Effects of the fungus <Emphasis Type="Italic">Lecanicillium lecanii</Emphasis> on survival and reproduction of the aphid <Emphasis Type="Italic">Schizaphis graminum</Emphasis>

This study investigated the effects of a strain of the fungus Lecanicillium lecanii (Zimm.) Zare and Gams (Hypocreales: Ascomycota) on the aphid Schizaphis graminum (Rondani) (Hemiptera: Aphididae). The fungus was administered to fourth instar nymphs and to alate and apterous adult morphs as a ground rice-kernel formulation. This study showed that L. lecanii formulation affected the survival of the aphids and interacted differently with the studied morphs, the Lethal Time values being lower for alate compared to apterous morphs and nymphs. The treatment also caused a significant reduction in the fecundity of the three treated aphid groups. Histological analysis revealed that the hyphae invaded the host hemocoel of a limited number of alate and apterous morphs: the fungus only entered through the spiracles. Scanning Electron Microscope observations revealed that L. lecanii adhered to the body surface of both adults and nymphs without differentiation. In conclusion, the present study suggests that this strain might be a good candidate for a programme of biological control of S. graminum and other aphid species.     

HOST ALTERNATION IN APHIS FABAE SCOP.

Experiments on the feeding preferences and relative fecundity of Aphis fabae among leaves of different ages and kinds were extended to the comparison of different forms of the aphid: apterous and alate virginoparae and gynoparae.
All three forms showed a preference for the primary host, Euonymus , over a secondary host, sugar beet, but this preference was strongest in the gynoparae, weaker in the alate virginoparae and weakest in the apterae. The relative fecundity of the aphids on the two kinds of leaf paralleled their feeding preferences most closely in the gynoparae, less so in the alate virginoparae and least in the apterae.
All three forms also showed some preference for growing over mature leaves of the same kind, but this preference was strongest in the apterous virginoparae, weaker in the alate virginoparae and weakest in the gynoparae. The relative fecundity of the aphids on the two ages of leaf paralleled their feeding preferences most closely in the apterae, less so in the alate virginoparae and least in the gynoparae.
The physiological, ecological and evolutionary significance of the results is discussed in the light of the dual discrimination theory of aphid host selection.     

Performance of clones and morphs of two cereal aphids on wheat plants with high and low nitrogen content

The great variability of the aphid life cycle and their tendency for host alternation gives rise to aphid clones and morphs. Inter‐ and intraclonal variability may be observed in the responses of aphids to various environmental factors. In this study we aimed to evaluate the influence of intrinsic factors (clone and morph type) on the intrinsic rate of increase (r_m) of the English grain aphid, Sitobion avenae (Fabricius), and the bird cherry‐oat aphid, Rhopalosiphum padi (Linnaeus). For each species four apterous clones were collected from established laboratory colonies and compared to assess their relative fitness on high‐ and low‐nitrogen wheat plants under laboratory conditions. The clones had significantly different intrinsic rates of increase on high‐ and low‐nitrogen plants. All R. padi clones had a higher intrinsic rate of increase and mean relative growth rate than S. avenae. Experiments were also conducted to compare the mean fecundity of apterous and alate morphs of S. avenae and R. padi clones on high‐ and low‐nitrogen wheat plants. On high‐nitrogen plants the apterous morphs of S. avenae clones had significantly higher mean fecundity than alate morphs. There were no significant differences between the mean fecundity of alate morphs of the same species on high‐ and low‐nitrogen plants. The results support the idea of better fitness of specific clones/morphs on certain host plants due to higher and lower intrinsic rates of increase.     

有翅型和无翅型大豆蚜卵巢和胚胎发育的差异

【目的】比较大豆蚜Aphis glycines有翅型和无翅型个体的卵巢发育,为从生理生化角度研究蚜虫翅型分化发生的繁殖适应性提供依据。【方法】在卵巢形态显微镜观察基础上,比较有翅型和无翅型大豆蚜卵巢小管数量、胚胎总数量、成熟胚胎数量以及卵巢小管中最大胚胎体积及其发育速率。【结果】有翅型和无翅型大豆蚜的3龄和4龄若蚜以及成蚜均有2个卵巢/雌,大多数蚜虫每个卵巢包含4条卵巢小管,可见一个卵巢包含5条卵巢小管的现象。有翅型和无翅型个体卵巢中胚胎总数量和成熟胚胎数量以及最大胚胎体积随发育时间增加均显著增大,但有翅型个体胚胎总数量和成熟胚胎数量以及最大胚胎体积均显著小于同一发育阶段无翅型个体。有翅型和无翅型的3龄和4龄若蚜以及成蚜卵巢中胚胎总数量与后足胫节长度均呈显著正相关关系。有翅型和无翅型大豆蚜卵巢小管中最大胚胎体积随发育时间均呈指数增长,但有翅型个体最大胚胎体积显著小于无翅型个体。【结论】有翅型大豆蚜相比于无翅型个体存在卵巢发育延迟现象,卵巢发育程度的差异可能与翅的发育相关。     

Dispersal to predator‐free space counterweighs fecundity costs in alate aphid morphs

1. Specialisation in dispersal by alate aphids often imposes constraints on other functions, particularly a reduction in fecundity due to wing development. Short‐distance flight from patches of high population density to uninfested plants may provide temporary predator‐free space, compensating for low fecundity. However, this theoretical prediction has not been explored experimentally. 2. To test this hypothesis, a field cage experiment was conducted in which Aphis glycines populations initiated with controlled proportions of apterous and alate individuals were exposed to predation, while predator‐free space was accessible only through flight. It was predicted that an investment in alate individuals would benefit a population under predation, regardless of associated costs to fecundity. 3. As expected, a strong trade‐off was observed between fecundity and wing development. However, populations initiated with a fixed proportion of alate and apterous individuals showed no reductions in final population size compared with populations initiated with apterous individuals exclusively. Moreover, the initial presence of alate individuals in the populations increased aphid prevalence (i.e. proportion of plants colonised). Similarly, both increased population size and prevalence were observed when predator‐free space was accessible through flight, as opposed to when it was inaccessible. 4. These results show that despite high costs to fecundity, an investment in alate individuals is neither beneficial nor detrimental to population size when predator‐free space is accessible, but increases aphid prevalence. It is concluded that prevalence might provide an ecological advantage important enough to warrant the production of alate morphs under intense predation.     

Morph‐specific differences in biochemical composition related to flight capability in the wing‐polyphenic Sitobion avenae

Flight performance at various times after emergence in the alate morph and age‐dependent changes in biochemical composition of winged and wingless morphs were evaluated in the wing‐polyphenic aphid Sitobion avenae (Fabricius) (Hemiptera: Aphididae). Alates exhibited the highest flight activity at 18–36 h after adult emergence. Throughout the nymphal and adult development, the whole‐body content of total lipid was significantly higher in the winged vs. wingless morph, whereas the content of water, soluble sugar, glycogen, phospholipid, and soluble protein showed significantly higher levels in the wingless vs. winged morph. There were no significant differences in the content of triglyceride and free fatty acid during nymphal and adult stages in both morphs. However, triglyceride content was significantly higher in the winged vs. wingless morph during adulthood. Differences in biochemical composition between morphs indicate that there is an energetic cost of flight capability. Our results from S. avenae adults showed that total lipid and triglyceride for the winged morph accumulated significantly to a maximum, and water content decreased significantly to a minimum, on days 1 and 2 after the final molt, exactly when the highest flight activity was reached. This study suggests that flight activity is associated with triglyceride and water content.     

Bottom‐up effects mediated by an organic soil amendment on the cabbage aphid pests Myzus persicae and Brevicoryne brassicae

Earthworm‐produced compost or vermicompost has been shown to increase resistance of plants to a variety of insect pests, but it is still unclear whether this resistance is dose dependent and whether the mechanisms responsible are the same for insect species with differing feeding habits and preferences. Therefore, we tested the effects of plants grown in various vermicompost concentrations (0, 20, 40, and 60%) on the preference and performance of generalist, Myzus persicae L., and specialist, Brevicoryne brassicae L. (both Hemiptera: Aphididae), aphid pests. Preference was evaluated with leaf disk (apterous) and whole plant (alate) choice assays. After 24 h of feeding, there was no significant negative effect on the feeding preference noted for apterae of either species of any of the treatments tested. To the contrary, apterae B. brassicae showed a significant preference for vermicompost treatments over control leaf disks. Alate M. persicae preferred alighting on control plants over vermicompost‐grown plants, but B. brassicae showed no preference toward any of the treatments tested. Both aphid species deposited significantly more nymphs on control plants than on those grown in 20% vermicompost. Furthermore, plants grown in soil amended with 20% vermicompost significantly suppressed mass accumulation, as well as numbers of adults and nymphs of both aphid species compared to controls. These data clearly show that vermicompost soil amendments can significantly influence pest aphid preference and performance on plants and that these effects are not dose dependent, but rather species and morph dependent.     

Body colour and genetic variation in winged morph production in the pea aphid

Aphids (Homoptera: Aphidoidea) produce a number of different phenotypes in their life-cycle, among which are winged (alate) and wingless (apterous) morphs. Lowe & Taylor (1964) and Sutherland (1969a, b) were the first to suggest that aphid clones differ in their propensity to produce the winged morph and that in the pea aphid (Acyrthosiphon pisum Harris), this propensity is linked to the colour of the phenotype. We tested for the occurrence of genetic variation in winged morph production by rearing individuals from red and green clones of pea aphid under wing-inducing (crowding) and control conditions, and scored the phenotypes of their offspring. Clones differed significantly in alate production and red clones produced on average a higher proportion of winged morphs than green clones. Importantly, however, there was considerable variation between clones of the same colour. Broad-sense heritabilities of winged morph production were 0.69 (crowding treatment) and 0.63 (control). Clones also differed in the number of offspring they produced. When exposed to the crowding stimulus, aphids deferred offspring production, resulting in a higher number of offspring produced in the crowding treatment than in the control.     

The effect of starvation and subsequent feeding on the reproductive potential of the grain aphid,Sitobion avenae

The short‐term starvation tolerance of alate and apterous morphs and the effect of periods of starvation on the longevity and fecundity of alate adults were evaluated in the grain aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae). Alate adults exhibited a proportionally larger length of survival compared with apterous adults under continuous starvation conditions. Newly molted pre‐reproductive adults were starved for 0–96 h and their survival rate on the 1st day after recovering with food was not significantly different from that of control aphids. Starvation reduced lifetime fecundity, but increased the reproductive rate immediately after nutrition being improved. Fecundity and longevity after 24, 48, 72, and 96 h of starvation were significantly higher than after 120 or 144 h of starvation. However, no significant differences were observed for alate adults after 24, 48, 72, or 96 h of starvation. This study suggests that the ability of alatae to adapt to brief periods of starvation could be one of the important factors affecting the reproductive success of aphids during delays in locating host plants.     

Redescription of Neoamphorophora ledi (Wahlgren, 1938) (Hemiptera: Aphididae) from Japan

Apterous viviparous females of Neoamphorophora ledi (Wahlgren, 1938) living on Rhododendron degronianum Carr. (Ericaceae) on Honshu island, Japan, are redescribed and the hitherto unknown alate viviparous females are here described. Rhododendron degronianum is a new host plant species for this aphid. This species is recorded for aphid fauna of Eastern Palearctic for the first time. Keys to species of Neoamphorophora based on apterous and alate viviparous females are given. A key to aphid genera with swollen siphunculi living on species of Rhododendron worldwide based on apterous viviparous females is also provided.     

Comparative life history and parasitism of a new colour morph of the walnut aphid in California

1 The walnut aphid Chromaphis juglandicola is a yellow aphid. In 2003, however, a white colour morph was discovered in the Sacramento Valley of California. The colour dimorphism occurs between clone lines and, when white morphs are present, they occur in mixed colour morph colonies on the underside of walnut leaves. 2 Laboratory experiments were undertaken to evaluate the thermal requirements for development, adult longevity and progeny production of the two colour morphs. Host instar preference of Trioxys pallidus, a parasitoid responsible for the successful biological control of the walnut aphid in California, was examined separately for each colour morph, and host colour preference was investigated for the preferred instar. 3 No differences in thermal requirements for development, adult size or mean longevity were detected between yellow and white colour morphs. A small difference in early reproduction was detected: white colour morphs produced more progeny on each of the two first days of adult reproduction than yellow colour morphs. 4 Trioxys pallidus showed a slight preference for the fourth instar of the yellow morph over the second‐ and third‐, but equal preference for second, third and fourth instars of the white morph. When offered equal numbers of fourth instars of the two colour morphs, T. pallidus did not show any colour preference. 5 The differences in early aphid reproduction and host instar preference by T. pallidus were combined in a stage‐structured matrix model. Model analysis showed a greater potential for population growth of the white morph over the yellow morph, with early reproduction having a greater influence than host instar preference.     

Wing development in parasitized male and female Sitobion fragariae

Abstract.Different stages of presumptive winged morphs (males, gynoparae and alate virginoparae) of the blackberry‐cereal aphid, Sitobion fragariae , were exposed to attack by Aphidius ervi . Even though the mechanism influencing wing development in the three aphid morphs differs, the effects of parasitism were similar. Alatiform structures were completely inhibited in all three morphs when the initial attack took place in their first or early second stadium. The disruption of wing development also resulted in apterous/alate‐intermediate forms when aphids were attacked from first (males and gynoparae) or early second (alate virginoparae) up to the fourth larval stadium. The fact that wing development was still disrupted when aphids with well developed wingbuds were parasitized indicates that the early stages of parasitization were influential. Thus, the morphogenetic effects may be exerted by the parasitoid egg or calyx fluid.     

Phenology of the black bean aphid,Aphis fabae,on organic crops and effect of parasitoid communities

1. Parasitoids represent the third trophic level in plant-insect food webs. They develop in or on herbivorous insects at the second trophic level, which in turn feed on plants that constitute the first trophic level. This food web system might be affected by agricultural landscape and practices.
2. We studied the phenology and population density of Aphis fabae (Hemiptera: Aphididae) and determined the impact of parasitoids in organic fields of beans and beet plants.
3. Twenty leaves per field were collected weekly. For each leaf, the total number of aphids, apterous and alate morphs, the number of mummies, and mortality of aphids were recorded.
4. Our results showed that the phenology of A. fabae varied throughout the season with maximal numbers observed at the beginning of summer. In addition, the production of alate morphs and the proportion of parasitism were positively correlated to an increase in aphid densities.
5. Six parasitoid species were recorded attacking A. fabae in the field, with Lysiphlebus fabarum and Binodoxys angelicae (Hymenoptera: Aphidiinae) being the most abundant parasitoids.
6. Field characteristics and availability of host plants in the surroundings affected A. fabae density. Lysiphlebus fabarum and B. angelicae appeared to be good biocontrol candidates against A. fabae.

     

Effect of Fusarium,Paecilomyces and Trichoderma formulations against aphid Schizaphis graminum

Fungal strains belonging to the genera Fusarium Paecilomyces and Trichoderma were tested in vitro in order to study their effects against Schizaphis graminum one of the major pests of cereal crops around the world. Biological assays were performed using a solid formulation that was obtained from fungal cultures grown on rice and then finely ground (0.2 mm). The occurrence of toxic secondary metabolites (fumonisin B₁ and beauvericin) produced by these fungi was also investigated. In each experiment, three groups of aphids: 15-hour old larvae, 5-day old nymphs with wing buds and wingless morphs were treated with a suspension of a fungal formulation. Some strains belonging to the genera Fusarium and Trichoderma significantly controlled the specimens of the three groups of S. graminum. The F. proliferatum strain ITEM 1407, producing a high level of fumonisin B₁ in the culture (1250 g/g), and F. larvarum strain ITEM 2139 had high insecticidal activity (>60%) within 10 minutes after application. As F. larvarum ITEM 2139 did not produce metabolites toxic to mammals, it might be a good candidate as a biocontrol agent of S. graminum in the field.This revised version was published online in October 2005 with corrections to the Cover Date.     

Differential inter- and intra-specific defense induction in Lupinus by Myzus persicae feeding

Experiments were conducted to investigate the potential induction of plant defenses by Myzus persicae Sulzer (Homoptera: Aphididae) feeding on five lupin, Lupinus spp. (Leguminosae), varieties with well‐characterized levels of aphid resistance. Myzus persicae feeding on L. angustifolius and L. luteus varieties induced genotype‐specific changes in their host that were not consistent with the level of aphid resistance or the plant species. The plant responses were systemically detected by apterous and alate forms of the aphids. Chemical assays revealed no induction of oxidizing enzyme (catalase, peroxidase, or polyphenol oxidase) activity, serine or cystein proteinase inhibitors, or soluble phenolics in any of the five varieties tested following 3 days of feeding by 10 or 30 aphids. However, there were significant differences among the five lupin varieties in the levels of peroxidase and polyphenol oxidase activity, proteinase inhibitors, and soluble phenolics.     

桃蚜不同蚜型DNA多态性的RAPD研究

采用RAPD方法,对全周期桃蚜的有翅产雌性母蚜、无翅性母蚜、雄蚜、卵、干母、干雌、有翅迁移蚜等蚜型的DNA遗传多态性进行了分析。结果表明：卵的DNA多态性最大,性蚜次之,孤雌生殖蚜最小;卵与其它蚜型之间在遗传上具最大差异,其中与孤雌生蚜的差异大于与性蚜的;干母、干雌和迁移蚜之间的遗传关系最近。     

Life table parameters affecting the population development of the woolly beech aphid, Phyllaphis fagi

A detailed study of the basic biological parameters affecting the population development of the woolly beech aphid, Phyllaphis fagi L. (Homoptera: Drepanosiphidae), was performed under field and laboratory conditions in order to obtain information about factors responsible for outbreak situations in forest nurseries. In the nurseries, the aphid eggs have found to hatch before budburst. The newly hatched nymphs were highly active in searching for feeding places, which resulted in higher nymph mortality in the first generation than in the following generations. Ten aphid generations were recorded in the nursery during one growing season. In the laboratory, development time, nymph mortality, reproduction, and adult lifetimes were assessed for P. fagi at four constant temperatures, i.e., 12, 15, 20, and 25 °C through four successive generations. Both temperature and aphid generation were found to affect life table parameters. The first generation, however, was less susceptible to changing temperatures than the following generations. Phyllaphis fagi reproductive effort was more dependent on temperature than on aphid generation. No significant difference was found in reproductive effort between apterous and alate females. The potential for outbreak situations therefore exists throughout the summer. The formation of winged morphs was not restricted to a few generations but rather continued for several months, with activity peaking in all years in mid-June. This had implications for migration to new seedlings in the nurseries. The highest r_m value was obtained at 20 °C. Nymphs born at higher temperatures were sometimes born deformed and unable to survive.     

The mycetocyte symbiosis of aphids: Variation with age and morph in virginoparae of Megoura viciae and Acyrthosiphon pisum

Prokaryotic symbionts of aphids, which are important to the survival of the insect, are housed in specialized cells, mycetocytes. In a study of the aphids Acyrthosiphon pisum and Megoura viciae, the mycetocytes were found to exhibit a consistent pattern of variation in both size and number, both with developmental age of the insect and between alate and apterous morphs. The number of mycetocytes ranged between 70–90 and 60–70 in 1-day old larvae of Megoura viciae and Acyrthosiphon pisum, respectively, and tended to 0 in post-reproductive individuals of both species, with a decrease of 50% between birth and the time of the final moult (days 7–9) in alates and in the late-reproductive period (days 17–18) in apterae. The volume of mycetocytes of M. viciae increased with age from 1.17 × 10⁻⁵ mm³ in 1-day old larvae to 7.63 × 10⁻⁵ mm³ and 5.09 × 10⁻⁵ mm³ in apterous and alate teneral adults (day 8), respectively, and this difference between the morphs closely mirrors the difference between the relative growth rates of apterous and alatiform larvae. It is suggested that mycetocyte loss may represent an important means by which the symbiont population is regulated. The results can also be interpreted as evidence for substantial variation in the characteristics of nutritional interactions between the aphid and its symbionts with age and morph of the aphid.     

Soybean cyst nematode effects on soybean aphid preference and performance in the laboratory

Herbivores on plants frequently interact via shared resources. Studies that have examined performance of herbivores in the presence of other herbivores, however, have often focused on above-ground feeding guilds and relatively less research has examined interactions between below- and above-ground consumers. We examine how soybean aphid, Aphis glycines (Matsumura) an above-ground phloem-feeding herbivore, interacts with a below-ground plant parasite, soybean cyst nematode, Heterodera glycines (Ichinohe) through their shared host plant, soybean (Glycine max L). Laboratory experiments evaluated the preference of alate (flight-capable) soybean aphids toward plants either infected with soybean cyst nematode or uninfected controls in a simple choice arena. Alate soybean aphids preferred uninfected soybean over soybean cyst nematode-infected plants: 48 h after the releases of alate aphids in the center of the arena, 67% more aphids were found on control soybean compared with nematode infected plants. No-choice feeding assays were also conducted using clip cages and apterous (flight-incapable) aphids to investigate effect of soybean cyst nematode infection of soybean on aphid performance. These studies had mixed results: in one set of experiments overall aphid population growth at 7 d was not statistically different between control and soybean cyst nematode-infected plants. A different experiment using a life-table analysis found that apterous aphids feeding on soybean cyst nematode-infected plants had significantly greater finite rate of increase (λ), intrinsic rate of increase (r(m)), and net reproductive rate (R(o)) compared with aphids reared on uninfected (control) soybean plants. We conclude that the below-ground herbivore, soybean cyst nematode, primarily influences soybean aphid behavior rather than performance.