Green Aphid Research Articles

Learning by the parasitoid wasp, Aphidius ervi (Hymenoptera: Braconidae), alters individual fixed preferences for pea aphid color morphs

Learning, defined as changes in behavior that occur due to past experience, has been well documented for nearly 20 species of hymenopterous parasitoids. Few studies, however, have explored the influence of learning on population-level patterns of host use by parasitoids in field populations. Our study explores learning in the parasitoid Aphidius ervi Haliday that attacks pea aphids, Acyrthosiphon pisum (Harris). We used a sequence of laboratory experiments to investigate whether there is a learned component in the selection of red or green aphid color morphs. We then used the results of these experiments to parameterize a model that examines whether learned behaviors can explain the changes in the rates of parasitism observed in field populations in South-central Wisconsin, USA. In the first of two experiments, we measured the sequence of host choice by A. ervi on pea aphid color morphs and analyzed this sequence for patterns in biased host selection. Parasitoids exhibited an inherent preference for green aphid morphs, but this preference was malleable; initial encounters with red aphids led to a greater chance of subsequent orientation towards red aphids than predicted by chance. In a second experiment, we found no evidence that parasitoids specialize on red or green morphs; for the same parasitoids tested in trials separated by 2 h, color preference in the first trial did not predict color preference in the second, as would be expected if they differed in fixed preferences or exhibited long-term (> 2 h) learning. Using data from the two experiments, we parameterized a population dynamics model and found that learning of the magnitude observed in our experiments leads to biased parasitism towards the most common color morph. This bias is sufficient to explain changes in the ratio of aphid color morphs observed in field sites over multiple years. Our study suggests that for even relatively simple organisms, learned behaviors may be important for explaining the population dynamics of their hosts.

Effectiveness of Hyaliodes vitripennis (Say) (Heteroptera: Miridae) predation in apple orchards

The biology of Hyaliodes vitripennis Say (Heteroptera: Miridae) and its potential for biological control of mites and aphids were studied for 3 yr in apple orchard settings. Results showed a significant repressive effect of H. vitripennis on the European red mite, Panonychus ulmi Koch, the two-spotted spider mite, Tetranychus urticae Koch and a significant augmentative effect on the green aphids ( Aphis pomi DeGeer and Aphis spiraecola Pagenstecher). The predator also precluded the action of naturally occurring predatory mites, either by resource competition or by direct predation, but the resultant effect was always detrimental to P. ulmi.

THE ITALIAN NATIONAL PEACH BREEDING PROJECT

In 1994 the Ministry for Agricultural and Forestry Policy (Mi.P.A.F.) has financed a national research program named “Fruit Growing”, coordinated by the Istituto Sperimentale per la Frutticoltura (ISF) and composed of several projects relevant to stone fruit breeding, pome fruit breeding, rootstock breeding, strawberry breeding, tree training, post harvest, and marketing. Working groups on peach are active within the stone fruit and rootstock breeding projects. The main objectives of the breeding programs were: improved fruit quality, resistance or tolerance to diseases and pests (both for scions and rootstocks), suitability for difficult soils (for rootstocks). Nine units, belonging to Mi.P.A.F. (Fruit Tree and Plant Pathology Research Institutes) and University (Bologna, Florence and Pisa), were involved. Up to now, 7 peach cultivars, 1 nectarine and 2 rootstocks have been commercially released and several scion advanced selections are under evaluation for brown rot, leaf curl, green aphid resistance or tolerance, and rootstock selections for chlorosis, asphixya, nematodes, Armillaria and Phytophthora resistance or tolerance.

L-Ascorbic acid is accumulated in source leaf phloem and transported to sink tissues in plants.

L-Ascorbic acid (AsA) was found to be loaded into phloem of source leaves and transported to sink tissues. When L-[(14)C]AsA was applied to leaves of intact plants of three different species, autoradiographs and HPLC analysis demonstrated that AsA was accumulated into phloem and transported to root tips, shoots, and floral organs, but not to mature leaves. AsA was also directly detected in Arabidopsis sieve tube sap collected from an English green aphid (Sitobion avenae) stylet. Feeding a single leaf of intact Arabidopsis or Medicago sativa with 10 or 20 mM L-galactono-1,4-lactone (GAL-L), the immediate precursor of AsA, lead to a 7- to 8-fold increase in AsA in the treated leaf and a 2- to 3-fold increase of AsA in untreated sink tissues of the same plant. The amount of AsA produced in treated leaves and accumulated in sink tissues was proportional to the amount of GAL-L applied. Studies of the ability of organs to produce AsA from GAL-L showed mature leaves have a 3- to 10-fold higher biosynthetic capacity and much lower AsA turnover rate than sink tissues. The results indicate AsA transporters reside in the phloem, and that AsA translocation is likely required to meet AsA demands of rapidly growing non-photosynthetic tissues. This study also demonstrates that source leaf AsA biosynthesis is limited by substrate availability rather than biosynthetic capacity, and sink AsA levels may be limited to some extent by source production. Phloem translocation of AsA may be one factor regulating sink development because AsA is critical to cell division/growth.

Impacts of seasonal kaolin particle films on apple pest management

AbstractThe impact of multiple applications of the kaolin-based particle film M96-018 on the population density of selected pests of apple, Malus domestica (Borkh) (Rosaceae), and their natural enemy populations were measured in several Washington State orchards from 1997 to 1999. Densities of western tentiform leafminer, Phyllonorycter elmaella (Doganlar and Mutuura) (Lepidoptera: Gracillariidae), were significantly higher and percent parasitism was generally lower in treated plots than in untreated plots. The effect of M96-018 on green aphids (Aphis spp.) (Hemiptera: Aphididae) was variable between orchards; however, populations of rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae), were higher in treated plots than in untreated plots. M96-018 reduced the mean density of the white apple leafhopper, Typhlocyba pomaria (McAtee) (Hemiptera: Cicadellidae), and the density of spiders (Araneae) compared with untreated plots. Fruit injury by codling moth, Cydia pomonella (L.), and fruittree leafroller, Archips argyrospilus (Walker) (Lepidoptera: Tortricidae), was significantly reduced in the treated plots compared with the untreated plots. The effect of M96-018 on the mullein bug, Campylomma verbasci (Meyer) (Hemiptera: Miridae), was variable between orchards and years. Stink bug (Hemiptera: Pentatomidae) density and related fruit injury were unaffected by M96-018. Fruit infestation by San Jose scale, Quadraspidiotus perniciosus (Comstock) (Hemiptera: Diaspididae), was significantly higher in treated plots than in untreated plots. Discontinuing applications of M96-018 at mid-season reduced the number of aphid-infested leaves and increased fruit injury by leafroller compared with a full-season program. No differences in pest densities occurred in plots treated for one versus two consecutive years; however, the density of phytophagous mites (Acari: Tetranychidae) was significantly higher the subsequent year after plots were treated with M96-018. Further studies are needed to elucidate how these disruptive impacts of particle films can be minimized.

The major carotenoid pigments of the grain aphid, Sitobion avenae (F.) (Hemiptera: Aphididae)

SummaryThe economically important grain aphid, Sitobion avenae (F.) shows colour polymorphism, with brown and green forms predominating. Colour is determined both genetically and in response to environmental factors, including nutrition. The biological significance of the colour polymorphism is unknown, although seasonal changes occur in the frequency of colour morphs in the field, whilst the brown morph may have adaptive significance in terms of hymenopterous endoparasitism. The ground colour of aphids is produced by haemolymph pigments, aphins (glucosides) and carotenoids. The latter may be under the synthetic control of intracellular endosymbiotic bacteria. In this study, the major carotenoid pigments of a brown and a green clone of S. avenae were examined using thin layer chromatography (TLC) and high‐performance liquid chromatography (HPLC), and their absorbance spectra recorded. Using TLC, the brown clone produced five bands of different Rf, ranging from yellow, to orange‐pink to pink in colour. In contrast, the green clone gave only a single yellow band of higher Rf than any of the bands of brown aphids. Following separation of carotenoids by HPLC, brown aphids gave seven peaks and green aphids five. Comparison of absorbance maxima with known published values for carotenoids provides strong evidence for the identification of four of the carotenoid pigments from brown aphids (RB‐4, 3,4‐didehydrolycopene; RB‐5, torulene; RB‐6; lycopene; RB‐7, γ‐carotene) and one from green aphids (RG‐2, α‐carotene). The other carotenoids remain unidentified. The biosynthesis and possible biological relevance of the various pigments of S. avenae are briefly discussed.

Strategies Involved in the Location of Hosts by the ParasitoidAphidius erviHaliday (Hymenoptera: Braconidae: Aphidiinae)

Abstract The parasitoidAphidius erviHaliday uses both semiochemical and physical cues to locate and recognize its main host, the pea aphidAcyrthosiphon pisum(Harris). In wind tunnel studies, it was demonstrated that plant volatiles, particularly those induced by aphid feeding, are important long-range cues in the initial stages of host location. Furthermore,A. ervidistinguished between plants damaged byAc. pisumand those damaged by the nonhost aphidAphis fabae(Scop.). Host-induced volatiles were emitted by young broad bean plants (Vicia faba) in sufficient quantities to elicit a flight response from female parasitoids after 40 aphids had been feeding for 72 h. Aphids confined to a single leaf caused systemic production of herbivore-induced volatiles throughout the plant. Previous experiences with hosts or host-related cues heightened parasitoid responses to host-induced volatiles and also triggered responses to other plant volatiles. This learning ability provides the parasitoid with behavioral plasticity to adapt its responses to suit prevailing foraging opportunities.A. ervifemales also responded to synthetic aphid sex pheromones in wind tunnel experiments, and attempts are being made to manipulate field populations using host pheromone lures. Contact kairomones in the host cuticle and cornicle secretion appear to be involved in host recognition and acceptance byA. ervifemales. In addition, visual cues play a role in host location and recognition, with color being an important short-range cue. Color alone stimulated attack responses;A. ervifemales attacked green aphids in preference to brown aphids and showed attack responses toward yellow paint pigments enclosed in glass capillary tips.

New Colour Form of Aphis Schneideri (Börn.) From Lithuania

A yellow colour form of Aphis schneideri (Born.) was found in Pilaitė (the surroundings of Vilnius, Lithuania) in 1994. Colour differences between yellow and green aphids of A. schneideri seem to have a genetic background. The yellow aphids were smaller, and the yellow clones did not finish their entire life cycle, thus supporting the idea of the reduced fitness of yellow mutants. There also exists the possibility of the hybridogenic origin of yellow colour forms in currant inhabiting species of the genus Aphis L.

Morphometric observations on three populations of Schizaphis graminum (Rondani), a main wheat aphid pest in Brazil

The green aphid Schizaphis graminum (Rondani) is an important pest of Graminae. Samples of this aphid were collected at three environmentally distinct Brazilian localities, Passo Fundo (RS), Jaguariuna (SP) and Dourados (MS). Alatae and apterous viviparous forms were reared on the BR-35 wheat (Triticum aestivum) strain under controlled laboratory conditions and studied as to their variability in measures of body size and production of progeny. Univariate (ANOVA) and multivariate (canonical discriminant functions) techniques were used to evaluate differences among the three populations. Conspicuous differences between populations were observed in the length of five structures of the alatae and eight of the apterous forms, as well as in offspring production. The greatest dispersion in the length of general structures of the individuals obtained by the canonical discriminant function was for Passo Fundo, where climatic conditions are more severe and where aphids cause the most serious damage to wheat crop.

Development and Reproduction of Two Color Forms of English Grain Aphid (Homoptera: Aphididae)

The life cycle of apterous and alate viviparae of pink and green color forms of the English grain aphid, Sitobion avenae (F.), were compared at 20 ± l°C and a photoperiod of 14:10 (L:D) h, using individually caged aphids that were examined daily on ‘Clintland 64’ oat, Avena sativa L. Two studies were conducted, using 22 replicates with apterous and alate S. avenae , and 132 replicates with only apterous forms. Alate aphids had a greater prereproductive period than apterous aphids, probably in part because their metabolism was directed towards wing development before reproduction. Apterous pink aphids had a shorter reproductive period than all other forms. This, together with their higher intrinsic rate of increase (rm), may represent an advantage over green aphids for colony growth, although this advantage may be reduced because alate pink aphids had the smallest rm of the aphid forms. Alate aphids tended to have a longer postreproductive period. The longevity of apterous pink aphids was shorter compared with the other forms, but this was compensated by their greater rm. The percentage of alate aphids was slightly larger in the pink (17.16%) than in the green form (14.97%), which may help the dispersal of the pink genotype over time. All parameters of the life cycle, except the reproductive period, showed differences between apterous green and pink S. avenae . The pre-, post-, and reproductive periods were shorter for apterous pink aphids, which was reflected in a shorter longevity, compared with apterous green and alate pink and green forms. However, apterous pink aphids had more progeny, which meant a larger rm, than green aphids. Variations in the life cycle like those between the green and pink forms observed in this study may occur among other clones of S. avenae (and possibly in other aphid species). Aphid studies should use >1 clone per species to obtain representative data of average populations.

Control of the Peach Green Aphid, Myzus persicae (Sulzer), on Peach-Tree by Petroleum Oil in Early Spring

Control of the Peach Green Aphid, <i>Myzus persicae</i> (Sulzer), on Peach-Tree by Petroleum Oil in Early Spring

Extracellular microtubules in aphid gut

The presence of extracellular microtubules on the microvillar surface of the intestine of a number of aphids was noted as early as 1972. The authors stated, “At present there is little evidence as to the true nature of these extracellular microtubules. We have used the term microtubule in the broad sense.” These microtubules are smaller than cytoplasmic microtubules reported earlier.In the present investigation we have studied the intestinal epithelium of the green pea aphid, A. pisum, using transmission electron microscopy. The epithelium consists of a single layer of pyramidal shaped cells with a striated border. In the anterior part of the intestine the striated border consists of a microlabyrinth (Fig. 1) similar to that previously described for the green peach aphid, Myzus persicae. In some regions of the microlabyrinth the microtubules are arranged at right angles to the length of the infoldings; in other regions microtubules run parallel to the length of the infoldings giving support to this structure.

Management of European Red Mite (Acari: Tetranychidae) and Several Aphid Species on Apple with Petroleum Oils and an Insecticidal Soap

Three petroleum oils and one insecticidal soap were evaluated in laboratory tests at different rates for ovicidal efficacy against overwintering Panonychus ulmi (Koch) eggs. Sunspray 6E and Volck Supreme oils caused the greatest mortality of all materials tested. Sunspray 6E+ caused less mortality than did the Sunspray 6E and Volek Supreme but greater mortality than Safer Insecticidal Soap Concentrate, which caused only slightly greater mortality than the distilled water check. Field applications of the same materials by airblast sprayer and high-pressure handgun caused less mortality of overwintering eggs than in the laboratory study. Summer applications of these materials were tested for their ability to suppress mite and aphid populations throughout the growing season. Applications of all materials provided significant control of populations of P. ulmi , rosy apple aphid, Dysaphis plantaginea (Passerini), and a green aphid complex made up of the apple aphid, Aphis porni De Geer, and the spirea aphid, Aphis spiraecola Patch. Spray volume, coverage, and rate of material applied were related to mite and insect control and plant phytotoxicity; the greater the volume, coverage, and rates used, the greater the control and phytotoxicity obtained. Volck Supreme oil, particularly at the high rate, caused more damage to fruit and foliage than did any of the other treatments. Suns pray 6E and Suns pray 6E+ appear to be equally safe to fruit and foliage based on phytotoxicity ratings taken throughout the growing season.

Geographic Distribution of Two Color Forms, Carboxylesterase Activity, and Chromosome Configuration of the Tobacco Aphid (Homoptera: Aphididae) in North Carolina

A statewide survey was conducted in tobacco fields throughout 17 counties in North Carolina to determine distribution and relative abundances of red and green color forms of the tobacco aphid, Myzus nicotianae Black man. Samples of tobacco aphids from infested fields were collected during the survey and used to establish 36 laboratory cultures. A carboxylesterase assay was performed on aphids from each established laboratory culture to determine general carboxylesterase hydrolyzing activities. Significant differences among cultures were observed. Activities ranged from 40.04 μM 1-naphthol produced per minute per red aphid in Wayne County to 77.36 in Bladen County. Activities in green aphids ranged from 17.12 in Johnston County to 53.52 in Watauga County. Aphids with high carboxylesterase activities (>40 IJ-MI-naphthol produced per minute per aphid) were of both colors; however, all aphids with low activities 40 μM I-naphthol produced per minute per aphid). The five cultures with normal karyotypes had low activities <22).

Control of Red and Green Morphs of Tobacco Aphids (Homoptera: Aphididae) in Flue-Cured Tobacco

Control of red and green morphs of the tobacco aphid, Myzus nicotianae Blackman, was investigated in field and laboratory tests on flue-cured tobacco in Georgia during 1987–1989. Acephate provided good control of both morphs at 0.75 and 0.5 lbs. AI/acre, and fair to poor control of both morphs at 0.25 and 0.125 lbs. AI/acre. Methomyl, endosulfan, and Endocide Plus (endosulfan plus parathion) also provided effective control of both morphs. Malathion, oxamyl, and tralomethrin provided significantly better control of the green morph than the red morph. Microencapsulated methyl parathion was totally ineffective in controlling either green or red color forms. In laboratory tests, the residual activity of acephate provided high mortality and a reduction in live nymphs produced for up to 14 days after application for both morphs, although these effects were more pronounced with green aphids. The residual activity of methomyl had no adverse effects on either morph 3 days after treatment.

COMPARISON OF A YELLOW FORM OF THE GREEN PEACH APHID, MYZUS PERSICAE (SULZER), AND A GREEN FORM OF THE TOBACCO APHID, MYZUS NICOTIANAE BLACKMAN, COEXISTING ON GREENHOUSE POTATO IN NEW BRUNSWICK

AbstractA dark green aphid was isolated from a greenhouse colony of green peach aphid, Myzus persicae (Sulzer), in Fredericton, N.B. The green aphid was shown to conform taxonomically and biologically to the recently named species Myzus nicotianae Blackman, except for its rare production of alatae. It is reported for the first time on greenhouse-grown potato where its population development is similar to that of the yellow holocyclic M. persicae from the same colony. The vector efficiency of the green and yellow aphids for potato virus Y0 is similar. The yellow aphid tends to be more susceptible to insecticides than the green aphid. Myzus nicotianae was not found in aerial aphid samples taken in New Brunswick in 1967 and 1987.

Release and establishment ofAphidiusspp. (Hymenoptera: Aphidiidae), parasitoids of pea aphid and blue green aphid in New Zealand

Abstract Three Aphidius spp. parasitoids of the lucerne aphids, pea aphid (P A) and blue green aphid (BGA), were introduced into New Zealand from 1977 to 1982. A. eadyi spread rapidly and now occurs in all the main lucerne-growing areas. In comparison, A. ervi was difficult to establish, failing to persist after several initial recoveries, but was eventually established from releases of se:parate strains in the North and South Islands, replacing A. eadyi as the predominant parasitoid in the North Island. Despite large releases, A. smithi has not established. A. ervi shows a preference in the field for BGA, but in the laboratory it demonstrated the ability to adapt from PA to BGA in two generations. Laboratory experiments showed that A. eadyi has a higher fecundity and faster development rate than A. ervi indicating that it competes better for PA. However, the polyphagy of A. ervi may be significant in its increasing predominance in the field. Comparisons are drawn with North American results.

Control of Soft Scale and Aphids in Red Ginger, Hawaii, 1986

Abstract Efficacy trials were conducted from 4 Aug through 2 Sep in field plantings of red ginger. Plots measured 9 × 10 ft with 11 plantings/plot arranged in a randomized complete block with 4 replications. Pretreatment counts of the number of flowers infested with green scales and aphids were taken on 31 Jul. Insecticides were applied to runoff (160 gal/acre) every 2 wk, for a total of 3 applications, using a compressed-air sprayer with an 8004 Teejet nozzle at 40 psi. A spreader sticker, Triton B 1956, was added to each treatment (including the check) at a rate of 3 fl oz/100 gal.

Morphological discrimination of a tobacco-feeding form from Myzus persicae (Sulzer) (Hemiptera: Aphididae), and a key to New World Myzus (Nectarosiphon) species

AbstractMultivariate techniques, principally the method of canonical variates, were used to investigate morphological variation within and between populations of the group of Myzus persicae (Sulzer) from North and South America, Europe, Africa and Asia. The scores on the first canonical variate of samples from tobacco in North America, the Mediterranean region, the Middle East, Africa and Sri Lanka all grouped consistently when compared with samples from other host-plants, even after aphids from tobacco had been reared for up to seven years on a non-tobacco host. Thus there is a widely-distributed tobacco-adapted form, closely related to M. persicae but with its own characteristic morphology. Morphological discriminants are given for the recognition of apterous and alate viviparae of this tobacco form, which is given the name M. nicotianae sp. n. Both M. persicae and M. nicotianae have 2n = 12, and both are frequently heterozygous for apparently the same autosomal translocation, which they must have acquired independently. M. nicotianae is presumably isolated from M. persicae by being permanently parthenogenetic. In Japan and Central Asia, however, aphids of the M. persicae group on tobacco can produce sexual morphs; the taxonomic status of these latter populations is still unclear. Multivariate comparison of European and North American populations of dark green aphids of the M. persicae group with 13 or 14 chromosomes in somatic cell nuclei instead of the normal 12, led to the conclusion that these all belong to one morphologically variable taxon, M. antirrhinii (Macchiati). Keys are provided to the apterous and alate virginoparae of the species of the M. persicae group in America.

Entomophthora planchoniana . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Entomophthora planchoniana . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Aphids (Hemiptera: Aphididae) including species of Cinarinae, Chaitophorinae and Drepanosiphanae which are not usually attacked by the other common species of the Entomophthorales . GEOGRAPHICAL DISTRIBUTION: Widespread, including Europe, N. &amp; S. America, Australasia, Asia. DISEASE: Aphids become infected by a germ tube from an adhering conidium penetrating the cuticle. Naturally green aphids killed by this species are straw coloured and those filled with resting spores are grey. Black aphids turn reddish-brown. The rhizoids issuing from infected large aphids viewed from the side suggest stout supports. In N. Europe this species persists in aphid populations in warmer and drier conditions than all the other species attacking aphids except Neozygites fresenii . It frequently infects cereal aphids infesting the ears of cereals whereas Erynia neoaphidis is usually restricted to aphids on the leaves of the plant where conditions are less extreme.