Showing papers on "Aphididae published in 1985"
115 citations
TL;DR: A study of searching behaviour on wheat and host preference of Aphidius rhopalosiphi (DeStefani‐Perez) is described.
Abstract: . 1. A study of searching behaviour on wheat and host preference of Aphidius rhopalosiphi (DeStefani-Perez) is described.
2. Parasitoids divided their time equally between the leaves but spent very little time on the ear.
3. After contact with honeydew or an aphid host, parasitoids were arrested in a particular area and increased the time spent searching.
4. Aphids feeding on the ear were parasitized less successfully, since their position between the grains protected them from parasitoid attacks.
5. A.rhopalosiphi exhibited no preference for Metopolophium dirhodum (Walker) or Sitobion avenae (Fabricius), although the handling time for the latter was significantly longer; this resulted in fewer S.avenae being parasitized when it was abundant. Parasitoids did not switch between hosts in these experiments.
6. As a result of its searching behaviour, A.rhopalosiphi will encounter and parasitize M.dirhodum feeding on the leaves more frequently than S.avenae, which feeds on the ear. This will limit the parasitoid's ability to regulate populations of the cereal aphid S. avenae.
75 citations
TL;DR: Small arenas in the field were used for observing adult Agonum dorsale (Pont.) foraging in a wheat crop to study their foraging behaviour and found it easy to observe their behaviour change during foraging periods.
Abstract: . 1. Small arenas in the field were used for observing adult Agonum dorsale (Pont.) foraging in a wheat crop.
2. The carabid showed no significant change in behaviour between low and high aphid density arenas.
3. Individuals foraged nocturnally and spent most of their time on the ground searching for prey. They climbed infrequently and then not high enough to reach aphid aggregations on the ears and flag leaves of wheat.
4. Gut dissection showed that more individuals had eaten aphids in the high aphid density arena than the low. Recording of aphid distribution within the arenas showed that this increase in aphid consumption could be explained by A.dorsale capturing aphids on the ground. Prey availability per unit area was in fact higher on the ground than on the wheat.
5. The contribution of ground-zone predators such as A.dorsale to the control of cereal aphids will be determined by the frequency with which aphids arrive on the ground and the proportion of these which reclimb the wheat and reproduce in the absence of predation.
73 citations
TL;DR: Female and male parasitoids did not respond to potato plants, the food plant of their host, but females were strongly attracted by odors from a preferred host, Macrosiphum euphorbiae (Thomas), and also from less preferred hosts such as Myzus persicae (Sulzer) andAphis nasturtii Kalt.
Abstract: The olfactory responses of the parasitoidAphidius nigripes Ashmead were investigated with a four-field airflow olfactometer. Female and male parasitoids did not respond to potato plants, the food plant of their host. However, females were strongly attracted by odors from a preferred host,Macrosiphum euphorbiae (Thomas), and also from less preferred hosts such asMyzus persicae (Sulzer) andAphis nasturtii Kalt. Moreover,A. nigripes females responded positively to odors from a nonhost aphid,Rhopalosiphum maidis Fitch. The honeydew produced by these four aphid species was also very attractive to females. Males did not respond to aphids or honeydew but were highly attracted by odors from conspecific female parasitoids.
62 citations
TL;DR: Low levels of JH III were detected in both aphid species, the first identification of a juvenile hormone from an homopteran insect.
Abstract: . Whole body extractions from larval and adult apterous forms of Megoura viciae, and from adult Aphis fabae, were analysed for the known insect juvenile hormones (JHs) by a gas chromatography-mass spectrometric method. Low levels of JH III were detected in both aphid species, the first identification of a juvenile hormone from an homopteran insect. Although the mean titre in adult M. viciae is higher in long-day than in short-day reared insects (0.12±0.03 v. 0.04±0.01 ng/g), titres were variable and measurements overlapped. The results are discussed in the context of the hormonal control of aphid polymorphism and the question of identity of homopteran and hemipteran JH.
51 citations
TL;DR: A study of variation in three peptidases in a parthenogenetic S. avenae field population at Rothamsted using serial one-dimensional polyacrylamide gel electrophoresis increased the overall number of “allozymes” (mobility variants) detected from 10 under standard conditions to 22, as well as revealing putative heterozygous banding patterns under some test conditions.
Abstract: A study of variation in three peptidases (PEP-3 to -5) in a parthenogenetic S. avenae field population at Rothamsted using serial one-dimensional polyacrylamide gel electrophoresis (involving changes of gel concentration and electrophoretic run-time) increased the overall number of "allozymes" (mobility variants) detected from 10 under standard conditions (6% gels, 2 h run-time) to 22, as well as revealing putative heterozygous banding patterns under some test conditions. However, an examination of another enzyme, 6-phosphogluconate dehydrogenase (6-PGD) in a sample collected at Rothamsted the following year failed, using a combination of serial methods (changes of gel concentration) and isoelectric focusing, to increase the total number of 6-PGD bands separated (seven, none of which appeared to be allelic in origin). Nevertheless, some major bands were split into several bands, whilst other infrequent bands were either gained or lost. The findings are briefly discussed.
44 citations
TL;DR: Caged experiments were conducted in the field during two crop seasons to assess population development and direct feeding effects of two cereal aphids, Rhopalosiphum padi (L.) and Schizaphis graminum (Rondani), on winter wheat planted in early September and infested during the two-leaf, four- leaf, and two-tiller stages of development.
Abstract: Planting winter wheat in early September is a common practice in much of eastern Washington. A number of agronomic benefits are associated with planting early, but there is also a higher risk of cereal aphids infesting the crop with early planting. Caged experiments were conducted in the field during two crop seasons (1979–1980, 1981–1982) to assess population development and direct feeding effects of two cereal aphids, Rhopalosiphum padi (L.) and Schizaphis graminum (Rondani), on winter wheat planted in early September and infested during the two-leaf, four-leaf, and two-tiller stages of development. Aphids were introduced at a rate of two to four per plant per species and allowed to feed uninterrupted until cold weather ended their activity in November. Data taken were: plant height, heads per plant, root and foliage weights, test weight, and grain yield. R. padi , singly or in combination with S. graminum , was generally more prolific than S. graminum . The largest aphid populations encountered were on wheats infested initially at the two-leaf stage. Injury to wheat was highest where aphid infestations started at the two-leaf stage, intermediate to none at the four-leaf stage, and none at the two-tiller stage. Mixed populations on two-leaf wheats caused the greatest damage, followed by pure populations of R. padi. S. graminum generally caused the least damage.
43 citations
TL;DR: It is suggested that resistant plant genotypes should have the following characteristics in their effects on the aphid: cause high nymphal mortality, cause prolonged development during early plant stages and cause low birth rate close to ear emergence.
43 citations
TL;DR: Time-specific life tables were constructed for three pea aphid,Acyrthosiphon pisum ( Harris) (Harris) (Homoptera: Aphididae), populations using a modification of Hughes' analytical procedure to provide a reliable estimate of potential population growth rate and was used in preference toHughes' approach of estimating potential population Growth rates directly from stage structure data.
Abstract: Time-specific life tables were constructed for three pea aphid,Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), populations using a modification ofHughes' analytical procedure. All populations were studied on second-growth alfalfa (mid-June to mid-July) in south central Wisconsin; data for two populations were collected during 1980, and data for the third population were collected during 1982. The intrinsic rate of increase (rm) estimated on a physiological time (day-degree) scale under field conditions but in the absence of natural enemies, provided a reliable estimate of potential population growth rate and was used in preference toHughes' approach of estimating potential population growth rates directly from stage structure data. Emigration by adult alatae and fungal disease were the major sources ofA. pisum mortality in each of the three populations studied. These factors were most important because of their impact on reducing birth rates within the local population. Parasitism was never greater than 9 percent. Mortality attributable to predation ranged from 0.0 to about 30.0%; however, even at the highest predator densitiesA. pisum populations increased exponentially.
40 citations
TL;DR: A relationship between plant samples and sweep samples is presented that shows the threshold based on sweep samples was equivalent to 2–3 aphids per tip of stem, which varied from season to season due, in part, to variation in potential seed weight caused by variation in precipitation and heat stress.
Abstract: Six insecticide regimes were tested between 1981 and 1983 in plots of field peas to determine the optimal time to control the pea aphid, Acyrthosiphon pisum (Harris), and to vary the density of the pest so that a relationship between yield and aphid density could be determined. Aphid populations rebounded rapidly after an insecticide application so that one early application did not protect the crop. Two or more sprays were uneconomical because they did not enhance yield more than a single spray applied as soon as 50% of the crop had young pods. Because the weight of 1,000 seeds provided a more precise measure of aphid damage than weight of seeds per unit area, this measurement was used to relate yield to pest density. The economic threshold was estimated to be 9–12 aphids per sweep when the crop began to flower. This threshold varied from season to season due, in part, to variation in potential seed weight caused by variation in precipitation and heat stress. A relationship between plant samples and sweep samples is presented that showsthe threshold based on sweep samples is equivalent to 2–3 aphids per tip of stem.
39 citations
TL;DR: Preliminary evidence suggests Illinois populations were not founded by aphids from the southern regions sampled, and the lack of heterozygosity in Illinois indicates that relatively few females may found northern populations.
Abstract: A survey of genetic variation at 21 electrophoretic loci in 15 natural populations of the corn leaf aphid Rhopalosiphum maidis reveals 8 loci useful for population comparisons. Within-population polymorphism levels range from 0–19% with Hillsboro, Tex., the most variable population sampled. Fixed genetic difference between northern (Illinois), Bristow (Oklahoma), and southern (all other) populations suggest regional populations are clonally derived. In addition, the lack of heterozygosity in Illinois indicates that relatively few females may found northern populations. These genetic differences offer a new tool to study annual migration in R. maidis with preliminary evidence suggesting Illinois populations were not founded by aphids from the southern regions sampled. The origins and maintenance of this variation pose questions of evolutionary interest.
TL;DR: The results show that predation and local interplant movement determine patterns of spatial overlap and mediate the impact of interspecific competition in aphid species faced with predator-mediated coexistence on a subdivided resource.
Abstract: Two abundant, widely co-occurring aphid species were exposed to natural or reduced predation on goldenrod transplanted as either solitary stems or small, discrete patches of plants. Local interplant movement increased colonization rates for both species, resulting in more and larger aphid colonies on patch plants than on solitary plants. Predator reduction increased aphid densities and produced evidence of increased resource limitation and interspecific competition, although the specific response differed between plant spacing treatments. On solitary plants, predator reduction resulted in a significant negative spatial association between the aphid species. Predator reduction in patches resulted in an increase in one species but a reduction in colony size of the other. In all cases, aphid abundance was negatively associated with plant health. Patterns of spatial association between the aphid species varied with experimental treatments. Aphids on solitary plants at reduced predation were spatially segregated. At reduced predation, aphids on patch plants showed no overall pattern of association. With natural predation, aphids on patch plants were positively associated, as were aphids within natural goldenrod patches in the field. The results show that predation and local interplant movement determine patterns of spatial overlap and mediate the impact of interspecific competition. Although resource limitation can influence aphid dynamics on a single goldenrod shoot, predation and interplant movement are considered to have a greater influence on community structure at a larger spatial scale. These results are discussed in terms of several recent models of predator-mediated coexistence on a subdivided resource.
TL;DR: Data from bioassays of field collected aphids, barley indicator plants exposed to natural conditions, and various types of aphid traps were used to describe the spread of barley yellow dwarf virus (BYDV) in wheat and barley near Prosser, Washington.
Abstract: SUMMARY
Data from bioassays of field collected aphids, barley indicator plants exposed to natural conditions, and various types of aphid traps were used to describe the spread of barley yellow dwarf virus (BYDV) in wheat and barley near Prosser, Washington. Bioassays were also used to assess the relative importance of local vector species.
Of alate aphids collected from grain in the 1982 and 1983 fall migration seasons, 3.4–14–5% transmitted BYDV. Data from concurrent and post-migration assays of resident aphids (apterae and nymphs) reflected an increase in the proportion of infected plants in the field. Maximum increase in the percentage of viruliferous aphids occurred in late November and December of 1982 and November of 1983. The 1982 increase occurred after aphid flights had ceased for the year, suggesting active secondary spread. Collections in pitfall traps and infected trap plants from November to February confirmed aphid activity and virus spread.
Rhopalosiphum padi was the most important vector in central Washington in 1982 and 1983 because of its abundance and relative BYDV transmission efficiency. Metopolophium dirhodum was more winter-hardy than R. padi and equal to R. padi in its efficiency as a vector; however, it was not as abundant as R. padi except during the mild winter of 1982–83, when it was a major contributor to secondary spread. Sitobion avenae may be important in years when it is abundant, but it was only a quarter as efficient as R. padi. Rhopalosiphum maidis was a much less efficient vector than R. padi and it only reached high populations in late autumn barley.
TL;DR: It is suggested that presence of fungal root rot disease may influence reproduction and movement of alate aphids and epidemiology of aphid-transmitted viruses during both fall and spring periods ofAlate aphid activity, when plants are in vegetative or reproductive stages, respectively.
Abstract: Reproduction and colonizing behavior of pea aphids, Acyrthosiphon pisum (Harris), were studied on reproductive arrowleaf clover, Trifolium vesiculosum Savi, using four treatments: healthy, infected with bean yellow mosaic virus (BYMV), infected with a Phytophthora sp. that caused root rot, or infected with both BYMV and the Phytophthora sp. Reproduction of aphids in no-choice experiments was significantly lower on plants in the two treatments with the root rot disease than on healthy or BYMV-infected plants. The highest level of reproduction was observed on healthy plants. Aphid colonization also was lower on fungus-infected plants whether BYMV was present or not. Results of these studies suggest that a complex relationship exists between aphid vectors, virus disease, and fungal root disease in arrow leaf clover. Presence of fungal root rot disease may influence reproduction and movement of alate aphids and epidemiology of aphid-transmitted viruses during both fall and spring periods of alate aphid activity, when plants are in vegetative or reproductive stages, respectively.
TL;DR: Two releases of the predatory midge,Aphidoletes aphidimyza (Rondani), effectively controlled green peach aphid on field-grown peppers by maintaining aphid populations at low levels throughout the season compared to the untreated control plots which were heavily colonized by the aphids.
Abstract: Greenhouse and field experiments were conducted to evaluate the potential of inoculative releases of the predatory midge,Aphidoletes aphidimyza (Rondani), on aphid populations on vegetables. The predator was collected from wild and cultivated plants in upstate New York and subsequently reared in the laboratory. Midges from the rearings were released, as pupae, into greenhouses and field plots where plants were infested with aphids, predominately the green peach aphid,Myzus persicae (Sulzer).
TL;DR: The nabid exhibited strong preference for the aphid; when both prey were present in equal numbers, the nabid consumed 3 times as many aphids.
Abstract: The preference of the nabid, Reduviolus americoferus (L.), for potato leafhopper nymphs, Empoasca fabae (Harris), and pea aphids, Acyrthosiphon pisum (Harris), was examined using functional response models. The nabid exhibited a type-II functional response to each prey. Handling time was much higher for the aphid than for the leafhopper (3.623 vs. 0.211 h). Instantaneous search rates were also higher for the aphid (0.096 vs. 0.020 h−1). A preference index was calculated using the ratio of the instantaneous search rates. The nabid exhibited strong preference for the aphid; when both prey were present in equal numbers, the nabid consumed 3 times as many aphids. The predator did not switch to leafhopper nymphs as the proportion of leafhoppers was increased.
TL;DR: Les variations de la «qualite» de l'arbre (Pinus sylvestris) d'annee en annee ou d'un arbre a l'autre sont de premiere importance pour determiner l'importance des populations de C.p.
Abstract: Les variations de la «qualite» de l'arbre (Pinus sylvestris) d'annee en annee ou d'un arbre a l'autre sont de premiere importance pour determiner l'importance des populations de C.p.
TL;DR: The spread of soybean mosaic virus (SMV) by aphid vectors was studied in central Illinois in 1978 and 1979 by monitoring sequentially planted plots of soybeans, with maximum spread of the virus occurring at times of greatest aphid abundance.
Abstract: The spread of soybean mosaic virus (SMV) by aphid vectors was studied in central Illinois in 1978 and 1979 by monitoring sequentially planted plots of soybeans, Glycine max (L.) Merr. Aphids transmitted SMV from about the third week in June until early September, with maximum spread of the virus occurring at times of greatest aphid abundance. The highest disease incidence (94%) was reached between 3 and 17 August 1978 during heavy flights of Rhopalosiphum maidis (Fitch), a vector of the virus. Field observations and aphid incidence monitored with a Johnson-Taylor suction trap showed that R. maidis settled on soybean plants and remained there overnight. Twelve of the 30 aphid species collected by horizontal ermine lime traps were known vectors of SMV. Two other species collected, Aphis helianthi Monell and Capitophorus hippophaes (Walker), are reported here for the first time as vectors of the virus. Vector species composed 78.0 and 67.2% of all specimens collected in 1978 and 1979, respectively. Myzocallis punctatus (Monell), which composed 9.0% of the aphid specimens collected both years, and Lipaphis erysimi (Kaltenbach), which represented 13.8% of all aphids caught in 1979, did not transmit SMV in laboratory tests. The vector status of 16 other collected taxa is unknown. Aphids in this group represented 6.1 and 14.7% of the specimens collected in 1978 and 1979, respectively.
TL;DR: The pea aphid, A. pisum, seems under biological control in North American alfalfa, primarily as a result of attacks by parasitoid wasps, although eight additional species are known from other studies elsewhere.
Abstract: The pea aphid, Acyrthosiphon pisum (Harris), seems under biological control in North American alfalfa, primarily as a result of attacks by parasitoid wasps. Of the 10 known primary parasitoids, an introduced aphidiid, Aphidius ervi Haliday, seems most important in Iowa and elsewhere in the East. Mummies of A. pisum collected in central Iowa during five seasons produced four species of hymenopterous hyperparasitoids, although eight additional species are known from other studies elsewhere. The Iowa species in descending order of abundance were: Asaphes lucens (Provancher) (Pteromalidae), Dendrocerus carpenteri (Curtis) (Mesaspilidae), Alloxysta victrix (Westwood) (Alloxystidae), and Pachyneuron siphonophorae (Ashmead) (Pteromalidae). Keys and descriptive notes are presented to allow identification of all known North American A. pisum hyperparasitoid species in their adult stages, and the known primary and hyperparasitoids by means of evidence left on or in vacated aphid mummies. Hyperparasitoids constituted a smaller proportion (17.8%) of the insects successfully emerging from Iowa A. pisum mummies than expected. Speculations about the reason for the low level of hyperparasitism and its implications for biological control are provided.
TL;DR: In this article, the authors found that the frequently observed slow increase in abundance of aphid predators in response to increasing aphid abundance may be an artifact resulting from using relative indices of abundance that make no correction for the effects of hunger on predator activity.
Abstract: Searching for adult coccinellids in large cages placed over sections of strawberry fields produced an average of 10 times as many coccinellids per metre of row as a relative method of sampling. Methods of converting relative indices to absolute indices of abundance were found. Results suggest that the frequently observed slow increase in abundance of aphid predators in response to increasing aphid abundance may be an artifact resulting from using relative indices of abundance that make no correction for the effects of hunger on predator activity. Calibrating the samples shows that numbers of adult coccinellids follow the trend of aphid abundance closely enough that coccinellid numbers may be predictable.
TL;DR: The number of ovarioles and the potential fecundity in first (fundatrigenia) and second generation emigrants of Rhopalosiphum padi was investigated and it was found that the former is higher than the latter.
Abstract: . 1. The number of ovarioles and the potential fecundity in first (fundatrigenia) and second generation emigrants of Rhopalosiphum padi (L.) was investigated.
2. The relationships between weight and host quality on ovariole number were investigated.
3. The first generation of emigrants had a greater number of ovarioles and a higher fecundity than the second.
4. There was a positive relationship between ovariole number and weight.
5. The number of ovarioles and weight decreased with decreasing host quality.
6. The results do not agree with a recently proposed reproductive strategy of aphids where the number of ovarioles are supposed to be independent of weight and host quality.
7. In years with a high initial population on bird cherry, the migration to grasses, e.g. cereals, will be earlier, probably larger and, to a greater extent, consists of aphids which have a higher reproductive rate than in years with a small initial number on bird cherry.
TL;DR: The potential of cereal aphid parasitoids to exhibit an economically useful suppression of their host numbers is considered in the context of the required accuracy of pest forecasting schemes and their consequent value over no control or prophylaxis.
Abstract: (1) A simulation model is described which demonstrates the role of parasitic Hymenoptera in influencing the numbers of the aphid Sitobion avenae (F.) on cereals. (2) It is based on dissection of field-collected aphids for immature parasitoid stages and the use of physiological time to predict mummification and therefore death. (3) The physiological time unit (quarter-instar period) was also used to calculate simulated aphid population development in the field in the absence of all mortalities, and the difference between the simulated and actual populations was attributed to 'total mortality'. (4) The predicted number of aphids mummifying in each instar-period was then subtracted from 'total mortality', leaving 'residual mortality', the components of which were not identified. (5) On average, simulated populations in the absence of parasitism increased at flowering to a level seven times higher than in simulations with this mortality included. In most fields, parasitism was initially the main mortality factor but later its influence was much less relative to residual mortality. (6) The potential of cereal aphid parasitoids to exhibit an economically useful suppression of their host numbers is considered in the context of the required accuracy of pest forecasting schemes and their consequent value over no control or prophylaxis.
TL;DR: Although much of the population dynamics of the aphid, especially in relation to its host plant, is now well understood, many uncertainties still remain concerning natural enemies, and as these organisms seem able to prevent cereal aphid outbreaks, these gaps are presently preventing the development of a reliable forecasting scheme.
Abstract: A simulation model explaining the population dynamics of the grain aphid (Sitobion avenae), a serious pest of wheat in Western Europe, is described. The model includes the effects of crop development and some natural enemies on the biology of the aphid. It is concluded that although much of the population dynamics of the aphid, especially in relation to its host plant, is now well understood, many uncertainties still remain concerning natural enemies. As these organisms seem able to prevent cereal aphid outbreaks, in some years, these gaps are presently preventing the development of a reliable forecasting scheme.
TL;DR: Spread of BYMV was attributed mainly to alate migrants of Myzus persicae and Macrosiphum euphorbiae, but other aphid species and morphs which occurred in high populations at the times of most rapid virus spread may also have had an active role as vectors of BYmV.
Abstract: SUMMARY
The effect of the insecticides malathion, demeton-S-methyl and disulfoton, and a barley barrier row on the rate and pattern of spread of bean yellow mosaic potyvirus (BYMV) and subterranean clover red leaf luteovirus (SCRLV) in Vicia faba was investigated in field plots with artificially introduced sources of viruses and vectors.
The systemic insecticide treatments reduced aphid populations in the plots and this was associated with reduced spread of SCRLV, but not of BYMV. The barley barrier did not affect aphid populations in plots; however, it reduced the spread of BYMV to rows 1 · 1 m from the source but had only a minor effect on the spread of SCRLV.
Apterae rather than alates of Aulacorthum solani were implicated in the spread of SCRLV. Spread of BYMV was attributed mainly to alate migrants of Myzus persicae and Macrosiphum euphorbiae, but other aphid species and morphs which occurred in high populations at the times of most rapid virus spread may also have had an active role as vectors of BYMV.
TL;DR: Chow and Mackauer as discussed by the authors reported on inter-and intraspecific larval competition between Aphidius smithi Sharma & Subba Rao and Praon pequodorum Viereck, when both were parasitizing the pea aphid, Acyrthosiphon pisum (Harris).
Abstract: Chow and Mackauer (1984) recently reported on inter- and intraspecific larval competition between Aphidius smithi Sharma & Subba Rao and Praon pequodorum Viereck (Hymenoptera: Aphidiidae), when both were parasitizing the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae). In interspecific competition, a 1st-instar Praon larva usually eliminated, by physical combat, an Aphidius larva that was up to 48 h older. However, circumstantial evidence suggested that once an Aphidius larva had reached an advanced stage of the final (4th) instar, it was able to complete development and pupate, even in the presence of a younger Praon competitor.
TL;DR: In laboratory trials to investigate the parasite/host spectra of certain aphid pests and hymenopterous parasites, the aphid Acyrthosiphon kondoi Shinji encapsulated the egg of the aphelinid parasiteAphelinus asychis Walker and as far as is known prevented the development of the parasite to the larval stage.
Abstract: In laboratory trials to investigate the parasite/host spectra of certain aphid pests and hymenopterous parasites, the aphidAcyrthosiphon kondoi Shinji encapsulated the egg of the aphelinid parasiteAphelinus asychis Walker. The resultant brown, sclerotic capsule was formed within 24 h of exposure of the aphid to parasitization and as far as is known prevented the development of the parasite to the larval stage. The capsule remained throughout the life of the aphid, whose longevity and fecundity were apparently not seriously impaired. A small number ofAphelinus escaped encapsulation, especially in aphids already containing capsule(s), and developed into normal, reproductive adults.A. kondoi did not encapsulate, andA. asychis was not encapsulated by any other species. However, thoughA. asychis readily parasitizedAphis citricola van der Goot,A. nerii Boyer de Fonscolombe andToxoptera citricidus (Kirkaldy), most of its progeny ceased development in these aphids before reaching the mummification stage, and died within the dead or dying, non-mummified aphid host.
TL;DR: The hymenopterous parasite, Aphidius sonchi Marshall, has been introduced into Australia as a biological control agent of the sowthistle aphid, Hyperomyzus lactucae (L.), the principal vector of lettuce necrotic yellows virus disease.
Abstract: The hymenopterous parasite, Aphidius sonchi Marshall, has been introduced into Australia as a biological control agent of the sowthistle aphid, Hyperomyzus lactucae (L.), the principal vector of lettuce necrotic yellows virus disease. Some aspects of its biology were studied in the laboratory. Females reared at 22°C contained a mean ± s.e. of 179·4 ± 10·26 eggs on emergence, and more eggs were formed during adult life. Unmated females produced male progeny only; mated females produced progeny of both sexes. At 22°C, both males and females mated within 12 h of emergence. Virgin females could mate successfully after having commenced oviposition and switch to producing progeny of both sexes. At 20°C, both virgin and mated females started oviposition within 7 h of emergence. The female oviposited in all nymphal instars and both apterous and alate adults of the host. Only one egg was laid per insertion of the ovipositor. Superparasitization was common, but only one parasite per aphid survived to the adult stage. Females at 22°C and LD 12:12 oviposited during both the photophase and the scotophase; the proportion of eggs laid in the scotophase was correlated with the availability of hosts. Adult females lived longer in the absence of hosts than in their presence and lived longer than males, and those supplied with water and honey lived longer than those without. Facultative diapause occurred. The integumental coloration of adults varied according to the temperature during their immature stages. Females of A. sonchi oviposited readily in Macrosiphum euphorbiae (Thomas), but their progeny did not develop beyond the egg stage. A. sonchi was parasitized by Alloxysta ancylocera (Cameron), Pachyneuron aphidis (Bouche) and Dendrocerus carpenteri (Curtis) in the field.
TL;DR: Within 10 days of infestation, aphid feeding significantly reduced plant dry weights and mean relative growth rates for the six plant–aphid combinations and the mean leaf area ratio was the same for infested and control plants.
Abstract: The effects of various densities of cowpea aphids (Aphis craccivora Koch) and pea aphids (Acyrthosiphon pisum Harris), both Homoptera: Aphididae, on the growth of cowpea (Vigna unguiculata (L.) Walp. cv. Caloona), broad bean (Vicia faba L. cv. Aquadulce), and garden pea (Pisum sativum L. cv. Victory Freezer) seedlings were investigated. Within 10 days of infestation, aphid feeding significantly reduced plant dry weights and mean relative growth rates for the six plant–aphid combinations. In all cases except one, the mean unit leaf or net assimilation rate was also significantly reduced within 10 days. The mean leaf area ratio was the same for infested and control plants. The aphid-induced changes in host plants appear to be due to changes in photosynthesis, respiration, and translocate removal from the phloem over the 10-day period. Changes in the growth patterns of the host plant within this period are similar, but the underlying physiological effects could vary among particular plant–aphid combinations.
TL;DR: Parathion and endosulfan insecticide resistant colonies of green peach aphids, Myzus persicae (Sulzer), collected from various potato fields in Wisconsin, reverted to susceptible conditions after being maintained in greenhouse insecticide-free enviroments.
Abstract: Parathion and endosulfan insecticide resistant colonies of green peach aphids, Myzus persicae (Sulzer), collected from various potato fields in Wisconsin, reverted to susceptible conditions after being maintained in greenhouse insecticide-free enviroments. The amounts of time which field-collected aphids remained as insecticide-resistant colonies varied from as few as 10 to as many as 27 generations after their collection from the fuield. Stability of resistance varied in splinter colonies which were derived from aphid colonies in different phases of transition from resistant to susceptible conditions. Reversions to parathion susceptibility were paralleled by near-simultaneous reversions to endosulfan susceptibility. Once begun, the reversion process proceeded rapidly and was completed within approximately four generations.
TL;DR: Nearly 200 varieties of cowpea, Vigna unguiculata (L.) Walp, were screened for resistance to thecowpea aphid, Aphis craccivora Koch, finding three varieties known to be resistant in West Africa.
Abstract: Nearly 200 varieties of cowpea, Vigna unguiculata (L.) Walp, were screened for resistance to the cowpea aphid, Aphis craccivora Koch. Three varieties known to be resistant in West Africa were highl...