A barley cysteine-proteinase inhibitor reduces the performance of two aphid species in artificial diets and transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis> plants

Cystatins from plants have been implicated in plant defense towards insects, based on their role as inhibitors of heterologous cysteine-proteinases. We have previously characterized thirteen genes encoding cystatins (HvCPI-1 to HvCPI-13) from barley (Hordeum vulgare), but only HvCPI-1 C68 → G, a variant generated by direct-mutagenesis, has been tested against insects. The aim of this study was to analyze the effects of the whole gene family members of barley cystatins against two aphids, Myzus persicae and Acyrthosiphon pisum. All the cystatins, except HvCPI-7, HvCPI-10 and HvCPI-12, inhibited in vitro the activity of cathepsin L- and/or B-like proteinases, with HvCPI-6 being the most effective inhibitor for both aphid species. When administered in artificial diets, HvCPI-6 was toxic to A. pisum nymphs (LC₅₀ = 150 μg/ml), whereas no significant mortality was observed on M. persicae nymphs up to 1000 μg/ml. The effects of HvCPI-6 ingestion on A. pisum were correlated with a decrease of cathepsin B- and L-like proteinase activities. In the case of M. persicae, there was an increase of these proteolytic activities, but also of the aminopeptidase-like activity, suggesting that this species is regulating both target and insensitive enzymes to overcome the effects of the cystatin. To further analyze the potential of barley cystatins as insecticidal proteins against aphids, Arabidopsis plants expressing HvCPI-6 were tested against M. persicae. For A. pisum, which does not feed on Arabidopsis, a combined diet-Vicia faba plant bioassay was performed. A significant delay in the development time to reach the adult stage was observed in both species. The present study demonstrates the potential of barley cystatins to interfere with the performance of two aphid species.     

The use of visual cues in host evaluation by aphidiid wasps I. Comparison between threeAphidius parasitoids of the pea aphid

Host evaluation behaviour was examined in three species of aphid parasitoids,Aphidius ervi haliday,A. pisivorus Smith, andA. smithi Sharma & Subba Rao (Hymenoptera: Aphidiidae). Parasitoids were provided under laboratory conditions with three kinds of hosts representing two aphid species: (green) pea aphid,Acyrthosiphon pisum (Harris), and green and pink colour morphs of the alfalfa aphid,Macrosiphum creelii Davis. Females of all threeAphidius species distinguished between aphids on the basis of colour, movement, and host species. Patterns of host acceptance by parasitoids were species-specific. InA. ervi, host preference was the same in light and dark conditions: pea aphid>green alfalfa aphid≫pink alfalfa aphid. In contrast,A. pisivorus attacked and accepted pea aphid and green alfalfa aphid equally in the light and preferred both of these over pink alfalfa aphid; however, it made no distinction between pea aphid and pink alfalfa aphid in the dark. Females ofA. smithi attacked all three kinds of hosts (pea aphid>green alfalfa aphid≫pink alfalfa aphid) but apparently laid eggs only in pea aphid. The frequencies of attack and oviposition by all wasps were higher on ‘normal’ pea aphids than on those anaesthetized with CO₂. Host recognition is confirmed by chemical cues in the aphid cuticle that are detected during antennation, and host acceptance is dependent on an assessment of host quality during ovipositor probing.     

Interspecific variation in the escape responses of aphids: effect on risk of predation from foliar-foraging and ground-foraging predators

A series of laboratory experiments was conducted to determine the effect of interspecific differences on prey defensive behavior on the susceptibility of two aphid species (Acyrthosiphon pisum and A. kondoi) to a ground-foraging predator, Harpalus pennsylvanicus, and a foliar-foraging predator, Coccinella septempunctata. These organisms are representative of a biologically and economically important predator/prey system in alfalfa. The primary defensive behavior of both aphid species toward C. septempunctata was to “drop” from the plant. Both aphid species were significantly more likely to drop from the plant in the presence of C. septempunctata. However, when C. septempunctata was present, a significantly lower proportion of A. kondoi individuals dropped (0.42 ± 0.07) compared to A. pisum (0.73 ± 0.08). As a result of their lower propensity to drop from the plant A. kondoi individuals are significantly more likely to be consumed by C. septempunctata. Conversely, the higher propensity of A. pisum individuals to drop increased their susceptibility to ground-foraging predators. When A. pisum was the prey species, ground-foraging predators made a significant contribution to overall aphid suppression and there was a significant synergistic interaction between ground and foliar-foraging predators. When A. kondoi was the prey there was no interaction between the predator species. As either a cause or consequence of its higher propensity to drop, A. pisum seems to be more adapted for survival and dispersal off the plant. In comparison to A. kondoi individuals, A. pisum individuals relocate plants more quickly (63 ± 41 s vs. 164 ± 39 s), disperse farther (18 ± 1.7 cm vs. 13 ± 0.66 cm), and survive longer (37 ± 2.0 h vs. 25 ± 2.0) off the plant. This study demonstrates the importance of prey defensive behavior in determining the susceptibility of a prey species to a multiple-predator complex. Received: 24 February 1997 / Accepted:17 December 1997     

High variation in host adaptation among clones of the pea aphid,Acyrthosiphon pisum on peas,Pisum sativum

The performance of one clone of the pea aphid,Acyrthosiphon pisum (Harris), was assessed on 37 different cultivars and species ofPisum L. In addition, random samples of 36 pea aphid clones collected on alfalfa and clover were tested on a selection of fivePisum sativum L. cultivars. Aphid performance was evaluated in terms of the mean relative growth rate (MRGR) during the first five days of life or other life history variables. The MRGR of the first-mentioned pea aphid clone differed little between cultivars. No significant differences in MRGR were found between wild and cultivatedPisum species or between modern and oldP. sativum cultivars. There was considerable variation in host adaptation among the 36 pea aphid clones within each sampled field. The pea aphid clones showed no consistent pattern in performance on four of the five pea cultivars i.e. there was a significant pea aphid genotype —pea genotype interaction. On one of the cultivars all clones performed well. Pea aphid clones collected from red clover generally performed relatively poorly on pea cultivars, in contrast to the pea aphid clones collected on alfalfa. There was no difference in performance between the two pea aphid colour forms tested. Possible reasons for the high variation and the observed adaptation patterns are discussed. The fact that all clones were collected in two adjacent fields indicates thatA. pisum shows high local intraspecific variability in terms of host adaptation.     

Characterization of a Facultative Endosymbiotic Bacterium of the Pea Aphid Acyrthosiphon pisum

The pea aphid U-type symbiont (PAUS) was investigated to characterize its microbiological properties. Fluorescence in situ hybridization (FISH) and electron microscopy revealed that PAUS was a rod-shaped bacterium found in three different locations in the body of the pea aphid Acyrthosiphon pisum: sheath cells, secondary mycetocytes, and hemolymph. Artificial transfer experiments revealed that PAUS could establish stable infection and vertical transmission when introduced into uninfected pea aphids. When 28 aphid species collected in Japan were subjected to a diagnostic PCR assay, four species of the subfamily Aphidinae (Aphis citricola, Aphis nerii, Macrosiphum avenae, and Uroleucon giganteus) and a species of the subfamily Pemphiginae (Colopha kansugei) were identified to be PAUS-positive. The sporadic incidences of PAUS infection without reflecting the aphid phylogeny can be best explained by occasional horizontal transfers of the symbiont across aphid lineages.     

Vector activity of three aphid species (Hemiptera: Aphididae) modulated by host plant selection behaviour on potato (Solanales: Solanaceae)

Viral diseases non-persistently transmitted by aphids are of great economic importance in several annual crops. Transmission efficiency of these non-persistent phytoviruses is dependant on vector efficiency (i.e. vector intrinsic ability to transmit the virus) but also on the vector activity that implies the early steps of aphid host plant selection process (i.e. brief intracellular stylet punctures after landing) and to their interplant movement ability. In Europe, Macrosiphum euphorbiae (Thomas 1878) is considered as one of the most serious virus vectors on potato (Solanum tuberosum L. 1753). Nevertheless, several alate aphid species that do not colonise potato plants are trapped in potato crops. Therefore, we investigated, through laboratory experiments, vector activity of one potato colonising aphid, M. euphorbiae, and two non-colonising potato aphids, the bird cherry-oat aphid Rhopalosiphum padi (L. 1758) and the pea aphid Acyrthosiphon pisum (Harris 1776). A settling experiment was used to evaluate dispersal activity, and the electrical penetration graph (EPG) technique was used to investigate probing activity on potato plants. Results showed that M. euphorbiae exhibited a better vector activity than other two aphid species in terms of landing and probing. By contrast, interplant movements were only recorded on non-colonising aphids, suggesting a better vector activity than M. euphorbiae in terms of locomotive behaviour. These data confirm the involvement of A. pisum and R. padi in the spread of non-persistent viruses.     

Toxicity of plant essential oil vapours to aphid pests and their coccinellid predators

The comparative toxicity of five essential oil vapours was tested against four aphid species, the black bean aphid Aphis fabae, the pea aphid Acyrthosiphon pisum, the chrysanthemum aphid Macrosiphoniella sanborni, the green peach aphid Myzus persicae and on two of the most common coccinellid predators, the seven-spotted ladybird Coccinella septempunctata and the two-spotted ladybird Adalia bipunctata. All essential oils were highly toxic to the aphid species tested with LC₅₀ and LC₉₉ values ranging between 0.17 and 1.92 and 0.44 and 4.83 µL/L air, respectively, depending on the aphid species and on the essential oil. Coccinellid predators were also highly susceptible to the essential oil vapours and the selective toxicity ratio varied depending on aphid species, coccinellid predator and essential oil. The possibilities for the utililization of essential oils as aphicides, especially in IPM programmes in glasshouses are discussed with regard to the present findings.     

Two new species of cystidicolid nematodes from the digestive tract of the deep-sea fish <Emphasis Type="Italic">Coryphaenoides mediterraneus</Emphasis> (Giglioli) (Macrouridae) from the Mid-Atlantic Ridge

Two new nematode species, Ascarophis longiovata n. sp. and Neoascarophis longispicula n. sp. (Cystidicolidae), are described from the digestive tract of the marine deep-water fish, the Mediterranean grenadier Coryphaenoides mediterraneus (Giglioli), from the Mid-Atlantic Ridge. The former species is characterised mainly by the structure of the mouth (large pseudolabia, each with well-developed dorsal and ventral extension and small apical protrusion; submedian labia almost absent), the large, elongate-oval, non-filamented eggs (60–66 × 18–27 μm), a cervical inflation of the cuticle, bifurcate deirids, and the length of the spicules (315–360 and 120–147 μm), whereas the latter (only males available) can be distinguished by the length of the spicules (960–1,149 and 258–351 μm) and their length ratio (1:1.91–2.71), the shape of the deirids (bifurcate, with long, narrow posterior arms), and the location of the excretory pore and deirids well posterior to the level of the nerve-ring.     

Feeding behavior of aphids on narrow‐leafed lupin (Lupinus angustifolius) genotypes varying in the content of quinolizidine alkaloids

Since the beginning of breeding narrow‐leafed lupins [Lupinus angustifolius L. (Fabaceae)] with a low alkaloid content, susceptibility to several aphid species has increased. Therefore, the probing and feeding behavior of Aphis fabae Scopoli, Aphis craccivora Koch, Acyrthosiphon pisum (Harris), Myzus persicae (Sulzer), and the well‐adapted Macrosiphum albifrons Essig (all Hemiptera: Aphididae) was studied over 12 h on narrow‐leafed lupin genotypes containing varying amounts and compositions of alkaloids. We used the electrical penetration graph (EPG) technique to obtain information on the influence of alkaloid content and composition on the susceptibility to various aphid species. Results indicated that the total time of probing of A. fabae, A. craccivora, A. pisum, and M. persicae increased with a reduced alkaloid content, whereas the alkaloid content had no influence on M. albifrons. Almost all of the individuals (>93%) conducted sieve element phases on the highly susceptible genotype Bo083521AR (low alkaloid content). A reduced occurrence of phloem phases was observed during the 12‐h recording on the alkaloid‐rich cultivar Azuro, especially for A. pisum (37.5%) and A. fabae (55.0%). Furthermore, aphids feeding on genotypes with low alkaloid content had in most cases significantly longer sieve element phases than when feeding on resistant genotypes (Kalya: low alkaloid content, yet resistant; Azuro: high alkaloid content, resistant), whereas M. albifrons showed the longest phloem phase on the alkaloid‐rich cultivar Azuro. As most significant differences were found in phloem‐related parameters, it is likely that the most important plant factors influencing aphid probing and feeding behavior are localized in the sieve elements. The aphids’ feeding behavior on the cultivar Kalya, with a low alkaloid content but reduced susceptibility, indicates that not only the total alkaloid content influences the feeding behavior but additional plant factors have an impact.     

Occurrence and Transmission of Facultative Endosymbionts in Aphids

The occurrence of a secondary bacterial symbiont (PASS) of pea aphid, Acyrthosiphon pisum (Harris), was detected by polymerase chain reaction (PCR) with specific nucleotide primers based on PASS 16S rDNA nucleotide sequences from over 80% (50/57) of clones of pea aphid collected from widely separated locations in California. PASS was also detected by PCR in both red and green phenotypes of rose aphid, Macrosiphum rosae (L.), but not in six other species of aphids examined, including blue alfalfa aphid (A. kondoi Shinji). The nucleotide sequences of the PCR-amplified, partial 16S rDNAs (1060 bp) from pea aphid and rose aphid were identical and 99.9% similar to the published 16S rDNA of PASS. PASS and a recently described new rickettsia of pea aphid (PAR) were transmitted by needle injection of hemolymph from positive pea aphid clones into negative clones and into blue alfalfa aphids. Both PASS and PAR were maintained in the offspring of some of the injected mother aphids via high rate of maternal transmission. Received: 18 September 1996 / Accepted: 30 September 1996     

A positive trait-mediated indirect effect involving the natural enemies of competing herbivores

Trait-mediated indirect effects can have important effects on food web dynamics but are still poorly understood in the field. In a previous population cage study of a small community of aphids and an aphid natural enemy it was found that a trait-mediated indirect effect involving the natural enemy’s behaviour was key to understanding community persistence. Here evidence is presented that a related phenomenon involving some of the same species occurs in the field. Surveys showed that two species of aphid (Acyrthosiphon pisum and Megourella purpurea) tended to share a host plant with a third generally unpalatable species (Megoura viciae) more often than expected by chance. Further evidence suggested this was not due to differential plant suitability or location, but to a positive effect of M. viciae on the performance of the other two species. To test this, field experiments were set up comparing the size and persistence of A. pisum colonies sharing or not sharing a plant individual with M. viciae colonies. A. pisum colonies tended to be larger and persisted for a longer period of time in the presence of M. viciae, an effect that was significant for small colonies exposed to many predators. When protected from predation the presence of M. viciae had no effect on A. pisum colonies. The positive effects of M. viciae on A. pisum is thus likely to be natural-enemy mediated rather than plant mediated. How predation by Syrphidae, the major group observed in the study, is affected by M. viciae is discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Prediction and comparison of the secondary structure of legume lectins

Secondary structure prediction for the 4 legume lectins: Concanavalin A, soybean agglutinin, favabean lectin and lentil lectin, was done by the method of Chou and Fasman. This prediction shows that these four lectins fall into a structurally distinct class of proteins, containing high amounts of β-sheet and β-turns. There is a notable similarity in the gross structure of these proteins; all four of them contain about 40–50% of β-sheet, 35–45 % β-turn and 0–10% of α-helix. When the secondary structure of corresponding residues in each pair of these lectins was compared, there was a striking similarity in the Concanavalin A-soybean agglutinin and favabean lectin-lentil lectin pairs, and considerably less similarity in the other pairs, suggesting that these legume lectins have probably evolved in a divergent manner from a common ancestor. A comparison of the predicted potential β-turn sites also supports the hypothesis of divergent evolution in this class of lectins.     

Pea aphids (Acyrthosiphon pisum Harris) reduce secretion of extrafloral nectar in broad bean (Vicia faba)

1. Herbivores sometimes suppress plant defences. This study tested whether the presence of pea aphids (Acyrthosiphon pisum Harris) on broad bean (Vicia faba) led to decreased secretion of extrafloral nectar (EFN) which functions as an indirect plant defence against herbivores. 2. To determine effects of aphid infestation on EFN secretion, a comparison was done between EFN secretion in uninfested plants and that in plants infested by A. pisum and another aphid species (Aphis craccivora Koch). 3. When broad bean plants were infested by A. pisum, they secreted significantly smaller amounts of EFN than did uninfested plants and A. craccivora‐infested plants. There was no significant difference in EFN secretion between uninfested plants and A. craccivora‐infested plants. The number of extrafloral nectaries did not differ among the three treatments. 4. These results suggest that A. pisum reduced EFN production in broad bean plants.     

Patterns of host selection by four species of aphidiid (Hymenoptera) parasitoids: influence of host switching

Abstract.

• 1 We tested switching behaviour in four species of aphidiid parasitoids, using a two-aphid experimental system consisting of second-instar nymphs of pea aphid (Acyrthosiphon pisum (Harris)) and alfalfa aphid (Macrosiphum creelii Davis) feeding on broad beans in the laboratory.
• 2 Aphidius ervi Haliday, A.pisivorus Smith, A.smithi Sharma & Subba Rao, and Pram pequodorum Viereck showed an innate preference for pea aphid when both host species were provided in equal numbers.
• 3 Wasps encountered both aphid species equally but differed in their acceptance of alfalfa aphid. Females of A.pisivorus and P.pequodorum accepted alfalfa aphids when few pea aphids were available, but A. smithi always concentrated attacks on pea aphid. Aphidius ervi super-parasitized an increasing proportion of pea aphids as their availability declined.
• 4 Switching to the alfalfa aphid occurred in A.ervi and P.pequodorum (but not in A.pisivorus and A.smithi) under the condition of a 1:3 ratio of pea aphids:alfalfa aphids. Wasps did not switch when more pea aphids than alfalfa aphids were provided (3:1 ratio).
• 5 Alfalfa aphids were more likely than pea aphids to escape from parasitoid attack.
• 6 Switching to the most abundant host may not be adaptive in these four species of aphid parasitoids. A foraging wasp incurs a potentially higher cost in lost opportunity time when attacking (and failing to oviposit in) alfalfa aphids. In addition, alfalfa aphids may have lower host quality than pea aphids, a difference that could influence offspring fitness.

     

Effects of predation pressure and prey density on short-term indirect interactions between two prey species that share a common predator

1. Generalist predators are important contributors to reliable conservation biological control. Indirect interactions between prey species that share a common generalist predator can influence both community dynamics and the efficacy of biological control. 2. Laboratory cage experiments investigated the impact of the combined consumptive and non-consumptive effects of predation by adult Hippodamia convergens as a shared predator on the population growth and relative abundance of Acyrthosiphon pisum and Aphis gossypii as prey species. Predation pressure and prey density were varied. 3. At low predation pressure the indirect interaction between aphid species was asymmetrical with a proportionally greater negative impact of predation on A. gossypii than on A. pisum. At intermediate predation pressure, the indirect interaction became symmetrical. At high predation pressure and higher levels of prey density, it was asymmetrical with greater negative impact on A. pisum, often driven to local extinction while A. gossypii populations persisted. 4. A linear mixed-effects model including early population growth of both aphid species and predation pressure explained 96% and 92% of the variation in the population growth of A. pisum and A. gossypii, respectively, over an 8-day period. The overall effect of shared predation on the indirect interaction between the two aphid species is best described as apparent commensalism, where A. pisum benefited from early population growth of A. gossypii, while A. gossypii was unaffected by early population growth of A. pisum. Considering these indirect interactions is important for conservation biological control efforts to be successful.     

The oviposition behavior ofAphidius ervi andMonoctonus paulensis (Hymenoptera: Aphididae) encountering different host species (Homoptera: Aphididae) in sequential patches

Two-day-old mated females ofAphidius ervi Haliday andMonoctonus paulensis (Ashmead) were each provided with two sequential host patches. Patches were comprised of plastic petri dishes containing either 15 pea aphids,Acyrthosiphum pisum (Harris), or 15 alfalfa aphids,Macrosiphum creelii Davis. Both wasp species parasitized more hosts in patches containing pea aphids than in those containing alfalfa aphids, regardless of sequence. Females ofA. ervi also laid more eggs per aphid in patches containing pea aphids than in patches containing alfalfa aphids. When both patches contained alfalfa aphids,M. paulensis females parsitized more aphids in the second patch than in the first. Fewer alfalfa aphids were parasitized in the second patch when the first patch contained pea aphids, and fewer eggs were laid per alfalfa aphid. Parasitoid females of both species exhibited consistently higher rates of oviposition into their preferred host species and adjusted their reproductive allocation to hosts and host patches as a function of their experience in previous patches.     

Lectin-induced alterations on the proliferation of three human prostatic cancer cell lines

Summary While lectins are known to influence the cell growth of several types of normal and neoplastic tissues, their roles in the case of prostatic cancer cells remain relatively unexplored. In the present work, we report thein vitro influence of five lectins, namely peanut (PNA), wheat germ (WGA), Concanavalin A (Con A),Griffonia simplicifolia (GSA-IA₄), andPhaseolus vulgaris (PHA-L) agglutinins, on the cell proliferation of one androgen-sensitive (LNCaP) and two androgen-insensitive (PC-3 and DU 145) human prostatic cancer cell lines cultured in either 10% or 1% fetal bovine serum (FBS)-supplemented media. The cell proliferation was assessed by means of the colorimetric 3-(4,5-dimethythiazol-2-yle)2,5-diphenyltetrazolium bromide. (MTT) assay. Four lectin concentrations were tested (i.e., 0.1, 1, 10, and 100 μg/ml) at five experimental states (i.e., 2, 3, 5, 7, and 9 d following the addition of each lectin to the culture media). Our results demonstrated that the five lectins under study had a globally significant dose-dependent toxic effect on prostatic cancer cell proliferation. Nevertheless, low doses of GSA-IA₄ and PHA-L significantly (P<0.05 toP<0.001) increased the cell proliferation of confluent PC-3 cells. Increasing the FBS from 1% to 10% in the culture media significantly antagonized lectin-induced toxicity in the three prostatic cell lines. In conclusion, the present data strongly suggest that some lectins might influence the proliferation of prostatic carcinoma cells. In addition, because lectins are present in our diet, and are able to pass into the systemic circulation and thus reach the prostate, the present results suggest that some lectins might exert an influence on prostate cancer growth under clinical conditions.     

Entomotoxic action of Sambucus nigra agglutinin i in Acyrthosiphon pisum aphids and Spodoptera exigua caterpillars through caspase‐3‐like‐dependent apoptosis

In this project, the toxicity and mechanism of action of the ricin‐B‐related lectin SNA‐I from elderberry (Sambucus nigra) in the pea aphid (Acyrthosiphon pisum) and the beet armyworm (Spodoptera exigua), two important pest insects in agriculture, were studied. SNA‐I is a chimeric lectin belonging to the class of ribosome‐inactivating proteins and consists of an A‐chain with N‐glycosidase activity and a carbohydrate‐binding B‐chain. Incorporation of 2 mg/ml of SNA‐I in the diet of neonates and adults of A. pisum caused 40–46% mortality within 2 days, while in third instars of S. exigua, the larval biomass was significantly reduced by 12% after feeding for 3 days on a diet containing 5 mg/g of SNA‐I. Interestingly, extracts of the (mid)gut of treated A. pisum and S. exigua demonstrated DNA fragmentation and this was accompanied with an increase in caspase‐3‐like activity. The involvement of cell death or apoptosis in the entomotoxicity of SNA‐I through induction of caspase‐3‐like activity was also confirmed by addition of the permeable caspase‐3 inhibitor III in the diet, leading to a rescue of the treated aphid neonates. Finally, similar to the chimeric lectin SNA‐I, the hololectin SNA‐II, consisting of two carbohydrate‐binding B‐chains caused high mortality to neonate A. pisum aphids with an LC₅₀ of 1.59 mg/ml, suggesting that the entomotoxic action of the lectins under study mainly relies on their carbohydrate‐binding activity. © 2010 Wiley Periodicals, Inc.     

Entomotoxic action of jackbean lectin (Con A) in bird cherry-oat aphid through the effect on insect enzymes

The mechanism of the toxicity of plant lectins is not clearly understood. The insecticidal activity of plant lectins results from effects on insect metabolism by interfering with gut enzymatic function. Thus, a greater understanding of the mechanisms of plant lectin toxicity in insects is required. This study reports the effects of dietary ingestion of the glucose-mannose binding lectin Concanavaline A (Con A) on bird cherry-oat aphid (Rhopalosiphum padi L.) enzymes involved in protein digestion [aminopeptidase N and cathepsin L (CatL)], sugar (α- and β-glucosidases), and phosphorus (alkaline and acid phosphatase) metabolism. An aphid bioassay test using artificial diets containing Con A is also presented. An increase in the concentration of Con A generally suppressed the activity of glucosidases and phosphatases, and increased the activity of CatL in apterae morphs. Bird cherry-oat aphid performance was affected by the presence of Con A in artificial diets. The lectin added to the liquid diet increased the pre-reproductive period, mortality, and the average time of generation development (T) and decreased fecundity and the intrinsic rate of natural increase (r_m). Aphicidal activity of Con A might be linked to its interference in the activity of digestive enzymes.     

A comparison between two strains from Japan and Europe of Aphidius ervi

A European strain of Aphidius ervishall be introduced into Japan for the control of Macrosiphum euphorbiaeon greenhouse tomatoes. We compared this strain, which is originating from The Netherlands (EVP), with a native strain from Hokkaido, Northern Japan (SPR) in several characteristics. The percentage of parasitism of SPR and EVP was significantly different, when attacking three aphid species: 13% and 30% on M. euphorbiaeon tomato, 68% and 93% on Acyrthosiphon pisumon broad bean and 10% and 42% on Aulacorthum solanion sweet pepper, respectively. SPR and EVP differed morphologically (in the colouration of the petiole) and in the esterase banding patterns. Furthermore, cross mating experiments showed that SPR and EVP are partially reproductively isolated from each other. Complete reproductive isolation is evident in the one direction cross (EVP females and SPR males).