Relationships among abundance of galls,survivorship, and mortality factors in a cynipid wasp, <Emphasis Type="Italic">Andricus moriokae</Emphasis> (Hymenoptera: Cynipidae)

We describe the relationships among patterns of abundance of galls, survivorship, and mortality factors in the sexual generation of a cynipid wasp, Andricus moriokae, and detail the impacts of abundant parasitoid species on the survivorship of the cynipid in relation to the abundance patterns of galls. The mean number of galls per shoot, the frequency distribution of number of galls on a single shoot, and the mean number of galls per shoot in respective shoot size classes (the number of leaves per shoot) did not differ significantly between two sample trees. The relative impacts of the three mortality factors differed between trees, having different consequences for the survivorship of the cynipid. The rate of parasitoid attack, the main cause of mortality, was higher in the tree on which the cynipids survived better. On the other hand, the mortalities caused by gall predation and gall abortion were higher in the tree with the lower survival rate of the cynipid. Galls appeared more frequently on larger shoots on both trees. However, the survival rate and the mortality rates caused by three mortality factors did not differ among shoot size classes within each tree. The species composition of the parasitoid assemblage changed with shoot size, but the patterns of change differed between trees with similar abundance patterns of galls. Thus, the survivorship and mortality factors of the cynipid were probably not related to the abundance patterns of galls.     

Roles of gall morphology in determining potential fecundity and avoidance of parasitoid attack in <Emphasis Type="Italic">Aphelonyx glanduliferae</Emphasis>

This study addresses the relationship between gall morphology and some fitness components in the agamic generation of Aphelonyx glanduliferae. Larger A. glanduliferae adults that showed higher potential fecundity developed in larger galls. No fewer than 60% of A. glanduliferae individuals were attacked by parasitoids, and cynipids in smaller galls suffered more parasitoid attacks. Thus, large galls are likely to provide considerable food resources and avoidance of parasitoid attack for A. glanduliferae. Both thickness of gall walls (barrier to the parasitoid attack) and diameter of larval chamber (open space for the cynipid larva to move away) were positively correlated with gall size. Mean gall-wall thickness was significantly larger in galls harboring a living cynipid than in those harboring a living parasitoid, but the difference in the mean larval-chamber diameter was not significant. These results suggest that gall-wall thickness plays an important role in avoiding parasitoid attacks. However, the mean ovipositor length of the abundant parasitoid species exceeded the maximum gall-wall thickness, indicating that these parasitoids are potentially able to attack large galls. The higher rate of parasitoid attack in smaller galls suggests that (1) an individual of A. glanduliferae, even if it grows in a small gall, is large enough to be a host for parasitoids, and (2) parasitoids can oviposit more easily on smaller galls of A. glanduliferae, which have thinner walls.     

Timing, light availability and vigour determine the response of Abies alba saplings to leader shoot browsing

Herbivore browsing on tree saplings is a common phenomenon that can cause damage particularly on preferred species. In this study, the combined effects of light availability and timing of browsing on the response of 9-year-old Abies alba saplings were tested experimentally. Leader shoot clipping was applied before budburst, shortly after budburst or in autumn on saplings grown in full light or under artificial shade. Timing of clipping, light availability and tree vigour (expressed as height and tree ring width before clipping) had an effect on the height after clipping. After clipping in autumn or before budburst, fast-growing fir saplings bent up twigs to form new leader shoots and overcompensated height loss; saplings characterised by intermediate growth rates formed new shoots out of regular visible lateral buds; and slow-growing saplings had no new shoot in the first year after clipping, such that the clipping-induced height difference even increased over time. Saplings clipped shortly after budburst elongated the remaining part of the shoot in the first year and developed shoots out of the most distal lateral buds in the second growing season, leading to complete height compensation. Multi-trunking was typical for all clipped trees. We conclude that the microscale conditions under which a tree is growing (i.e. which affect tree vigour) are highly important for determining whether the height reduction imposed by browsing is offset by overcompensation or increases over time relative to unclipped trees. This response can partly be influenced by forest management via enhancing tree vigour via the light regime.     

Manipulation of tannins in oaks by galling cynipids

We measured the protein precipitation capacity of tannins in the tissues of Quercus crispula and Quercus serrata galls induced by a cynipid (Trigonaspis sp.) to examine the nutrition hypothesis on gall induction. The protein precipitation capacity was significantly lower in the nutritive tissues of galls, on which the cynipids feed, than in ungalled sound leaves and in the outer gall tissues. In addition, the protein precipitation capacities in the leaves and in the outer gall tissues were significantly larger in Q. crispula than in Q. serrata samples, whereas that of the nutritive tissues did not differ between these oak species. These results suggest that gall induction is one of the adaptations of galling cynipids to host–plant defensive compounds, and support the nutrition hypothesis.     

Differential host residence of adult cryptomeria bark borer,Semanotus japonicus Lacordaire (Coleoptera: Cerambycidae), in relation to tree size of Japanese cedar,Cryptomeria japonica D. Don

To understand factors involved in tree-size dependent vulnerability ofCryptomeria japonica to damage bySemanotus japonicus, residence of adultSemanotus japonicus on host trees was assessed in twoCryptomeria japonica stands, using band trap method and mark-recapture techniques. Adult capture distributions among trees were analyzed in relation to diameter size of each tree. Female adults consistently exhibited more frequent residence on larger trees, under different field conditions. Females that made inter-tree movements preferentially chose larger trees as their destinations. Frequent residence by females on large trees was associated with high productivity of progeny adults. Male adults were also more frequently resident on larger trees. These results suggest that tree-size dependent oviposition accounts for the tree-size dependent vulnerability ofCryptomeria japonica to damage bySemanotus japonicus. Possible causes underlying the differential host residence of adultSemanotus japonicus are discussed.     

Gall density of Retinia resinella (Lepidoptera,tortricidae) in relation to pine stand development

Patterns of host plant utilization of the pine resin gall moth Retinia resinella in a young Scots pine stand were studied along a belt transect in southeastern Finland. The gall distribution in 1984–1989 was retrospectively analysed. The moth preferred leaders to lateral shoots. In 1984, 60% of the galls occurred on the leaders, while the respective proportion was 40% in 1986 and 38% in 1988. The mean height of pines attacked by the moth changed from 74 to 127 cm. In 1984, moth galls on leaders occurred on higher and better‐growing trees than the average, while the opposite was true in 1988. There was an indication of clumping of R. resinella, with clumps spaced about 20 m apart which may be‐due to microhabitat distribution, the behaviour of ovipositing females or spatial dynamics of predators. The galls occurred more frequently on trees with a previous year's gall, but this tendency was not observed in the leader galls. The results support the view that the pattern of host plant utilization by a herbivore may profoundly depend on the successional stage of the habitat.     

两种接种方式下角倍蚜虫瘿对寄主盐肤木枝叶生长的影响

[目的]明确两种接种方式(自然迁飞和人工挂袋)下角倍蚜虫瘿的数量和分布及其对寄主盐肤木枝叶生长的影响。[方法]在自然迁飞和人工挂袋形成虫瘿的盐肤木林内,按随机区组设计设置样地,在样地内随机选取有虫瘿树和无虫瘿树,分别测量和统计盐肤木及虫瘿的生长指标,采用方差分析虫瘿对盐肤木生长的影响。[结果]在自然迁飞和人工挂袋两种接种方式下,盐肤木单株虫瘿数没有显著差异。但人工挂袋时,单片复叶的平均虫瘿总体积为170.92±14.85 cm~3、小叶总面积为616.26±32.73 cm~2,显著高于自然迁飞形成虫瘿的总体积85.82±9.40cm~3和小叶总面积482.81±28.51 cm~2。表明人工挂袋接种可以增加虫瘿的总体积,从而提高角倍产量;同时,较大体积的虫瘿还促进了盐肤木小叶的生长,使小叶面积增大。[结论]角倍蚜虫瘿对寄主盐肤木的枝叶生长具有促进作用,且这种生长促进与虫瘿的体积呈正相关。与自然迁飞接种相比,人工挂袋接种更能发挥盐肤木的生长和结倍潜力,提高角倍产量。     

角倍蚜干母分批上树对虫瘿数量和分布的影响

对角倍蚜分批上树及接种方法对虫瘿数量和分布的影响进行了研究,结果表明:(1)迁飞接种(同批上树)时,单株虫瘿数为15.65个,而迁飞加挂袋(分批上树-A)及挂袋2次(分批上树-B)时,单株虫瘿数分别为48.39个和161.84个,增加了2.09倍和9.34倍;同时单叶虫瘿数也从1.69个增加到2.77个和3.42个;单株有虫瘿复叶数从8.70片增加到17.87片和46.00片;有虫瘿枝条率从21.65%增加到59.74%和91.58%。(2)迁飞接种时,虫瘿分布于当年生枝条第1~7片复叶,其中1~5片复叶为虫瘿主要分布叶片;迁飞加挂袋及挂袋2次时,虫瘿分布于当年生枝条的第1~8片及第1~11片复叶,其中第3~6片复叶为虫瘿主要分布叶片。(3)无论是干母同批上树还是分批上树,单叶虫瘿数均以1~3个为主,虽然分批上树时单叶平均虫瘿数从1.23个增加到1.47个和2.53个,但仍然低于单叶最适虫瘿数5~6个,对虫瘿的大小和生长没有不良影响。综上所述,干母分批上树可以显著增加角倍蚜虫瘿数量,提高虫瘿的分散度,充分发挥盐肤木形成虫瘿的潜力。     

Differences in Agrobacterium infections in silver birch and Scots pine

The aim of this study was to investigate the differences in infections caused by Agrobacterium tumefaciens in a conifer, Scots pine (Pinus sylvestris), and in a non-host deciduous species, silver birch (Betula pendula). All the Agrobacterium tumefaciens strains tested caused crown-gall formation in both tree species, but the infection rates varied remarkably. In Scots pine, the development of galls was rare, and slower than in silver birch. Inoculation into the base of the stem were the most successful in gall induction. Silver-birch galls were large, often surrounding the whole stem, in contrast to Scots pine galls, which were characterized by their small size and neck-like connection with the host plant. In silver birch, no other morphological changes could be seen. In Scots pine, abnormal phenotypes with proliferating short shoots above the galls were observed during the second and third growing season. The results indicate that, of the two non-host tree species, the deciduous one, silver birch, is more susceptible to an A. tumefaciens infection than the conifer, Scots pine. The matrix for A. tumefaciens infection in silver birch differs from that in Scots pine, since the terpene compounds of Scots pine seem either to kill the agrobacteria or to suppress their growth. The differences between the species could be partly caused by their difference in sensitivity to phytohormones. These features reflect evolutionary incompatibility between A. tumefaciens and a gymnosperm.     

Histology of Diplodia pinea in diseased and latently infected Pinus nigra shoots

Diplodia tip blight is a serious disease of >30 conifer species worldwide. Symptoms are particularly severe on non‐native, two‐needled Pinus species, and typically include stunted, necrotic needles and shoots and a general decline of the tree. Latent Diplodia pinea infections occur in current‐year shoots of some symptomless pines, and in some apparently healthy current‐year shoots of diseased pines. Latent infections also occur in symptomless terminal buds. A histological approach was used to investigate the nature of latent infections in shoot stems and terminal buds of landscape Pinus nigra. Fungal colonization was compared in healthy, diseased and latently infected tissues. A nested‐PCR technique that is specific for D. pinea was used to differentiate latently infected tissues from uninfected ones. Latent D. pinea infections were localized in the outer stem cortex, usually in the vicinity of needle scales at leaf axes. In contrast, pathogenic D. pinea infections were characterized by fungal colonization throughout the shoot stem tissues, even very early in symptom development. The presence of necrophylatic periderms in two of the latently infected samples suggests that host defences play a role in the production and maintenance of latent stem infections. Latent infections of terminal buds appeared to originate from the distal bud scales of axillary buds in the terminal bud cluster, and not from the subtending shoot. Fungal tissues were never observed inside asymptomatic, PCR‐negative shoots.     

Shoot production through cutting culture and micrografting from mature tree explants inAcacia tortilis (Forsk.) Hayne subsp.raddiana (Savi) Brenan

Shoot propagation from mature tree explants ofAcacia tortilis subsp.raddiana, a tropical tree legume, was studied. The effects of (i) the size of cuttings and (ii) a recut treatment of the donor trees, on axillary bud growth from multinodal horticultural cuttings are reported. Apices from seedlings, axillary buds from young lignified branches of mature trees, and axillary buds obtained through in vitro axillary branching from microcuttings isolated onto mature trees were all successfully micrografted on seedling rootstocks. A sterilization procedure for field explants is reported. Propagation via cuttings and via micrografting are discussed with regard to rejuvenation of mature donor trees.     

Effect of galls induced by Endocronartium harknessii on stem hydraulic conductivity and growth of lodgepole pine

To test the hypothesis that galls resulting from infection by western gall rust [Endocronartium harknessii (J. P. Moore) Y. Hiratsuka] on lodgepole pine [Pinus contorta Dougl. ex Loud.] create hydraulic constrictions that reduce tree growth, the hydraulic conductivity (K_ψ; m² s^?1 Pa^?1), leaf area (A_L) and sapwood area (A_S) were measured on 6‐ to 15‐year‐old trees having galls encircling 0–100% of the stem. Increases in gall encirclement were accompanied by decreases in K_ψ, foliar nitrogen concentration, A_L and A_S, although the A_L:A_S ratio remained constant. Dye flow patterns through galled stem sections indicated that water moved primarily through the non‐galled portions of the stem. In a second field study, xylem and phloem wounds were applied to 13‐year‐old galled and non‐galled trees on either the galled or non‐galled side of the tree. Although both galls and xylem wounds reduced K_ψ, radial and height growth were unaffected. In aggregate the two experiments showed that although trees are quite tolerant to small galls and short term reductions in K_ψ, the disruption of water movement by larger galls may be sufficient to initiate a chain of events leading to tree death, especially in very dense stands with high levels of intraspecific competition.     

Phenology and growth dynamics in Mediterranean evergreen oaks: Effects of environmental conditions and water relations

Budburst date and shoot elongation were measured in two mature Mediterranean evergreen oaks (Quercus suber and Quercus ilex) and their relationships with meteorological and tree water status (predawn leaf water potential) data were analysed. Experimental work took place at two sites: Mitra 2 - Southern Portugal (2002-2003) and Lezirias - Central Portugal (2007-2010). Quercus suber phenology was studied at both sites whereas Q. ilex was only studied at Mitra 2. Quercus suber budburst date occurred at a photoperiod around 13.8 h (± 0.26) - late April/early May - and was highly related to the average daily temperature in the period 25 March - budburst date (ca. 1.5 months prior to budburst), irrespective of site location. In that period, budburst date was much more dependent on average maximum than average minimum daily temperature. Base temperature and thermal time for Q. suber were estimated as 6.2 °C (within the reported literature values) and 323 degree-days, respectively. Q. ilex budburst occurred about 6 weeks earlier than in Q. suber (photoperiod: 12.3 h (±0.3)). Relationships of Q. ilex budburst date and temperature were not studied since only 2 years of data were available for this species. Q. suber shoot elongation underlying mechanisms were quite different in the two sites. At Mitra 2 (Q. suber and Q. ilex), there was a considerable tree water stress during the dry season which restricted shoot elongation. Shoot growth was resumed later in the wet autumn when tree water status recovered again. At the Lezirias site Q. suber water status was not restrictive. Therefore, shoot elongation was mainly dependent on nutrient availability in top soil, as suggested by the strong and positive relationships between annual shoot growth and long-term cumulative rainfall (2-4 months) and short-term average temperature (1 month) prior to budburst. Annual shoot elongation at this well-watered site was higher than in Mitra 2, and variability of growth between trees was enhanced after warm, wet springs when shoot elongation was higher. Results obtained are relevant to the carbon balance, productivity and management of evergreen Mediterranean oak woodlands, particularly under the foreseen climate change scenarios.     

Bark thickness of host pine trees and female body size affecting ovipositional success ofSirex nitobei matsumura (hymenoptera: Siricidae)

We examined the effect of bark thickness of host trees on the ovipositional success ofSirex nitobei in relation to female body size by analyzing the relationships between female body-weight and ovipositor length and between bark thickness ofP. densiflora andP. thunbergii trees and oviposition proportion (the proportion of eggs laid to the potential female lifetime fecundity) of the woodwasp. The ovipositor length ranged from 6 to 14 mm and was correlated positively with the fresh body-weight of females. The bark thickness of host trees had no significant correlation with the oviposition proportion of large females of more than 100 mg f.wt, whereas it was correlated negatively with that of small females of less than 100 mg f.wt. Thus,P. densiflora, which has thinner bark as a whole thanP. thunbergii, may be more suitable for oviposition, especially for smaller females. Research Fellow of the Japan Society for the Promotion of Science. This study was supported in part by a Grant-in-Aid for Scientific Research from the Japanese Ministry of Education, Science, Sports, and Culture (No. 80003292).     

Unterschiede im Befall der Fichtengallenlaus Sacchiphantes abietis L. an Fichtenkreuzungen

Zusammenfassung An jungen Fichten 9 verschiedener Kreuzungen wurde das Vorkommen von Gallen vonSacchiphantes abietis L. untersucht. Es traten genetisch bedingte Unterschiede in der Stärke des Gallenbefalls auf. Die Häufigkeit der Gallen war nicht vom Zeitpunkt des Knospenaustriebs abhängig. Fichten mit Gallenbesatz hatten im Durchschnitt besseren Höhenzuwachs als Bäume ohne Gallen. Gallen m Gipfeltrieb hemmten den Höhenzuwachs. Die Stärke des Gallenbefalls war positiv von dem Vorkommen von Prolepsis beeinflußt. Es bestanden Beziehungen zwischen der Häufigkeit der Gallen und der Anzahl überwinterder Läuse.

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Differences in attack of the spruce gall aphid Sacchiphantes abietis L. in a Norway spruce progeny trial

The occurence of galls caused by the spruce gall aphid (Sacchiphantes abietis L.) was studied on young Norway spruce progeny from 9 different full sib families with parents from Sweden and Western Europe. The frequency of galls was found to vary significantly with genetic origin. Time for bud flushing did not influence the frequency of galls. Attacked trees had on verage better height increment than trees without galls. Galls on the leading shoot reduced height increment. The frequency of galls was positively influenced by the occurence of prolepsis. The abundance of hibernating aphids was positively correlated to the frequency of galls.

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Mit 4 Abbildungen und 6 Tabellen     

Host-tree conditions affecting the oviposition activities of the woodwasp,Sirex nitobei Matsumura (hymenoptera: Siricidae)

Experiments were conducted to elucidate how the oviposition activities ofSirex nitobei Matsumura could be affected by different conditions of the host trees, using logs from felled healthy trees and the dead and living trees ofPinus densiflora Sieb. et Zucc. According to days elapsed after tree-felling, the proportions of oviposition defined as the proportion of eggs laid to the potential fecundity of a female during her lifetime, could be divided arbitrarily into three groups. The proportions of oviposition on the logs within 0–3 days after felling,i.e fresh logs, varied greatly from log to log, and about half of female adults showed proportions of oviposition under 50% (mean ±SD: 39±32%). However, all the females that oviposited on the logs 4–24 days after felling,i.e. intermediate logs, invariably showed proportions of oviposition over 50% (88±1.5%). On the other hand, proportions of oviposition in most of the females that oviposited on the logs over 25 days after felling,i.e. old logs, were less than 50% (26±17%). The proportions of oviposition were significantly different between intermediate logs and old logs. The mean proportion of oviposition on living trees and that for dead trees were 45 and 58%, respectively. Thus,S. nitobei in the field would exhibit its preference for weakened trees ofP. densiflora as oviposition sites, as it did for the logs 4–24 days after felling in this study.     

Effect of dothistroma needle blight on needle and shoot lengths

The needles of pine trees are indicative of the overall health of the tree, and their length is affected by many factors. This study describes the effect of high levels of pathogen infection on lengths of both needles and shoots. Dothistroma septosporum is an important foliar pathogen of pines causing necrosis and premature defoliation with successive years of high infection leading to growth reduction and in extreme cases tree death. Corsican pine trees with all foliage infected by D. septosporum had needles of primary, secondary and tertiary shoots reduced by 31.8%, 44.0% and 64.2%, respectively, compared to non‐infected trees. Needle lengths were reduced both in the upper and lower portions of the canopy, with a greater reduction lower in the canopy. Trees with high levels of infection had shorter shoots in the upper canopy with fewer, shorter needles on these shoots compared to trees with low levels of infection. The results demonstrate the substantial negative effect on needle and shoot lengths of trees with high levels of D. septosporum infection, comparable to factors such as water and nutrient availability known to have a strong influence on these parameters. The reductions in length reduce the photosynthetic capacity of the tree and compound the immediate reductions caused by necrosis and premature defoliation. These effects on needle and shoot lengths contribute to the reductions in volume growth of affected trees and, moreover, are longer lasting than the immediate effects of necrosis and premature defoliation.     

Schädlichkeit der LinsenblütengallmückeContarinia lentis Aczél (Diptera,Cecidomyiidae) und ihre Verbreitung in der ČSSR

There has been an outbreak of lentil gall midgeC. lentis on lentil in Czechoslovakia since 1984. Its extent and cause are given below. Infestation symptom—the gall—is described. The level of damage is defined as percent rate of the amount of galls and flower buds containing eggs ofC. lentis from the amount of pods, flowers, galls, flower buds containing eggs and flower buds not containing eggs. As estimation is taken mostly at the end of lentil vegetation the level of damage is simplified to percent rate of the amount of galls from the amount of galls and pods. The level of damage of small parts of lentil stands can achieve 80%. Single plants with 95% level of damage were found. Proportional dependence of thousand-kernel weight on the level of damage was found out. Two functions of dependence of yield on the level of damage were compared: a simple linear one and a quadratic one which included the dependence of thousand-kernel weight on the level of damage. The generally valid linear function of dependence of yield y on the level of damage x is recommended: y=0.01 e (100?x) where e means yield at 0% damage level. Recent distribution area of this species in Czechoslovakia is given. In 1985–1988 the average level of damage of lentil stands from outbreak centre ranged from 3.08 to 52.05%. The average yield losses in Czechoslovakia were 5.49% in 1985, 4.98% in 1986, 2.87% in 1987 and 3.97% in 1988. Concentration of lentil fields in a small area was recognized as the main cause of the outbreak ofC. lentis in Czechoslovakia.     

Effect ofl-phenylalanine on rooting of shoots from axillary buds of adultLarix leptolepis

Rooting of shoots derived from axillary buds was examined to establish an efficient shoot culture system of clonal micropropagation in adult tree ofLarix leptolepis Gord. (Japanese larch). Nine out of ten shoots induced calli (90%) on their shoot bases, and the two of them formed root primordia with a red pigment (20%) on the calli surface within 5 weeks after culturing on modified Murashige and Skoog (MS) medium supplemented with 1.5 μM of indolebutyric acid (IBA) and 1.5 μM of naphthaleneacetic acid (NAA). However, the primordia did not elongate actively. The addition of 10 mMl-phenylalanine in the MS medium with the auxins resulted in the formation of roots at high frequency, about 80%, and they elongated actively. Although callus was formed in all the shoots cultured on the medium withl-phenylalanine, it appeared that the callus development was less as compared to the medium withoutl-phenylalanine. Consequently, the rooting might be associated with the suppression of the induced callus.