THE GREEN-STRIPED FOREST LOOPER ON VANCOUVER ISLAND'

G. T. SILVER , D . G. COLLIS, N. E. ALEXANDER, AND S . J . ALLEN2

Introduction of the tree and two on the sh a ded The green -striped forest looper. side. Sample positions were against Melanolophia imitata Wlk., was not th e base of the tree and midway be­ regarded as a paten tially dangerous tween the base of the tree a nd the forest insect until it caused h eavy periphery of the crown. Three trees defoliation in 1960 on the west coast were sampled at each a rea. The a ver­ of Vancouver Island. As this is the age number of pupae in the 12 first record of M. imitata caus ing ser ­ samples was considered representa ­ ious damage to fo r ested regions in tive of the pupal population in each Bri tish Columbia the results a re a rea. worthy of a historical note. The moths of this looper emer ge in Results April or May, mate, and each femal e Extent and Intensity lays an a verage of 80 eggs. The sex Survey records show that in 1951 ratio is approximately 1: 1. The larvae larval populations of the gr een­ feed from June to September. West­ striped forest looper increased a long ern hemlock, T suga heterophylla the west coast of Vancouver Isla nd. (Raf.) Sa r g., is the preferred host. The build-up r eached its h eight in Foliage of all ages is eaten but one­ 1952 on the south side of Barkley year-old needles are preferred. When Sound, but defoliation did not exceed feeding is completed the larvae drop 30 per cent and that only in one to the ground and the insects over­ small a r ea. The population decreased winter as pupae in the duff. in 1953 , and remained at a low level Methods until 1957. Data on annual population fluctu­ The population of the green-striped ations were obtained by analysing forest looper started to increase again random 3-tree beating samples col­ in 1957 as shown by the occurrence of lected on the west coast of Vancouver larvae in collections (Table 1) . Both Island. The extent and intensity of occurrence and number of larvae defoliation in 1960 was obtained by increased in 1958, and by 19 59 high aerial s urveys. Plots and sample populations were present in the west poin ts were established in localities coast drainages of Vancouver I sland , selected to represent light, m edium, two of which are shown in Ta ble 1. and heavy defoliation. and records The outbreak reach ed a peak in 1960 , were obtained on defoliation and tree particularly in dra inages 005 ancl 023 . mortality. Smvey activities on the west coast The method adopted for pupa l were seriously curtailed in 1960 due counts, based on preliminary sampl­ to boat troubles, so no collections ing to obtain data on the distribution were made in the infestation a rea of pupae, was to take four one-foot­ during the larva l per iod. Heavy de­ square duff samples from beneath foli a tion was reported in early Sep­ each tree. These were taken a long a tember, a nd aerial surveys la t er in straight line, two on the exposed sid e September recorded defoliation r a n g­ ing from light to h eavy in 32 loca lities 1 ContriiJution ' :0 . ~OO J Forest Entomolog," ('IIll! Pa lh o J og~ ' B r a nc h . lJ epil r ll1lenl or Forest r ." . O l· extending from Herbert Inlet to l awa ~ C;lIl ada. Naspart i Inlet. The total a rea of 2 Forest F:nloll1o \og)' a nd ]la th olng,\ L aiJo r a tor." , \·ie-to ria. D. C. visible feeding was calculated at :30

TABLE I.- Summary oj Green-s triped Forest Loe per La rva,) Found in Beating Samples From Drainage Divi ~ ions 0 11 the "V est Coast of Va ncouver Island. ';; samples including Av. no. larvae ' Year larvae sample containing larvae DD 005' DD 023 2 DD 005 DD 023 1956 o 0 1957 20 14 2 4. 1958 47 82 2 14 1959 88 72 45 31 1960 85 0 59 1961 61 61 58 7 , Alberni Inlet to Escalante Pt. 2 Escalante P l. 1.0 sout h oJ Cape Ccoke on Brooks Peni nsula.

22,755 acres, of which 4,640 had sus­ caged for adult emergence, only four tained heavy, 13,120 acres medium, produced moths, twenty were para­ and 4,995 acres light defoliation. The sitized, and the remainder died of defolia tion limits established during other causes. The moth fiight at the the aerial survey were 0-25, 25-50, end of May was very light, and only and over 50 per cent for light, med­ a small number of eggs was found in ium, and heavy, respectively. The limited sampling'. At this point it was infested areas ranged from 30 to believed that the 1961 population 6,340 acres. would be too small to cause appre­ Visual estimates of defoliation on ciable defoliation. The predicted drop plot trees, and pupal coun ts made in in larval numbers was confirmed by the same localities, a re shown in the reduced numbers obtained in Table 2. The average number of beating samples (Table 1), and by the pupae in areas of m edium and heavy relative number of larvae per sample defoliation was about the same. collected from the same points in There was, however, no way of know­ 1960 and 1961. Some of these were ing wha t 2.0 pupae per square foo t (1961 in brackets ) : White Pine Cove. meant in terms of expected larval 444 (11) ; Herbert Inlet, 262 (4) ; population or defoliation. Although Beddingfi eld Bay, 460 (40); Millar ch emical control was not recom­ Channel, 486 (120) ; a nd Tofino Inlet, m ended, the need for such action was 215 (28). considered a possibility in 1961. Natural Control Efforts were made in the spring of Parasites - The effect of parasites 1961 to a ppraise the anticipated out­ on the large population of 1960 is not break. Of 75 pupae coll ect ed and full y known as no samples were

TABLE 2.- Defolialion and Numbers of Green-striped Forest Looper Pupae at Sample Plots. Septem be l' , 1960. Degree of P ercentage Av. no. Locaiity defoliation defoliation pupae reprcsen ted ' (western per sq. ft. hemlock) of dull Ououk!ll sh Inl et light 21 0.44 Port Eliza medium 54 0.46 Milb' Channel " 32 202 Beddingfield Bay 40 l.92 E c lstolV Passage heavy 50 1.46 Villa verde Is. " 91 2.06 Bligh I". 81 0.50

I Defoliation limits determin 2il by aerial s urvey. obtained from most of th e more exerted, but it is believed that C. hea vily infested areas. Of 563 la rvae militaris caused considera ble pupal collected up to early September and mortality, and was probably one of reared, only 28 or fiv e per cent died of the factors involved in the population parasites. Of 133 larvae collected after decrease in 1961. mid-September, 70 per cent died of parasites, and of a total of 317 pupae Defoliation and Tree Mortality collected, 104 or 32.8 per cent were Defoliation estimates, made by paras i tized. crown levels and crown classes, show tha t feeding was, without exception, The figure of 70 per cent larval h eaviest in the upper crown levels of parasitism may be unreliable. As these all classes of trees. Trees of all crown collections were made late in the sea­ classes from suppressed to dominant son, many healthy larvae might have were fed upon, but defoliation was already dropped to the duff and heaviest in the intermediate trees. pupated, leaving the retarded para­ sitized larvae on the trees. The figure Mortality, in the plots analysed, was of 32.8 per cent pupal parasitism restricted to trees which were 90 per appears to be more reasonable, and cent or more defoliated. Most of the is supported by collections made in remaining trees in this defoliation the spring in which 26.7 per cent of class were top-killed; in some in­ the pupae died of parasites. stances the upper 2 3 of the crown was dead in 1961. Although no mor­ Seven hymenopterous parasites tality occurred among' trees with less were reared from the 1960 collections. than 90 per cent total defOliation, Dusona pilosa (Walley) and Asti­ top-kill occurred among those which phromma strenuum Holmberg were were less than 50 per cent d efoliated. the ma jor larval parasites and were Aerial and ground surveys indic­ recovered only from larvae. Other ated that mortality occurred only in species reared from la rvae were the stands which had been heavily Euceros thoracicus Cresson, M eteorus defoliated in 1960. The heaviest dam­ sp., and Zele sp. Aoplus ce stus (Cres­ age occurred on Villaverde Island son) was the most numerous pupal where loss was calculated at 7,300 cu. parasite, followed by Gravenhorstia. ft. per acre for the 260 acres. Av erage alaskensis Ashmead. Three E. thor­ tree mortality for the remainder of a.cicus Cresson were also reared from the area was calculated at 116 cu. ft pupae. It is not certain if the numbers per acre. Total mortality, up to the of parasites recovered from rearings fall of 1961 , was estimated at 2,400 ,- are related to their importance as 000 cu. ft. of western hemlock. This con trol factors in the field popula tion. figure could be conservative as some Disease- On May 5. 1960. while trees which were heavily defoliated searching for pupae, small orange may die in the next one or two years. fruiting bodies about % inch long were observed protruding from the Discussion duff. I n every case these grew out The rapidity with which the green­ from a Melanolophia pupa. The striped forest looper population in­ fructifications were identified as the creased to tree-killing proportions perfect state of Cordyceps militaris and then collapsed, allowed little time (Fr.) Link. The fruiting bodies were to obtain specific data on sampling plentiful in early May but appeared techniques. With the exception of only in shaded locations at the end of the occurrence and average number the month. Sampling was not inten­ of larvae per collection no data were sive enough to determine the control obtained to show correlation between population levels and defolia tion. Al­ trict) in 1958, and reached a level in though pupal counts were made in 1959 whi'c h must now be regarded a s the fall of 1960, there was no way of da ngerously high. Populations r e­ determining if the numbers found ma ined high or increased in 1960 only represented a potentia ll y da n gerous in isol a ted localities along the west population. Because of the reduced coast of Vancouver Island; elsewhere population in the s pring of 1961 it the number of larvae dropped. was not feasible to develop a m ethod Defoliation h eavy enough to be ob­ for sampling eggs. served from the air occurred in 32 A n umber of na tura l control fact­ localities, tota lling less than 23 ,000 ors contributed to the decrease of the acres, scattered along 80 lineal miles population . Larva l parasites, although of inaccessible coast li ne. Of this area not numerous enough to exert a ny only 4,640 acres were h eavil y defoli­ great degree of control, were present ated , and over three-quarters of the in a pprecia ble numbers. Pupa l para­ total tree mortality of 2,400,000 cu. ft. sitism accounted fo r a bout 30 per cent occurred on a few s mall isla nds of mortality in the overwintering' popu­ only 260 acres. It' fu ture outbreaks lation, but does not account for th e fo llow a simila r pattern very compre­ hea vy pupal mortality a nd the r esul t­ h ensive a nd d etailed surveys would ing low moth emergence. COl'dyceps be required to detect and take action is an unknown factor. but could h ave to prevent such heavy mortality from played a significant role in the col­ occurring again on other sma ll islands lapse of the ou tbreak. or inlets along the coast. One of the aspects in the outbreak Summary which is difficult at this time to explain is the severe tree mortality on The green-striped forest looper Villa verde Island. Aerial surveys, which started to increase in 1957 supported by ground observations, reached severe outbreak proportions indicate that tree mortality was rela­ in 1960 in a large number of small tively light on Bligh Isla nd, although separate localities along the west it is near Villaverde Island and also coast of Vancouver Isla nd. The popu­ received h eavy defoliation. lation decreased to a low level in The nature of the recent infesta­ 1961. Tree mortality, up to the fall of tion pOints out one of the great 1961, was estimated at 2,400 ,000 cu, ft. difficulties in dealing with looper out­ of western hemlock. breaks. The population started to This species must be added to the increase throughout most of Vancou­ growing lis t of defoliators capable of ver Isla nd (in fact throughout most causing damage to forests in British regions of the Va ncouver Forest Dis- Columbia.

Note on the reference collection of inflated larvae at the Forest Entomology Laboratory, Vernon, B.C. Over thf' past few years the refere nce col­ The co llection contains most co mmon a nd lecti on of inflated larvae of lepidopterous many uncommon defoliators found in the and h ~ ' menopl e r ous t rce defoliators haS forests of interior British Columbia. The been expanded gff~ a tl y . The coll ection is le pidopterous fa milies are r epresented by a chie fl y used as a reference a id in ide ntifying I'a ried num bel' of species; for example, the lar Vae' take n in Survey coll ections or sub· coll ectiun contains 130 species of Geometri­ mitted by persons in fo rest ind ustry a nd dae, 75 sp('cies of Noctuidae and 15 species r f' lated fi e ld s. of Notodontidae. The total number of in­ Hepresented in the coll ection (I re: na~ e d iarvae is about 1.530. This note is published to make local ento­ Lepidoptera Hymenoptera mologists [l\Va r e of the existe nce of the col­ Famili es 34 6 lection a nd to invite them to usc it. Genera 209 20 .t. fl' . // ff/'/")/ ff/lfl iJ . .- 1. 1,' ()88 . /-' I)n'sl /':/llu­ Species 350 23 II / ollJ.'I .1J L rtlif)ru/fJ/'./f. \ ' e j '/flJlI . N.f' ,