Host plant preference of Diuraphis noxia (Kurdj.) (Hom., Aphididae)

Host plant preference of the Russian wheat aphid Diuraphis noxia (Kurdj.) was studied on 11 cultivars of 9 plant species: winter barley, spring barley, winter wheat, spring wheat, rye, oat, Triticale, canary grass, red millet yellow millet and maize. Seeds of the host plants were sown in a circle near the edge of pots. The host plant choice was evaluated 24 hours after releasing 55 Diuraphis noxia female adults in the middle of each pot. The suitability of different hosts for aphid development was evaluated 2, 7 and 14 days after infestation based on the mean number of Russian wheat aphid individuals per plant. Red millet, yellow millet and maize were chosen by significantly fewer aphids than grain crops. Winter and spring barley were chosen as hosts most frequently, and the progeny production was also the highest on these plants. The growth rate of D. noxia was significantly affected by the host plants and the date of assessment and their interaction.     

Opportunistic changes in the host range of<Emphasis Type="Italic"> Lysiphlebus testaceipes</Emphasis> (Cr.), an exotic aphid parasitoid expanding in the Iberian Peninsula

Lysiphlebus testaceipes (Cr.), an exotic aphid parasitoid, but widespread along the West Mediterranean and Atlantic coastal areas, was regularly found in the northeastern part of the Iberian Peninsula parasitizing several aphid hosts, inland and in the Pyrenees. It was found that the environmentally induced restriction of available host species together with the opportunistic response and host alternation of the parasitoid contributed to the successful and on-going expansion and establishment of L. testaceipes from the coast to the inland montane areas of the Iberian Peninsula. Also, a comparison of the overall host range of L. testaceipes in several areas of the West Mediterranean/Atlantic (southern France, Spain, Portugal) demonstrated a rapid increase in the host range in these areas.     

Impact of indigenous aphids on development of the invasive common ragweed (<Emphasis Type="Italic">Ambrosia artemisiifolia</Emphasis> L.) in Hungary

The common ragweed, Ambrosia artemisiifolia is a widespread invasive weed species in Europe. In order to estimate the deteriorative effect of native arthropods on the invasive ragweed the effect of three indigenous aphid species on plant development and pollen production was studied. Common ragweed plants grown in a greenhouse were artificially infested with five apterous individuals of either Aphis fabae, Brachycaudus helichrysi or Myzus persicae at the 4-leaf stage. Feeding by all three aphid species over a 5-week period significantly reduced plant height, the number of male inflorescences, the length of racemes, pollen emission and plant dry mass. Brachycaudus helichrysi produced the largest colonies, followed by A. fabae and M. persicae. In a host plant choice test, B. helichrysi showed significant preference for ragweed over sunflower, whereas A. fabae preferred sunflower and M. persicae did not show any preference. In a field experiment, the growth rate of A. fabae on caged ragweed plants was similar to that in the greenhouse, but the final numbers of B. helichrysi and M. persicae after 30 days was ten and seven times lower than under greenhouse conditions, respectively. On exposed field plants, B. helichrysi was more abundant than other species. However, no aphid species affected the height or dry mass of either caged or exposed plants during a 30-day period. Under controlled conditions aphids effectively hampered development and pollen production of ragweed, however, under Hungarian field conditions the development of ragweed was much more dynamic, therefore no deleterious effect of aphid feeding occurred.     

Exotic earthworms of great lakes forests: A search for indicator plant species in maple forests

The invasion of exotic earthworms in previously earthworm-free northern deciduous forests has been linked to the disappearance of forest floor litter, declines in plant species richness, and the development of monotypic stands of Carex pensylvanica. However, the impact of exotic earthworms on the regeneration of trees and understory plants is largely unknown. We examined the relationships between earthworm density, plant species richness, leaf litter accumulation, number of tree (Acer) seedlings, and cover of C. pensylvanica at 14 sites in mesic hardwood forests of the Chequamegon-Nicolet National Forest in northern Wisconsin. Earthworm biomass, especially of the genera Lumbricus, Aporrectodea, and Octolasion was negatively associated with leaf litter mass and number of Acer seedlings. Nine plant species, including two spring ephemerals (Dicentra cucullaria and Osmorhiza claytonii), a sedge (Carex deweyana), and an invasive mint (Galeopsis tetrahit) were negatively correlated with exotic earthworm densities. Dryopteris intermedia and Allium tricoccum, on the other hand, were associated with high earthworm densities. The activities of exotic earthworms appear to have significant impacts on Acer regeneration and the persistence of many herbaceous plants. Our findings suggest that the effects of exotic earthworms on litter mass are strongly related to the observed effects on species composition. Sensitive species can be used as indicators of high and low earthworm densities and might be useful for identifying forests of high conservation value where future invasions of exotic earthworms should be prevented.     

Bumble-bees (Hym., bombidae) associated with the expansive touch-me-not,Impatiens glandulifera in wetland biocorridors

Nine bumble-bee (Bombus)-species (listed) were determined to visit flowers of an exotic invasive species,Impatiens glandulifera Royle in the wetland biocorridors in the Czech Republic. None of the species was found specific to the target plant and the dominant part of the guild represented common eurytopic species.I. glandulifera was classified as an important source of nectar and pollen, and the significance of this source increased with the decreasing season as the bloom period lasted much longer than that of most of the native plant species. Despite its invasive effects on the native plant communities in wetlands,I. glandulifera contributed to the conservation of common bumble-bee species, as well as to an over-all positive role of wetlands in the cultivated landscape.     

Colonisation of native and exotic conifers by indigenous bark beetles (Coleoptera: Scolytinae) in France

Planting exotic conifers offers indigenous forest insects an opportunity to extend their host range and eventually to become significant pests. Knowing the ecological and evolutionary modalities driving the colonisation of exotic tree species by indigenous insects is thus of primary importance. We compared the bark beetle communities (Coleoptera: Curculionidae, Scolytinae) associated with both native and introduced conifers in France. The aim of our study was to estimate the influence of both host- and insect-related factors on the beetles’ likelihood to shift onto new hosts. We considered the influence of host origin (i.e. native vs. exotic), host tree species identity, tree bark thickness and tree taxonomic proximity, as well as insects’ host specificity. A field inventory using trap trees was carried out in two regions in France (Limousin and Jura) during two consecutive years (2006 and 2007) on three European native conifer species [Norway spruce (Picea abies); Scots pine (Pinus sylvestris) and European Silver-fir (Abies alba)] and five North American [Sitka spruce (Picea sitchensis); Eastern white pine (Pinus strobus); Grand fir (Abies grandis); Douglas fir (Pseudotsuga menziesii) and Western red cedar (Thuja plicata)]. A total of 18 indigenous and 2 exotic bark beetle species were collected. All exotic conifer species were colonised by indigenous bark beetle species and no significant difference was observed of the cumulated species richness of the latter between native and exotic tree species (13 vs. 14, P < 0.05). The ability of indigenous bark beetles to shift onto exotic conifers appeared to strongly depend on host species (significantly structuring bark beetle assemblages), the presence of phylogenetically related native conifer species and that of similar resources, in combination with insect host specificity. Host tree species status (native or exotic) also seemed to be involved, but its effect did not seem as essential as that of the previous factors. These findings are discussed in terms of adaptation, plasticity and practical aspects of forest management.     

Potential role of botanic garden collections in predicting hosts at risk globally from invasive pests: a case study using <Emphasis Type="Italic">Scirtothrips dorsalis</Emphasis>

Increasing trade in plants and plant products across continents heightens the risk of exotic insect pests expanding geographically into new habitats. This threatens not only the production and economic value of widely traded crops but the survival of species grown or sought by low-income communities. The first European outbreak of Scirtothrips dorsalis was detected in the Palm House collections at Kew in 2007 and triggered a monitoring program. This monitoring along with a robust review of the literature brought together information on new and known hosts for S. dorsalis. Further to this, we used molecular characterization techniques to identify which proposed cryptic species of S. dorsalis was present in this outbreak. The study revealed that 39% of the species of plants among the collections supported the proposed S. dorsalis South Asia 1 cryptic species, with over 50% of those species supporting immature life stages of the thrips confirming that they are suitable breeding hosts. Of particular importance are the newly identified hosts that are crops, and two further hosts reported as endangered/critically endangered. This study demonstrates the role that botanic garden collections can play in generating host relationship data that can feed into the development of robust predictive risk assessments for invasive insects. This can provide plant health authorities with the scientific basis for prioritizing management plans to protect important, vulnerable crop and non-crop plant species.     

Spring aphid-parasitoid (Hom., Aphididae,Hym., Braconidae) associations and interactions in a Mediterranean arable crop ecosystem,including <Emphasis Type="Italic">Bt</Emphasis> maize

Conspecific and heterospecific associations of aphid parasitoids (Hymenoptera, Braconidae, Aphidiinae) were used to determine the interactions between crops forming the main arable crop ecosystem (wheat, alfalfa, isogenic and [Bt Bacillus thuringiensis] transgenic maize) in an irrigated area in Catalonia, Spain. Species composition and instars of parasitized aphids (mummies) were used to detect the parasitoid population movements between the crops and proved interactions (alternation) between the crops, including transgenic maize. Parasitoid interactions were species-dependent, appearing in the movements between alfalfa-wheat-maize in the individual species. Aphidius ervi Hal., A. rhopalosiphi DeSt.-Perez, A. uzbekistanicus Luzh., Lysiphlebus testaceipes (Cress.) and Praon volucre (Hal.) were classified as key-stone species in the target agroecosystems in the area. No differences were found in aphid-parasitoid associations on Bt transgenic maize and isogenic maize for aphid species composition and associated parasitoid guild.     

Expansion of the aphid Myzocallis (Lineomyzocallis) walshii (Monell) on the red oak Quercus rubra, and adaptation of local parasitoids in the northeastern Iberian Peninsula (Hom., Aphididae, Calaphidinae; Hym., Braconidae, Aphidiinae)

An ongoing expansion of Myzocallis (L.) walshii (Monell) in the NE Iberian Peninsula was detected. The aphid species was recorded in Catalonia, Andorra and Navarra. Adaptation of local native parasitoids (at least Trioxys pallidus Haliday and T. tenuicaudus Stary) to the new immigrant was documented, together with background information on their host range in the native environments. The detection of parasitoids of M. walshii is the first published evidence in Europe. The new evidence for M. walshii in the NE Iberian Peninsula also supports the warning of the expansion of the aphid as a pest of Quercus rubra over Europe.     

Parasitoid complex of alfalfa aphids in an IPM intensive crop system in northern Catalonia

Alfalfa aphids were monitored and aphid parasitism was determined in three crop-growing seasons (2007–2009) in commercial alfalfa fields in valleys close to the Pyrenees, where an intensive arable crop rotation is practised under non-tillage and an integrated pest management system. Acyrthosiphon pisum, Therioaphis trifolii, and Aphis craccivora were the aphid species colonizing alfalfa fields but their occurrence varied between years. Thirteen Aphidiinae parasitoid species and four Aphelinidae from the genus Aphelinus sp. were recorded. Aphidius ervi was the prevalent parasitoid species associated with A. pisum but Praon barbatum was also noticeable, especially during the first year. Trioxys complanatus and P. exsoletum were the only species associated with T. trifolii. Lysiphlebus fabarum was the prevalent parasitoid species associated with A. craccivora. The occurrence of Lysiphlebus testaceipes parasitizing A. craccivora on alfalfa is a new record for the study region because this parasitoid species had only been previously found on weeds. Only A. pisum and A. craccivora were parasitized by Aphelinus sp. Whereas A. abdominalis and A. semiflavus were associated with A. pisum, A. chaonia, and Aphelinus sp. nr. albipodus were associated with A. craccivora. Associations between aphid species and Aphidiinae or Aphelinidae parasitoid species emphasize that individual aphid species also possess individual parasitoid complexes (guilds) which do not interfere with each other in alfalfa. Alloxysta victrix, A. macrophadna, Alloxysta spp., Asaphes suspensus, A. vulgaris, Dendrocerus aphidum, Pachyneuron aphidis and Syrphophagus aphidivorus were the hyperparasitoids associated with aphid–parasitoid complexes. Our study showed A. ervi, T. complanatus, P. exsoletum, and L. fabarum as potential candidate species which could provide biological control of their respectively aphid hosts in alfalfa.     

Host range, distribution, and natural enemies of Bemisia tabaci ‘B biotype’ (Hemiptera: Aleyrodidae) in Turkey

The whitefly Bemisia tabaci (Gennadius) has caused notable damage to vegetable and cotton crops in the eastern Mediterranean region since about 1994, and has become particularly problematic in southern Turkey beginning in 2000. The development of squash silverleaf symptoms in Cucurbita species and the unprecedented high population levels in the region suggested that the B biotype, notable for the latter phenotypes, had been introduced. To test this hypothesis and determine the host distribution of the suspect introduced B biotype and its associated natural enemies, B. tabaci immature instars and adults, and the associated natural enemies were collected from cultivated and uncultivated plant species. From the southern Turkey collections, B. tabaci was found to colonize 152 species from 43 plant families. Of the plant species upon which B. tabaci was found to reproduce, 152 of them were reported as hosts of B. tabaci in Turkey. Five species of predators and two species of parasitoids were identified as natural enemies of the B biotype of B. tabaci in southern Turkey. Using the mitochondrial cytochrome oxidase I gene all B. tabaci were identified as the B biotype of the B. tabaci complex, at 96–100% shared identity with reference B biotype sequences. Results indicate that this invasive biotype has displaced the local Turkey-cotton haplotype that was known to occur previously in southern Turkey.     

Patterns of exotic plant invasions in Pennsylvania’s Allegheny National Forest using intensive Forest Inventory and Analysis plots

Intensive Forest Inventory and Analysis (FIA) plot data collected in the Allegheny National Forest (ANF), Pennsylvania, between 1999 and 2006 were evaluated for their ability to predict ANF’s vulnerability to invasion by exotic plants. A total of 26 variables classified by biotic, abiotic, or disturbance characteristics were examined. Likelihood of colonization by invasive exotic and non-invasive exotic plants was analyzed using a logistic regression model. Approximately, 11% of the 449 species documented in these plots were exotic, which is higher than has been found in other northeastern forested plots. Only 1% of the ANF flora was invasive exotic plants and these were at low abundance, confirming that most invasions are still at an early stage of establishment. Sites richer in native or non-invasive exotic plants and with more alkaline soils were more likely to be invaded. Younger forests, forests with non-forest patches present, and forests rich in native species were more likely to be colonized by exotic (invasive or non-invasive) plants. Frangula alnus, which is starting to spread locally, differed from the other invasive exotic species in terms of its association with high sapling density to tree density ratios, high soil nitrogen levels, and the presence of fire. Variables representing mortality due to beech bark disease and distance to the nearest exotic planting manifested counterintuitive results. In both cases, the combined occurrence of mortality due to beech bark disease or a close (less than 500 m away) known propagule source and the presence of an invasive or non-invasive exotic plant was rare. We encourage increased use of intensive sampling for FIA in the U.S.A. and similar monitoring programs in other countries, but suggest adding a step to the plot selection phase that would allow forest-wide or regional stratified sampling of typically coarse-scale variables, such as historic or predicted defoliation or fire events, and forest or land type. A more accurate picture of the importance of disturbance variables in defining forest vulnerability to plant invasion may be achieved.     

Suction air traps vs. crops in monitoring Russian wheat aphid, Diuraphis noxia (Kurdj.) in Central Europe (Hom., Aphididae)

Summary The Russian wheat aphid (=RWA), Diuraphis noxia (Kurdj.) is an exotic expansive aphid on the small grains determined in the Czech republic since 1993 (1995). Determination of RWA flight patterns by suction air traps (= SATs) between 1994-1998 indicated some banker, less important, or indicated RWA distribution areas. A comparison of the RWA monitoring by SATs and by crop samples in areas more or less distant from individual SAT locations manifested a high silmilarity of RWA evidence in its overall distribution and area-influenced population numbers. Owing to geographic area-dependent features of its life-cycle (holocycly) and host plant preferences, RWA seems to be most injurious to spring barley. In spite of the role of SATs in aphid forecasting, RWA samples are recommended to be taken also from the crops at the early ripening stage as the respective SAT evidence reflects only the emigration of the alate aphids originating from the decreasing populations. In general, RWA detection by SATs was either simultaneously or successively found to reflect the RWA presence in the more or less distant crops. The 30km perimeter of a SAT is agreed to be representative for mon-toring RWA populations in a sampled area.     

Performance of Lipaphis erysimi (Homoptera: Aphididae) on different Brassica species in a tropical environment

A 2-year study on the preference and performance of Lipaphis erysimi on different Brassica species in the field and under greenhouse conditions revealed that rapeseed (B. campestris var. BSH-1, B. campestris var. YSPB-9) and mustard (B. juncea RH-30) were better hosts for this aphid than other Brassica species (B. napus, B. nigra, Eruca sativa, B. carinata). On the first group of plants, the rate of nymphal development, longevity and fecundity of this pest were significantly less than on the second group of plants. Development was significantly prolonged when the aphid was reared on second group of plants.     

Pathogenic polypores in Argentina

We surveyed the polypore species associated with living hosts in Argentina. We reviewed the literature on polypores found in Argentina and, in addition with the study of unpublished herbarium material, present a list of 87 species decaying living trees in native forests and introduced plantations. The rot type, host(s), distribution and remarks are presented for each species. Among 87 species found, 71 produce a white rot and 16 a brown rot in wood; 61 species were exclusively found on native hosts and 7 on exotic, cultivated hosts, while 18 were found on both types of substrates; one species, Amylosporus campbellii, was exclusively found associated with grasses. For most cases, there are no pathological studies based on rot measurement and culture isolation to determine incidence and severity of the decay.     

Parasitoid complex (Hymenoptera, Braconidae, Aphidiinae) of Aphis craccivora Koch (Hemiptera: Aphidoidea) in Iran

The parasitoids (Hymenoptera, Braconidae, Aphidiinae) of the cowpea aphid, Aphis craccivora Koch, were investigated throughout two far distant provinces, Tehran and Sistan-Baluchestan. Colonies of the cowpea aphid were collected from different host plants and reared under laboratory conditions until the parasitoids emerged. The aphids were parasitized by an expected range of parasitoids. The species were Aphidius colemani Viereck, Lysiphlebus fabarum (Marshall), Lysiphlebus confusus Tremblay and Eady, Lysiphlebus testaceipes (Cresson), Binodoxys acalephae (Marshall), Binodoxys angelicae (Haliday), Praon volucre (Haliday) and Ephedrus persicae Froggatt. L. testaceipes is reported here for the first time in Iran. The most common species was L. fabarum followed by B. acalephae and L. confusus. A key is provided for identification and host plant associations are considered.     

Aphid aqueous-extract as a source of host searching kairomones for the aphidophagous predatorCoccinella septempunctata L. (Col., Coccinellidae)

AdultCoccinella septempunctata, a coccinellid predator of the bean aphidAphis fabae Scop., responded to aqueous extract containing kairomones of the prey. The crude aphidextract was topically dropped onto either clean leaves ofVicia faba or clean Petri-dishes. After application of aqueous-extract at different aphid densities, the predator showed variations in the attractivity and searching behaviour in comparisons with control. The variations are summarized as follows: (1) the aqueous-extract of aphids attract or directC. septempunctata adults to the treated vials at all aphid densities. The number of attracted or directed coccinellid adults was directly proportional with aphid concentrations; (2) the predatorC. septempunctata adult intensified its searching behaviour by increasing the total path length walked; (3) the number of turns exhibited is significantly higher as compared with those of control; and (4) the arrested time spent by coccinellid adults with treated plant is much more than that with clean plant at all aphid densities. The present results show that the aphid aqueous-extract contains the active ingredients (kairomone) which induce considerable changes in the searching pattern of the predator coccinellid adults.     

The <Emphasis Type="Italic">Betula</Emphasis> aphids of Turkey

To date, about 400 aphid species have been recorded in Turkey (see References). However, this is the first paper which 3 aphid species determined in 3 genera on Betula spp. in Turkey. These species, namely Calaphis flava Mordvilko, Callipterinella calliptera (Hartig) and Euceraphis punctipennis (Zetterstedt) all belong to the family: Aphididae, subfamily: Myzocallinae, tribe: Calaphini and none of the species has previously been recorded in aphid fauna lists on Betula spp. in Turkey. Their synonyms, morphological characteristics and biological data, supported by literature, were also considered.     

全球松树枯梢病发生状况与防治策略

松树枯梢病是一种世界性病害。该病寄主范围广,可侵染8个属约60种（含变种）针叶树。对全球松树枯梢病为害较严重国家（新西兰、南非、美国和中国等）的发生状况以及近年有关该病发生发展的流行诱因和抗性研究等进行了概述,并提出以树种生态适应性、提高寄主生长势为主以及控制病菌增量的防治策略。     

Beobachtungen zur Entwicklung der Frühjahrspopulationen vonMetopolophium dirhodum (Wlk.) auf dem Winterwirt

The rose-grain aphid,Metopolophium dirhodum (Wlk.), is a species living onRosa spp. as winter hosts and Gramineae as summer hosts. Thus, the planting of roses along roadsides and highways may be of importance in connection with the migration of the aphids to cereals. In March 1982 the nymphs hatched from eggs, which were laid in autumn on long shoots. One or two days after hatching they fed on buds in batches up to 15 individuals. Somewhat later they dispersed on the hostplants. The nymphal mortality of the first generation was high, namely about 79%. For further population development the number of fundatrices was less important due to their high reproduction capacity. Nymphs and adults of the first generation often changed their feeding site on the shoots. The specimens of the 2nd and 3rd generation were more stationary and formed dense colonies. The population density drastically increased during the 3rd generation. The development of the aphid populations on the primary host took place during 2–3 generations and lasted until the beginning of June, when the winged forms left the hosplant. In the second generation, i. e. at the beginning of May, the first emigrantes appeared and the size of the aphid colonies increased up to 115 individuals. Most colonies consisted of less than 11 aphids namely 30.9%. Natural enemies were present in large numbers during the end of May when the populations of aphids decreased due to emigration. They did not influence the density of aphid colonies, except the predacious larvae of hover-flies. Trophobiosis between ants and rose-grain aphids was not observed on the primary hostplant.