of in festat ion. 1936-After an int er"al of four years, small outbreaks occurred in Douglas-fir tree s nea r farm buildings in the Arm-strong and Sa lmon Arm districts . 1937- Addition a l outbr eaks appeared in g roups of Douglas-fi r trees ;lbout farm buildings n ea r Armstrong. Small in-festa tions occurred a t Vernon . 1938-The infes tati ons a t Vernon and Arm-strong increased a litt le in extent but no new outbreaks were reported. 38 ENTOMOLOGICAL SOCIETY OF BRITISH COLUMBIA. PROC. (1957). VOL. 54. DEC. 16. 1957 CHASE. CACHE. CREE.K KAMLOOPS ARMSTRONG ASHCROFT MONTE LAKE VERNON HEDLEY OLALLA CASCADE -~ -M ::!HI 1916 20 24 SEVERE INFE.STATION -~ -28 32 • I2J 1 ::: ~n:T::jEillll 36 YEAR 40 kmM E -. ,,:] . ::::'1 to:: "H HJIlH I2J 44 48 m UITI:Dl 58 MEDIUM INFESTATION Fig. I.-Records of occu rrence of Hemerocampa pseudolsugata McD. infestations from 1916 to 1956 in the interior of British Columbia. 1939-The anticipated increase in I,opulation did not materialize. Although larvae were numerous during June and July near Vernon. Larkin. and Armstrong. there was a genera l populatio n collallse apparent ly due to a virus . An out-break reported from the North Thomp-son Valley during 193') also subsided. 1945- The Douglas-fi r tu ssock m o th re-appeared at Vernon and H edley. Small outbreaks were o bserved near Luild-in gs at these localit ies. 1946-The infestations at Vernon and Hed-ley continued. and tu ssoc k m o th activ-ity was report ed f rOIl1 Chase and Princeton. 1947- Young Douglas-fi r trees near Chase, Squilax. Pritchard. ~Io nt e Lake, StUIl1P Lake. Oregon J ac k C reek, Hedley. Vernon. and Arm strong we re se'/e re ly defolia ted. 1948-Damage by tu ssock m o th larvae was widespread. Infes tatio ns were observ-ed at Armstrong. V e rno n. Oregon J ack Creek. Ashcroft. L ower Hat Creek Valley. Walhachin. North Thompson River Valley from Kamloo ps no rth to Barriere. and l\f o nt e Lake west to Monte Creek. M o rtality o f Douglas-fir and pond e rosa pine trees occu rred at all infes tatio n s. 1949-The infestations subs ided. A survey in th e spring of 1949 indicated that the only persistent large population was in the vicinity of Savona. This popu-lat io n collapsed during the summer due mainly to a virus. 1954--A small outbreak was noted at Cas-cade. 1955- The ou tbreak at Cascade subsided. A virus a pparently was res ponsible. A lig ht population was discovered at Olalla. 1956-Tussock moth activity near Olalla ceased during the summer. At the time o f writing. the cause had not been de termin ed. From the above li sted outbreaks of Dougla s-fir tussock moth it is appar-ent that severe infestations have re-curred at intervals (Fig. 1) in a rather limited part of interior British Col-umbia (Fig. 2). Most of the out-breaks have been in open-grown stands of Douglas-fir trees. The infestations appear to build up quickly in a rela-tively few suitable sites, last for a short period, and then collapse. Be-tween outbreaks, there are years when ENTOMOLOGICAL SOCIETY OF BRITISH COLUMBIA, PROe. (195 7 ) , VOL. 5·i , DEe. 16, 1957 39 Fig. 2.-Location of past outbreaks o f HelllefOcam pa pseudo/JIIga/a :-!.cD. in British Columbia. no larvae are taken in the routine survey samples over most of the range of the Douglas-fir tussock moth. On the other hand, there are a few' localitie s, such a s Lung :'Ilountain near Oyama. vvhere outbreaks ha ve been unknown, but which usually have a small per-sistent population. e(lell/lrgina erechtea Blkme. Th e following notes are s upplement a ry to m y a rticle on the s pecics in th e 1'roc. Ent. Soc. of D.C. 52 : 16-21 , 1956 Ova were obtained from th e summ er form on July 20, 1956. These hatched on July 30. Th e larvae wcre full y fed about August 26, and pupated soon afterwards. Adults emerg-ed September 21 to 26, all of the la rge summer fo rm. :-Jatings occurred and ova were obtained October 8, a nd fo r a few day s after. Some of the ova hat ched, but th e la rvae did no t feed; the remaind er fail -ed to hatch though the embryos were full y fo rmed. From material in coll cc ti ons it was assumcll that t he s ummer brood would have ove r-\\'inte red in th e pupal stage, g iving rise to the small sprin g fo rm. HO\\'ever, these obse rva -tio ns suggest that t\\·o generations o f th e summer form arc usual in thi s area; and it is conce ivahl e that, g ivc n ideal g rowin g co nditi on s, and a long summer seaso n, tIllS s,pecies mi g ht be triple-broodcd. In that case proge ny from a n ea rl y, third gencration would develop suffi cicntl y to produce over-wintering pupae.-George A. Hardy, Pro'vil/cia! Museum, Vic/orid, B.C. 

A brief history of outbreaks of the Douglas-fir tussock moth, Hemerocampa pseudotsugata McD., in British Columbia

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A brief history of outbreaks of the Douglas-fir tussock moth, Hemerocampa pseudotsugata McD., in British Columbia

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