P. B. CARNE*, R. T. G. GREAVES? and R. S. MCINNES*

Transcription

1 J. Aust. ent. Sac., 1974,13: INSECT DAMAGE TO PLANTATION-GROWN EUCALYPTS IN NORTH COASTAL NEW SOUTH WALES, WITH PARTICULAR REFERENCE TO CHRISTMAS BEETLES (COLEOPTERA : SCARABAEIDAE) P. B. CARNE*, R. T. G. GREAVES? and R. S. MCINNES* *Division of Entomology, CSIRO, Canberra City, A.C.T ?Forest Research Institute. Austrulian Dcpurtment of Agriculture. Canberru, A. C'T Abstract The Christmas beetles Anoplognathus chloropyrus and A. porosus feed on the leaves of eucalypts, particularly E. grandis, in plantations established for wood pulp production. A. chloropyrus is highly gregarious, causes more damage than does A. porosus, and tends to be present in high numbers in alternate years. Because of the timing of the insects' life cycles, and their feeding preferences, defoliation levels below about 50% are unlikely to reduce the rate of tree growth. Severe defoliation is limited to young trees planted on old grasslands which provide a favoured breeding place for the insects. Possible methods of minimizing damage by A. chloropyrus are discussed. Introduction In Australia, woodland eucalypts and eucalypts grown in plantation are attacked by a wide variety of phytophagous insects (Jacobs 1955). During the past decade, the damage caused by insects feeding on planted eucalypts has ceased to be a problem limited to shade trees in pastoral areas and to urban amenity plantings. Since 1960 large commercial plantations of eucalypts have been established to provide wood pulp for the paper industry. Near Coffs Harbour, on the north coast of New South Wales, a private company has established some 4,000 ha of plantation, to which a further 500 to 600 ha are being added annually. Some of the eucalypt species planted are severely attacked by leaf-eating or wood-boring insects. In some years the former have almost completely defoliated large numbers of young trees, particularly in plantations of the species (Eucalyptus grandis (Hill)) most extensively planted. Many trees have been lost through structural damage caused by birds which feed on wood insects. Insects have damaged forest eucalypts regenerated after logging in central Tasmania (Greaves 1966), and they pose a threat to both regeneration and plantations in the north of that State (Mr K. L. Taylor, personal communication, 1972). Damage by insects which may lead to a reduction of the potential volume increment of planted trees is of concern to an industry in which maximum production and short rotations are of great significance. A growth rate of not less than 15 m3/ha on a 12 to 15 year rotation is considered necessary to provide pulpwood at an economic cost in the Coffs Harbour area (Pryor, Chandler and Clarke 1968). It seems likely that the plantation-grown eucalypts will be used increasingly in Australia as a means of supplementing the supply of wood pulp obtained from natural forests (Cree 197 1). Consequently, an assessment of the entomological problems likely to be encountered in extensive, even-aged, single-species stands is very desirable. Although much progress has been made by forestry research workers in developing techniques for site preparation, nursery establishment and plantation management, the situation remains sufficiently flexible for modifications of management practices to be introduced if they can be shown to minimize, at an economic cost, the losses caused by insects. In this paper we describe the biology and behaviour of 2 closely related species of Christmas beetle, and the effects of defoliation by them on the growth of the trees. Studies on several of the other insects mentioned are in progress, and will be reported in subsequent papers.

2 190 P. B. CARNE, R. T. G. GREAVES and R. S. McINNES The study areas The plantations within which our studies were made lie within a 50 km radius of Coffs Harbour, New South Wales, approximately 434 km NNE of Sydney. Most of the plantations have been established on the coastal plain which is some 8 to 16 km in width and is drained by the Bellinger River. The river occupies 2 valleys; the earlier established plantations, in which most of our studies were carried out, lie in the North Arm valley (Fig. 1). ~~ I0 km-, SCALE FIG. l.-map showing the!ocation of Coffs Harbour, and the two valleys of the Bellinger River (redrawn from Warner (1969) with permission of the author). The climate of Coffs Harbour is subtropical. Average monthly temperatures (for the 20-;year period to 1971) ranged from a minimum of 6.6"C in July to a maximum of 26.6 C in January. Annual rainfalls averaged 1770 mm (range 1070 to 2881 mm). The rainfall increases towards the Dorrigo plateau to the west, and decreases to the south. Warner (1969) estimated mean annual rainfalls of 1880 mm for the North Arm valley, and 1575 for the South Arm valley. The predominant soils are derived from Palaeozoic shales and phyllites, and from deeply weathered granitic intrusions. Red and yellow podzolic soils predominate but recent alluvium occurs adjacent to watercourses and there are small areas of soils derived from Tertiary basalt flows. The soils are invariably acidic, and deficient in phosphorus, potassium and nitrogen, especially in former grasslands. The original vegetation was eucalypt forest, dominated by blackbutt (E. piluluris Sm.) on the ridges, and by flooded gum (E. grundis (Hill)) in the gullies. Both species occurred on the middle slopes, together with Sydney blue gum (E. sulignu Sm.). There are several large State Forests in the area, although most of the river flats were cleared for dairying upwards of 100 years ago. Much of the area has become uneconomic for dairying, and it is largely on the old grasslands that plantations have been established. Some farms, not available for purchase, remain as "islands" of open pasture within large areas of plantation. Planting began in 1959, and reached the

3 CHRISTMAS BEETLE DAMAGE TO EUCALYPTS 191 current rate of 500 to 600 ha p.a. in Pryor and Clarke (1964) and Pryor, Chandler and Clarke (1968) give detailed accounts of the processes of plantation establishment and management. Eucalyptus grandis, by virtue of its high growth rate and excellent pulping qualities, is the species most widely planted. It has proved capable of good growth in a wide range of sites, including areas considerably removed from its natural habitat. E. pilularis and E. saligna were at first planted on sites believed to be unsuited to E. grandis, but in recent years plantings have consisted almost exclusively of the latter species. Nursery-grown seedlings are planted out at a spacing of 2.7 x 3.3 m, yielding approximately 1090 trees per ha. With the establishment and fertilizing practices adopted, annual growth rates of about 3 m in height, and 25 mm in diameter over bark, are achieved in the absence of attack by phytophagous insects. The insects attacking trees in plantations Our first inspection of the plantations was made in the summer of 1966/67 at which time damage by leaf-eating insects was severe. The trees in several hundreds of hectares of plantation, particularly E. grandis, were almost defoliated. Regular observations began in late 1967, and since then damage by a variety of phytophagous and wood-boring insects has been recorded. The most conspicuous leaf-eating insects were Christmas beetles (Anopfognathus spp.), leaf beetles (Paropsis and Chrysophtharta spp.) and sawflies (Pergidae). A sap-sucking bug (Eurymefa sp.) was abundant in the 1968/69 season, and localized but often severe outbreaks of psyllids (predominantly Cardiaspina muniformis Taylor and C. jiscella Taylor) have occurred frequently since first observed in Eriococcus coriaceus Maskell a common and often serious pest of plantation-grown eucalypts elsewhere in Australia, was observed only on isolated trees until late 1971 when a localized but severe outbreak occurred in a young plantation of E. grandis. Sporadic outbreaks have occurred in young plantations since that year. In 1971/72 and 1972/73 very high numbers of Chrysophtharta cfoelia StPl occurred in 1 to 3 year old plantations of E. grandis. Wood borers were common in many plantations, particularly in those where the young trees had been stressed by grass competition or by frost damage. A very high proportion of windthrown trees was found to have been infested by a cossid moth (Xyfeutes sp.), and mechanically weakened by Yellow-tailed Black Cockatoos (Cafyptorhynchus funereus Shaw) which tear away the bark and large volumes of wood in searching for the larvae (Came and McInnes, unpublished data). Our appraisals of the situation in 1966/67 and 1967/68 indicated that Christmas beetles were at that time the most damaging and widespread of the defoliating insects present, and our early studies were therefore largely restricted to those species. Field collecting and light trapping showed that 7 species of eucalypt-feeding Christmas beetle species occurred in the area. These were : Anoplognathus porosus (Dalman), A. chloropyrus (Drapiez), A. viriditarsis Leach, A. olivieri (Dalman), A. concofor Burmeister, A. prasinus (Laporte), and A. rhinastus Blanchard. Of these species, only the first 3 occurred in large numbers. Although abundant in a light trap operating close to natural forest, A. viriditarsis did not seriously defoliate the planted trees. All significant damage by Christmas beetles in plantations was due to A. porosus and A. chloropyrus. In A. porosus was the predominant species seen in the field. In some subsequent years, however, A. chloropyrus was predominant in many plantations. Damage was restricted almost entirely to trees of E. grandis, and to small plantings of E. dunnii Maiden. Very little feeding occurred on trees of either E. safigna or E. pilularis. The Christmas beetles, A. porosus and A. chloropyrus Distribution and taxonomy The most recent review of the genus Anopfognathus Leach is that of Carne (1957). Recent collecting has shown that the taxon A. porosus includes several forms

4 192 P. B. CARNE, R. T. G. GREAVES and R. S. McINNES of undetermined status. The form occurring in the Coffs Harbour district is one common to a large portion of eastern Australia extending from north Queensland to the central coast of New South Wales. It is largely confined to the coastal plain, but does extend to the New England Tablelands of New South Wales. A second form occurs on the southern coast of New South Wales, and a third on the Southern Tablelands of that state. The form at Coffs Harbour has the pronotum and elytra of a pale biscuit colour, and the pygidium with bright metallic green reflections. A. chloropyrus is also a variable species, the form occurring at Coffs Harbour having elytra of a much paler colour than those of the form occurring on the tablelands. General biology and behaviour The adult stage.-the first beetles of the season appeared on the trees between mid November and mid December. A second and smaller peak usually occurred in January, followed by a rapid decline during February. Adults were rarely seen after the end of that month. On alighting beside a female, the male immediately attempts copulation but is usually rejected. It mounts the female and remains in a precopulatory position for many hours, intermittently attempting intromission, and is unable to feed. The female continues to feed throughout the day, although feeding becomes desultory or ceases when air temperatures exceed 32 C. Copulation occurs in the early evening, or during late afternoon when the sky is overcast. After mating, the male leaves the female and begins feeding, but usually remains in her vicinity during the night. The next morning, the male either attempts further copulation with the same female, or flies off in search of another. Marked females of A. porosus were observed to remain feeding on the same shoot for several days before leaving the tree and entering the soil for oviposition. The females burrow into the soil to a depth of from 5 to 10 cm and lay their eggs, each in a separate small cavity. The female apparently burrows laterally during oviposition, as the eggs were usually found in small groups spaced several centimetres apart. During the latter half of the flight season, a proportion of the females feeding on trees was found to have partially or completely spent ovaries indicating that, following oviposition, they leave the soil and resume feeding. Dissection of the ovaries of both A. porosus and A. chloropyrus showed that both species mature approximately 40 eggs. The immature stages.-the pearly white eggs are at first oval and do not occupy the full volume of the individual soil cavities in which they are laid by the female. During incubation, which occupies 10 to 14 days at Coffs Harbour, the eggs swell to a near-s herical form and almost fully occupy their soil cavities. Just prior to hatching, t R e eggs of A. porosw measure 3.0 to 3.3 mm in diameter; those of A. chloropyrus are somewhat smaller. The larvae pass through 3 instars, the durations of which vary within very wide limits not yet fully determined. Sampling of field populations at intervals throughout the year and laboratory rearing indicated that both species normally have a 2-year life cycle, but that a small roportion of the larvae may complete their development within a single year, The R rst instar occupies at least 4 to 5 weeks, and the second instar about 5 months. Moulting to the third instar occurs mostly in August. A few larvae moult earlier, in some cases as early as late April; they may represent that portion of the population capable of completing development within 12 months. The majority of larvae feed throughout the summer months, and pupate and emerge in the following spring and summer. The form of A. porosus occurring on the New England tablelands also has a 2-year life cycle (Hassan 1971). The larvae feed primarily on organic matter in the soil, and do not appear to seek out plant roots. Fully fed larvae are readily distinguished from those which are still feeding. The fully fed larva seals itself off in a distinct earthen cell, 5 to 15 cm below the ground surface. The inner wall of the cell is smooth and compacted, the larval gut empty, and the whole body an opaque creamy yellow with accumulated fat body. The actively feeding larva is not found in a discrete cell; the hindgut is distended with

5 CHRISTMAS BEETLE DAMAGE TO EUCALYPTS 193 ingested soil which imparts a bluish-grey colour to the abdomen, and fat body development is incomplete. Immediately prior to pupation a prepupal stage is entered. The prepupa, if removed from its cell, is incapable of crawling or of other organized movement. The pupal stage lasts about 2 weeks, and hardening of the newly transformed adults occupies a similar period. A B Y C r i FIG. 2.-Stages in the destruction of E. grandis leaves by Anoplognathus porosus. A. Initial feeding cuts, showing their characteristic zig-zag pattern. B. A partly destroyed leaf; note the tendency to feed within the leaf margin. C. A leaf at the conclusion of feeding (J. P. Green). Feeding behaviour and host preferences Whereas most leaf-eating insects cling to the margins of leaves and gradually pare away the tissue, Anoplognathus adults settle on the leaf lamina (usually facing towards its apex), anchor themselves with their long opposable claws, and feed whilst in this position. Feeding cuts begin at the leaf margin (Fig. 2A), and then follow a characteristic zig-zag pattern within the leaf blade as the beetle moves backwards. The beetle later moves forward again, and further feeding partly destroys this pattern (Fig. 2B). The beetles are wasteful feeders : although they do not consume the tissues of the leaf margin, these are severed by subsequent feeding cuts and fall to the ground. At the conclusion of feeding by the beetle, the E. grandis leaf usually consists of the midrib, bordered by small irregular areas of unconsumed tissue and, very characteristically, the basal portion of the original leaf margin (Fig. 2C). When feeding on their preferred food plant (E. dunnil), A. chloropyrus frequently destroy the entire leaf, and feed readily on leaves of all ages, including the terminal leafy shoots (Fig. 3). Whereas eucalpyts in cooler areas may bear leaves up to several years of age, young trees of E. grandis at Coffs Harbour rarely retain leaves more than 12 months old. Growth does not cease completely at any time of the year, although it is minimal in July-August. Consequently it was not possible to recognize distinct cohorts of leaves within the crown. However, at the beginning of the flight season in November

6 194 P. B. CARNE, R. T. G. GREAVES and R. S. McINNES or December, three broad age classes of leaves could be recognised: a minority of leaves produced during the preceding summer, which were losing their photosynthetic ability and which were shortly to be shed by the tree; a majority of mature, functional leaves produced during the autumn, winter and spring; and a minority of immature leaves produced within the preceding few weeks. The latter graduated into the second class during the course of the flight season, and were replaced by further new growth. On trees of E. grandis, the beetles fed almost exclusively on leaves of the intermediate class. The older leaves were partly consumed only when the beetles were extremely numerous, while the terminal new growth appeared to be virtually immune to attack. Toward the end of the flight season, the trees shed most of the leaves damaged by the beetles. As vigorous new growth continued after the fights ceased, it was often difficult to identify, by April or early May, those trees that had been extensively defoliated in December and January. Of the main eucalypt species planted at Coffs Harbour, E. grandis was preferred by both A. porosus and A. chloropyrus. The insects rarely fed on trees of E. safigna and were never recorded on those of E. pilularis. E. dunnii, a species that does not occur naturally in the area, has been planted experimentally in small blocks within areas planted mainly to E. grandis. A. chloropyrus exhibited a very marked preference for this eucalypt. Whereas pure stands of E. grandis were often attacked by both A. porosus and A. chloropyrus, in the vicinity of stands of E. dunnii very few A. FIG. 3.-Total defoliation of a young tree of E. dunnii by Anoplognathus chloropyrus (L. D. Pryor).

7 CHRISTMAS BEETLE DAMAGE TO EUCALYPTS 195 chloropyrus were found on E. grandis, most of the beetles congregating on the E. dunnii. In a plantation where E. grandis was replaced by E. dunnii in every fourth row, counts of beetles were made on eight occasions during the 1969/70 season. In 3 counts made shortly after beetle flights began (9 to 16 December) 82 to 88% of the total A. chloropyrus present were on E. dunnii. In 5 counts made during the peak of the flight season (18 December to 8 January), 93 to 97% of the A. chloropyrus were on E. dunnii. The extent of defoliation was assessed by eye within a rating scale of 0 to 5: 0 = no evidence of feeding 1 = <20% of leaves damaged by feeding 2 = >20% ~40% of leaves damaged by feeding 3 = >40% <60% of leaves damaged by feeding 4 = >60% 40% of leaves damaged by feeding 5 >80% of leaves damaged by feeding Samples of 50 trees were examined and the extent of feeding on each assessed within this scale. The average defoliation rating for trees in the samples provided a statistic that enabled the abundance of the insects in different sites to be compared. Although occasional trees of E. grandis attacked by A. porosus alone were rated in scale 3 or 4, average ratings rarely exceeded 2.0. Where A. chloropyrus predominated, some trees of E. grandis were rated in scale 4 or 5, with average ratings as high as 4.0. Trees of E. dunnii were often very severely defoliated by A. chloropyrus, and average ratings of 4.5 to 5.0 were not uncommon. The relationship between average defoliation rating and the proportions of trees defoliated to different extents was determined from data for 117 assessments made in 13 study sites. The data for trees defoliated to scale 3 or more are summarised in Table 1. TABLE 1 PERCENTAGES OF TREES IN 50-TREE STUDY SITES WITH VARIOUS LEVELS OF DEFOLI- ATION, IN RELATION TO AVERAGE DEFOLIATION RATINGS OF THE SITES. Average defoliation rating of Percentage of trees scored in site Predominant insect species defoliation ratings <1 >1 t <3 > A. porosus t l nil nil A. porosus 12 <I nil A. chloropyrus 35 3 nil A. chloropyrus The trees were rarely attacked until they exceeded 2.0 to 2.5 m in height. As few trees attained this height by the end of their first growing season, the onset of attack was normally associated with the second summer after planting, when the majority were some 3.0 to 3.5 m in height. Occasionally the upper crowns of 1 year old trees were fed upon, but such trees were always conspicuously taller than those surrounding them (Fig. 4A). Carne (unpublished data) observed a similar phenomenon in the feeding behaviour of other species of Anoplognathus. The predominant species attacking E. blakelyi Maiden on the Southern Tablelands of New South Wales, A. montanus Macleay, did not feed on trees less than 2.5 to 3.0 m in height. However, when the shoots from smaller, unattacked trees were placed in the crowns of taller trees being attacked, the beetles fed readily on their foliage. Likewise, when shoots from both very small and larger trees were presented to caged beetles, leaves from both were eaten to an equal extent. It thus appears that the immunity of small trees from attack may be due to a preference of the insects for feeding at a certain minimum height above ground rather than to an attribute of the leaves themselves. Trees in their second, third and sometimes fourth years of growth were subject to defoliation by the beetles. Thereafter, attack declined and became negligible in most plantations aged 6 years or more, except for trees on their margins. The decline

8 196 P. B. CARNE, R. T. G. GREAVES and R. S. McINNES Z? 8 Z 5 n z I t 3 Y U + 2 w Y U U a plantation continues FIG. 4.-Beetle attack (solid) in E. grandis plantations of different ages. A. Beetle attack restricted to the upper crowns of exceptionally tall trees in a very young plantation. B. Beetle attack at the beginning of the flight season in a susceptible plantation. Feeding is concentrated on the trees bordering the plantation and access tracks within it. Beetle attack extends into the body of the plantation during the course of the flight season. C. Beetle attack in an older plantation with closed canopy is restricted to the marginal trees throughout the flight season. of attack was associated with increasing closure of the canopy, usually complete when the trees were 3 or 4 years old. However, in poor sites, canopy closure was delayed and beetles were recorded in appreciable numbers until the trees were 5 or 6 years old. In one site where canopy formed when the trees were 2 years old, attack was restricted to trees in the 2 outer rows. Similarly, attack occurred only on the marginal trees where forest abutted on open grassland, Our observations suggested that the beetles did not enter dense, closed-canopy stands. Damage to trees was also observed along access tracks. At the beginning of the flight season, most beetles seen were on marginal trees (Fig. 4B). In stands where canopy was not complete, this concentration of beetles was transient for they dispersed into the plantation later in the season. In older plantations the beetles were restricted to the marginal trees throughout the flight season (Fig. 4C). Occasional groups of beetles were found within larger plantations following canopy closure but only in places where open space resulted from trees failing to establish, or where established trees had been windthrown. Such areas were characterised by persistence of the grass-dominant sward which, under closed-canopy conditions, was largely replaced by herbaceous and woody perennial species. Fig. 5 represents diagrammatically a hypothetical plantation aged 3 years, just prior to canopy closure. It is bounded by an older, closed-canopied plantation to the west, by mature natural forest to the east, and by open grasslands to the north and south. The diagram shows the concentration of attack on the marginal trees of all 3 stands where they abut on grassland, and on the trees bordering access tracks within the younger plantation. It also illustrates damage in an open area within the body ofthe plantation.... Distribution of the immature stages Using a special sampling plough (a modification of that described by Roberts and Ridsdill Smith 1972) we investigated the distribution of the immature stages of A. porosus and A. chloropyrus. Preliminary checks showed that larvae were rarely found deeper than 10 cm in the soil. The width of the trench cut by the plough was fixed at 15 cm, the depth at 10 cm. Larvae were recovered from the trench or from the inverted sod.

9 CHRISTMAS BEETLE DAMAGE TO EUCALYPTS I97 FIG. 5.--A hypothetical plantation bordered by grassland, an older, closed-canopy plantation, and mature forest. Each circle represents a tree; those attacked by beetles are shown solid. In the central plantation, just prior to canopy closure, beetle feeding is concentrated on trees adjacent to grassland and access tracks, and on those in an area (left of centre) where some trees died and left a relatively open area within an otherwise dense stand. Feeding on trees in the older plantation and in natural forest is restricted to those on their extreme margins. The sampling data obtained are not adequate to describe the distribution of larvae due, in part, to the low population levels of the insects in many plantations and in part to the extreme difficulty of sampling in older plantations with a dense understorey of woody shrubs and an uneven surface resulting from the Mathis plough method of establishing these stands (Pryor, Chandler and Clarke 1968). Nevertheless, certain trends were reasonably clear. The larvae were most abundant in grazed pastures and in young plantations established on old pasture lands, and least numerous in the older plantations where woody perennials had replaced the pasture. Those larvae found in the older plantations were mainly located in the same situations as were the adults, i.e. near their margins, adjacent to access tracks within them, and in grassy openings where canopy was incomplete. The highest larval densities were almost invariably associated with moist deep soils on creek benches and valley bottoms. Very few larvae were recovered from the drier and shallower soils of hill slopes. A. chloropyrus appeared to occupy an even moister environment than A. porosus. Whereas the pattern of abundance of the larvae of A. porosus was broadly consistent with that of the subsequent adult stage, such consistency was not found for A. chloropyrus (see next section). Behavioural diflerences between the two species A. porosus and A. chloropyrus are closely related species (Came 1957), and exhibit similar feeding and mating behaviour patterns. However, they differ markedly in adult gregariousness. In a young plantation attacked by A. porosus the beetles were more or less evenly distributed between the trees throughout the period of peak abundance. Apart from sexual pairing, the adults were not markedly gregarious, and they occurred in all portions of the crown which bore foliage of the preferred age-class. Defoliation was a gradual process; the beetles rarely dispersed from a tree as a consequence of having stripped it of all suitable foliage. In the low-lying sites where A. chloropyrus predominated, a very different pattern of attack was observed. Except when its numbers were high, and all the trees were attacked, the adults aggregated in high numbers on a relatively small proportion

10 198 P. B. CARNE, R. T. G. GREAVES and R. S. McINNES of the trees in the area. Aggregations of beetles often began on particular portions of the crown of a tree although, eventually, the whole crown was fed upon. These differences were very noticeable in plantations where the 2 species coexisted. Counts of beetles on 50 trees were made in a plantation near Valery in the 1969/70 season. The data for total beetles, number of trees attacked, and the average number of beetles per attacked tree are shown in Table 2. It will be seen that, as numbers of A. porosus increased the beetles were found on a progressively higher proportion of the trees, and that the average number of beetles per attacked tree consequently remained fairly constant. The highest number of beetles (260) was distributed between 82% of the trees. In contrast, as A. chforopyrus numbers increased, so did the average number of beetles per attacked tree. Even when the maximum number of 744 beetles was recorded, these were distributed between only 627; of the trees. TABLE 2 DATA ILLUSTRATING THE GREATER DEGREE OF GREGARIOUSNESS EXHIBITED EY BEETLES OF A. CHLOROPYRUS THAN BY THOSE OF A. POROSUS; 13 SETS OF DATA FROM 50 TREE SITE AT VALERY, SEASON (NOT IN DATE SEQUENCE). No. of No. of attacked A. porosus trees Average no. bettles per attacked tree No. of Average no. No. of attacked beetles per A. chloropyrus trees attacked tree O 1.o I Due to their capacity to aggregate in high numbers, A, chloropyrus beetles frequently stripped the crown of a particular tree within a period of a week or less. They then moved en musse, within a period of a few hours, to an adjacent tree which had previously borne few or no beetles. Counts of beetles were made at intervals of from 1 to 6 days on several hundred 2 year old trees of E. grundis near Bonville in the summer of The counts for 5 of the trees are tabulated below, and illustrate this abrupt change in numbers. Asterisks indicate the date on which each tree was almost completely stripped of foliage : Tree Numbers of A. chloropyrus present on number 28 Jan 30 Jan 5 Feb 6Feb 10Feb 11 Feb * * * * * 0 0 Sampling of the larval stages in the soil of young, open-canopied plantations gave estimates of the abundance of A. porosus which correlated closely with the abundance of their adults subsequently recorded on nearby trees. In the case of A. chforopyrus, the number of larvae found was usually far less than the subsequent number of adults counted on adjacent trees. It seems that A. porosus is the less mobile of the two species and that it breeds, while the environment remains favour-

11 CHRISTMAS BEETLE DAMAGE TO EUCALYPTS 199 able, in the vicinity of its food trees whereas A. chloropyrus must be presumed to disperse more widely prior to oviposition, and to fly longer distances in search of its preferred host trees. Fluctuations of abundance Methods of study.-we measured the abundance of the several species of Christmas beetle by two methods: (1) A light trap, operated near Bonville approximately 13 km S of Coffs Harbour, was situated in open grassland bordered by eucalypt plantations of several species and age classes, and by relics of natural forest. The trap had a 160 W Mazda mercury vapour discharge lamp and was operated nightly from 1800 to 0600 h during the flight season. The daily catch was stored in polythene bags and deep frozen for later sorting and counting. (2) A number of 50-tree study sites in widely separated 2 year old plantations of E. grandis was established each year. Fifty trees distributed between 3 or 4 adjacent rows, were individually tagged before flights began in early summer. The sites were visited at intervals of 2 or 3 days throughout the season. On each occasion, the number of each species of beetle present on each tree was recorded. The accumulated data enabled the seasonal increase and decline of numbers within sites to be followed, and comparisons to be made of the timing of life cycle events and abundance of the insects in different sites. In cooler parts of Australia, where the growth rate of eucalypts is much less than at Coffs Harbour, it was possible to use the same group of trees to assess the level of beetle populations for 3 or 4 years. This could not be done at Coffs Harbour where the majority of 3 year old trees of E. grandis were too tall to permit identification and accurate counting of the beetles present on them. This difficulty was overcome to some extent by carrying out annual surveys of all the plantations of susceptible age classes, noting the species of beetle present, and assessing their abundance in terms of defoliation ratings. These surveys indicated that light trap catches provided an acceptable index of gross changes of beetle abundance, and of changes in the predominance of species, from one season to the next. A ' B 1969 I970 FIG. 6.Seasonal trends in the abundance of two species of Anoplognathus on young trees of E. grandis in plantations near Coffs Harbour in the 1969/70 summer. Based on actual counts of the beetles present on 50 trees in each site. The figures illustrate the rapid increase of beetle numbers to a major peak at the beginning of the flight season, the occurrence of a second peak later in the season, and the difference in beetle abundance between sites. A. A plantation at Valery, N.S.W. (location shown in Fig. 1). B. Steele's plantation, 16 km SSW of Valery.

12 200 P. B. CARNE, R. T. G. GREAVES and R. S. McINNES Trends in beetle abundance during theflight season.4ount.s of the beetles in 50-tree sites showed that both A. porosus and A. chloropyrus frequently exhibited two distinct peaks of abundance about three weeks apart. Following the onset of flights, numbers on the trees usually rose steeply to a major peak in early to mid December, and then declined even more rapidly to a low level of abundance in early January; numbers then increased again, although to a lower level than in December, before decreasing to zero. Typical examples of such fluctuations are shown in Fig. 6. In 10 representative sets of data for A. porosus from 50-tree sites during 3 different seasons, the period between peaks ranged from 11 to 46 (average 20) days. The second peak involved about half as many beetles as the first one. Light trap catches reflected this bimodal distribution but the peaks were less well defined. Day to day fluctuations of light trap catch were due, not only to changes in the abundance of beetles but also to influences, such as high winds or cold changes, that affected either the activity of the beetles or the efficiency of the trap. The observed bimodal distribution could not be interpreted in terms of the influence of seasonal temperature or rainfall. To account for the phenomenon, we set up the following hypothesis. The great majority of beetles emerge over a short period of time at the beginning of the flight season, producing the usual sudden rise in numbers on the trees, and causing the first peak in December. As the females mature their eggs and enter the soil for oviposition, abundance on the trees declines. Following oviposition, numbers on the trees again increase as the females return for further feeding, thus causing the second peak. Because of mortality during the oviposition phase, abundance is decreased and the second peak is smaller. Dissection of beetles collected by sweep net from trees at weekly intervals throughout the flight season confirmed that females with partially or completely spent ovaries first appeared about half way through the flight season, and that the proportion of such females increased abruptly in the last quarter of the season. This hypothesis was inadequate to account fully for the observed fluctuations. Firstly, our samples showed that recruitment of newly-emerged adults to the population on the trees continued throughout the greater part of the season. Secondly, the hypothesis requires that the proportion of males in the population on the trees should increase during the period when the females are ovipositing: the expected change of sex ratio was not detected. We conclude that the bimodality of beetle abundance in time may be due in part to the movement of females to and from the trees, but also in part to variations in the pattern of beetle emergence. We suspect that newly-emerged adults which contributed to the second peak may have derived from larvae which completed their development in twelve, instead of the more usual twenty-four, months. Inter-site diferences.-records from 50-tree sites showed that, in any one season, the dates of first appearance and final disappearance of beetles, as also the dates of peak occurrence, varied appreciably. Thus, at Valery in 1969/70, A. chloropyrus began flying in late November and reached maximum numbers about 20 December (Fig. 6A). However, at Steele s block, approximately 16 km SSW ofvalery, this species was already present on the trees in late November, and reached peak numbers about 12 December (Fig. 6B). Displacements of this order in the timing of life cycle events were frequently recorded in sites only a short distance apart. They presumably reflected the effects of minor environmental differences between sites. The onset of flights as recorded by the light trap near Bonville was usually preceded by heavy rain following a period of high temperatures. Thunderstorms in the area are often highly localized; sometimes 30 to 50 mm of rain fell in one site while little or none fell in others. Such erratic rainfall patterns could well be responsible for differences in the timing of flights from one site to another. Inter-seasonal $uctuations.-total light trap catches of the several species of Christmas beetle for the 6 seasons 1967/68 to 1972/73 (Table 3) show a striking alternation of years of high and low numbers. No light trap was operated in the 1966/67 season, but field observations indicated that the numbers of A. porosus were higher then than in all subsequent seasons, and that A. chloropyrus was relatively

13 ~~ ~ CHRISTMAS BEETLE DAMAGE TO EUCALYPTS 20 1 scarce. Whereas the abundance of A. porosus differed little in 5 out of 6 seasons, that of A. chloropyrus (in 5 successive seasons) and A. viriditarsis (in 6 successive seasons) fluctuated regularly over wide ranges. Comparable fluctuations occurred in the plantations. In 1968/69 and 1970/71 field trials that required the presence of at least moderate numbers of beetles (e.g. trialsdesigned to measure the loss of increment due to defoliation) had to be abandoned because of the paucity of beetles. TABLE 3 SEASONAL CATCHES OF CHRISTMAS BEETLES IN A LIGHT TRAP NEAR BONVILLE, N.S.W. Species of beetle All ofher Total Season A. porosus A. chloropyrus A. viriditarsis species beetles , , > ~ I ~,-- i9ioj7i , , / Field sampling of the larval stages indicated that most individuals of all 3 species have 2-year life cycles. It would appear, therefore, that there is a large difference in the size of the 2 broods of both A. chloropyrus and A. viriditarsis, and that these differences have persisted for at least 5 or 6 years. Defoliation studies Introduction Kulman (1971) has reviewed the surprisingly small literature on the effects of defoliation by insects on the growth and mortality of trees and noted that, in the majority of studies, loss of increment was proportional to the extent of defoliation. Very little work has been carried out on the effects of defoliation of eucalypts. Mazanec (1966, 1968) reported that moderate defoliation of E. delegutensis R. T. Baker by the phasmatid Didymuria violescens (Leach) resulted in a 50% reduction of diameter growth in the following season. He also (Mazanec 1967) noted that, following defoliation by the same insect in 2 successive seasons, the diameter growth of trees of E. regnuns F. V. Mueller was significantly reduced for the 2 following seasons. Defoliation of both E. delegutensis and E. regnuns resulted in a high level of tree mortality. These 2 species belong to a group of eucalypts which is far more sensitive to defoliation than most of their congeners (Campbell 1960). Baur (1959) showed that E. grandis seedlings are sensitive to severe defoliation. However, under plantation conditions at Coffs Harbour, we recorded no instances where trees of this species died as a result of defoliation by Christmas beetles; recovery was normally rapid and complete (see section Feeding behaviour and host preferences, p. 193). Bamber and Humphreys (1969, using iodine spectrophotometry, demonstrated that starch reserves in the wood of a range of forest species fluctuated annually, being lowest at the end of the growing season, increasing during the winter and reaching a peak just before new growth began in the spring. They studied the effects of artificial defoliation and defoliation by insects, and showed that starch levels declined as the trees were defoliated, and that the reduction of reserves following defoliation was significantly greater than the normal seasonal starch reduction in undamaged trees. They suggested that repeated defoliation by insects resulted in the depletion of starch reserves to a level which, in the absence of foliage, was inadequate to support respiration or growth. Defoliation of lesser severity, which permits the tree to survive, might be expected to result in some loss of growth, particularly if imposed at a time of naturally low starch reserves. Thus trees defoliated in late summer or in autumn would be more seriously affected than those defoliated in the spring or early summer. Using subjective assessments of starch levels based on the iodine stain reaction of sectioned shoots and roots, Cremer (1965) also showed seasonal fluctuations of

14 202 P. B. CARNE, R. T. G. GREAVES and R. S. McINNES these reserves in intact trees, and their depression following defoliation. However, he was unable (Cremer 1973) to confirm these findings when he used a more sophisticated, quantitative technique for starch estimation. Nevertheless, there is no doubt that the effects of defoliation are greatly influenced by the time at which it occurs, and that defoliation by Christmas beetles occurs at a season when the effects are likely to be relatively slight. Natural defoliation Attempts were made to measure the loss of height increment of trees due to defoliation by A. porosus and A. chloropyrus. Field trials were carried out in 3 successive years, in which up to 100 two year old trees of E. grandis, in 5 rows each of 20 trees, were sprayed at 10 to 14 day intervals with 0.2% DDT to protect them from insect attack. To provide suitable controls, and to minimize the effects of possible spray drift, we sprayed each fourth row of trees; the rows on either side of the sprayed row were left as a buffer zone, and the trees in the median row used as controls. The heights of the trees in the treated and control rows were measured in August, at which time growth was minimal, and again during the following winter or spring. In each of the 3 trials, beetle abundance in the experimental area was low, the trees in the control rows suffered only slight defoliation, and differences in the height increments of trees in the treated and control rows were not significant. In an attempt to ensure that trials were camed out in areas of plantation where high beetle numbers occurred, we planned to delay selection of the trial until flights began. This proved to be impracticable for a number of reasons. In some seasons (1968/69 and 1970/71) beetle numbers were unfavourably low throughout all the plantations. In seasons more favourable for trials of this kind, adequate populations were sometimes located only in sites inaccessible to the motorized spraying equipment required for treatment. Once flights began, numbers commonly increased to recorded maxima rapidly (see, for example, Fig. 6A). Some potentially suitable sites had to be abandoned because heavy rain, or other unfavourable circumstances, prevented application of the first protective spray before extensive defoliation had occurred ; as a consequence there were no undamaged trees available for use as controls. Artificial defoliation Significant differences of height increment were obtained only when trees were artificially defoliated. It was not possible to more than crudely simulate the effects of insect feeding, and it was recognized that defoliation imposed by artificial means might have a more or less severe effect on the tree than the removal of a comparable proportion of the tree s photosynthetic tissues by the beetles (see Kulman 1971). However, as the difficulties of measuring the effects of beetle feeding seemed insuperable, we carried out 3 trials involving artificial defoliation. Various methods of removing foliage were first tried; that adopted as simulating most closely the effects of feeding on E. grandis involved the drawing of a closed gloved hand along the leafbearing shoots, removing only the foliage of the intermediate age class usually eaten by the beetles (see section Feeding behavwur and host preferences, p. 193). Breakage usually occurred at the junction of the leaf blade and petiole, thus leaving the latter, and the naked bud in its axil, intact. We considered that beetles effectively destroyed the leaf, for the midrib and basal margin of the leaf which were normally left intact (see Fig. 2C) desiccated rapidly and would have contributed a negligible amount of photosynthate to the tree before being shed. Our removal of the entire leaf was therefore considered unlikely to be more damaging to the tree. Trees in the experimental plantations varied considerably in height at the time of defoliation. Measurement of the growth of undefoliated control trees showed that the taller trees grew more rapidly than did the smaller trees. Regression equations relating height increment to initial height were prepared for the control trees in the first 2 trials, and the loss of increment of the defoliated tree calculated as the difference between the height actually attained by each tree, and that attained by control trees of the same initial height. It was planned to protect the test trees with insecticide

15 CHRISTMAS BEETLE DAMAGE TO EUCALYPTS 203 to prevent defoliation by insects but, as numbers were low on all occasions, it was unnecessary to do so. In the first trial in 1968/69, an estimated 90 to 95% of the pertinent foliage was removed to simulate near extreme defoliation (Scale 5). Groups of trees were defoliated on dates corresponding to the beginning, middle and end of the flight season. The results are summarized in Table 4. TABLE 4 ESTIMATED HEIGHT INCREMENT LOSSES OF TREES OF E. GRANDIS MANUALLY STRIPPED OF 90-95% OF THEIR FOLIAGE. SETS OF TREES WEREDEFOLIATED ON THREE DIFFERENT OCCASIONS DURING THE 1968/69 SUMMER. No. of trees in PUP Mean height of trees in group at October 1968 (m) Date of defoliation Mean height incremeni'at August 1969 *(m) Expected Actual % loss attributable to defoliation Nov ' Jan ' Fei, ' *For explanation, see text. As subsequent observations suggested that defoliation of the order of 90 to 95% was exceptional, the degree of defoliation imposed in a further trial in 1969/70 was reduced to an estimated 75 to 80% of the preferred foliage. Separate groups of trees were defoliated on 7 occasions during the flight season, and the results are given in Table 5. No mortality of trees occurred in this, or in the 1968/69 trial. TABLE 5 ESTIMATED HEIGHT INCREMENT LOSSES OF TREES OF E. GRANDIS MANUALLY STRIPPED OF 75-80?; OF THEIR FOLIAGE. SETS OF TREES WERE DEFOLIATED ON SEVEN DIFFERENT OCCASIONS DURING THE 1969/70 SEASON. No. of Mean height of Mean height % loss trees in trees in group Date of increment at attributable groups at Sept defoliation May 1970 to defoliation (4 (4 Expected* Actual Nov Dec Dec Jan Jan Feb Feb *For explanation, see text. One obvious difference between natural and artificial defoliation is that, whereas the former takes place over a period of time, the latter is virtually instantaneous. A small trial was conducted in 1970/7 1 in which defoliation was imposed progressively, on the same set of trees. An estimated 30% of the preferred foliage was removed on each of 3 occasions (mid November, mid December and mid January). The trial employed 20 treated and 20 control trees, alternating in the rows. Subsequent inspection of the trees suggested that defoliation in this trial had had little or no effect on height growth, and this was confirmed by a comparison of the mean heights of the two sets of trees, thus: Date of Mean heights (m) measurement of Defoliated trees Control trees November & & 0.25 August f f 0.43

16 204 P. B. CARNE, R. T. G. GREAVES and R. S. McINNES Discussion It is perhaps not surprising that no tree mortality resulted from defoliation of E. grandis by Christmas beetles, nor that high levels of defoliation were required to cause a significant loss of growth increment. Christmas beetles are active during a period when the effects of defoliation are minimal and, when feeding on E. grandis, do not destroy the apical buds shown by Cremer (1972) to be so important for tree growth. The effect of defoliation extending into the autumn, combined with damage to at least a proportion of the buds, was noted following an outbreak in some of the E. grandis plantations of a chrysomelid, Chrysophtharta cloelia in Both the adults and larvae of this insect fed on the trees throughout the spring, summer and autumn. Prior to entering hibernation in late May of 1972, the beetles fed vigorously on the young leaves and terminal shoots, defoliating the trees almost completely. Some of the trees so damaged have since died, and those which survived showed, as late as February 1974, evidence of incomplete recovery from a severe check to their growth. If the relationship between extent of defoliation and increment loss is linear, as suggested by Kulman (1971), a projection from the data in the preceding section suggests that little increment loss is likely to result from defoliation levels below about 65%, i.e. a defoliation rating exceeding scale 4.0. Allowing a margin for experimental error in the limited data available, and for a possible departure from a linear relationship at lower levels of defoliation, we consider it reasonable to assume that no increment loss occurs at defoliation levels below scale 3.0, corresponding to >40% (60% of the preferred foliage lost. In plantations where A. porosus predominated, average defoliation ratings did not exceed 2.0. This appeared to be due in part to the nature of the distribution of the adults of this species (see section Behavioural differences between the two species, p. 197). The number of beetles er tree was usually too low to cause severe defoliation ; indeed, production of new fo P iage often conspicuously exceeded the loss caused by the insects. The data presented in Table 1 show that, at most, only 12% of trees were defoliated by this species to the assumed threshold for increment loss, and less than 1 % were defoliated beyond this level. In plantations where the highly gregarious A. chloropyrus predominated, the situation was markedly different, average defolition ratings being in the range 2.0 to 4.0. Within this range, as shown in Table 1, defoliation either attained or exceeded the threshold for increment loss in a significant proportion of the trees. General discussion Surveys of woodland insects during the past ten years, and detailed studies of Anoplognathus montanus Macleay on the Southern Tablelands of New South Wales (Carne and McInnes, unpublished records), permit certain generalizations concerning the ecologies of Anoplognathus spp. to be made. A range of species (including the 3 most common at Coffs Harbour) feed on the foliage of trees in open woodland, and of regeneration in previously cleared areas of sclerophyll forest in southern N.S. W. and in Victoria. The larvae were often extremely numerous in natural and improved pastures, but were not found in the soils under closed-canopy forest. The nature and distribution of defoliation observed at the present time is consistent with the hypothesis that the extensive clearing which has occurred since settlement has greatly increased the area of suitable breeding habitats, whilst greatly diminishing the food supply of the adults (Day 1965). The remaining trees are steadily becoming senescent and, in the absence of recruitment due to grazing, their morbidity is being accelerated by phytophagous insects. Our studies in the Coffs Harbour area have shown that the distribution of Christmas beetles there conforms with the general pattern observed elsewhere. On

17 CHRISTMAS BEETLE DAMAGE TO EUCALYPTS 205 dairy farms the beetles feed on the available shade trees, and on the marginal trees of adjacent forest. Where farms have been converted to plantations, the young trees present an accessible food supply which may be extensively utilized by beetles emerging from the old grasslands. Young plantations have some ecological affinities with areas of natural woodland regeneration. However, as the trees grow, canopy forms, the ground flora changes, and the structure of plantations progressively approximates to that of natural forest (although with reduced species diversity), and the plantations cease to provide a suitable breeding habitat for the beetles. Extensive regeneration of forest species has occurred on dairy farms which have been abandoned for many years. When country of this type has been cleared for plantations, and particularly if it is remote from open grasslands, few beetles were present and the trees formed canopy without having suffered appreciable damage. The problem seems, in the longer term, to be essentially of a self-curing nature. In a large proportion of the existing plantations, beetle numbers have already declined to insignificant levels. We expect that, as the plantations mature and are logged, the sites will be replanted before a grass-dominant ground flora could become re-established and so render them once again suitable as breeding places for the insects. The evidence presented in this paper suggests that A. porosus is rarely the cause of significant loss of growth increment in E. grandis. However, A. chloropyrus is capable of causing appreciable loss of increment. If establishment ofplantations of E. grandis continues in the Coffs Harbour area, the threat of damage to young trees in the low-lying areas favoured by A. chforopyrus will be no less than that posed to the present plantations at the time of their establishment, particularly if grasslands comprise a significant proportion of the areas planted. Several ways of minimizing losses might be considered : (i) the use of silvicultural practices that accelerate the growth of the trees, shortening the period of maximum susceptibility to attack. (ii) if the annual alternation of high and low numbers of A. chforopyrus persists, there would be advantage in planting susceptible sites in years of low beetle numbers. The second growing season of the trees, normally that in which attack is most serious, would coincide with the next following year of low numbers. (iii) the very marked preference of A. chforopyrus for the foliage of E. dunnii is such that negligible feeding occurred on the foliage of E. grandis if E. dunnii was present in the vicinity. The planting of E. dunnii in occasional rows within an E. grandis plantation, or in perimeter rows around blocks of E. grandis, would provide a simple means of minimizing damage to E. grandis. (iv) the use of less susceptible eucalypt species in high risk areas. Trees of E. pilufaris and E. safigna were not subject to significant defoliation during the course of our study whereas those of E. grandis were affected, to a varying degree, by Christmas beetles (since prior to 1966/67), psyllids (since 1969/70), and by chrysomelids (since 1971/72). E. grandis was also the species most vulnerable to infestation by cossid moth larvae, and to windthrow following damage by cockatoos searching for the larvae. The increased use of E. grandis in the plantations preceded the first outbreaks of both psyllids and chrysomelids, and measurement of windthrow due to cossid/cockatoo attack. This growing evidence of the vulnerability of E. grandis to insect attack when grown in large monocultures suggests that in the longer term it might be wise to select other species, even if these are less desirable in terms of growth rate or pulping quality, for planting in areas where the risk of insect damage is known to be particularly high. Acknowledgments We record our sincert: thanks to the following persons and organizations for their help in our investigation : A.P.M. Forests Pty. Ltd. for financial support, and members of the Company s staff at Coffs Harbour, particularly the Forest Superintendent Mr B. Clarke, and

18 206 P. B. CARNE, R. T. G. GREAVES and R. S. McINNES Mr V. Turnbull, for generous assistance in the establishment and maintenance of field trials. Professor L. D. Pryor, Department of Botany, Australian National University for much valuable discussion, and for permission to publish the photograph forming Fig. 3. The Division of Science Services, N.S.W. Department of Agriculture, for information on the soils of the Bellinger River Valleys. Messrs E. Tulley, A. T. Dunn and N. R. Mitchell (CSIRO), and Messrs A. K. Irvine, H. J. Elliott and K. Oswald (Forest Research Institute) for invaluable assistance in the field and laboratory, and Mr J. P. Green and Mrs G. C. Palmer (CSIRO) for photographic and art work. References BAMBER, R. K. and HUMPHKEYS, F. R. (1965).-Variations in sapwood starch levels in some Australian forest species. Aust. For. 29: BAUR, G. N. (1959).-Raising and planting Flooded Gum. Res. Notes Div. Forest Mgmt. V.S.W, No. 4. CAMPBELL. K. G. (1960.-Preliminarv studies in DoDulation estimation of two sdecies of stick insect ' (Phasmatidae: Phasmatodia) occurring in- plague numbers in highland lorest areas of southeastern Australia. Proc. Linn. SOC. N.S.W. 85: CARNE, P. B. (1957).-A revision of the ruteline genus Anoplognathus Leach. (Coleoptera: Scarabaeidae). Aus~. J : CREE, C. S. (1971).-Assessment of Australian forest resources in relation to forestry development. Proc. XV For. Prod. Res. Conf. Melbourne, May 31-June 4, CREMER, K. W. (1965).Seasonal variations in food reserves and recovery from defoliation or cutting in evergreens. Paper presented to 4th Conference of Institute of Foresters of Australia, Hobart, May CREMER, K. W. (1972).-Effects of partial defoliation and disbudding on height growth of Eucalyptus regans saplings. Aust. For. Res. 6 (1): CREMER, K. W. (1973).-Ability of Eucalyptus regnans and associated evergreen hardwoods to recover from cutting or complete defoliation in different seasons. Aust. For. Res. 6 (2): DAY, M. F. (1965).-The role of insects in wildlife conservation. Paper presented to Seminar on Wild life Conservation in Eastern Australia, Armidale, N.S.W., January GREAVES, R. T. G. (1966).-Insect defoliation of eucalypt regrowth in the Florentine Valley, Tasmania. Appita 19: HASSAN, S. T. (1971).Survival in soil at high temperatures, with differing moisture conditions, of first instar larvae of the Christmas beetle Anoplognathus porosus (Dalm.) (Coleoptera : Scarabaeidae) Thesis for B.Sc. (Hons.), University of New England, Armidale, N.S.W. JACOBS, M. R. (1955).--Growth habits of the eucalypts. (Government Printer, Canberra, A.C.T.) KULMAN, H. M. (1971).-Effects of insect defoliation on growth and mortality of trees. A. Rev. Ent. 16: MAZANEC, Z. (1966).-The effects of defoliation by Didymuria violescens (Phasmatidae) on the growth of Alpine Ash. Aust. For. 30: MAZANEC, Z. (1967).-Mortality and diameter growth in Mountain Ash defoliated by phasmatids. Aust. For. 31: MAZANEC, Z. (1968).-Influence of defoliation by the phasmatid Didymuria violescens on seasonal diameter growth and the pattern of growth rings in Alpine Ash. Aust. For. 32: MCINTYRE, D. K. (1967).-Mineral nutrition in planted Eucalyptus grandis. Thesis for M.Sc., Aust. National University, Canberra, A.C.T. PRYOR, L. D. and CLARKE, B. (1964).-Reforestation of former farm sites on the north coast of New South Wales. Amt. For. 28: PRYOR, L. D., CHANDLER, W. G. and CLARKE, B. (1968).-The establishment of Eucalyptus plantations for pulpwood production in the Coffs Harbour region of New South Wales. APM Forests Pty. Ltd. Bulletin No. 1, June 1968, South Melbourne, Victoria. ROBERTS, R. J. and RIDSDILL-SMITH, T. J. (1972).-A plough technique for sampling soil insects. J. UPPI. Eco~. 9: WARNER, R. F. (1969).-Terraces in the Bellinger Valleys of New South Wales. Paper presented to Section 21, ANZAAS Congress, Adelaide. South Australia, August [Manuscript received August 22, 19731