32 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL. 21, 1974

INSECTS DAMAGING BEECH (NOTHOFAGUS) FORESTS

R.H. MILLIGAN

Production Forestry Division, Forest Research Institute, Rangiora

INTRODUCTION different subdivisions of the Spermatophyta. The distribution ofliving and fossil Nothofagus A further reason for attempting such a in the southern hemisphere (Skottsberg 1949) comparison arises because Pinus has been suggests the possibility that it once played a part extensively managed in conjunction with its in colonising primitive and unstable soils endemic complex of and diseases, while comparable with that played by Pinus in the stem rots and damage in untended stands northern hemisphere. Each includes of New Zealand Nothofagus have seriously species which colonise rocky soils of mountain restricted utilisation Oohnston 1972). There is ranges and glacial, alluvial and volcanic deposits; little doubt that the New Zealand beeches - each genus is, or has been, represented from especially silver beech (N. menziesii) - could circumpolar regions to the highlands of the become a much more valuable hardwood tropics. Those species best adapted as pioneers resource if insect and rot defects could be are most tolerant of variations in soil moisture, obviated. With this purpose in mind, it is relevant nutrients and temperature, but either require to enquire whether the insect problem is any less insolation of the soil for germination or are capable of solution in Nothofagus than it is in intolerant of shade as seedlings so that HItle Pinus. regeneration survives under closed canopy. Since adjacent trees are commonly THE INSECTS INFESTING PINUS ANDNOTHOFAGUS interconnected through root grafts, deaths of It seems characteristic of forest trees belonging individual stems do not normally provide root to pioneer genera that they support a numerous space for the development of seedlings. Larger and diverse fauna of insects, a few of which gaps in the canopy resulting from storm damage precipitate the local losses of canopy trees which or other natura] causes of group mortality tend these tree genera are so well adapted to to be rapidly filled with dense regeneration. For withstand. Most of the insects which utilise living these reasons, forests of pioneer species are tree tissues are present in numbers which are typically even-aged except near advancing controlled by the physiologicalstate of the host as margins or where group mortality has occurred well as by parasites and predators. Water stress in (Wardle 1970, Wardle 1974, p. 23 for Nothofagus the host has the effecI of reducing the solandri). Mortality as a result of competition in translocation of photosynthesate; increased even-aged stands ensures a continuing supply of photosynthesate levels in foliage accelerate the host material in addition to that provided development of defoliators and sapsuckers. intermittently by climatic damage and Water stress in the stem has the effect of senescence for those organisms which thrive on reducing the rate of flow of gums and resins weakened or moribund tissues. Such a coupling which are produced in response to wounding, so of extensive geographic distribution and that insects and attendant fungi can enter and mortality resulting from intraspecific establish themselves more readily. Nitrogen competition has probably provided levels in soils affect the water uptake of roots environments conducive to the evolution of (Goyer & Benjamin 1972) and thus affect the aggressive insects and pathogens of forest trees. susceptibility of trees to insect damage. Pioneer To the extent that this is so, comparison of the trees persist on infertile and shallow soils from insect complexes of Pinus and Nothofagus may be which highly soluble nitrogenous compounds meaningful although the genera belong in tend to be leached. In brief, it appears that the 33 INSECTS DAMAGING BEECH FORESTS susceptibility of pioneer species to insects is controlled by parasitic fungi. When moist directly related to moisture stress - in part conditions are restored, the fungi rapidly regain induced by overstocking and hence intraspecific control and crowns appear to recover competition, in part by seasonal variations in soil completely. moisture, and in part because of impaired root Whereas Nothofagus recovers well after uptake of moisture associated with the low outbreaks of sap-sucking insects, resin reactions nitrogen levels of the soils where they persist. to stylet punctures in Pinus tend to restrict Whether onc considers Pinus or Nothofaf:Us, few conduction and this may result in the death of of the insects arc restricted to one host species, smaller stems. though the relative abundance may vary both between hosts and between sites. 2. Defoliators and Foliage Miners Amongst other defoliators and foliage miners I. Sap-suckers feeding on Nothofagus are three species of Eriophyid gall mites are associated with all Proteodes (Oecophoridae). p, earnifex occurs on all New Zealand species of Nothofagus. Pouch galls the species, normally in low numbers. Outbreaks certainly occur on leaves of N. fusca and N. of P. carnifex, which may persist and spread for solandri and probably on the other two species. several seasons, are known oniy or~ N. solandri. Flower buds ofN.fusea are galled, and other bud During outbreaks, ti'ees may be severely galls occur in all the species. Most conspicuously, defoliated during the summer but usually terminal buds of N. menziesii form "witches' produce some new foliage before the winter. brooms" when they are invaded by eriophyids. Occasionally no new foliage appears until the Eriophyidae seem to be mOfC common on following spring. Even with two successive angiosperms than gymnosperms. seasons of severe defoliation there is no indication that trees are either killed or so Heavy attacks by spittle bugs belonging to the weakened that they succumb to other insects or genera TiloPhora and APhroPhora (Cercopidae) pathogens, Other tineoid defoliators of may kill tops, branches and sometimes young trees of Pinus. t'me aphids (Eulachnus and Cinara) Nothofagus are sometimes common on the foliage and Pinus spp, (Adelgidae) are common, of larger trees though the irDury they cause especially when are subject to drought. The appears to be well tolerated. scale insects of Pinus include species of Tortricoid defoliators of Pinus include the Matsucoccus and Drosicha (Margarodidae), budworms (Choristoneura spp.) which prefer Toumeyella (Coccidae) and the armoured scales to feed on the bases of the most recently LePidosaPhes and Phenacaspis (Diaspidae), produced needles. Defoliation for several Nothofagus is not affected by spittle bugs or successive years greatly reduces wood growth aphids. Nothofagus solandri growing in dry and may so weaken the trees that they become regions supports large numbers of susceptible to bark attack. Nothofagus Ultracoelostoma assimile (Margarodidae) on thick supports a number of Tortricidae at least three barked parts of the stem, Honey dew is produced of which also occur on other hosts. Epu:horista by scale insects in such quantities on the stems of emPhanes, which feeds exclusively on Nothofagus N. solandri that it is utilised by commercial spp., is the only one of these which occurs in apiarists. On N othofagus the Eriococcidae are outbreak numbers. Outbreaks have been represented by 22 species, of which only one has localised, do not appear to last for more than one other hosts. An armoured scale, Inglisia sp., season and are not known to cause any long term occasionally reaches outbreak levels on N. fusca injury to the trees, A related family affecting during seasonal droughts. During droughts the Pinus, the Olethreutidae, includes the pine tip upper crowns can become completely defoliated (Rhyacionia spp.), the shoot moths and the lower foliage and that of the understorey (Eucosma spp.), and the pitch nodule moths is smothered with sooty moulds. It appears that (petro va spp.), While lacking olethreutids, all populations of this scale insect are normally species of Nothofagus are affected by Carposina 34 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL 21, 1974 eriPhylla (Carposinidae) the larva of which teeds pests which have no counterpart on NothoJagus. on inner bark and callus at the margins of Some adult buprestid , e,g. Buprestis wounds. Its chief importance seems to be that it apricans, teed on pme needles for several weeks enlarges wounds made by other insects and before mating and ovipositing. Each adult delays healing, Nascioides en)'si has been found to consume ten Caterpillars and pyraloid moths which affect leaves of N. menziesii per day (Morgan, 1866). In Pinus include the webworm TetraloPha robustella each case adulI buprestids are plainly a part of (Pyralidae) in the eastern U.S,A., the inner bark the defoliating complex of insects, but in neither borers, or pitch moths, of the genus Dioryctria. case has their relative importance been Dioryctria spp. cause the formation of resin established, Adult chafer beetles () pockets which become included in the wood. No feed on foliage of both Pinus and Nothofag"U.s Pyralidae damage Nothofagus. while their larvae feed on roots. Several species of Odontria are numerous in monotypic N. Bombycoidea arc represented on Pinus by solandri forest but as yet their significance is Dendrolimus spectabilis (Lasiocampidae) and unknown. Coloradia spp, (Saturniidae). Most damaging lasiocampids (e,g. Malacosoma spp.) and In general, in their countries of origin, Pinus saturniids are associated with hardwood hosts, species are periodically subjected to severe but the former do not occur in New Zealand and defoHation by a great variety of caterpillars and the latter are represented only by the introduced sawfly larvae. During outbreaks severe eucalypt silk mOIh Antheraea ew:alypti. defoliation may check wood growth, \,,'eaken trees so that they become susceptible to bark Butteryfly larvae which feed on Pinus foliage beetle attack and even kill them. On the other include those of SPindasis takanonis (Lycaenidae) in Korea and Japan and the ponderosa pine hand outbreaks of an oecophorid which last for more than one season and extend over butterfly NeoPhasia menaPia (Pieridae) of western North America which may kill its preferred host considerable areas affect only one of the during outbreaks. Nothofagus species do not indigenous Nothofagus species (N. solandri); even in this case the trees rapidly regain full foliage support butterfly larvae. and no long term injuries stem from defoliation. The Geometridae which feed on Nothofagus' include the general feeders Selidosema suavis and 3. Inner Bark Feeders floccosa. S. productata is common on beech The bark feeding habits of caterpillars of but also occurs on other hosts. D. feredayi and Carposina eriPhylla in Nothofagus and Di(1)'ctria Tatasoma fasciata appear to occur exclusively on spp. in Pinus have been briefiy mentioned above Nothofagus. Outbreaks of these geometrids on and many of the sap-sucking insects are Nuthofagus are unknown, although local essentially dependent on these tissues. In outbreaks of S. suavis have occurred on Pinus addition, the larvae, the adults (or both) of radiata in Canterbury. Geometridae are usually beetles belonging to the Buprestidae, of minor significance on endemic Pinus though a Cerambycidae, Scolytidae and CurcuHonidae number of species belonging to Semiothisa, feed on inner bark. Ectropis, Zethenia, Nepytia, Lambdina, Eufidonia, etc., are known to feed on pine needles. Buprestids belonging to the genera Melanophila and Chrysobothris are especially The larva of the black hawk moth, Hyloicus associated with suppressed, dying or freshly caligineus (Sphingidae) occurs on pine foliage in felled Pinus, Eggs may be laid on living trees China, Japan and Korea, but again there is no which are growing very slmvly, but development counterpart affecting the New Zealand beeches. of the larvae is retarded until radial growth Sawflies belonging to the genera NeodiPrion, ceases (Anderson 1960). Two buprestids, NesodiPrion and Diprion (Diprionidae) and Neocuris eremita and Nascioides enysi, are found in Acantholyda and Cephalcia (Pamphiliidae) Nothofagu5 forests. Larvae of the former occur in defoliate Pinus. Some of these are serious forest small diameter dead branches of Nothofagus but INSECTS DAMAGING BEECH FORESTS 35

are not restricted to beech. Nascioides enysi has Some species of bark beetles belonging 10 the long been regarded as an important cause of genera Dendroctonus, Ips, Blastophagus beech mortality ( Cockayne 1926, Morgan 1966) (Myelophi!us) and Cryphalus (Scolytidae) are the and is restricted to the beech species. The writer cause of most insect damage in the areas where has recently suggested (Milligan 1972) that N. Pinus is endemic. Outbreaks are commonly enysi larvae do not develop beyond the first instar initiated by wind throw or droughts. Blastophagus unless they reach the inner phloem, and are PiniPerda and B. minor occur throughouI the prevented from doing so by host gum reactions Palaearctic region but are absent from North as long as the tissues remain alive. Still more America. Broods are reared in the inner bark of recently, it has been observed a.A. Wardle pers, recently killed trees and the beetles feed in the comm.) that early larval mines of the buprestid in leading shoots of young Pinus before they pole sized N. solandri occur exclusively in those establish brood galleries, Damage to apical shoots stems in which growth is suppressed. It follows during maturation feeding leads to the from this observation that ovipositing N. enysi formation of bushy trees which are of little use must select specific physiological conditions in for timber production. Aggressive species of the host. Similar conditions must prevail, at least Dendroctonus, Ips and Cryphalus bore into and feed temporarily, in branches of healthy trees since on the inner bark of living Pinus. While larvae also occur there. Since N. enysi do not Dendroctonus attacks tend to occur mostly in the oviposit when the temperautre is below 22'C, and lower parts of the trunk, those of Ips are higher temperatures are required in the absence concentrated in thinner barked regions and of direct sunlight (Morgan 1966), it seems likely CryPhalus attack branches and tops, Sapstain that stem moisture stress is associated with fungi carried either in specialised organs or attractiveness to ovipositing females. If the stress externally on the body surface is of a temporary nature the larvae fail to (Francke-Grosmann 1963) invade sapwood develop; if it is indicative of a moribund adjacent to the tunnels and playa part in condition they are able to reach the cambial zone interrupting conduction so that the crown wilts and to complete their development. Nothofagus and the tree dies when a sufficient number of mortality previously attributed to N. enysi is now attacks are concentrated on it. Brood galleries more convincingly interpreted as a consequence may extend from the initial feeding tunnel or of Platypus attack (see below): the part played by may be made in other parts of the killed tree. N. enysi appears to be closely comparable with Although weakened trees are preferentially that played by MelanoPhila gentilis and M. attacked, adjacent healthy trees are killed when drummondi in the death of pines. broods emerge some 4-5 weeks later. This leads to group mortality, which occasionally extends The larvae of many longhorn beetles over large areas. Up to five broods are produced (Cerambycidae) feed in the inner bark of forest over the warmer months, so outbreaks develop trees. As a rule, the trees are dead when they are rapidly, Losses (of the order of I billion board selected as host material. The sawyer beetles, ft/year) caused by D. brevicomis attack on Monochamus spp., lay their eggs on dying and ponderosa pine in the Pacific Cost States of freshly felled Pinus. Later, larval mines enter the U.S.A. over a 25 year period were almost I y, wood causing appreciable losses of otherwise times the increment, and more than 10 times salvagable standing timber and of stockpiled greater than losses by fire (Anderson 1960). pulpwood. In parts of Japan adults of a species of Bark below the green crown may be completely Monochamus have the habit of biting holes in the stripped by feeding adults of Ips grandicollis, thin bark of the upper stem of pines, and in which later make brood galleries in the lower doing so infect the wounds with a nematode parIs of the killed tree, Outbreaks of Ips avuLsus which invades the wood and rapidly kills the trees. Longhorn beetles which damage during droughts in Texas, U.S.A., have Nothofagus are essentially wood feeders, and will necessitated extensive sanitation salvage be considered below. operations. The role of Cryphalus species in tree 36 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL 21, 1974 mortality is less well documented, but some are Pinus is affected by Hymenopterous said to predispose trees to attack by other bark wood-borers belonging to the family Siricidae, beetles. The Scolytidae of indigenous Nothofagus As a rule these are of minor importance in are represented by one (or perhaps two) species endemic pine forests, butSirex noctilio, which has of Hypocryphalus. These are commonly found in been accidentally introduced into New Zealand small branches of felled trees and seem to be and Tasmania, has occasionally caused extensive restricted to dead or moribund tissues. damage in plantations of . Outbreaks have been associated with sustained droughts and overstocked stands. SiTex noctilio 4 . Wood-borers lays its eggs in the wood of living trees, often in Pinus is little affected by wood-boring greatest numbers just below the green crown. A caterpillars, though minor damage is caused in fungal symbiont introduced with the eggs causes North America by larvae of the clear-wing moth willing of the crown and death of the tree. Only if ParhaTmonia Pini (Aegeridae). All species of the wood dies do the larvae develop. Brood is also Nothofagus are susceptible to damage by the reared in logging wastes, windthrown trees and larvae of the ghost moth, Aenetus virescens those snapped off in gales or snowfalls, The (Hepialidae), bUIA, viTescens fortunately is absent nearest relative of the siricids in Nothofagus is from the South Island, Early ins tars of A , virescens Xiphidryia dunniana (Xiphidryidae), Ihe larva of feed under a silken tent, often at twig bases, on which develops in dead twigs and small branches. the bark of seedlings. As they grow the larvae There is no evidence that X. dunniana kills the migrate to larger and woodier stems in which twigs which it utiJises. they bore "7"-shaped refuges, the long arm Buprestid and cerambycid wood-borers parallel with the stem axis and the shorter one associated with Pinus seem able to gain entry to extending to the surface. From this shelter, and the wood only through wounds which are concealed from the outside by a silk tent, the incompletely covered with resin and are larva feeds on inner bark and callus induced at therefore unimportant except in forest produce the margins of the wound. The bark is often and as agents which break down the stumps and eaten away for more than half the circumference other forest wastes. Upper parts of Nothofagus of small stems and branches, and the wounds are regeneration are girdled and killed by larvae of a common cause of breakage during gales or the longhorn beetle Navomorpha lineata, which snowfalls. When the bark of poles becomes too later hollow out the lower living stem. Eggs of N. difficult for the larvae to penetrate they tend to lineata are frequently laid at wounds such as those move further up the stems; old damage then made by ovipositing cicadas. Similar damage becomes overgrown by new wood. Cores of occurs in small branches of Nothofagus trees and damaged wood tend to be of greater diameter in occurs in many other hosts. Where poles or lar- N. menzwsii than inN.Jusea or N. truncata, and this g-er trees of N. solandri (and occasionally N. fusca) appears to reflect the earlier development of closely associated with Leptospermum they may be resistant bark in the latter two species. 'Vetas damaged by larvae of the longhorn beetle (Hemideina spp. : Tettigoniidae) take over the OchTocydus huttoni, for which Lepwspermum is the caterpillar refuges, enlarge them and keep the usual host. Larval tunnels in the sapwood are entrances open for many years. When the wetas large, predominantly vertical, and free of frass. emerge to forage after dark they serve as vectors The frass is ejected through small openings of sapstain and rot fungi. As long as the tUnnels which are cut from the larval galleries to the are kept open, aerobic conditions favour the exterior. Wetas utilise the flight holes, pupal spread of rots, Core rots associated with old ghost chambers and larval galleries of O. huttoni just as moth damage are usually most extensive in N. they use ghost moth refuges, Damage is unusual, menzwsii. Current ghost moth damage may be except inN. solandri (which is little sought after as found in the branches of mature trees of all the a timber producing species) and even in this host, Nothofagus species as well as in hosts belonging to diminishes in frequency with distance from scrub . other families. margms. INSECTS DAMAGING BEECH FORESTS 37

Species of Platypus (Platypodidae) are amongst transmitted by the beetles and becomes the first invaders of Pinus killed by bark beetles established initially in the innermost sapwood but do not invade the living stems. Coster (1969) where wood moisture content is least. Butcher found that P. flavicornis bored into Pinus trees (1968) found that Ceratocystis piceae was the main four to six days after they were infested by Den- cause of staining in untreated sapwood of N. droctonusfrontalis. Damage was restricted to the fusca, and noted that the same fungus occurs in lower few feet of wilting stems where wood mois- N. menziesii. Staining caused byC.pu:eae was ture content would remain highest. In New Zea- associated with discolouration of ray cell contents land Nothofagus forests there are three species of rather than with pigmented fungal hyphae. Platypus - P. apicalis White, P. gracilis Broun and When Platypus .invades living trees, or when P. caviceps Broun - which readily breed in scrapings from- nests are introduced into holes freshly fallen trees, logs and stumps. Platypus drilled in living trees, a sapstain fungus which caviceps is not known to br'eed in any other hosts does have pigmented hyphae and which causes but the other two may breed in' a variety of extensive reactions in living wood cells, advances hardwoods and softwoods. All three species will further than other fungi from the wound (Faulds attack living and apparently healthy Nothofagus 1973). This'fungus, designated "Fungus A" by trees. Rarely, stems only six centimetres in Faulds, is associated with progressive death of diameter are attacked, but abortive attack is not inner regions of the sapwood, It is readily uncommon iri those 15 em or more in diameter. cultured, and the pathogenicity of cultures is Brood of P. apicalis and P. gracilis are known to being examined; but, so' far, it has not been emerge from nests in large diameter trees which identified. On the other. hand, . a species of are still alive, but attempted nests of P. ciwiceps' Ceratocystis is the dominant component of the fail unless the tree dies. Attacks of P.apicalis and flora..of older parts of Platypus tunnels. The P. gracilis are concentrated on the lower' six genus Ceratocystis (Ceratostomella) includes a metres of the living tree; those of P."caviceps also number of sapstain fungi which are transmitted occur in this region but extend up to a height of by the bark beetles which damage pines. 21 m. This distribution of attack by the Platypus Whereas the bark beetles. feed on the inner species on living'trees is perhaps. comparable bark, through. which. they tunnel,' Platypus and with that of Dendroctonus, 'Ips andCryPhaluson other ambrosia beetles do not feed on wood. . .,., . living Pinus." . Freshly bored' tunnels of the New. Zealand WhenNothofagus trees of sufficient diameter to species soon acquire a lining of yeasts which are contain heartwood are attacked, the initially. the primary food of both adults and larvae. radial Platypus tunnel curves through a right Yeasts are also transmitted by bark beetles, occur angle as. the transition zone is approached and in all the feeding stages and are digested, but then continues tangentially close to this zone. It their. precise role in the nutrition of bark beetles has not been determined (Callaham & Shifrine . seems that this change of direction is linked with . progressive reduction ~f moisture content of the. 1960). sapwood. In stems with no heartwood the tunnel Aggregation of attack on particular trees is continues towards, and sometimes through. the characteristic of, and essential to, aggressive b~rk organic centre. If small stems have been attacked beetles. Unless a sufficient number of wounds in a previous season. resulting in a core of dead are made, and a sufficient pa'rt of the sapwood and discoloured wood, the tunnels deviate as the exposed to the sapstain fungi which interrupt its outer margins of the dead core are approached. conducting function; the tree will not die and so Fungal hyphae, tyloses in the .vessels and dark will not become a suitable medium for the contents in the ray cells and vertical parenchyma rearing of brood. Aggregating mechanisms have are found in such dead cores. In contrast with been demonstrated in a number of cases. Those heartwood" these cores are readily invaded. by beetles which initiate the galleries produce sapstain and rot fungi (Milligan 1972). volatile chemicals in the hind gut which, in Evidently a pathogenic sapstain fungus is combination with volatiles emanating from the 38 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL. 21, 1974

wounded host, serve as powerful attractants to either case reduced wood moisture is favourable others of both sexes. The insect-produced for the spread of sapstainfungi introduced by volatiles (pheromones)becomeadsorbedon faecal the bark beetles. As a practical expedient, logs material which is discharged an hour or two after are stored in ponds or under water sprays so as to feeding begins. Madrid, Vite & Renwick (1972) limit. the spread of sapstain. Although the fungi have recently shown that. aggregating associated with pine bark beetles have not been pheromones are also produced in the hind gut of found to be particularly virulent pathogens, their male P. flavicornis. Observations on the association would appear to be an essential one behaviour of New Zealand Platypus have for for the success of both organisms. When small some time indicated the existence of such diameter Nothofagus trees are attacked by aggregating pheromones. During the 1972-73 Platypus the associated pathogen first establishes flight season it was found that freshly emerged itself in the drier, innermost sapwood and then males of P. apicalis emit an odour which is so spreads oUtwards until it reaches limits imposed distinctive that the sexes can readily be separated by wood moisture and defensive reactions of the on this basis alone. So far it has not been shown outer sapwood. Duriug seasonal droughts, and that the odour is attractive to others of the species especially on severely drained sites, centrifugal under laboratory conditions. In earlier field advance of the fungus may be accelerated. Radial experiments it was found that trees near cages prolongations of killed sapwood occur at the containing emerging beetles became heavily tunnels and where spearheads of the advancing attacked by wild populations. Since the caged fungus break through gum barriers. As a rule beetles could not reach these trees it appeared these small trees do not die, even though they are that additional odours from the wounded host severely attacked. On the other hand trees which were not initially essential for attraction of were only lightly and abortively attacked have others. On these grounds the existence of an succumbed to the pathogen when a drought attractant originating from the beetles was occurred in the following summer. even without deduced. a second attack in the drought year. This iridicates that the pathogen can survive for at Attempts to test the attractiveness of chemicals least a year in trees which were only abortively to P. aPicalis in the laboratory have been attacked by Platypus. Surviving trees are left with confronted with the difficulty that freshly a core of pathological wood which is often stellate emerged adults are initially attracted to light, and in section, or, if not stellate, then with the this attraction over-rides those of a chemical boundaries only rarely coincident with the nature. Immediately before boring into the wood growth rings. Rot fungi may erode these cores, in the case of the male, or before a female joins a especially where aerobic conditions prevail close male in a tunnel, the attraction to light must be to the Platypus tunnels. In field experiments, all reversed. Such a phototropic reversal probably N. fusca over 35 em in diameter which were occurs as a result of flight (Graham 1961). The severely attacked died within two to four years. "male odour" of P. apicalis is emitted soon after One tree, attacked over the summer of 1965-66 beetles emerge, so if the odour detected indicates suddenly died in the following October, that is in the emission of an aggregating pheromone some less than a year. Though susceptibility to this sort aggregation should occur in flight as well as at the of mortality is not necessarily equal in the various surface of host material. species of Nothofagus, none is immune. Platypus Droughts have long been recognised as a and the associated pathogen have been found to common cause of bark beetle outbreaks in be involved in most instances of deaths of mature coniferous forests. That flooding may also Nothofagus examined since 1965. An important render trees susceptible to bark beetle attack exception is the recent deaths of N. truncata eight (Anderson 1960) is comprehensible if it results in to ninety centimetres in diameter in the Rai partial death of the root systems, so that the Valley-Whangamoa area, where dieback and uptake of water by Ihe roots becomes less than deaths were associated with a stem canker not transpiration losses during warmer weather. In caused by fungi and not linked with insect attack. INSECTS DAMAGING BEECH. FORESTS 39

Nowhere else in the world have species of difficulties in sawing, seasoning and treating. Platypodidae been implicated as vectors of There are, especially in western Southland, tree-killing pathogens, so their role in forests has extensive areas of N. menzwsii which'is sawn, not been 'related to that of aggressive Scolytidae. seasoned and treated without undue difficulty. Nevertheless a number of similarities appear. Furthermore,' in mixed N.fusca and N. menziesii One that is perhaps crucial is that dfought, and forests elsewhere, the proportion of the latter hence wood moisture of the stem,'immediately could readily be increased by selective thinning affects the spread of fungi which are introduced of the regeneration. Natural Nothofagus forests by both groups of insects. Only if the fungi all suffer from the prevalence of insect and rot spread rapidly is the tree killed. In the case of a defecIs so Ihat little interest has been aroused for bark beetle which completes its life cycle in about their"managemell;t on ,a commerCial s(:ale. two months, eggs are laid about a week after the It seems that much of the stem, defect arises attack starts, hatch a week after laying and larvae directly from sublethal Platypus attack on are fully grown after feeding for three weeks growing trees, but rots of the upper stem are (Anderson 1960). Newly hatched larvae commonly associated with dead branches, If probably have least capacity to 'overcome host pathological wood has been formed below the resin reactions to wounding, so tissues near the crown, rots entering through dead snags, may egg gallery must be effectively dead two weeks more readily s'pread downwards. D.A. Franklin after attack starts if the larvae are to survive. (pers. comm.) has shown that rot fungi are absent Anderson remarks that, once large bark. beetle from branch tra<;es p!,~ned fjve years previously, populations are developed. even the most so there seems;' a real' prospect 'of minimising vigorous trees are attacked and' killed, but the defects if trees are pruned to the height required number of offspiing produced in such initially for a merchantable log, espeCially if pathological vigorous trees"is )ow. Death of vigorous' trees, wood caused by Platypus attack can be minimised whether of Pinus or Nothofagus, depends on there at the same time (see also Frankliii 1974, p.19). being large numbers of inoculated wounds at any i'," ", '-\,' .., .," :.-;..'-': " one level between roots and crown - or upOn A silvicultural regime which would produce concentratioy ofi~se~t 'attack. TO. ensure high beech logs wiIh least defect in the shortest time is density attack; aggregating mechanisms are plainly'needed. Widely spaced saplings of N. me'nzwsii;' nUrSe necessary, so it is hardly, surprising that initial arising" in a 'low' crop such as evidence of aggregating behaviour has been FUchsin or Lepwsj"mnum will break crowns from found in New Zealand Platypus. Platypus life heights of about six metres and such trees, with qicles are completed in approximately two years, large' crowns 'and correspondingly large root circles, are' known to increase in 'diameter at rates .: and small grou ps of eggs are laid over a :. ':', ..'-~" considerable period, so it is less dependent on of up to 16 mm a year. Short, large diametertrees rapid tree death than are the bark beetles. which were resistant to windthrow could also be Furthermore, when it attacks living trees in produced by thinning the thicket stage of dense which heartwood is developed, wood with a regeneration to final crop spacing as soon as the reduced moisture content for the initial minimum of height growth was obtained. establishment of Ihe pathogen is always available Pruning to an appropriate height would be at the transition zone. In fact rapid drying of the required. The thinning operation would create stem above a block in conducting tissue may be minimal Platypus hazard because the wastes inimical to the development of brood which would be too small to support broods, and the depend on yeasts rather than on sapstain fungi. crop stems would be below the diameter susceptible to attack. Windthrow, which favours PLATYPUS AND BEECH MANAGEMENT local outbreaks of Platypus in untended stands, Johnston (1972), referring to West Coast would be least likely in a stand of short trees with Nothofagus and beech-podocarp forests, reports large root circles. Large crowns would promote that the beech component has been little utilised most rapid attainment of merchantable because of extensive hidden decay and diameters, reducin!( the period of growth during 40 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL. 21, 1974

which the crop was susceptible to Platypus FRANCKE-GROSMANN,H. 1963. Die Ubertragung der Pi!lOora damage. The only stage when the crop trees bei dem Borkenkiifer Ips acuminatus Gyll. Zeitschriftfilr would be prone to damage would be when Angewandte Entomologie 52: 355-61. harvesting commenced, when Platypus from the FRANKLIN,D.A. 1974. Beech silviculture in the South Island. surroundings would be attracted by stumps and Proceedings of the New Zealand Ecowgi¤al Society: 21. logging wastes. However, logging of such a high quality tended stand is at least 50 years away, so GOYER,R.A.; BENJAMIN,D.M. 1972, Influence of soil fertility there is ample time to perfect methods of on infestation of jack pine plantations by the pine root weevil. Forest Scieru;e 18: 139.47, controlling Platypus populations. None of the other insects associated with GRAHAM.K. 1961. Air-swallowing: a mechanism in photic Nothofagus seem likely to create serious problems reversal of the beetle Trypodendron. Nature 191: 519.20. ' in the management of N. menziesii. JOHNSTON, A.D. 1972. Management of West Coast beech forests. New Zealand journal of Forestry 17: 180-8.

MADRID.F.; VrTF.,J.P.; RENWICK,j.A.A. 1972. Evidence of aggregation pheromones in the ambrosia beetle Platypus REFERENCES flavicornis (F.). Zeitschrift filr Angewandie. Entomowgie 72: ANDERSON,R.F. 1960. Forest and Shade Tree Entomology. John 73-9, Wiley & Sons, Inc., New York. 428 pp. ' Mr'LLIGAN,R.H.' '1972. A review of beech forest pathology. ~, BUTCHER,] .A. 1968. The causes of sapstain in red beech. New New Zealand journal of Forestry 17: 201~11. Zealand Journal of Botany 6: 376-85. MORGAN.F.D. 1966. The biology and behaviour of the beech CALLAHAM, R.Z.; SHIFRINE,M. 1960. The yeasts associated buprestid Nascioides enyci (Sharp) (Coleoptera: with bark lJe-etles. Forest SciRnce 6: 146~54. ' Buprestidae) with notes on its eco}ogy and possibilities for its contro!.' Transactions of the Royal Society of New COCKAYNE,L. 1926. MonograPh on the New Zealand Beech Zealand 7; 159.70. ' 'Forests, Part 1. "New Zealand State Forest Service Bulletin NO.'4, Government, Printer, Wellington, SKOTTSBERG,C. 1949. Influence of the Antarctic Continent on the vegetation of southern lands. Proceedings of the 7th COSTER, J.E. 1969. Observations on Platypus fiavicornis Pacific Scie1u:e Congress (New Zealand) 5: 92.9. . (Coleoptera: Platypodidae) in southern pine beetle WARDLE, .A. 1970, Ecology of Nothofagus solandri. New infestations. Annals of the Eniomologic'al Society. of AmeriCa J 62: 1008.t 1. . Zealand journal of Botany 8: 494~646.

FAULDS, W. 1973. Discolouration, associated witli Platypus WARDLE,, j.A. 1974. The life history of mountain beech wounds in living Nothofagusfusca. New Zealandjournal," of (Nothofagus solandri var Cliffortwides). Proceedings of the Forestry Science 3: 331~41. New Zealand Ecologi¤al Society 21: 21-6