Sampling conditions for reliable routine detection by enzyme-linked immunosorbent assay of three ilarviruses in fruit trees

Enzyme-linked immunosorbent assay (ELISA) was used to test plum trees for prune dwarf (PDV), Prunus necrotic ringspot (NRSV) and apple mosaic (ApMV) viruses, cherry trees for PDV and NRSV, and apple trees for ApMV. Optimum conditions were determined for sampling in large-scale surveys for these viruses. All three viruses were detected throughout the growing season in individual samples of young leaves, or twigs with newly formed buds. However, when single infected leaves were combined with different numbers of healthy leaves, tests were most successful for all three viruses early in the growing season. PDV was detected in 1/40 (infected/total leaves) cherry leaves in April and May and 1/40 plum leaves until July, whereas NRSV was detected in 1/20 cherry leaves until July and 1/20 plum leaves until May. ApMV was detected in 1/20 apple or plum leaves until June but was detected less readily in mature leaves after June than either NRSV or PDV. There was no evidence of uneven distribution of virus infection in the trees. The viruses were detected in leaf samples kept for 8 wk at 3°C but freezing was less reliable for storage especially with ApMV. ApMV was detected in tests on plants held for several weeks at 25°C, and PDV and NRSV in plants held at 30°C.     

Baseline susceptibilities to imidacloprid for green apple aphid and spirea aphid (Homoptera: Aphididae) collected from apple in the Pacific northwest

Susceptibilities to the neonicotinyl insecticide imidacloprid were determined for clones of apple aphid, Aphis pomi De Geer, and spirea aphid, Aphis spiraecola Patch, collected from conventional and organic apple orchards and from crab apple and wild apple in Washington state and British Columbia over a period of 6 yr. For aphids collected during 1996--1998, adults were dipped in test solutions by using the Food and Agriculture Organization protocol, and third instars and adults were reared on treated apple leaf disks. During the final 3 yr of study, bioassays involved only third instars on treated leaf material. Tests showed that A. spiraecola was significantly more tolerant to imidacloprid compared with A. pomi. Depending on the bioassay method and aphid developmental stage, average LC50 values for A. spiraecola were 4.4 -5.7 times higher than those for A. pomi established under the same test conditions. Clones of both species from Washington were marginally more tolerant to imidacloprid than clones from British Columbia, but the differences were generally not significant. Average measures of susceptibility for clones from organic orchards or unsprayed trees also did not differ from those for clones from conventional orchards, and there was no evidence for increasing LC50 values over the 6 yr of study. Differences in susceptibility to insecticides between these two anatomically similar species should be considered during the testing of new products for use on apple.     

Effects of orchard host plants on the oviposition preference of the oriental fruit moth (Lepidoptera: Tortricidae)

Recently, the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), has emerged as a major problem on apples (Malus spp.) grown in the mid-Atlantic and midwestern United States, despite its historically important and frequent occurrence as a peach (Prunus spp.) pest. It is possible that host-driven biological phenomena may be contributing to changes in G. molesta population dynamics resulting in outbreaks in apple. Studies were designed to examine the effects of host plants on oviposition behavior, in an effort to clarify the host association status of eastern U.S. populations and also to gain insight into how pest modeling and management efforts may be altered to take into account various host-associated effects. G. molesta adults exhibited ovipositional preference for nonbearing peach trees over nonbearing apple trees in close-range choice tests conducted in the field, regardless of the larval host origin. A significant preference for peach shoots over apple shoots was observed on six of 12 sampling dates with a wild G. molesta population at the interface of adjacent peach and apple blocks. Numbers of eggs found on apple fruit were higher after peach fruit were harvested and apple fruit began to approach maturity (during the flight period for third and fourth brood adults). Possible implications for population modeling and integrated management of G. molesta are discussed.     

First report of white stain of apple caused by Trichothecium kashmeriana in India

White stain symptoms were observed on the 05 apple varieties during the harvest season in India. The white stain appearance is due to the predominance of dense bunches of conidiophores and conidia. In samples collected from the 39 infected plants, a new pathogenic fungal species, Trichothecium kashmeriana sp.nov. has been isolated. The morphological and molecular mycotaxonomic characterisation revealed by double beam scanning electron microscopy followed by rDNA barcoding sequence analysis of Internal Transcribed Spacer region followed by the phylogenetic interpretations, marks the evolution of T. kashmeriana sp.nov. with genetic variance of 0.06 from the closely related species under the geographically distinct conditions. The pathogen is having a dramatic lethal effect on the natural populations of apple in India.     

Does dust result in mite outbreaks in apple orchards?

The effect of dust on phytophagous mite numbers was examined in five apple orchards situated in the dry, inland apple producing Ceres area, South Africa. The study was conducted over three seasons. The season with the most dust had the least number of mites. There was no relationship between the amount of dust on leaves and mite numbers from different orchards. Of the 15 correlations between the amount of dust on individual trees and the number of mites on these trees, two were marginally not significant and one was highly significant, but negative. Therefore, seasons during which there is a lot of dust did not result in mite outbreaks nor did dusty orchards harbour elevated mite population levels, and trees with a lot of dust did not necessarily harbour more mites than trees with less dust. However, if there is enough dust to cause stress to the trees, phytophagous mite outbreaks could occur.     

Seasonal variations in the activity in soil of Phytophthora cactorum, P. syringae and P. citricola in relation to collar rot disease of apple

Phytophthora species were isolated from infested orchard soils using apple fruit as bait at intervals during the periods July 1956 to August 1957, January 1957 to June 1958, and January 1969 to June 1970. When baited soils were kept out of doors P. cactorum and P. citricola were isolated only from April or May to October, when mean temperatures exceeded 8 and 10 °C respectively; P. syringae was isolated in all months except June, July and August.
The results did not suggest that the incidence of these species was particularly associated with apple as a host plant, but the periods of activity of P. cactorum and P. syringae in soils coincided closely with the periods when apple trees were susceptible to infection by either pathogen. With collar rot disease caused by P. cactorum it was considered that, the time of commencement of activity of the pathogen in the soil, together with the availability of water, might be critical in determining the severity of disease outbreaks.     

The role of the perennial stinging nettle, Urtica dioica, as a reservoir of beneficial natural enemies

A wide range of natural enemies, including predators, parasites and entomophagous fungi were observed to feed on the stinging nettle aphid, Microlophium carnosum, populations of which increased rapidly in late April and early May. Patches of stinging nettles thus served as an important alternate feeding site for some beneficial natural enemies before pest aphids appeared on cultivated plants. Anthocoridae, Miridae and Coccinellidae were the most abundant specific predators sampled on nettles; only the Coccinellidae appeared to disperse over a defined period to other habitats. The hymenopterous parasites Aphidius ervi and Ephedrus lacertosus parasitized up to 10% of M. carnosum populations in June: two species of the fungus Entomophthora occurred spasmodically. Cutting patches of nettles in May or June had the most striking effect on the species and numbers of Coccinellidae. Cutting in mid-June might increase the numbers and impact of natural enemies on nearby pest infestations.     

秋末苏南茶园昆虫的群落组成及其趋色性

苏南地区名茶荟萃,而虫害历来较为严重。秋末选丹阳市一片无公害茶园,使用纯白、桃红、墨绿、果绿、湖蓝、天蓝、素馨黄、芽绿、土黄、桔黄、大红和紫色12种粘性色板诱虫。结果表明:① 4日内捕获7目42科85种30455头昆虫,其中优势类群是同翅目、膜翅目和双翅目,三者个体数分别占总个体数的86.5%、8.8%和2.5%。②主要害虫是假眼小绿叶蝉和茶蚜,分别占总个体数的15%和71.5%。③ 捕获的中华蜜蜂占总个体数8.2%。④捕获天敌昆虫1034头,其中,瓢虫类32头,占3.1%,主要种类是异色瓢虫和黄斑盘瓢虫;草蛉类582头,占56.3%,包括中华草蛉、大草蛉和丽草蛉;伞裙追寄蝇和蚕饰腹寄蝇等5种寄生蝇类111头,占10.7%;门氏食蚜蝇和黑带食蚜蝇等7种食蚜蝇类110头,占10.6%;螟蛉瘤姬蜂和花胸姬蜂等5种姬蜂类、茶尺蠖绒茧蜂和单白绵绒茧蜂等7种茧蜂类个体数分别占3.9%和9.4%。⑤ 芽绿、素馨黄和桔黄色板显著地引诱假眼小绿叶蝉和茶蚜;芽绿、素馨黄色板显著地引诱姬蜂和茧蜂;芽绿、土黄和果绿色板明显地引诱草蛉类;果绿、天蓝和紫色色板引诱较多的蝇类和蚊类等双翅目昆虫;素馨黄引诱的各类昆虫种数最多;纯白板上各类昆虫的多样性指数最大,表明其对许多昆虫都有引诱效应。秋末时节查明即将越冬的害虫和天敌昆虫种类、数量和益害比、以及优势种害虫和优势种天敌数量,探明多种色彩引诱益、害虫的差异,对于有效实施无公害封园防治,以压低越冬基数有重要意义。     

Stomatal sensitivity to vapour pressure deficit of temperate and tropical evergreen rainforest trees of Australia

Although rainforests of eastern Australia grow in regions of high precipitation, there is a shift from a summer dry season in the temperate south to a winter dry season in the tropical north. Therefore, rainforest trees of eastern Australia provide an opportunity to investigate stomatal sensitivity of mesic trees to vapour pressure deficit (VPD) along a gradient in seasonality of precipitation. Eight rainforest canopy tree species were selected to cover the latitudinal range of rainforests in eastern Australia. Seedlings of these species were grown for a year in glasshouses under ambient conditions or at low VPD and water vapour exchange of leaves was measured during summer. Tropical species, which experience summer-dominant precipitation, showed higher stomatal sensitivities to VPD than temperate species, which experience winter-dominant precipitation. Growing plants under a low VPD increased stomatal sensitivity to increasing VPD in most species. The high stomatal sensitivity to VPD of the tropical species is consistent with the infrequent water stress experienced during their growing season and suggests a high susceptibility to water deficits. In contrast, temperate species may use other mechanisms to maintain photosynthesis under the relatively drier conditions of the temperate growing season.     

THE OCCURRENCE OF PHYTOSEIULUS PERSIMILIS ATHIAS-HENRIOT (ACARINA:PHYTOSEIIDAE) IN AN ORCHARD IN VICTORIA

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High numbers of the predatory mite, Phytoseiulus persimilis , were found on apple and nectarine trees in a commercial orchard at Werribee, Victoria in February 1981. In the following season, again it was not detected on trees or broad-leaved weeds in the orchard until late summer. Slide-dip tests on the Werribee population of P. persimilis and a population originating from strawberries in Sydney, New South Wales, showed that azinphos-methyl was equally toxic to the 2 strains and DDT was considerably less toxic to both.     

Parasitoid exploitation of the seasonal variation in host plant volatile emission for herbivore location

Volatile compounds from the apple, Malus domestica Borkh. (Rosaceae), change considerably as the season progresses, and this is successfully exploited by the female codling moth Cydia pomonella L. (Lepidoptera, Tortricidae), as it searches for oviposition sites. In this study, we investigated the effect of seasonal emissions of apple fruit volatiles on the host location behaviour of a parasitoid of the codling moth larvae, Hyssopus pallidus (Askew) (Hymenoptera: Eulophidae). In dual choice olfactory bioassays, the behaviour of the parasitoid in response to apple cues was observed over the complete 2003 growing season. Our results show that codling moth infested apples evoked a strong response from the parasitoid at the beginning of the season, until July. Then, attraction dropped drastically, increasing again at the beginning of August. At the end of the growing season, just prior to harvest, infested apples hardly evoked any behavioural response. Interestingly enough, mid‐season emissions of healthy apples were per se attractive to the parasitoid, and even preferred over volatiles from infested apples. Simultaneous volatile collections from healthy apples on twigs in the field were analysed throughout the season, showing that the overall quantity of headspace volatiles peaks at the beginning of June and mid‐August. The seasonal volatile emission is correlated with the behaviour of the parasitoid during the fruit ripening stage. The results are discussed in relation to the use of H. pallidus as a potential biocontrol agent, in order to enhance current integrated pest management (IPM) programs.     

Overwintering Mite Diversity and Their Habitats in Apple and Pear Orchards of Korea with Emphasis on Phytoseiidae and Tetranychidae

Overwintering mite diversity and their habitats were studied in apple and pear orchards during 2002-2003 winter season. Twospotted spider mite was mostly found under the tree barks and fabric strips. European red mites were from crevices of twigs. Tydeid, tarsonemid and oribatid mites were mostly from soil and ground vegetation. Even in the protected overwintering habitat such as artificial fabric strip, twospotted spider mite suffered 81-91% mortality during winter. Predaceous phytoseiid mites found were Amblyseius womersleyi, A. makuwa, A. orientalis, A. rademacheri A. obtuserellus, and A. eharai. Amblyseius womersleyi was the most dominant species in both apple and pear orchards, followed by A. obtuserrellus in apple orchards and A. makuwa in pear orchards. Most phytoseiid mites were found on ground vegetation while their potential prey items were remained on the tree. Implication of the findings for conservation of beneficial mites and biological control of spider mite during season was further discussed.     

Factors promoting infestation of newly planted, nonbearing apple orchards by dogwood borer (Lepidoptera: Sesiidae)

The initiation and level of infestation by dogwood borer, Synanthedon scitula (Harris), was tracked over three consecutive years in two nonbearing apple (Malus spp.) orchards in West Virginia and Virginia. The orchards were planted on a number of rootstock-variety (approximately cultivar) combinations and grown using different cultural practices. Infestations were detected during the first season after planting and continued to increase annually. The amount of burr knot tissue had the greatest impact on dogwood borer populations, because increasing amounts of burr knot tissue resulted in higher infestation rates. The use of plastic spiral wrap tree guards seemed to increase the development of burr knot tissue, resulting in significantly greater infestation compared with trees without tree guards in the West Virginia orchard. Variety also had a significant effect, because 'Idared' trees on M.26 had significantly greater levels of infestation compared with 'Buckeye Gala' on M.26, with or without tree guards, in the Virginia orchard. Mounding soil around the rootstock to a height just above the graft union prevented or tremendously curtailed infestation by dogwood borer, but it led to scion rooting that seemed to have an impact on size-controlling features of dwarfing rootstocks. Removal of the mounds at the beginning of the third growing season resulted in infestation of the rooted tissue during the same season. As long as apple cultivars continue to be planted on size-controlling rootstocks, dogwood borer will likely remain a serious pest, requiring either chemical treatments or a behavioral control strategy, such as mating disruption, to protect trees from infestation and damage.     

Evaluating the necessity of additional aquatic plant testing by comparing the sensitivities of different species

At present, at least three and up to five plant species are required to assess the potential risks of herbicides to non-target aquatic plants. Several regulatory authorities are considering whether there should be further requirements based on concerns about the possible selectivity of herbicides (e.g., specific modes of action against dicotyledonous plants). The relative sensitivity of a range of aquatic plants is assessed in our work in order to evaluate the implications of differences in species sensitivity for aquatic risk assessment of herbicides. We therefore present results from ecotoxicological tests performed at Syngenta Crop Protection AG on various aquatic plants and compare them to available studies and results in literature. The criterion used for sensitivity ranking is the EC50 (median effect concentration) value, which allows a better comparison of values from different testing methods and conditions. The overall results obtained in the present work show that the aquatic risk assessment procedure for herbicides based on Lemna sp. and algae is sufficiently protective while identifying potential toxicity to non-target plants. Only few exceptions concerning herbicides with selective modes of action (e.g., auxin simulators) may require additional species testing for proper risk assessment.     

Flower strips increase the control of rosy apple aphids after parasitoid releases in an apple orchard

Mass releases of two parasitoid species, Aphidius matricariae and Ephedrus cerasicola, may provide an alternative measure to pesticides to control the rosy apple aphid Dysaphis plantaginea in organic apple orchards. As an exploratory study, we tested if the presence of flower strips between apple tree rows could improve the action of three early parasitoid releases––and of other naturally present aphid enemies––on the control of aphid colonies and the number of aphids per tree. Apple trees located at various distances from parasitoid release points were monitored in plots with and without flower strips in an organic apple orchard over two years, along the season of aphid infestation (March to July). Our case study demonstrated that the presence of flowering plant mixes in the alleyways of the apple orchard reduced the presence of D. plantaginea by 33.4%, compared to plots without flower strips, at the infestation peak date. We also showed a negative effect of increasing the distance to parasitoid release points on aphid control. However, our results at the infestation peak date suggest that the presence of flower strips could marginally compensate for the detrimental effect of increasing distance to the release point, probably by improving the persistence and dispersal capacities of natural enemies. Despite high variations in aphid population dynamics between years, we conclude that combining flower strips with early parasitoid releases in apple orchards is promising for biological control of the rosy apple aphid, although the method merits to be further refined.     

Population dynamics of Cacopsylla melanoneura (Homoptera: Psyllidae), a vector of apple proliferation phytoplasma in northwestern Italy

Apple proliferation is a phytoplasma-associated disease transmitted by insects causing serious damage and economic losses to apple orchards. Investigations were carried out in 1999 and 2000 in northwestern Italy to identify the vector of apple proliferation and to study its population dynamics. Yellow sticky traps and beat tray samples revealed the presence of the psyllid Cacopsylla melanoneura (Forster) in eight apple orchards in the Aosta Valley. The species completes one generation per year; the overwintered psyllids colonized apple trees beginning in late January, whereas the springtime generation was observed beginning in early May. The offspring adults remained in apple orchards until the end of June, when they began to move onto other hosts. During 1999 and 2000, all apple trees present in the investigated orchards were visually checked to assess the fluctuation of disease symptoms. Polymerase chain reaction and restriction fragment-length polymorphism confirmed the presence of the apple proliferation phytoplasmas in both overwintering and offspring insects as well as in symptomatic apple plants. The ability of C. melanoneura to vector the disease was assessed by preliminary transmission trials. Overwintered psyllids, collected in the most affected orchards, caged on healthy apple test plants transmitted apple proliferation phytoplasmas.     

Relative developmental, environmental, and tree-to-tree variability in buds from field-grown apple trees

High-throughput genomic technologies are becoming more accessible to nonmodel plant species, and therefore, tissue collected outside controlled environments is being increasingly used for microarray analyses. In this study, we present a 15,720-feature apple microarray analysis of the variability of gene expression in buds from field-grown apple trees. Tree-to-tree and day-to-day variances were assessed during two different seasons: summer, when the meristems in the buds were undergoing the first stages of floral development, and autumn, when the buds were undergoing transition to winter dormancy. We found that apple trees with the same scion and rootstock cultivars, grown in a standard orchard environment, had small tree-to-tree variation. Gene expression differences caused by season was the dominant cause of variance while using false discovery rate control with a threshold of α* = 0.01 to select significantly different expression between genes. At this threshold, the environmental and location effects accounted for less than 10% of the genes selected. Consequently, we have shown that field microarray experiments are a viable approach for measuring seasonal changes in gene expression during apple bud development. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Fruiting phenology in a tropical dry evergreen forest on the Coromandel coast of India in relation to plant life-forms,physiognomic groups,dispersal modes,and climatic constraints

The fruiting phenology of 22 woody plant species belonging to 19 families was studied with respect to life-forms, physiognomic groups and dispersal modes, for 1 year at monthly intervals, in a tropical dry evergreen forest at Oorani (12°11′N, 79°57′E) on the Coromandel coast of India. At the community level, bimodal fruiting pattern prevailed, with a major peak in the dry season and a minor one in the early rainy season. An annual fruiting pattern was observed in many species and among the studied species fruiting lasted for 2–9 months. There was no significant difference in the frequency of species at three fruiting stages across the life-form categories and many species of upper and lower canopy trees and lianas were in the ripe fruiting phase during the late dry season. Plant physiognomic groups displayed distinct seasonality in fruiting pattern. The fruit maturation period was much longer for the wet season fruiting brevi-deciduous species than evergreen and deciduous species that fruited during the dry season. The variation in timing of fruiting behaviour among zoochorous species demonstrated less seasonality and zoochorous fruits were available throughout the year. Fruiting in anemochorous species peaked during the driest months and dryness favoured the dissemination of seeds. The fruiting patterns observed in the studied tropical dry evergreen forest across various plant traits were comparable with patterns recorded in other tropical seasonal forests.     

哀牢山中山湿性常绿阔叶林木径向生长季节动态及其对气候因子的响应

研究采用树木生长环在哀牢山中山湿性常绿阔叶林持续9年(2009—2017年)监测了2个常绿树种(厚皮香,Ternstroemia gymnanthera;南亚枇杷,Eriobotrya bengalensis)和2个落叶树种(西桦,Betula alnoides;珍珠花,Lyonia ovalifolia)的树干月生长量,采用逻辑斯蒂生长模型(Logistic model)模拟树木径向生长量和物候参数,并分析了年、季尺度上径向生长与主要气候因子的关系。结果表明:1)4个树种年平均生长量为6.3 mm,落叶树种年平均生长量(10.6 mm/a)显著高于常绿树种(3.0 mm/a);2)雨季(5—10月)是哀牢山中山湿性常绿阔叶林树木生长的主要时期,4个树种雨季平均生长量为5.9 mm,占全年总生长量的93%,其中落叶树种雨季生长量占全年的96%,而常绿树种雨季生长量占全年的86%;3)常绿树种生长季长度为169天,长于落叶树种(137天),而落叶树种最大生长速率(0.14 mm/d)显著高于常绿树种(0.03 mm/d),最大径向生长速率能很好地预测树种年生长量;4)低温、雾日和光合有效辐射是影响哀牢山亚热带常绿阔叶林4个研究树种径向生长的重要环境因子,其中温度对常绿树种径向生长具有显著影响,而雨日、雾日与空气湿度等水分因子对落叶树种径向生长更为重要。常绿树种年生长量对旱季气候因子的响应相比落叶树种更为敏感,树木旱季生长量除了受低温限制外,也受到水分供给的影响。气候变化可能改变不同物候类型树种在哀牢山中山湿性常绿阔叶林中的生长状态与分布格局。