NEW ZEALAND STATE FOREST SERVICE.

CIRCULAR No. 33.

A. D. McGAVOCK, Directol' of FoPestry,

Reprint from Journal of Science and Technology, ·vol. XIV, No. 1.

THE PINE-BARK , HYLASTES ,ATER, IN NEW ZEALAND.

BY ARTHUR F. CLARK,

Forest Entomologist.

WELLINGTON. W. A. G. SKINNER. GQVE,RNMENT PRINTER.

1932. NEW ZEALAND STATE FOREST SERVICE.

CIRCULAR NO. 33.

A. D. McGAVOCK, Director- of Forestry.

Reprint from Journal of Science and Technology, Vol. XIV, No. 1,

THE PINE-, HYLASTES ATER, IN NEW ZEALAND.

By AB,THUR F. CLARK, Forest Entomologist, State Forest Service.

INTRODUCTION. ALTHOUGH the Coleoptera is the best represented of any order in New Zealand, there are but few species of the family Ipidae. This is rather surprising when it is considered that the Dominion originally possessed very large areas of coniferous and hardwood forests, some four million acres of which still remain in their virgin state, and, further, that many species of other families of associated with forests, such as the Cerambycids and Colydiids, are to be found. The arrival and establishment of Hylastes ater Payk., which is the first introduced Ipid beetle to become so estab­ lished, adds to the number of the native species, but is nevertheless a very unwelcome addition. Forestry conditions in New Zealand differ to some extent from those existing in the Old World, in that attempts to regenerate the native timber trees are still in their infancy. Whilst the planting of introduced tree species dates from the earliest days of settlement, during the last decade a programme of extensive establishment of introduced conifers has been carried out, with the result that more than 500,000 acres are at present under this type of forest, the greater part of which has been established since 1921. The planting has been undertaken by various authorities, such as the State, Plantation Boards, County Councils, com­ mercial concerns, and private individuals, but there is no legislation which gives the State any powers of supervision or of control of areas other than those which it directly administers. The majority, particularly of the more recently established areas, is planted in pure blocks, and of the species selected Pinus radiata Don. is easily the most favoured. The State owns approximately 160,000 acres of pure P. radiata, and commercinl concerns are responsible for a further 200,000 acres, both of these totals increasing annually. It can therefore readily be seen that the advent of any new forest , particularly if it attacks P. radiata, is not viewed with equanimity, and without doubt H. ater is the most serious of the introduced which at present attack this tree species. 2

A single specimen of a beetle was sent to the writer from Foxton, in the , in August, 1929, and was accompanied by a small piece of a damaged seedling of P. radiata. Identification, which was later checked by the Imperial Institute of Entomology, did not prove difficult, and the writer left immediately for the scene of the outbreak. Here it was found that a small stand, mainly of introduced conifers, of which the greater part had been logged and replanted, was very heavily infested, the overwintering larvae and adults of H. ater being present in large numbers, the latter attacking the young trees. The plantation, although divided into several blocks, totalled only some 70 acres, and, being established upon a site the soil of which was almost pure sand, the question of the possible eradication of the insect by means of intensive destruction of stumps and other infested material was con­ sidered. The first step being the defining of the limits of the infestation, a rapid survey was made of an area having a radius of some ten miles, with the infested area as its centre. The survey revealed, unfortunately, that the beetle was established at many points throughout this area, and that the utilization of methods designed to effect its complete eradication was impracticable. As later investigations proved, the beetle was even then established in a large number of districts. A study of the behaviour of the beetle under New Zealand conditions, its potential powers oi damage, and means of controlling its activities was commenced. It is unfortunate that the investigation should have coincided, during its later stages, with a period of acute economic depression, which neces­ sitated the drastic curtailing of travelling and consequently the total abandonment of some experiments before they had been completed. Opportunity is taken of recording the writer's appreciation of the most valuable assistance in connection with field and sample-plot work given by Mr. J. F. Field, Senior Ranger, State Forest Service, Palmerston North. To Karl Schedl, of the Division of Forest Insects, Ottawa, Canada, the writer tenders his thanks for assistance in the interpretation of the male genitalia. Thanks are extended also to Miss H. V. Kirby, assistant photo­ grapher at the Cawthron Institute, for the excellent photographs forming figs. 10 to 14. Frequent reference will be found to the paper by Munro(l) upon the genus Hylastes, the detailed work by this author being an invaluable guide in the present investigation. Munro took H. ater as the type for his study, and but little, therefore, will be added upon the question of morphology, only the male genitalia and the proventriculus being briefly described and figured. SYSTEMATIC POSITION. Hylastes ater Payk. was described by Paykull(2) as Bostrichus ater. His original description, in Latin, translates as follows:- Glabrous, black, opa.que, elytra twice as long as broad, punctate-striate, interstices raised. Ilabitat.-Beneath bark 0£ pines. Head black, punctulate, deflexed, antennae rufescent. Thorax black, structurally similar to preceding species* but more densely and deeply punctulate. Scutellum punctiform, black. Elytra black, length twice width (width same as that of thorax),

* Bostr. piniperda F. 3 convex-cylindric, puncta.te-striate, with numerous raised interstices. Wings pELle­ hyaline, veins indistinct. Feet piceous, tibia dilate serrate, tarsi less stout. Slightly smaller than the preceding species. Eyes fringed with very short sparse greyish pilosity. Observati'.ons.-Closely related to Cure. chloropus or Onrc. ater, but differing in the clubbed antennae, elytra less deeply striate, thorax shorter, tibia dilate serrate, com­ pressed. Sent formerly to Fabricimi, but his description in the reference by no means conforms. Variety B.-Piceous, dorsal surface of thorax, elytra, and feet ferruginous. Habitat similar to preceding. PaykuU gives the fo]Jowing references :- Fabr., Ent. Syst., l p., 2 p., 368, 20 : Bostr. ater ? Herbst., Col., [) p., III, 9, t. 48, 9 : Bostr. angustatirn. So far as can be judged, it seems that Paykull forwarded specimens to Fabricius(3), whose description is referred to by Paykull (Z.c.) but is queried by him. Fabricius (Z.c.) indicates in his description that his specimens were obtained from Paykull. Paylrnll has long been recognized as the author of Bostr. ater, although from examination of the literature alone it would appear that Fabricius has some claim. Fabricius(4) later moved his Bostr. (tter to his genus Hylesfrius, giving Bostr. ater Payk. as a synonym. Hagedorn(5) confuses matters somewhat by giving Hylesinus ater F. as a synonym of Hylastes ater Payk., which appears to be in favour of any claim that Fabricius may have. However, since the matter can only be satisfactorily investigated by reference to types, it must be presumed that this has long since been done. Erichson did not recognize Fabricius, so that when he erected his genus Hylastes in 1836 he took Bostr. ater Payk. as a type. Erichson's original description, in Latin, of his genus Hylastes, given by Hagedorn(6), translates as follows:- Antennae with 7-jointed funicle, club orbicular, compressed, 4-jointed. Tibiae extemally denticulate. Maxillary palps somewhat short, conical. J.,abium bare, simple, subcordate, labial palps jointed, lst joint largest, 2nd a third or less, indistinct. Antennae with scape elongate, 2nd joint globose, 3rd ohconicaJ, remainder short gradually widening. Body elongate or oblong, cyJindric. Rostrum distinct, pros­ ternum with deep a.nterior impression. Anterior coxae approximate. Swaine(7) briefly discusses the position of the genus, which is uncertain, and, while favouring its replacement by Toniicus Lat., he continues its usage solely upon the grounds that a change would cause confusion.

DISTRTBCJTION AND STATUS IN OTHER COUNTRIES. During the last fifteen years H ylastes ater has been recorded from the following countries: England, Scotland, France, Germany, Spain, Italy, Norway and Sweden, Russia, and the central European States. It is. there­ fore, widely distributed throughout Europe generally, but is not, apparently, found in America or Canada. In Europe its status appears to have been obscured to some degree by the fact that the damage caused by H. ater was confused with that caused by the weevil Hylobiits abietis L., the latter insect being held responsible for damage caused by the former. Munro (Z.c.) appears to be the first to realize its true status, and gives a clear account of the damage caused by the beetle. In Europe H. ater is often recorded in association with other species of bark beetles and weevils commonly found in coniferous forests. Amongst these insects occur further species of the genus Hylastes, but, as none of its associates occurs as yet in New Zea] and, no confusion can arise here , regarding its status. H. ater is generally noted in Europe in a non-epidemic capacity, it then breeding in dead and dying standing trees; its status changes, however, as soon as it becomes associated with newly planted or replanted areas. The writer has not found many definite records upon a quantitative basis of the damage caused by H. ater in Europe, but Munro (l.c.) gives an account of an infestation in Scotland where out of ap­ proximately 60 per cent. of deaths occurring in a young stand 45 per cent. of them were attributable to H. ater and H. cunicularis Er. together. Regarding the age of the trees selected for attack, in Britain those up to six years are liable to be damaged. Wi:ilker(8) notes that trees of ten years have been destroyed in Germany. That the susceptibility of trees to attack can be increased by the primary damage of another insect is recorded from Italy, where Pinus pinea which has been defoliated by the pine processionary moth, Cnethocampa pityocampa Schiff., has, through its lowered powers of resistance, been successfully attacked by H. ater and other bark-beetles. The following species of newly planted or established trees are recorded in Europe as being attacked by H. ater : Pinits sylvestris, P. Laricio, P. strobus, Picea sitchensis, Larix europaea, Pseudotsu,ga taxifolia, and -Abies pectinata.

DESCRIPTION AND HABITS OF THE INSECT. The Adult. The adult beetle (fig. 1), which varies in size from 3·5 mm. to 4·0 mm., is shining black. The prothorax finely and the elytra coarsely punctate, the former with a median conspicuous ridge, which is impunctate. The antennae with a 7-jointed funicle and conspicuous club. The males are distinguishable from the females by the formation of the ultimate sternite (figs. 2, 3), which is less convex and has a conspicuous finely pubescent depression. As pointed out by Munro (l.c.), this character forms a constant , and valuable sex distinction. Newly emerged adults are distinguishable _by the fact that they are a light brown, which in time gradually darkens, finally changing to black. The adult insects are easily handled, usually feigning death when dis­ turbed. Flight is strong, especially in bright sunlight, isolated infested trees being found as much as ten miles from the nearest breeding-ground. H. ater is monogamous, and apparently but a single mating takes place. The egg-laying tunnel, which is kept clear and free from debris, is bored by both sexes, the female proceeding first and the male clearing away the refuse. Munro (l.c.) states that the adults are easily examined during the formation of· tunnels, but the writer does not agree, finding, in his case, that the insects are inclined to abandon burrows which have been opened for examination, even when the bark has been replaced. To a certain extent the adults show a tendency to be gregarious, as during breeding experiments it was noted that when several roots sunk in soil, all apparently in the same condition, were placed in the same cage, and pairs of adults placed separately with each root, the beetles at times migrated, all ultimately boring in the same root. The Larva. The larva (fig. 4) is of the usual Ipid type, legless, white, with a well­ defined yellowish head and darker jaws. The larvae are not easily worked with, and do not appear to be capable of being transferred from feeding·· tunnels. 5

2 3

FIG. I.-Hylastes ater: Adult. (Enlarged.) FIG. 2.-Apex of abdomen of male: Ventral view. (Enlarged.) FIG. 3.-Apex of abdomen of female: Ventral view. (Enlarged.)

FIG. 4.-Larva. (Enlarged.) FIG. 5.-Pupa. (Enlarged.) 6

Cb. Lav. Lrw.

ad. La

Bl. Bl. Lav. Lav.

Ds. Pal.

Sp.v Par M Rad.

;----Pep

I f------h.p

6 7

T Ppl.

Apl. l 9

Fms. 6--8.-The Penis. Bl, basal lobe ; Ob, caudal branch ; D, disc; Ds, dorsal suture; Lad, laminae dorsales;. Lav, laminae ventrales; J.11., metula; Pal, pallidium; Par, parameren; Pe.p, pedicu1i penis; Rad, radix ; Su.s, sulcus seminalis. FIG. 9.-The Proventriculus. Apl, anterior plate; Abd, abdachung; Est, burste; Krl, kreuzlinie; Ppl, poster10r­ p1ate; Spb, sperrborsten; Zrh, zahnreihen ; Zbst, zahnborsten. 7

When fully grown, the larva excavates a pupal cell in one of three places. The cell may be no more than a widening and deepening of the larval burrow and the use of some coarsely shredded materjal, or when the bark is very thin, such as in billets from sapling-tops, the fully fed larva may bore directly into the wood to a depth of l in. and there construct a cell running longitudinally with the fibre of the wood, the entrance being plugged with shredded material ; and in the Jast case, when the bark is thick, the larva bores outwards and the pupal cell is excavated in the outer bark, but some distance from the surface. (Fig. 10.)

The Pupa. The pupa (fig. 5) is soft yellowish-white, free, with two conspicuous caudal processes upon the 9th abdominal segment. Spines are conspicuous upon the head, pronotum, and abdomen. As pupation advances, the pupa darkens, the eyes, wings, head, and thorax becoming dark brown, the wings tipped with black ; the abdomen develops later. The pupae can be removed successfully from the pupal cells, if necessary, and reared in tubes filled with frass. It is essentiaJ that a large amount of frass be taken, as it then tends to retain the natural degree of moisture. The rearing­ tube, plugged lightly with cotton-wool, should be placed in a dark, cool locality, and there remain as little disturbed as possible.

The Eggs. The eggs are ovoid, pearly white, and measure 0·9 mm. in length and 0·5 mm. in width. Each female is capable of laying a considerable number of eggs, over 100 being frequently recorded in the one egg-laying tunnel.

The Penis. (Figs. 6, 7, 8.) The morphology of the penis of Ipidae 'Nas first investigated by J...1indeman(9). The terms which were then used have since been amplified by various workers, of wbom Schedl(lO) is the latest. Since the penis as a character for identification will undoubtedly be used to a much greater degree in the future than it has been in the past, it is essential that some generally acceptable system of terminology be adopted as early as possible. Though further rernarch may lead to change.s, it is believed that the terminology which Schedl (l.c.) ha8 adopted is the most convenient. Speci­ mens of the penis and the drawings were submitted to this worker, who, in addition to his assistance in the work of interpretation also revised the drawings. The penis consists of three main parts, as follows :- The Outer Cover.-This is a membranous, transparent, but fairly tough tube, bordered cephalacl by the parameren. The parameren (ring, Munro) is open dorsally, and bears ventrally a small sharply pointed process, the iiletula. The Inner Covers.--These enclose the body of the penis, and consist of three parts--the laminae dorsales, the laminae ventrales, and the pediculi penis. The laminae ventrales are not divided ventrally, and overlap to. the dorsal side, where they form a distinct small lobe, bearing sensory papillae. The lobe has been designated the dorsal lobe by Fuchs. Caudad the laminae ventrales are partly separated from the laminae dorsales by a broad suture. Basally the laminae dorsales and laminae ventrales form a tube with a heavily chitinized ridge iuterno-laterally, which might be 8 designated as the junction between the dorsal and ventral plates. Dorsally this tube is separated by a distinct double suture. The laminae dorsales are large, and appear to be a projection of the laminae ventrales. The pediculi penis are long and slender, and originate from the radix. The enclosed parts consist of the sulcus seminalis (Schedl), the rinne, and two long lobes. These lobes are partly connected with the laminae ventrales, and may be homologous with the radii of Fuchs. S1Jiculum Ventrale.-The spiculum ventrale is stout, longer than the penis, and bears cephalad a large disc; caudad it forks, forming the caudal branch. Munro (l.c.) found the spiculum ventrale, which he terms the "fork," a useful specific character for those species with which he dealt. The Proventriculus. (Fig. 9.) The proventriculus is a comparatively large structure in the form of an octagonal tube. The eight plates of which it is comprised are them­ selves each divided longitudinally into two, but the division is only apparent posteriorly. Each division consists of the posterior plate and the anterior plate, the former bearing an arrangement of teeth in which the btirste> abdachung, and the sperrborsten are distinguishable. The sperr­ borsten are particularly well developed, a number of large teeth being present. The anterior plate is characterized by the presence of the kreuzlinie, a row of teeth arising from the lateral margin, running diagonally toward the posterior margin. The presence of the kreuzlinie is used as a generic character by some authors. Posteriorly are a number of rows of small teeth, the zahnreihen, running across the plate, but these gradually lose their regularity and give place to sharper bristle-like teeth, the zahnborsten. NEMATODES CONNECTED WITH H. ATER. The occurrence of Nematodes under the elytra of the beetles and also amongst the frass in the feeding-tunnels was noted early in the investiga­ tion. Upon the beetles they occur invariably, and in large numbers. While the writer can throw little light definitely upon the relationship of the eelworms to their host, the fact that the former are found also in the hind gut of the beetle is of interest. They were not disco-vered in the body­ ca vity of the beetle, and the circumstances point to their being commensals rather than parasites. The Nematodes, together with specimens of the host, have been sent for determination and study to Dr. Steiner, Senior Nematologist to the U.S.A. Department of Agriculture.

LIFE-·RISTORY IN THE FIELD. · The insect overwinters in the adult and larval stages, the latter being fully fed in some cases. Commencing in late July, the adults emerge and seek feeding-grounds. Eggs are found in November and December, and pupae in October and November. Pupae are again found in January-February, and, lastly, late in March and April; while eggs occur again in mid-January and February, in March and April, and again in May and June. Adults and larvae are present all the year round, and there are three broods which, to some extent, may overlap, the later-developing pupae of the one brood then coinciding with the early pupae of the next brood. The occurrence of the last batch of eggs in May and June accounts for the f~ct that newly emerged and feeding larvae are found in the winter months. 9 The chart of the life-historv in the field which was studied.in the 1929-30 season is as follows :-- " 1929 1930 Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apl. l\lay June July ++++ +-:·++ ++++ ++++ +-:-++ ++++ +++1· ++++ ++H- ++++ ++++ ++++ • ••• •• •• •@ ••

+=-Adult •=Pu.pa - =Larva

BREEDING EXPERIJ\'.IENTS. Two series of breeding experiments were undertaken in the l 930-31 season in order to ascertain the behaviour of the adult beetles which occur. The breeding-media were of three kinds-roots placed in soil in large cages, billets 4: ft. long lightly covered with soil, and isolated stumps. In all cases Pinits radia.ta was used. The first series was commenced by taking pupae which resulted from overwintering larva,e. These were collected in the field and reared in the laboratory. The adults so :reared were placed in November--three pairs to each of six roots, four pairs to each of three billets, and six pairs to one fresh stump. Eggs were recorded in January and February, and the larvae fed until the end of March and then pupated. The pupae were removed and reared, and the adults again used similarly early in April. Eggs were recorded in May and June from these adults, and the resulting larvae, together vvith the adults, overwintered. The second series was commenced with pupae which were produced by overwintering adults. Billets were placed in the field in early August, and were infested by the emerging adults which had overwintered, these adults laying eggs from which the pupae were obtained. The history of these overwintering adults was not known, however, so that the series was again started with the pupae. Adults reared from these pupae were used in the same manner as in the first series, being placed in February. Eggs were recorded in March and April, and the resultant larvae overwintered together \vith the adults, the larvae being fully fed. The chart for these experiments is as follows :- 1930 1931 Aug. Sept. Oct. Nov.•• Dec. Jan. Feb. Mar. Apl. May June July + ++++ ++++... .. ------• •• +++- ++++ ++++ ++++ .. 0 .. ------·- * ...... ++++ ++++.. ++++.. ++++ ++++ ++++ ------* * Pupated in November +=Adult e =Pupa - =Larva •=Egg It was found that the billets did not always make satisfactory breeding­ material, the difficulty being to keep the inner bark tissues from drying out. Tbe stumps were used as checks, their examination usually entailing the removal of the bark, often in large pieces, which could not, of course, be replaced. Roots form excellent breeding-media, provided they are well sunk in earth which is reasonably moist. It is as well to use roots which are Im;et-Plne-bark Beetle. 10 free from forking and irregularities, as H. ater shows a preference for breed­ ing in these places, and the tunnels are difficult to examine. Bark which has been lifted 0-uring examination should be carefully replaced, it being found that very thin celluloid held in position by press-pins assisted materially in holding this bark back in position, and also in preventing to some degree the escape of moisture. Neither roots nor billets which are being used for breeding purposes should be directly exposed to the weather, as heavy rain may cause the burrows to become flooded. The incubation period of the eggs was found to be from two to three weeks, and the pupal stage quite short, from eight to twelve clays. The larvae feed for six to seven weeks, and when fully feel pass to a distinct resting stage prior to pupation. This resting stage varies in length accord­ ing to the brood, being of one to two weeks in the summer, but of very much greater length in the case of those larvae which overwinter, as shown in the chart. TYPES OF TUNNELS. The egg-laying tunnels (fig. 11) are distinctive, and have been termed "mother galleries " or "crutch tunnels." As previously noted, both sexes partake in the formation of the tunnel, which has been fully described by Munro (l.c.), and is commenced by the insects boring an entrance-hole through the bark, often in a fissure, or .at times from a cut surface. In the tunnel, niches are cut in both sides and the eggs are packed in position with wood material. (Fig. 12.) Upon hatching, the larvae construct feeding-tunnels. The tunnels are at first formed approximately at right angles to the egg-laying tunnel, and frequently run in a parallel series for some distance. Gradually, however, they turn, widen, and lose regularity, finally forming a rather confused patterning, with no distinctive arrangement such as is found at times in connection with other bark-beetles.

BREEDING-GROUNDS. H. ater breeds in the roots and under the bark of fresh stumps, at the base of dead and dying trees, or in logs. Here the larva feeds upon the inner bark and earn bium, and it is essential that these tissues be in a fresh condition. If they have become dry, or decay from bacteria or fungi has commenced, they do not· serve as a suitable med.ium. While, as in Europe, the beetle shows some preference for breeding in roots-i.e., underground--­ it will also breed freely in material above ground, it having been found as much as 10 ft. from the ground surface in a fire ·killed tree ; in this case the host was Pinus pinaster. With regard to logs, the insect favours the under-surface which usually i8 in direct contact ViTith the ground, and where conditions as to moisture and probably temperature are favourable. The top and exposed surfaces of the log are not usually favoured unless the log is heavily shaded. The insect has been recorded breeding in Pinus radiata, P. pinaster, P. ponderosa, and P. muricata.

SPECIES OF YoUNG TREES ATTACKED IN NEW ZEALAND. The species of young trees attacked by the insect in other parts 0£ the world have been listed. In New Zealand, under field conditions, Pinus radiata, P. rnuricata, and .P. pinaster have been found to be attacked by the adult beetles. In forestry practice so far in this country, clear cutting and subsequent replanting of the area have, with but few exceptions, been the general rule . .Natural regeneration, where it occurs, is usually not the result of the workings of any silvicultural system, but is purely a chance occurrence. l l

Fm. 10.-Pupae in cells in thick bark.

Fm. 11.-Egg-laying tunnel.

Fro. l ~.-J i~ ggs in tunnel. 12

The attack upon P. rad,iata has been noted in the case of both artificially established trees and those naturally regenerated. With regard to P. ·rnuri­ catrt and P. pinaster, only cases of attack upon naturally regenerated trees have been recorded. This, however, is only for the reason that artificially established stands of these two species do not occur in areas infested with H. ·ater. In both cases the regeneration had resulted from sm:an groups of trees situated in close proximity to the breeding-ground of' the .insect. Without doubt, artificially established seedlings of both species would also be attacked. · '"' In order to ascertain whether or not the insect would attack other species, a series of starvation tests was carried out. Six plants of each species were established in pots, and light wire and muslin cages \vhich fitted over the plant and tied round the pot were used. Four beetles, taken just before emergence, were placed in each cage, and the following results were obtained

No. Species. Results.

l Pinirs 'l'lnr.'.rf Pr'n.~r1. AJl plants a,ttack0d and killed. 2 Pinns All plants attacked and killed. 3 Sequoia sempervirens Three plants attacked and killed; three plants attacked but not killed. 4 All slightly attacked but not killed. 5 ::ttfacked. Being under starvation conditions, the tests are indicative only of the ability of the insect to attack successfully those species so recorded when no other host is available. Whether the insect will attack these species in' the field depends entirely upon the conditions obtaining at the time ; the matter is discussed in a later section. The fact remains, however, that the insect can and will attack these species when no other food phtnt is available.

DISTRIBUTION AND STATUS OF H. ATEit IN NEW ZEALAND. H. ater has been recorded from both the North and South Islands. In the former it is found from Shannon to just north of Feilding, and at Featherston and Eketahuna in the W cllington Province, from "\Voocl ville to Waipukurau in the Hawke's Bay Province, and from Rotorua to ten miles east of Taupo in the . Province. In the South Island in­ festations have been noted in the Nelson, Foxhill, Moutere, and Tasman districts of the ; at Seddon and Hillersclen in the l\farl­ borough Province, and at Hanmer Springs in the . The only case in which it is of immediate concern is in the Foxton district of the \Vellington Province, where it has caused severe loss in a young pine stand which had been re-established after logging operations. In all other districts it occurs in such a manner that it has no opportunity of causing such loss, the absence of young or newly planted areas in the immediate or near vicinity being the saving factor. The insect is found in stumps, logs, and dead standing trees, which are to be found scattered in so many districts. Its presence in isolated areas is not of serious moment, but when found in large stands the matter is more serious. The ability 0£ the insect to breed in dead standing trees is perhaps the most serious aspect, as this type of host is found all too frequently in neglected stands throughout the Dominion. A striking example of this is noted at Hillersden, in the South Island. Here, solely through neglect, trees which have died through suppression are numerous, and, as the stands are now 13 being clear-cut, the large number of stumps will form extensive breeding­ grounds. It is proposed to replant these areas, so that some loss can be expected in this district. The utilization of stands of introduced conifers has not yet become a general practice in New Zealand. The largest areas upon which milling and re-establishment have been carried out are in the Province of Canter­ bury, but in parts of that province where, fortunately, the insect has not yet been recorded. In Nelson, Rotorua, and other districts a large number of hosts is provided by fire-killed trees. These burnt areas serve as centres in which H. ater is able to breed extensively and become distributed over a wide

------"'------~- FIG. 13.-Tree killed by beetles, showing Fm. 14.-Typieal bark- stripping by poor root-system. beetles upon young tree. field. No case of the beetle leaving the burnt treeR and attacking those which are unburnt has yet been recorded. H. ater is therefore a serious pest only in the Fox:ton district ; but in other districts it.s status may change when milling and replanting are undertaken. MODE OF ATTACKING YOUNG PLANTS. Young plants are attacked by the adult beetles, firstly, at ground-l ~ vel, the bark and cambium being eaten in large patches. The insect then works both upwards and downwards, but mainly downwards, stripping t.he outer tissues and forming a distinctive grooving in the soft material. (Fig. J.3~l- - 14 The effect of the attack is to cause the death of the plant in most cases, although it is possible for those which are only slightly injured to recover, provided that all other conditions are favourable. Frequently a large number of insects will attack the same plant simultaneously, the maximum thus recorded being no less than twenty-seven. The beetle does not breed in the plants, but returns to stumps, roots, logs, or dead and dying standing trees for that purpose.

APPEARANCE AND OccmrnENCE OF INJUHED PLANTS. Injured plants can usually be detected by the wilting of the foliage and general sickly appearance. In the later stages there is no difficulty, the foliage turning a bright-red colour in many cases, and becoming hard and brittle. Plants which require to be examined are best removed with a quantity of earth, for the twofold reason that, firstly, the beetles, if present, are not shaken off, and, secondly, the root-system is not destroyed, and the plant can be replaced if desired.. Injured plants tend to occur at times in patches in the immediate vicinity of an infested stump or log, although, owing to the very consider­ able powers of flight of the beetle, young plants at some considerable distance from the breeding-grounds may also become infested.

EXTEN'J.' OF DAMAGE CAUSED IN NEW ZEALAND. In order accurately to obtain information regarding the actual loss caused by H. ater, three sample plots were established at Foxton and records of the deaths of the young trees kept. Unfortunately, plot No. 1 was damaged by fire when 16·3 per cent. of loss from the beetle had been recorded upon it, and no further results could be obtained. The plots, which were approximately each an acre in extent, were established in areas which had been planted in August, 1929. Actual counts were made upon nine occasions during a period of fourteen months, and the results obtained were as follows :-

Number of Number Deaths Count No. Date. Trees recorded at caused by Survivals. planted. First Count. H. ater.

PLOT No. 2.-Species: P. radiata. 1 5/2/30 781 765 136 116 513 2 18/3/30 781 765 58 l 454 3 23/5/30 781 765 6 l 447 4 26/6/30 781 765 .. .. 447 5 26/7/30 781 765 l l 445 6 30/9/30 781 765 7 l 437 7 15/12/30 781 765 1 .. 436 8 27/2/31 781 765 l .. 435 9 24/4/31 781 765 .. .. 435

TotaIs .. 781 765 210 120 435

PLO'r No. 3.--Species: P. radiata. 1 18/2/30 840 823 174 101 548 2 18/3/30 840 823 J6 3 529 3 23./15/30 840 823 12 I 516 4 26/6/30 840 823 3 .. .5rn 5 26/7/30 840 82:3 2 .. 511 6 30/9/30 840 823 14 (3 4Dl 7 15/12/30 840 823 I .. 490 8 27/2/31 840 823 I .. 489 9 24/!/31 840 823 .. .. 489 Tofals .. 840 823 223 Ill 489 15 Taking both plots together we find that the percentage of deaths from all causes was ·1-1·58, of which H. ater was responsible for 27·03. The difference between the number of trees planted and that recorded at the first count is accounted for by the fact that some had been removed for examination prior to the demarcation of the plots. Considerable care was taken upon all occasions to ascertain in every case so recorded that the death of the tree had been definitely caused by the beetle. It will be noted that the effect of the beetle was serious during t he first year after planting, but was very markedly less so from then onwards. The reason for this appears to be not so much that the stumps, roots, and other breeding-places had become exhausted, although this had occurred in some degree, but that the young t.rees had become firmly established

Frn. 15.-Area at Foxton. Note the high stumps and wasted logs.

and were growing very strongly. It is probable that the rapid rate of growth that Pinus radicita develops upon many sites when once it has be­ come established will be a factor of considerable importance in determining the extent of damage caused by t he beetle to this species of conifer.

FACTORS INFLUENCING AN O UTBREAK OF H. ATER. Since, as has been shown, the only case where extensive damage.has been caused in New Zealand is at Foxton, it is as well to examine the factors which Jed to the outhreak. The stand, previous to milling, was one of some thirty-five years, and composed of Piniis radiata, P. pinaster, and a small number of Eucalyptus sp. It had at no time been under any form of forest mana,gement, but had, like so many other pl antations in the Dominion, been allowed to grow untended. Further, spasmodic fe llings, apparently unauthorized by the owners, had taken place to such an extent, 16 that by the time the timber was measured it was found that the stand had been reduced by 10 per cent. through these fellings. It is highly probable, therefore, that H. ater, having been supplied for a considerable number of years· with a continuous succession of hosts in the form of dying trees and also fresh stumps, was present in considerable numbers immediately before logging was commenced. The standard of utilization when logging was undertaken was by no means good, with the result that much material, in the form of unduly high Btumps and wasted logs (fig. 15) was left, forming a very extensive breeding-ground. The amount of this material could have been consider­ ably reduced had the utilization been closer, and a corresponding lessening of the available breeding-ground would have resulted. Although the area was burned over prior to replanting, this had very little effect upon the essential inner bark tissues of the stumps and logs, owing to the .resjstance offered by the thick outer bark, while the roots were, for the very great part, totally unaffected. The nursery stock which was used was not uniformly good, and had in some cases been severely pruned just prior to planting. The method of planting was that generally adopted in New Zealand-the notch system­ and this system, if carelessly employed, results in the roots of the plants becoming bent upward, and the occurrence of partial or complete root­ strangulation. Fig. 13 shows a root-system resulting from poor planting. A plant in this condition stands little or no chance of resisting successfully an attack by H. ater, and it is evident that such plants occurred. The time of replanting coincided with the emergence of the overwintering adults ; the young plants being, therefore, in a weakly condition, had little power of resisting the immediate attack of the beetle.

TRAPPING EXPERIMENTS. The use of traps as a means of controlling H. ater has been advocated, particularly by Munro (l.c.), the principle being to offer the adults beetles, upon emergence, some other form of food than young plants, and also a breeding-medium in which they can be controlled. It was decided to carry out trapping upon a small scale at Foxton in order to ascertain whether the use of traps in New Zealand was feasible. The traps consisted of billets of Pinus radiata 4 ft. to 5 ft. in length, having the bark intact. Two classes of material were used-firstly, that taken from the branches of old trees, in which case the bark was thick and firm, and, secondly, that taken from young saplings. The reason for taking the two classes of material is that in some cases it is proposed to grow P. radiata upon very short rotations, and if trapping has to be carried out upon the8e areas only sapling material will be available for traps. Forty-eight traps were set at Foxton in early August, the billets being placed slantwise in the soil with half their length exposed. After two months a single trap was removed to the laboratory in Nelson and used to check the development of the insect at Foxton. The check-trap was opened in November, and the following result obtained:- Trap No. 29.-Adults, 9 ; pupae, 77 ; larvae, 107 : total insects in all stages, 193. Oheck.-Material from old trees. It was decided to remove the traps, and twenty of them were carefully examined, the remainder being destroyed. The results of the examination of these traps were as follows:- 17

'.Traps set early Aiigu8t, removed late Nm,ember.

Type of Trap No. Adults. Pupae. Larvae. Material. Remarks.

20 37 1 Nil From saplings Fairly well preserved. 44 Nil Nil Nil Bark completely perished. 43 2 Nil Nil 35 23 22 8 Bark in f~ir condition underground. 14 Nil Nil Nil Nil Bark completely perished. 48 Nil 1 1 2 47 38 2 l 41 Larger tra;p' from base of tree. I 42 1 10 53 Ditto. 42 44 3 1 48 40 50 15 21 86 25 25 41 104 170 From ~id trees W~ll preserved. 16 52 46 194 292 41 2 21 189 212 6 45 44 66 155 46 108 106 109 323 9 168 37 36 241 7 133 13 12 158 5 69 50 61 170 38 12 11 40 63 Bark in''fair condition.

The difference in the number of insects recorded from the two types of traps is very marked. The reason for this result is mainly that the bark upon the sapling traps, particularly those taken from high up the bole, was thin and quite failed to withstand the weather conditions. Above ground it dried out and peeled, and in many cases below ground it had rotted and a profuse growth of vegetable material had taken place between the bark and the wood. It is, therefore, not surprising that few insects were recorded in this type of trap. Further, the very thin bark contained many resin pockets, and these may have interfered to some extent with the con­ struction of .tunnels. On the other hand, the very strong odour from this material undoubtedly makes it very attractive. The larger traps-those cut from the base of the saplings-gave better results, the bark being thicker and more resistant. The traps cut from older trees proved to have very resistant bark as a rule, the number of insects recorded from these being high. In cases where some shading was afforded, the traps were attacked freely a hove ground, as well as below. A further aspect of these traps was considered-namely, the question as to whether the thin-barked traps would, in spite of their tendency to decay, and possession of numerous resin pockets, still serve as efficient traps in that the adult beetles could feed and oviposit in them and the larvae be automatically destroyed with the perishing of the bark. Two sets of traps were set in January, one of thick-barked and the other 6£ thin-barked material. Unfortunately, this experiment could not be carried to a conclusion, though figures obtained by examination of half the traps six weeks after setting pointed to the fact that, by a count of the egg-tunnels, there was but little difference between the two types. Further, the number of adult beetles in each was very similar. From the incomplete figures; the thin-barked type of trap was slightly the more successful. 18

As a further variation, half of the traps in the last experiment were placed in small trenches scooped out, and their whole length lightly covered with soil. Pilot pegs were placed, in order that the traps might be readily discovered. It was found that traps set in this manner were markedly more successful than those set with half their length only in the ground, the whole length of the trap now being attacked. Unfortunately, this experiment was not concluded, but the results secured pointed favourably to this method of setting.

PREVENTIVE AND CONTROLLING MEASURES AGAINST H. ATER. The method of control by the use of traps has already been detailed and experimentally demonstrated in New Zealand. Undoubtedly, for small areas it is a feasible method, but its application upon an extensive scale has yet to be investigated, when more data, particularly those relating to costs, must be considered. The success of the trapping method depends upon an accurate knowledge of the life-history of the insect in the field which determines the times at which the traps must be placed and removed. The most suitable times are as follows :- First set of traps placed late July, removed middle December; second set of traps placed early January, removed early July. It is possible that seasonal changes may, from time to time, influence these periods in some degree, but observations taken prior to placing and removing the traps will soon determine the degree of variation. It is recommended that where thin-barked material is used the traps be buried for their whole length as previously detailed. Oare should be taken that the traps set in early January remain in as fresh a condition as possible, to catch both of the sets of adults emerging in the summer. No difficulty was experienced in this direction at Foxton. When the traps are removed steps must be taken to ensure that the insects which they contain are destroyed. Burning the infested· traps immediately suggests but it may be possible in some cases to utilize them profitably. The arrangement of the cutting series in such a manner that the areas annually or periodjcally cut over are as widely spaced as possible has been suggested by Munro (l.c.) as a means of reducing the breeding-area. The suggestion is one to be thoroughly investjgated according to forestry con­ ditions, and, if adopted, must be incorporated in the working plan of the forest. The proposal would appear to be quite sound, as the contim~ed production of breeding-grounds which are adjacent to each other must inevitably produce a serious concentration of the beetle, with consequent increased difficultjes of control. Careful planting is an essential where areas infested II. ater are being re-established, and the system of notch planting must be used with the greatest of care. Good nursery stock is also an essential. The working plan for the forest must be strictly adhered to, so that haphazard fellings such a.s occurred at Foxton, which serve to supply the insect with a continuous succession of hosts in the form of fresh stumps, do not occur. Silvicultural operations should be carried out regularly and thoroughly, thus avoiding a series of suppressed and dying trees such as is found in many neglected plantations. The ability of the insect to breed in tbis type of host is a serious aspect, and has led in a large measure to its present widespread distribution. 19

While local climatic and soil conditions largely determine the time for vlanting, consideration should be given, particularly when re-establishing cut over areas, to early planting. If the young trees are planted as long as possible before the emergence of the beetles in late July, they may have a chance to become established in some degree, and thus be in a better condition to resist attack. A change of species when re~estahlishment is carried out may be a method whereby damage is avoided. In New Zealand, especially vvith the earlier plantings, little consideration was given to site factors. The result has been generally to dem.oustrate the apparent adaptability of Pinus rndiata, this tree often being established successfully upon sites quite suitable for other coniferous species. The changing of the species after logging is in some cases, therefore, a possible method of combating the insect. Such a change may be madf:, using a species which has been tested and given a positive result under starvation conditions ; but whether the insect wm attack the new species planted, or seek other feeding-grounds, will depend eutirely upon :field coDditions. \Vhere such conditions are favourable, and the experiment desirable, it is worth attempting. As regards biological control, Munro (l.c.) gives a short list of parasitic and predacious insects occurring in Scotland, but gives no indication of their relative influence upon H. a-ter. The matter is at present being investigated in Britain, and will probably lead to an attempt to establish one or more of such insects in New Zealand. While the writer can find no case in which the biological control of bark-beetles has been attempted successfully, such an attempt could certainly be made with advantage in the Dominion, as conditions in some cases favour this method of control. It is desirable that these attempts should be commenced as speedily as possible, in order that the insects may be given a chance to establish in this country before the extensive utilization of the introduced coniferous foreRtS is C~mmenced, when, if established, the beneficial insects will be given a chance to increase and spread with their host. Collinge(ll) notes that the beetles form part of the food of woodpeckers in England, while in Northern America these birds are noticeable for their habit of feeding upon bark-beetles. New Zealand possesses no birds comparable to the woodpecker, but it is not considered desirable to introduce such birds into the Dominion. CONCLUSION. Forestry in New Zealand during the last decade has been dominated by the planting of large pure areas of introduced pines, the greatest pro­ portion· of which is :pure Pirius radiata. Without doubt, the establishment of these very large areas of P. radiata is of striking significance. Since it should be the aim of those responsible for the study and planning of control measures against forest insects to endeavour so to formulate their measures that the working plan for the forest is as little disturbed as possible, the question of how these large pure areas of P. radiata are to be managed immediately arises. The growing of introduced conifers in New Zealand is in the early stages, and much investigational work remains to be done, as the behaviour of any introduced tree must necessarily be uncertain for very many years. Pure stands of P. radiata and other introduced conifers have been grown to maturity in some parts; but these stands have been small, and have not been under any system of management, thus few relevant data were obtainable from them. 20 While it is quite possible to take too serious a view of the presence of H. ater, nevertheless the matter must be viewed with some concern, and it ·is apparent that consideration should be given to the presence of the insect by those responsible for the management of large pure stands of P. radiata and of othe1· introduced conifers, particularly where extremely short rotations are propo8ed.

REFERENCES. (1) MUNRO,

Printed at the Government Printing Office, Wellington, N.Z. [500/7/32-4600 PUBLICATIONS

ISSUED BY

STATE FOREST SERVICE.

s. d. New Zealand Forestry, Part I (Hutchins) . . 3 O Fixation of Dunes in Gascony . . o 6 Trees of New Zealand (Cockayne and Phillips Turner). (Bound copies) . . 6 6 Professional Paper No. 1 : Some New Zealand Woods {Garratt) 1 o Bulletin No. 1 : Small Sawmills-their Erection and Management {Malfroy) 1 6 Bulletin No. 2 : Forest and Timber Insects {Miller) 4 O Bulletin No. 4 : Monograph of the New Zealand Beech Forests, Part I {Cockayne) 4 O Bulletin No. 4 : Monograph of the New Zealand Beech Forests, Part II {Cockayne) 2 6 Bulletin No. 5 : Properties and Uses of Pinus radiata. Bulletin No. 6 : Pulping and Papermaking Properties or Selected New-Zealand- 2 6 grown Woods Circular No. 16 : Schools Forestry and Plantations. Circular No. 18 : Sap-stain in Timber of Pinus radiata (insignls). Circular No. 19 : Preservative Treatment of Fencing Posts. Circular No. 20: Eucalypts in New Zealand. Circular No. 21 : The Air-seasoning and Kiln-drying of Timber. Circular No. 22 : Forestry in New Zealand. Circular No. 23 : Butter-box Tests. Circular No. 24 : Cheese-crate Test. Circular No. 25 : Farm Shelter. Circular No. 26 : Prevention of Sap-stain in White-pine. Circular No. 27 : The Flora and Vegetation of New Zealand. Circular No. 28 : Paper Pulp from New-Zealand-grown Woods. Circular No. 30 : "Medium" Class Rimu. Circular No. 31 : Trees used in State Afforestation in New Zealand. Circular No. 32 : Insects infesting Pinus radiata in New Zealand.

PAMPHLETS AND 'LEAFLETS. The Propagation of Forest Trees. Leatlet No. 1 : Properties and Uses ot Pukatea. Leaflet No. 5: The Preservation Treatment of Fencing Posts. Leaflet No. 6 : Butter-box Tests : The Coombs Test. Leatlet No. 7a : Commercial Forestation. Leaflet No. 10 : Taxation of Land and Standing Timber in Plantations and Indigenous Forests. (Supersedes Circular 4.) Leaflet No. 11 : Firewood on the Farm. Leaflet No. 12 : The Properties and Uses of Tawa. Leaflet No. 14 : The Properties and Uses of Silver Beech. Leaflet No. 15 : The Properties and Uses of Taraire. Leatlet No. 16 : The Properties and Uses of Kahikatea. Leaflet No. 17 : The Properties and Uses of Rimu. The above-mentioned publications may be obtained by application to the Director of Forestry, State Forest. Service, Wellington.

PRIVATE PUBLICATIONS. Vegetation of New Zealand-2nd Edition (Cockayne). Trees from other Lands in New Zealand-Eucalypts (Simmonds,. Plants of New Zealand (Laing and Blackwell). New Zealand Trees and Shrubs and how to identify them (Allan).