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 insects and diseases, while comparable with that played by Pinus in the stem rots and insect damage in untended stands northern hemisphere. Each genus 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 pines 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), pine 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 beetle 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 moths (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 beetles, 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 (Scarabaeidae) 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