Leaf Galls Research Articles

Negative impact of leaf gallers on arctic-alpine dwarf willow, Salix herbacea

According to available evidence, leaf gallers have only minor impacts on their plant hosts. We hypothesised that the relatively large leaf gallers formed by Eupontania sawflies on small, creeping arctic-alpine willows have a strong influence on their host plants. In this study, we specifically tested the effects of leaf galler (Eupontania aquilonis) on the survival and growth of dwarf willow (Salix herbacea) in a mountain snow-bed in northern Finland. We marked galled, leaves-removed and untreated ramets in experimental blocks. In the following year, we measured the growth and survival of the ramets. The mortality of galled shoots was approx. 40% higher, and the mortality of galled ramets approx. 25% higher than in the control ramets and in the leaf-removal treatment. The leaf biomass of galled ramets and the number of leaves were significantly less in galled ramets than in untreated or leaves-removed ramets. It is possible that galling causes fatal resource depletion of shoots in its host plant. The results show that leaf gallers are ecologically more influential than previously thought.

Grape Phylloxera Gallicole and Radicicole Activity on Grape Rootstock Vines

The objective was to explore temporal distribution of grape phylloxera, Daktulosphaira vitifoliae (Fitch), gallicoles on grapevine rootstocks (Vitis sp.) and determine how this distribution arose. We tested the hypothesis that leaf galls are created by individuals arising from the soil in the spring. Galls begin to appear at budbreak and gall averages per leaf increase variably as the season progresses. Initial galling appears to be associated with dry conditions and gall populations decline with rain. Emergence-trap catches show that phylloxera maintain populations on rootstock roots and that these populations disperse above ground. Aerial trap data demonstrated wind dispersal of crawlers and alates. Shielding of canes from soil-emerging phylloxera largely prevented early gall formation. These results suggest alternative testable hypotheses for explaining overwintering of phylloxera in rootstock vineyards.

Evidence of plant–insect interactions in the Upper Triassic Molteno Formation of South Africa

The Molteno Formation of Late Triassic (Carnian) age in South Africa has yielded more than 200 plant species from 100 plant assemblages at 69 localities (30 000 catalogued slabs) as well as more than 300 species of insect. Damage to leaves caused by insects is widespread on many plant species at numerous localities. The damage includes feeding traces, predominantly continuous marginal feeding traces, leaf mines including linear and possible blotch varieties and probable leaf galls. Damaged taxa include a wide variety of gymnosperms including the conifer Heidiphyllum , the ginkgoaleans Ginkgo and Sphenobaiera , the peltasperms Dicroidium and Dejerseya , the pentoxyalean Taeniopteris and the gnetopsid Yabeiella . Quantitative data (>3000 specimens examined) on the insect damage were obtained for four sites: Aasvöelberg, Birds River, Kapokkraal and Waldeck. Quantitative data indicate that leaf damage between sites varies from 3 to 25% and within species from 1 to 50%. The variation in damage to the same taxon between sites, and even in the overall folivory seen at the four sites, makes the interpretation of the general levels of herbivory in the Molteno difficult to assess. Herbivory levels in Northern Hemisphere Triassic plant assemblages appear to be significantly lower than those in the Molteno, and succeeding Jurassic floras worldwide also show a low level of plant–insect interactions. It is not yet clear to what extent taphonomic bias may influence the calculation of overall herbivory levels for a given time period.

Effects of Gall Formation by Neothoracaphis yanonis (Hemiptera : Aphididae) on Shoot,Fruit,and Seed Production of Its Host Plant,Distylium racemsum (Hamamelidaceae)

Effects of leaf gall formation by Neothoracaphis yanonis (Hemiptera: Aphididae) on the growth and reproduction of its host plant, Distylium racemosum (Hamamelidaceae), were studied in a viewpoint of sink-source relationship. Gall formation on the leaves of current-year spring shoots did not affect the production of lammas shoots in later seasons of the current year and of spring shoots in the following year. Many galled leaves abscised in late May and early June after the gall dehisced and alates left the galls, but the abscission of galled leaves appeared unrelated to the production of lammas and spring shoots. The leaf gall formation reduced significantly the production of fruit and seeds. In particular, the abscission of galled leaves affected the seed production more severely than the fruit production.

Variation in Lupinus arboreus alkaloid profiles and relationships with multiple herbivores

Variation in plant defensive profiles can be affected by environmental factors, genetic factors, and their interactions, and different feeding guilds may have different responses to variation in defenses. Here we present results of a factorial breeding design in Lupinus arboreus from three sites of origin to determine how parental effects, population differences, and environmental effects influence alkaloid profiles and resistance to multiple herbivores. Alkaloids were identified and quantified in seeds and adult plants grown at each of the three sites. We also censused five different herbivores on plants over 2 years and determined the relationship between each herbivore density and total alkaloids, alkaloid profiles, plant size and site. We found strong effects of origin, maternal parent, and maternal×paternal interactions on seed alkaloid profiles, and effects of origin, destination site, their interactions, and maternal×paternal interactions on leaf alkaloid profiles. However, there was no correlation between alkaloid concentration or specific compounds in seeds and full-sib adult plants. Density of the leaf galler Dasineura lupinorum and the fungus Colletotrichium spp. was affected by total alkaloid concentration and alkaloid profiles, while density of apical flies and bud gallers was not affected by any alkaloid measure. Red and green forms of the leaf galler had different responses to alkaloids, and green leaf gallers and fungi had opposite responses to measures of alkaloid profiles. These results highlight the complexity of interactions between herbivores and plant defenses, and indicate that measuring selection for defense traits may not be straightforward in natural environments that include multiple herbivore guilds.

Evidence of Insect-plant Interactions From the Upper Gondwana Sequence (Lower Cretaceous) in the Rajmahal Basin, India

The present paper reports significant evidence of insect-plant interactions in the Upper Gondwana sequence (Early Cretaceous) from various localities of the Rajmahal Formation in the Rajmahal Basin of Jharkhand State, India. This evidence is among the first Early Cretaceous evidence of phytophagy and is recognised by various types of feeding traces namely continuous marginal, discontinuous marginal and non-marginal. These traces may indicate herbivory of pinnate leaves ofPtilophyllurn (Bennettitales) and these herbivores may have assisted the plants in pollination. Additional evidence for a plant-insect relationship is on the lamina o f Phyllopteroides pinnae (Osmundaceae) which was used for ovipostional sites containing oval egg impressions that occur along the veins in the leaf lamina. Further, the evidence of insect galls recognised on a Nipaniophyllurn (Pentoxylales) leaf surface indicates that the lamina was used as a shelter habitat for insect larvae. These galls show some similarity with extinct leaf galls reported on Glossopteris (Glossopteridales) leaves recorded from the Permian of Kashmir Himalaya, India as well as on galls on Sophora (Fabaceae) and Eomangferophyllum (Anacardiaceae) leaves from the Neogene flora of India. Similar spherical leaf galls are induced by Diptera (Cecidomyiidae) and Hymenoptera (Pteromalidae) on leaves of modern Anadenanthera peregrina from Brazil. The present findings from the Upper Gondwana Sequence of India reveals that these types of insect-plant relationships existed during the Gondwana time and continued up to the recent, perhaps having a role in the co-evolution of present flora and fauna.

Fine-scale genetic structure of grape phylloxera from the roots and leaves of Vitis.

Patterns of variation at microsatellite loci suggest that root populations of the pest grape phylloxera (Daktulosphaira vitifoliae) are largely parthenogenetic in Australian vineyards. To investigate reproduction in leaf galling phylloxera and the association between these individuals and phylloxera on roots, we examined in detail genetic variation in phylloxera from a vineyard block. Some genotypes found on leaf galls within this block were not present on roots, whereas others spanned both zones. There was no evidence that genotypes on roots were the product of sexual reproduction in leaf galls. mtDNA variation was not associated with the location of the phylloxera clones. The spatial distribution of genotypes within a root population was further investigated by intensively sampling phylloxera from another vineyard block. Join-count spatial autocorrelation statistics were used to explore fine-scale spatial structure. Clones were nonrandomly distributed within the block and there was evidence that the distribution of clones followed rows. These findings suggest firstly that there is limited dispersal of root and leaf feeding phylloxera, and secondly that factors, other than vine host, are likely to be important and contribute to clonal structure within populations.

Distribution and oviposition preference of galling sawflies in arctic Canada

The distribution and ecology of insects in arctic regions are poorly known. The aim of this study was to determine the distribution of galling sawflies in the Canadian arctic and their oviposition preference. The Swedish Tundra Northwest 1999 expedition visited 17 sites in the Canadian arctic. We determined the occurrence of galling sawflies at all the sites and studied the oviposition preference of two leaf-galling sawflies, Eupontania arctica and Pontania nivalis, on Salix reticulata and S. glauca, respectively. Galling sawflies were abundant at only one site, the mainland site at Ivvavik National Park. Only a few galls in total were found at the remaining sites, suggesting that galling sawflies are rare in the higher arctic, and potential explanations for this pattern are discussed. Shoots with leaf galls were longer than shoots without galls on both S. reticulata and S. glauca. These differences could not be explained by a higher number of leaves on longer shoots. This suggests that long shoots are preferred by sawflies because of faster development and better survival of larvae on long shoots.

Influence of air pollution on leaf chemistry, herbivore feeding and gall frequency on Tibouchina pulchra leaves in Cubatão (Brazil)

Fully expanded leaves of trees of Tibouchina pulchra were collected at three sites around the industrial complex of Cubatão: the valley of Pilões river (VP), bearing virtually undamaged vegetation; Caminho do Mar (CM), affected mainly by petrochemical industries; and the valley of Mogi river (VM), severely affected by pollution. The amounts of leaf nitrogen, soluble phenols, tannins, lignins and dietary fibers were determined. Leaf area consumed by herbivores and numbers of leaf galls were used to evaluate the influence of fluctuations of those parameters on the leaf damage caused by herbivores. Comparing with the reference site, leaves from VM and CM were shown to have higher amounts of nitrogen and dietary fibers and lower amounts of soluble phenols and tannins. The highest, lowest and intermediate amounts of lignins corresponded, respectively, to CM, VM and reference site. The largest, lowest and intermediate leaf area consumed by herbivores corresponded, respectively, to VM, CM and reference site. The observed percentages of galled leaves were higher at VM and lower at CM in comparison with the reference site. In all sites, the amounts of nitrogen, fibers and lignins in 1997 were higher than in 1996, but the reverse occurred as to the total soluble phenols. Leaf areas consumed by herbivores were not different in 1996 in comparison with 1997, but galled leaf percentages were lower at VM in 1997. Although air pollution damage is evident at the selected sites and certain chemical parameters and leaf herbivory are significantly correlated, the coefficients of explanation in regression analysis are low.

Gall‐forming insect species richness along a non‐scleromorphic vegetation rainfall gradient in South Africa: The importance of plant community composition

Abstract Currently there is no single accepted hypothesis to explain gall‐forming insect species richness at a particular locality. Hygrothermal stress, soil nutrient availability, plant species richness, plant structural complexity, plant family or genus size, and host plant geographical range size have all been implicated in the determination of gall‐forming insect species richness. Previous studies of such richness at xeric sites have included predominantly scleromorphic vegetation, usually on nutrient‐poor soils. This study is the first to investigate gall‐forming insect species richness of xeric, non‐scleromorphic vegetation. Two habitat types were sampled at each of five localities across a rainfall gradient in the savanna biome of South Africa. The habitat types differed with respect to plant species composition and topography. Gall‐forming insect species richness did not increase with increasing hygrothermal stress or decreasing soil fertility. Rather, gall‐forming insect species richness was largely dependent on the presence of Terminalia sericea as well as other members of the Combretaceae and Mimosaceae. Plots where all these taxa were present had the highest gall‐forming insect species richness, up to 15 species, whereas plots with none of these taxa had a maximum of four galling‐insect species. Despite herb, shrub and tree strata not differing in gall‐forming insect species richness, insect galls were more common on woody than non‐woody plants. Also, stem galls were more frequent than apical or leaf galls. An alternative hypothesis to explain local gall‐forming insect species richness is suggested: galling insects may preferentially select those plant species with characteristics such as chemical toxicity, mechanical strength, degree of lignification or longevity that can be manipulated to benefit the galler. Thus plant community composition should be considered when attempting to explain gall‐forming insect species richness patterns.

Biologia de Neotrioza tavaresi Crawford, 1925 (Hemiptera, Psyllidae), galhador da folha do araçazeiro (Psidium cattleianum)

Biology of the leaf gall inducer Neotrioza tavaresi Crawford, 1925 (Hemiptera, Psyllidae) on strawberry guava tree (Psidium cattleianum). A field study was conducted in Curitiba region, State of Parana, southern Brazil, to describe the life cycle of Neotrioza tavaresi Crawford, 1925, a leaf galling insect in strawberry guava trees (Psidium cattleianum). Three cycles were observed (1997, 1998, 1999) during regular field trips and the insects were observed in Piraquara municipality, where 15 samples with 50 infested leaves were sampled in the 1997-98 cycle. Galls were dissected for detailed studies. Neotrioza tavaresi has a univoltine cycle in which adult individuals were found inside the galls from August onwards. The sexually mature insects with sex ratio 1, emerged from the galls after their dehiscence caused by feeding of the adult insects on the gall walls. Adult emergence started in early October and ended by early December, with its peak in November. Copulation took place as soon as adults exit the gall and egg laying started the next day. Females had more than 100 ovarioles containing 218.7±44.7 (n=50) fully formed eggs. This indicated the short sexual adult life-span (aprox. 5-7 days) of the species, also characterized by a concentrated oviposition. Adult individuals fed and laid their eggs on younger shoots of the plant. The bottoms of the yellowish eggs were inserted into the leaf tissue, mainly on its adaxial edge (78.1%). The nymphs hatched and, as they fed on the adaxial side of expanding leaves, modified the cell growth pattern and the round-shape galls developed on the adaxial side with one insect inside. The gall wall showed distinct layers, with the inner one suppliyng the food to the insects, and the outer layer supplying gall protection. Nymphs went through five instars and the exuviae remained stuck on a ball of wax inside the gall. All parasitoids found were Hymenoptera belonging to Chalcidoidea: Eulophidae (1 sp), Pteromalidae (2 spp) and Encyrtidae (3 spp). The findings suggest that leaf gall inducer and parasitoids insects and plant life cycles are closely connected and both leaf sprouting and gall opening seem to be triggered by the same environmental and plant conditions. The high abundance of shoots may favor insect performance as adult individuals can easily find an ideal place for feeding, copulating and laying eggs.

Rathayibacter caricis sp. nov. and Rathayibacter festucae sp. nov., isolated from the phyllosphere of Carex sp. and the leaf gall induced by the nematode Anguina graminis on Festuca rubra L., respectively.

Two novel species, Rathayibacter caricis sp. nov. (type strain VKM Ac-1799T = UCM Ac-618T) and Rathayibacter festucae sp. nov. (type strain VKM Ac-1390T UCM Ac-619T), are proposed for two coryneform actinomycetes found in the phyllosphere of Carex sp. and in the leaf gall induced by the plant-parasitic nematode Anguina graminis on Festuca rubra L., respectively. The strains of the novel species are typical of the genus Rathayibacter in their chemotaxonomic characteristics and fall into the Rathayibacter 16S rDNA phylogenetic cluster. They belong to two separate genomic species and differ markedly from current validly described species of Rathayibacter at the phenotypic level. The most striking feature differentiating Rathayibacter caricis sp. nov. from other species of the genus is the presence of fucose in its cell wall and Rathayibacter festucae sp. nov. can be easily recognized among other yellow-pigmented rathayibacters because of its rose-orange-coloured colonies.

Identification of the bacterial endosymbionts in leaf galls of Psychotria (Rubiaceae, angiosperms) and proposal of 'Candidatus Burkholderia kirkii' sp. nov.

This paper reports the identification of bacterial endosymbionts inhabiting the leaf galls of Psychotria kirkii. A phylogenetic approach was used to reveal the identity of these as yet uncultivable bacterial endophytes. Based on the analysis of 16S rDNA sequences, evolutionary trees were constructed that place the endosymbiont in the genus Burkholderia. Low levels of sequence identity and rather large evolutionary distances to the closest validly named relatives indicate that these symbiotic bacteria represent a novel species. Until cultivation is successful or until more phenotypic data become available the provisional name 'Candidatus Burkholderia kirkii' sp. nov. is proposed.

Identification of the bacterial endosymbionts in leaf galls of Psychotria (Rubiaceae, angiosperms) and proposal of 'Candidatus Burkholderia kirkii' sp. nov

Identification of the bacterial endosymbionts in leaf galls of Psychotria (Rubiaceae, angiosperms) and proposal of 'Candidatus Burkholderia kirkii' sp. nov

Rathayibacter caricis sp. nov. and Rathayibacter festucae sp. nov., isolated from the phyllosphere of Carex sp. and the leaf gall induced by the nematode Anguina graminis on Festuca rubra L., respectively

Rathayibacter caricis sp. nov. and Rathayibacter festucae sp. nov., isolated from the phyllosphere of Carex sp. and the leaf gall induced by the nematode Anguina graminis on Festuca rubra L., respectively

Community structure, survival and mortality factors in arctic populations of Eupontania leaf gallers

We studied survival, mortality factors, and community structure of nine species of leaf-galling sawflies, Eupontania spp., living on ten willow species (Salix spp.) at six sites on the Russian arctic tundra. The sawfly species represented two different gall types: the viminalis-type, which forms pea-shaped galls on the underside of leaf blades, and the vesicator-type, which forms bean-shaped galls on both sides of the leaf blade. Gall communities in the northernmost site had only one parasitoid species, but up to six parasitoids were found at the southernmost site. Inquiline parasitoids were encountered only in the two southern sites. Survival of the larvae varied between 20.0 and 82.8% among galler species at different sites. Parasitoids were the most important mortality factor for the sawflies. They caused mortality of 7.8-65.4%, depending on galler species and site, and it was highest in the northernmost site. Plant-specific mortality varied from 1.7 to 28.4% by galler species and it tended to decrease towards the north. Mortality from parasitoids was greater in the vesicator-type gallers than in the viminalis-type gallers. The total mortality caused by parasitoids in the arctic communities does not appear to differ from that in the diverse southern communities of Eupontania in Middle Europe, Scandinavia and North America, despite the assemblage having only a few members in the Arctic. The largest difference between the southern and the northern communities was the lack of inquiline parasitoids in the north. Our data do not support the hypothesis that abiotic, rather than biotic, factors would be more important in determining the abundance of populations of herbivorous insects in the harsh arctic environment.

Insect herbivory, plant defense, and early Cenozoic climate change.

Insect damage on fossil leaves from the Central Rocky Mountains, United States, documents the response of herbivores to changing regional climates and vegetation during the late Paleocene (humid, warm temperate to subtropical, predominantly deciduous), early Eocene (humid subtropical, mixed deciduous and evergreen), and middle Eocene (seasonally dry, subtropical, mixed deciduous and thick-leaved evergreen). During all three time periods, greater herbivory occurred on taxa considered to have short rather than long leaf life spans, consistent with studies in living forests that demonstrate the insect resistance of long-lived, thick leaves. Variance in herbivory frequency and diversity was highest during the middle Eocene, indicating the increased representation of two distinct herbivory syndromes: one for taxa with deciduous, palatable foliage, and the other for hosts with evergreen, thick-textured, small leaves characterized by elevated insect resistance. Leaf galling, which is negatively correlated with moisture today, apparently increased during the middle Eocene, whereas leaf mining decreased.

Spatial Distribution and Parasitism of Leaf Galls Induced byCallirhytis cornigera(Hymenoptera: Cynipidae) on Pin Oak

Callirhytis cornigera (Osten Sacken) is a gall wasp that has alternating agamic and sexual generations that develop in large, woody stem galls and small, blister-like leaf galls, respectively, on pin oak, Quercus palustris Muenchhausen. We assessed the spatial distribution of the leaf galls within leaves, shoots, canopy levels, and whole trees, and examined the relationship between leaf gall density and various tree parameters. Within leaves, proportionately more galls were located on primary lateral veins (59.5%) or midveins (38.1%), as compared with the petioles (2.0%) or secondary lateral veins (0.4%). As many as 18 galls occurred on individual leaves, but most leaves contained 0–4 galls. Some current-year shoots contained as many as 132 leaf galls, but most shoots had <20 galls. Leaf gall density did not vary significantly among heights within individual tree canopies, but was highly variable between trees. Leaf gall density at the whole tree level was not related to the tree’s rate of leaf- or shoot expansion. There was no relationship between tree-wide density of leaf galls and overall levels of foliar nitrogen, nonstructural carbohydrates, or protein binding capacity. The leaf galls supported a complex of hymenopteran parasitoids, including Aprostocetus spp., Pentastichus spp. (Eulophidae), Sycophila spp., Eurytoma sp. (Eurytomidae), Brasema sp. (Eupelmidae), and Ormyrus labotus Walker (Ormyridae). Parasitoids and inquilines accounted for nearly 80% mortality of C. cornigera within leaf galls; however, parasitism was only weakly density-dependent, regardless of spatial scale. Implications of these findings for management of C. cornigera are discussed.

Biology and Management of the Horned Oak Gall Wasp on Pin Oak

The horned oak gall wasp (Callirhytis cornigera) induces large, woody galls on twigs of oak; these galls can disfigure trees and result in extensive branch dieback. This paper reviews our recent research on the pest's biology and management on cultivated pin oaks (Quercus palustris) in Lexington, Kentucky, U.S., especially aspects that are of greatest relevance to tree care professionals. The gall wasp has alternating agamic (all female) and sexual generations that develop, respectively, in multi-chambered twig galls and single-chambered leaf galls along veins. Wasp development required about 33 months in twig galls and about 3 months in leaf galls. The number of gall wasps developing within twig galls ranged from 1 to 160, and was dependent on gall size. Numerous other insects, including parasitoids and inquilines, were found within the galls. Natural enemies accounted for high mortality of C. cornigera, especially in the leaf-galling generation where 70% to 80% of the larvae were parasitized. The dogwood borer (Synanthedon scitula) infested about 15% of the succulent 2- to 3- year-old twig galls. Adult S. scitula moths had a similar, bimodal emergence period regardless of whether they originated from dogwoods or horned oak galls. Insecticidal controls targeting the leaf galling stage of C. cornigera killed the pest, but also its parasitoids. Therefore, no reduction in the number of twig stem galls was achieved. Difficulties in managing this pest in outbreak situations are discussed.

Gall thrips of the Austro-Pacific genus Euoplothrips Hood (Thysanoptera), with a new species from Australia

AbstractThe members of Euoplothrips are probably all kleptoparasites on various gall-inducing thrips. A new species of the genus, E. platypodae, is described from Gynaikothrips leaf galls on Ficus platypoda in Western Australia. Three different species from Tonga, Samoa and the Solomon Islands are each known from leaf galls on Ficus. In contrast, the eastern Australian species E. bagnalli is recorded from the leaf galls of other thrips on Smilax australis and Alyxia spicata. E. armatus Moulton from Papua New Guinea is included as a further synonym of E. bagnalli. A key is provided to distinguish these five species. E. malabarica is also included although it is known only from the original description and is probably not congeneric.