Bioassay of Entomophthora against the spotted alfalfa aphid Therioaphis trifolii f. maculata

A method for the bioassay of Enthomophthora spp. against aphids is described. Twenty-four isolates comprising five species of fungi were screened for activity against Therioaphis trifolii f. maculata. The only isolates with a high level of activity were those of E. sphaerosperma obtained from aphids. The initial bioassays with E. sphaerosperma indicated that aphids, starved for 24 hr during inoculation with E. sphaerosperma primary spores, were less susceptible than those removed from the plants, for just the period of exposure to the primary spore shower. Using the latter procedure, five assays of the most pathogenic isolate gave a mean LC₅₀ of 11.3 primary spores/mm² while bioassays of four other isolates gave LC₅₀ values ranging from 15.7 to 27.3 spores/mm². The potential of E. sphaerosperma as a microbial control agent for T. trifolii f. maculata in Australia is discussed.     

Responses of a compatible lucerne variety to attack by spotted alfalfa aphid: Changes in the redox balance in affected tissues

The spotted alfalfa aphid,Therioaphis trifolii maculata (Buckton), caused local browning of cells surrounding feeding sites on lucerne plants (cv. Hunter River). Aqueous extracts of infested leaves underwent a marked browning process that did not occur in extracts of healthy leaves. The process was accelerated by addition of tyrosinase and peroxidase and reversed by reducing agents such as ascorbate and glutathione. In the presence of added reducing agents, the extracts produced brown precipitates, probably conjugates of phenolics with leaf proteins similar to those involved in the sealing of damaged tissuesin vivo. Partially autoxidised catechin (PAC) solutions showed an absorbance peak at 438 nm that was increased by polyphenol oxidase and decreased by ascorbate and glutathione. When extraction of tissues into PAC was used to assess redox activities, healthy tissues showed a rapid, short lived oxidising activity combined with a much more persistent reducing activity, whereas infested leaves had even greater oxidising activity and no detectable reducing activity. Soluble phenolics increased in infested leaves and stems. Total protein decreased, but the specific activity of peroxidase, catechol oxidase and superoxide dismutase relative to protein content increased. The ability of extracts to reduce cytochrome c increased, indicating an overall increase in superoxide radicals in attacked tissues. These results are consistent with a general disturbance of redox balance induced in tissues by aphid feeding, including accumulation of oxidases and phenolic substrates and loss of reducing activity and protein.     

Acceptance of low-saponin lines of alfalfa with varied phenolic concentrations by pea aphid (Homoptera: Aphididae)

This research aims to examine the effect of phenolics on pea aphid (Acyrthosiphon pisum) (Homoptera: Aphididae) development and feeding behaviour, on leaves of selected low-saponin lines of Radius alfalfa (Medicago sativa). There was a slight, negative correlation (Spearman rank correlation r _s = −0.80) between concentrations of saponins and phenols. Lines with higher concentrations of saponins had less phenolics. Levels of phenolics in low-saponin lines of alfalfa cv. Radius were related to their acceptance by the pea aphid. Our data revealed an inverse relationship between level of phenolics and the aphid abundance and its biology on studied alfalfa lines. Larval development of the pea aphid was longer, reproduction period was shorter, and the fecundity was lower on low-saponin lines with higher level of phenolics. There were observed some tendencies in the pea aphid feeding behaviour on these lines: prolonging the probing of the peripheral tissues (epidermis and mesophyll) and shortening the period of phloem sap ingestion. The better hosts for the pea aphid were low-saponin lines with low levels of phenolic compounds.     

Evaluation of the establishment of Aphidius ervi Haliday (Hymenoptera: Braconidae) in lucerne aphid populations in New South Wales

The aphid parasitoid Aphidius ervi was released in the major lucerne-growing areas of New South Wales (NSW), Australia, between 1978 and 1981. With the collaboration of district agronomists of the New South Wales Department of Agriculture, five State-wide surveys were conducted in 1982–1983 to determine the success of the release program. In each survey, the distribution of the parasitoid was checked in relation to populations of the aphids Acyrthosiphon kondoi Shinji and Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae). The surveys confirmed the successful dispersal and establishment of A. ervi in the major lucerne-growing areas of NSW. They demonstrated its ability to survive and recover rapidly after a severe and widespread drought.     

An account of the alienicolous morphs of the aphid Patchiella reaumuri (Kaltenbach, 1843) (Homoptera: Aphidoidea)

The alienicolae of Patchiella reaumuri (Kaltenbach), which is heteroecious between Tilia x vulgaris Hayne and roots of Arum species, are here described from material reared on Arum maculatum L. and A. italicum Mill. in 1977. The sexupara morph is also described for the first time from specimens obtained in the same culture. Key couplets are offered whereby this morph can be separated from sexuparae of other British Pemphiginae.     

Spatio‐temporal association of Therioaphis maculata and Hippodamia variegata in alfalfa fields

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Presence of two host races of Aphis gossypii Glover (Hemiptera: Aphididae) collected in Turkey

The aphid, Aphis gossypii, is a primary pest of citrus, cotton, cucurbits and greenhouse‐grown vegetables in Turkey and throughout Europe. There is some previous empirical data suggesting that host‐adapted genotypes of this aphid exist which may in fact be host‐races. To determine if host races of A. gossypii are indeed present in the eastern Mediterranean region of Turkey, reciprocal host transfer experiments and life table analyses were performed with multiple asexual lineages (= clones) of the aphid collected from different hosts. The collection hosts included citrus, cucumber, eggplant, okra, sweet pepper and cotton. Aphid developmental times on the host from which the aphid was originally collected (= collection or natal host) were shorter (5.2–6.0 days) and had a higher intrinsic rate of population growth (r_m = 0.25–0.44) than the 6.6–7.3 days required when the aphid was reared on a non‐original collection host (= non‐collection host or non‐natal host) and had r_m = 0.03–0.30. Total immature mortality of the cotton clone, especially in the first nymphal stage, was high (51–100%) with low r_m (0–0.03) on cucumber, citrus and sweet pepper. Aphid populations transferred from citrus, eggplant and okra to cotton (r_m = 0.29–0.30) did not differ significantly in their performance from that of the cotton population on cotton (r_m = 0.34), whereas that from sweet pepper and cucumber populations (r_m = 0.22–0.24) were significantly lower. These data have allowed us to separate A. gossypii into two distinct biological groups: (a) a ‘generalist’ population obtained from cucumber, sweet pepper, citrus, eggplant and okra which exhibited statistically better development on cotton; versus (b) a population from cotton which, by comparison on reciprocal hosts, developed poorly on non‐natal hosts except on eggplant. Development of the cotton clone on cucumber and okra was not improved after four successive generations on the non‐natal host. The good development of A. gossypii from eggplant and cotton on these reciprocal hosts suggests that these particular clones were similar, if not identical, host races.     

An analysis of the deterrent effect of aphids on cabbage root fly (Delia radicum) egg-laying

Abstract. 1. The cabbage root fly, Delia radicum (L.), was deterred from laying eggs on brassica plants with >250 cabbage aphid, Brevicoryne brassicae (L.), or peach-potato aphid, Myzuspersicae (Sulz.).
2. Flies did not lay on plants infested with >250 aphids.
3. Preparations of (E)-β-farnesene, the aphid alarm pheromone, deterred the flies from laying only at the extremely high dose of 32 mg/plant.
4. Although M. persicae secreted large (1 ng/insect) amounts of alarm pheromone and B. brassicae extremely small (<0.01 ng/insect) amounts, both aphids equally deterred D. radicum from laying.
5. The deterrent effect appeared to result from the aphids physically disturbing the flies during host-plant selection.     

Trichomes of Lycopersicon spp. and their effect on Myzus persicae (Sulzer) (Hemiptera: Aphididae)

Abstract The green peach aphid ( Myzus persicae ) is becoming resistant to many of the pesticides used in the tomato ( Lycopersicon esculentum ) industry. A potential alternative method of control is host-plant resistance, which may be mediated by trichomes. Resistance to the green peach aphid was assessed for six accessions of L. hirsutum, three of L. pennellii and a L. esculentum control. Mortality, entrapment and number of aphids unaffected by trichomes were recorded 24, 48 and 72 h after placement. Using multiple regression against counts of glandular and non-glandular trichomes, the role of foliar pubescence in resistance to the aphid was established. Lycopersicon pennellii possessed the highest level of resistance after 72 h and type IV trichome density accounted for 26.5% of variance in mortality ( P  < 0.001). Low densities of type IV and high densities of type VII trichomes increased the number of aphids 'unaffected' by trichomes, a relationship accounting for 29% of variance ( P  < 0.001). Information on which types of trichomes most strongly affect resistance to insect pests will aid future breeding and L. pennellii shows potential for use in breeding programs to increase levels of host-plant resistance in L. esculentum.     

多种植物提取物对桃蚜和萝卜蚜的拒食活性研究

采用改进的蜜露色斑法 ,测试 34种植物乙醇提取物 (0 0 1g干重·mL-1,0 0 1gDW·mL-1)和几种天然源药剂对桃蚜Myzuspersicae(Sulzer)和萝卜蚜Lipaphiserysimi(Kaltenbach)取食的影响。结果表明 ,白蝴蝶Syngonium podophyllumSchott.、苍耳XanthiumsibiricumPrtr.etWidd、白花非洲山毛豆Tephrosiavo gelliHook .的提取物对两种蚜虫的活性均较高 ,2 4h对桃蚜的拒食率分别达 0 6 82、0 6 2 9和 0 80 6 ,对萝卜蚜的拒食率分别为 0 4 0 5、0 370和 0 383,与对照之间差异极显著 ;油茶Camelliaoleifera和花椒Zanthoxylumschinifolium的提取物拒食作用亦较强 ,2 4h对桃蚜的拒食率分别为 0 5 5 2和 0 5 14 ,对萝卜蚜的拒食率分别为 0 5 70和 0 5 18。三种药剂 (0 3%印楝素乳油、鱼藤酮精、机油乳剂 )在所测试的浓度对两种蚜虫的拒食率均达 0 719以上 ,拒食效果显著。     

Behavior and Population Development of <Emphasis Type="Italic">Phorodon humuli</Emphasis> (Schrank) (Homoptera: Aphididae) on Two Hop Cultivars of Different Susceptibility

The two hop cultivars “Hallertauer Magnum” (HM) and “Spalter Select” (SE) are regarded by growers as extremely different in their susceptibility to the damson-hop aphid Phorodon humuli (Schrank). To investigate these anecdotal observations, spring migration and initial population development of P. humuli were monitored on the two cultivars in 1998 and 1999 in an experimental hop garden. Numbers of migrant aphids on SE were significantly lower, comprising 18.8 and 30.2% as compared to HM in 1998 and 1999, respectively. Population development of apterous aphids on these two cultivars differed significantly. At the end of the monitoring period numbers of aphids on SE were 7.5 and 14.2% as compared to HM in 1998 and 1999, respectively. In behavioral studies of P. humuli alates released on glasshouse plants, those on SE spent significantly more time in motile behavior patterns than aphids on HM. In the glasshouse, population development also differed significantly and the number of aphids developing on SE was 12.9% of that on HM after 28 days. It is concluded that SE exhibits a certain repellent effect on P. humuli and, compared to HM, is possibly nutritionally less suitable to the aphid.     

Microsatellite markers for the Mexican spotted owl (Strix occidentalis lucida)

A genomic cosmid library was used to develop seven highly polymorphic microsatellite markers for the Mexican spotted owl (Strix occidentalis lucida). These are the first reported microsatellite markers derived from this species. The cloned and sequenced repeat motifs include a triplet repeat of (AAT)_n, two tetranucleotide repeats of (GATA)_n, a tetranucleotide repeat of (ATCC)_n, a compound repeat of (GA)_n(GATA)_n and the two pentanucleotide repeats (AGAAT)_n and (ATTTT)_n. The microsatellites described represent six presumably independent loci with the two pentanucleotide repeats having originated from a single cosmid. Primer pairs allow locus‐specific amplification of each marker from Mexican spotted owl genomic DNA.     

Energy flow in an apple plant-aphid (Aphis pomi De Geer) (Homoptera: Aphididae) ecosystem,with respect to nitrogen fertilization

The effect of nitrogen fertilization on the life table parameters of green apple aphids, feeding on apple saplings of different nutritional quality, was investigated. The experiments were carried out with cloned apple plants (cv. Golden Delicious), all originating from one seed, growing in a climate chamber under constant conditions. The apple saplings were irrigated with nutrient solutions containing different nitrogen levels (0.2, 0.5, 1, and 3 N), and infested with Aphis pomi De Geer. The 1 N treatment corresponded to a 15 mM nitrogen concentration, containing NO₃ ^- and NH₄ ⁺ in a 14:1 ratio. The levels of nitrogen fertilization studied here influenced the life table parameters of A. pomi in the following way: the mean generation time of A. pomi, growing on the 0.5 N treatment, was lower than the corresponding values found on the 0.2 and 1 N treatments. The highest net reproduction rate was produced on low (0.2 N) nitrogen nutrition. The intrinsic rate of natural increase was highest on the 0.5 N treatment.     

Life table and heat tolerance of Acyrthosiphon pisum (Hemiptera: Aphididae) in subtropical Taiwan

The effect of temperature on the life table of Acyrthosiphon pisum reared on Pisum sativum was evaluated under laboratory conditions using temperatures of 10, 15, 20, 25, 30, and 35°C. The development time of juvenile A. pisum decreased with increasing temperature (from 21.3 days at 10°C to 4.7 days at 35°C). Adult longevity also decreased with increasing temperature (from 53.2 days at 10°C to 2.3 days at 35°C). Interestingly, 70% and 25% of A. pisum nymphs reared at 30°C and 35°C, respectively, successfully developed into adults. These temperatures have previously been considered unsuitable for A. pisum development. However, adult aphids reared at 30°C and 35°C failed to reproduce. Linear regression analysis revealed that the lower development threshold of A. pisum was 153.1 degree‐days above 1.9°C. Maximal average reproductive capability was observed at 10°C for A. pisum adults, with each adult producing more than 120 nymphs. The intrinsic rate of increase (r_m) of A. pisum increased from 0.124/day at 10°C to 0.337/day at 25°C, whereas opposite trends were observed for the net reproductive rate (R₀) and the mean generation time (GT). At 20°C and 25°C, the intrinsic rate of increase of A. pisum was significantly higher than at 10°C and 15°C (P < 0.0001), indicating that 20°C and 25°C are within the optimal range for the growth of A. pisum, and that 30°C is beyond the upper threshold limit for reproduction, which involves a temperature range that is narrower than that of the survival range (upper limit is unknown, but above 35°C).     

Nonoccluded baculovirus- and filamentous virus-like particles in the spotted cucumber beetle,diabrotica undecimpunctata (coleoptera: chrysomelid)

Nonoccluded baculovirus-and filamentous virus-like particles were found in nuclei of hemocytes or midgut cells of field-collected spotted cucumber beetles. Each type of particle was associated with a different type of virogenic stroma containing various viral components similar to those referred to as capsid, nucleocapsid, viroplasm, and viral envelope in other known baculovirus infections. Nucleocapsids of the virus which occured only in hemocytes were rod-shaped particles approximately 230 nm long and 52 nm wide and were enveloped singly by a trilaminar unit membrane. Enveloped and partly enveloped particles appeared to be released from the nucleus to the cytoplasm by budding through the nuclear envelope acquiring additional membranes. The nucleocapsids of the virus which occurred only in nuclei of midgut cells were filamentous particles with an average diameter of 25 nm and variable length up to 2 μm. Some extremely long particles were bent almost 360° near the middle, resulting in a hairpin-like configuration. The particles were always enveloped singly. No particles budding through the nuclear envelope were observed.     

Additions to the British aphid fauna (Homoptera: Aphidoidea)

Twenty-five species and two subpecies of aphids are listed and dicussed as additions to the Brutish fauna since publication of "Additions and amendment to the Cheack List British aphids" subspecies is described as new to sicence.     

Characterization of microsatellite loci in the aphid species Metopeurum fuscoviride (Homoptera,Aphididae)

Small distance movements are of great importance for the dynamics of local populations of insects and can indirectly be assessed using molecular markers. We isolated six polymorphic microsatellite loci in the aphid species Metopeurum fuscoviride Stroyan, monophagous on the common Tansy (Tanacetum vulgare L.). Twenty‐five to 30 aphids from seven populations were analysed. Between three and 17 alleles were found per locus and expected heterozygosities ranged from 0.14 to 0.79. In total, 114 multilocus genotypes were found in 192 parthenogenetic aphids analysed, indicating that the resolution will be high enough to study differentiation on a small spatial scale.     

Effect of various cauliflower cultivars on population density fluctuations of the cabbage aphid,Brevicoryne brassicae (L.) (Hom.: Aphididae) and its parasitoid Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae)

In this study, population density changes of the cabbage aphid, Brevicoryne brassica (L.), were tested in the field during 2011 under natural infestation at research field of the Shahed University (South of Tehran). This investigation was conducted on the eight cauliflower cultivars including Smilla, Snow mystique, White cloud, Buris, Galiblanka, Snow crown, SG and Tokita in randomised complete block design with five replications. Sampling was done after starting of aphid activity in the field every week and the total number of adult aphids and nymphs were counted in three leaves of the upper, middle and lower parts of the plant. In addition, the percentage of parasitism of the cabbage aphid by Diaeretiella rapae was evaluated. Results of the sampling showed that peak of the aphid population were at the first half of November. The parasitism percent of the cabbage aphid by D. rapae was significantly different among studied cultivars (p?<?0.05). Therefore, it can be concluded that using of Smilla, Buris and SG cultivars probably increases the efficiency of D. rapae in the control of the B. brassica (L.).