scispace - formally typeset
Search or ask a question

Showing papers on "Aphid published in 1993"


Journal ArticleDOI
TL;DR: It is suggested that EDTA‐exudation may be a useful technique to study nutritional correlates of aphid life cycles, e.g. the time of migration between primary and secondary plant hosts.
Abstract: . 1The amino acid content of phloem exudates from leaves and of aphid honeydew were adopted as indices of the nutritional quality of phloem sap for aphids. Four plant species and associated leaf-dwelling aphids were investigated: the sycamore Acer pseudoplanatus and sycamore aphid Drepanosiphum platanoides; Prunus domestica (victoria plum) and the mealy plum aphid Hyalopterus pruni; and the spindle tree Euonymus europaeus and broad-bean Vicia faba, both hosts of the black bean aphid Aphis fabae. 2The concentration of amino acids in the phloem exudates varied with: (a) plant species (greater in the herb Vicia than in the tree species), (b) season (greater in the autumn than summer for Acer and Euonymus), and (c) position (greater in flush leaves than mature leaves of Prunus). 3For Acer and Prunus and their aphids, the concentration of amino acids in phloem exudates was significantly correlated with the amino acid content of the aphid honeydew. 4The amino acids in all exudates and honeydew were dominated by non-essential amino acids (glutamic acid, glutamine, asparagine or serine, varying with season and between plant species). The sole major discrepancy between the amino acid profiles of exudates and honeydew was the production of asparagine-rich honeydew by aphids feeding on leaves, whose exudates were dominated by glutamic acid; this applied to both H.pruni on mature Prunus leaves and Drepanosiphum platanoides on summer-leaves of Acer. 5It is suggested that EDTA-exudation may be a useful technique to study nutritional correlates of aphid life cycles, e.g. the time of migration between primary and secondary plant hosts.

263 citations


Journal ArticleDOI
01 Oct 1993-Ecology
TL;DR: Results demonstrate that although in- dividual lady beetle response to aphid density is extremely weak, the cumulative effect of many individuals can produce strong population-level aggregation of lady beetles in areas of high aphiddensity.
Abstract: We investigated the response of two species of lady beetle, Coccinella 7-punctata and Hippodamia variegate, to spatial variation in the density of aphids on fireweed, Epilobium angustifolium. Our approach involved experimental manipulations of aphid densities and field observations of lady beetle foraging at three different scales: (1) individual lady beetles on individual fireweed stems, (2) populations of lady beetles on individual fireweed stems, and (3) populations of lady beetles in populations of fireweed stems. At the finest scale, we found that individual lady beetles remained on single fireweed stems longer in the presence of large aphid colonies. However, this behavioral response to aphid density was weak, explaining only 11 and 4% of the total variance in the length of time C. 7-punctata and H. variegate remained on the stems. To examine directly the population-level effects of this individual lady beetle behavior, we conducted a second series of experiments that focused on the response of populations of lady beetles; we released large numbers of lady beetles into field plots in which we had manipulated the number and size of aphid colonies. By sampling the distribution of lady beetles, we showed that the number of lady beetles found on fireweed stems depended significantly on the presence and size of aphid colonies. The average number of both C. 7-punctata and H. variegate found on a stem was 10-20 times greater when the stem contained a large aphid colony than when the stem contained no aphids. Finally, we examined the consequences of these patterns at the scale of populations of lady beetles and populations of fireweed in 25-iM2 field plots. We found that the number and size of aphid colonies within the plots explained 50 and 90% of the variation among plots in the average length of time that C. 7-punctata and H. variegate remained. Taken together, these results demonstrate that although in- dividual lady beetle response to aphid density is extremely weak, the cumulative effect of many individuals can produce strong population-level aggregation of lady beetles in areas of high aphid density.

207 citations


Journal ArticleDOI
TL;DR: It is proposed that a wasp's reproductive strategy, as opposed to hyperparasitism, is the dominant factor in aphidiid population dynamics, and that a parasitoid's potential to regulate the host population is largely determined by its foraging strategy.
Abstract: Aphidiid parasitoids (Hymenoptera: Aphidiidae) of aphids generally exploit only a small percentage of the available host resources in the field. This limited impact on aphid populations has often been explained as a consequence of hyperparasitism. We propose that a wasp's reproductive strategy, as opposed to hyperparasitism, is the dominant factor in aphidiid population dynamics. A wasp's foraging efficiency and oviposition decisions are influenced by several variables, including searching behaviour between and within patches, host choice (as modified by the aphids' defensive behaviours), and plant structural complexity. Two broadly different patterns of host exploitation have evolved in aphidiid wasps in relation to ant-aphid mutualism. Firstly, in species that are exposed to predation and hyperparasitism, a female may leave a patch before all suitable hosts are parasitized. Because predators and hyperparasitoids tend to aggregate at high aphid or aphidiid densities, or in response to aphid honeydew, this strategy enables females to reduce offspring mortality by “spreading the risk” over several host patches. Secondly, in species that have evolved mechanisms to avoid aggression by mutualistic ants, females are able to exploit a hyperparasitoid-free resource space. Such species may concentrate their eggs in only a few aphid colonies, which are thus heavily exploited. Although hyperparasitism of species in the first group tends to reach high levels, its overall impact on aphid-aphidiid population dynamics is probably limited by the low average fecundity of most hyperparasitoids. We discuss the foraging patterns of aphidiid wasps in relation to aphid population regulation in general, and to classical biological control in particular. We argue that a parasitoid's potential to regulate the host population is largely determined by its foraging strategy. In an exotic parasitoid, a behavioural syndrome that has evolved and presumably is adaptive in a more diverse (native) environment may, in a more uniform (managed) environment, result in suboptimal patch-leaving and oviposition decisions, and possibly increased resource usage.

187 citations


Journal ArticleDOI
TL;DR: If various viral infections affected aphid performance differently, and if so, whether any order in the performance response of the aphid was discernible according to the type of virus‐vector relationship is evaluated.
Abstract: Growth, reproduction and survival (= performance) of the aphid Myzus persicae Sulzer was measured on virus-free and virus-infected potato plants. The principle objective was to evaluate if various viral infections affected aphid performance differently, and if so, whether any order in the performance response of the aphid was discernible according to the type of virus-vector relationship. Three viruses varying in their dependency on M. persicae as a vector were used. Plants infected with potato leafroll virus (PLRV), a circulative virus highly dependent upon M. persicae for dispersal and transmission, were superior hosts as determined by the significantly greater mean relative growth rate (MRGR) and intrinsic rate of increase (rm) of M. persicae compared with those of aphids reared on other plants. Plants infected with potato virus Y, a noncirculative virus less dependent upon M. persicae for dispersal than PLRV, were intermediate in their quality based upon intermediate MRGR and rm values. Plants infected with potato virus X, a nonvectored virus independent of M. persicae, were least suitable hosts along with the group of virus-free plants according to the lower MRGR and rm values.

163 citations


Journal ArticleDOI
TL;DR: The ability of five cereal grain aphid species to acquire four vector-specific isolates of barley yellow dwarf luteoviruses was tested, and aphids from New York clones of Rhopalosiphum maidis, R. padi, Schizaphis graminum, and Sitobion avenae acquired the New York type isolates when fed on infected plants, regardless of the ability of each species to transmit the virus.
Abstract: The ability of five cereal grain aphid species to acquire four vector-specific isolates of barley yellow dwarf luteoviruses was tested. Aphids from New York clones of Rhopalosiphum maidis, R. padi, Schizaphis graminum, and Sitobion avenae acquired the New York type isolates of MAV, PAV, RMV, and RPV when fed on infected plants, regardless of the ability of each species to transmit the virus. Aphids from a California clone of Metopolophium dirhodum acquired MAV, PAV, and RMV, but not RPV []

155 citations


Journal ArticleDOI
TL;DR: Data collected in 1983-89 from cereal fields was analysed to elucidate the relationships between the primary parasitoids and hyperparasitoids of cereal aphids and establish whether or not hyperparASitoids interfere with the impact of primary Parasitoids on cereal aphid populations.
Abstract: 1. We analysed data collected in 1985-89 from cereal fields to elucidate the relationships between the primary parasitoids and hyperparasitoids of cereal aphids. The analysis aimed to establish whether or not hyperparasitoids interfere with the impact of primary parasitoids on cereal aphid populations. 2. From more than 10000 parasitized aphids, 14 primary parasitoid and 18 hyperparasitoid species were reared. The five most common hyperparasitoids attacked the five most common primary parasitoids, which, in turn, parasitized most frequently the most abundant aphid species, Sitobion avenae (F.). 3. Levels of aphid primary parasitism never exceeded 33%, whereas levels of hyperparasitism often reached 100% in the latter part of the season. However, the low rates of aphid primary parasitism could not have been solely the result of hyperparasitism: if primary parasitoid females which emerged early continued to deposit eggs before the collapse of the aphid populations, those females should have been numerous enough to parasitize large numbers of their hosts before hyperparasitoid pressure became high. 4. We hypothesize that primary parasitoid females leave areas which develop high hyperparasitoid densities. A multiple linear regression model was used to test the hypothesis. The observed declines of aphid primary parasitism were quantitatively related to hyperparasitoid density. 5. The results of this study and additional theoretical considerations are in favour of the above hypothesis. However, other factors such as mortality other than that due to hyperparasitoid attack, and aestivation acting together may also contribute to the low abundance of primary parasitoid females later in the season.

138 citations


Journal ArticleDOI
01 Jun 1993-Ecology
TL;DR: It is suggested that sexual reproduction may be more sensitive to damage than asexual reproduction in perennial plants and the common assumption that plants are better able to compensate for herbivore damage at higher levels of soil fertility must be reconsidered.
Abstract: Plant responses to herbivore damage vary enormously, but the causes of this variation are not well understood. We examined how both insect feeding style and soil fertility influence the severity of herbivore impacts, by measuring the effects of feeding by a leaf-chewing beetle (Trirhabda sp.), a xylem sap-feeding spittlebug (Philaenus spu? marius), and a phloem sap-feeding aphid (Uroleucon caligatum) on growth and reproduc? tion of goldenrod (Solidago altissima). Our goals were to determine (1) whether these three insects differentially affect plant fitness, (2) whether soil fertility affects a plant's ability to compensate for damage, and (3) whether soil fertility and insect feeding style interact in determining herbivore impacts. Plants were grown outdoors in large pots at two levels of soil fertility, and insects were placed on them at a range of densities. Insects fed on the plants for ? 3 wk in spring, and then the plants were grown insect free for the rest of the season. We used insect mass gain per plant as the basis for comparing the effects of three insects, since the insects differed greatly in size. Spittlebug feeding reduced plant growth rates 3 times more than beetle feeding; aphid feeding had no detectable effect. The plants grew faster at higher soil fertility, but there was no interaction between insect impact and fertilizer level. Stem heights at the end of the season were increased by fertilizer and not affected by herbivory. Spittlebug feeding, and to a lesser extent aphid feeding, decreased the number of lateral stems, and again there was no interaction with soil fertility. Soil fertility had strong effects on plant sexual and asexual reproduction. Plants at the high level of soil fertility showed a three-fold increase in total seed production, a 5% increase in mean achene mass, almost a two-fold increase in rhizome mass, and increased percent nitrogen in seeds and rhizomes. Total seed production was reduced by herbivory. The pattern was the same as for plant growth rates; the spittlebug caused the strongest decrease, beetle feeding was second, and aphid feeding caused slight reductions. There was a strong interaction between insect impact and soil fertility. Total seed production was reduced only at the high level of soil fertility for all three insects. Spittlebug and beetle damage also delayed flowering, but only at the high level of soil fertility. Rhizome mass, mean achene mass, and percent nitrogen in seeds and rhizomes were not affected by herbivory. The common assumption that plants are better able to compensate for herbivore damage at higher levels of soil fertility must be reconsidered. This study also suggests that sexual reproduction may be more sensitive to damage than asexual reproduction in perennial plants.

116 citations


Journal ArticleDOI
TL;DR: Analysis of the direct versus indirect effects of these compounds indicates that the volatile aldehydes had both direct effects on aphid fecundity and indirect effects due to induced changes in the leaves upon which the aphids were feeding, while only indirect effects were observed for the alcohols.
Abstract: A role of some volatile compounds produced by plant tissues may be as defensive molecules against various pests, including arthropods. Volatile six-carbon compounds derived in plant tissue from polyunsaturated fatty acids via lipoxygenase/hydroperoxide lyase reduced tobacco aphid fecundity at certain concentrations when added to headspace vapor to which aphids were exposed. Both C6 aldehydes and alcohols were effective, with the alcohols having greater activity. (Z)-3-Hexenyl acetate at levels in the headspace similar to those of the alcohols and aldehydes did not reduce aphid fecundity. A 6-hr exposure period to the C6 aldehydes and alcohols was needed for maximum effect on the aphids feeding on tobacco leaves. Analysis of the direct versus indirect effects of these compounds indicates that the volatile aldehydes had both direct effects on aphid fecundity and indirect effects due to induced changes in the leaves upon which the aphids were feeding, while only indirect effects were observed for the alcohols. Tomato leaves have the capacity to produce volatile compounds at levels that impact aphid population increase, with the volatiles produced from crushed leaves having a much larger effect. The C6 aldehydes and alcohols may be components of the fecundity reduction seen with tomato volatiles; however, volatile terpenes showed no effect. These results can be of significance for the genetic alteration of plants for improved aphid resistance.

114 citations


Journal ArticleDOI
01 Jun 1993-Ecology
TL;DR: To measure insect impacts on plant size as a function of herbivore loads, and to determine the mechanisms by which insect feeding affects plant growth, using the techniques of plant growth analysis, are measured.
Abstract: Many plants support both leaf— and sap—feeding insects, yet comparative studies of plant responses to different types of damage are rare. I compared the impacts of a leaf—chewing beetle (Trirhabda sp.), a xylem sap—feeding spittlebug (Philaenus spumarius), and a phloem sap—feeding aphid (Uroleucon caligatum) on growth of goldenrod (Solidago altissima). My goals were (1) to measure insect impacts on plant size as a function of herbivore loads, and (2) to determine the mechanisms by which insect feeding affects plant growth, using the techniques of plant growth analysis. Plants were grown outdoors in large pots, and insects were placed on them at a range of densities. A series of four whole—plant harvests was performed, with the final harvest occurring after 3 wk of insect feeding. Insect mass gain per plant was used as the basis for the comparison, since the insects differed greatly in size. Spittlebugs were the most damaging insect, beetles were intermediate, and no effects of aphid feeding were detected. After 3 wk of feeding, both spittlebugs and beetles reduced total leaf mass, total leaf area, and root mass, and the impact of the spittlebug was 5—6 times greater than that of the beetle. Spittlebug feeding also reduced the mass of the apical buds, stem mass, and the number of lateral stems, while beetle and aphid damage had no effect on these variables. Dry mass allocation to leaves, stems, and roots was generally not affected by insect feeding, resulting in smaller but proportionally similar plants by the end of the feeding period. Plant relative growth rates (dry mass increase per unit dry mass per day) were reduced by both spittlebugs and beetles but not aphids, and the impact of the spittlebug was more severe than that of the beetle. None of the insects affected net assimilation rates (dry mass increase per unit leaf area per day), indicating that the insects did not reduce plant growth by altering plant physiology. Instead, reductions in relative growth rates were explained by changes in plant morphology; feeding by both spittlebugs and beetles strongly reduced specific leaf area (leaf area/leaf mass). This reduction of leaf area relative to leaf mass was the mechanism by which both insects decreased plant relative growth rates. This result suggests an explanation for why simulated damage frequently fails to mimic damage by actual herbivores. When leaves are artificially removed by clipping there will be an immediate change in dry mass allocation patterns, but specific leaf area will not necessarily be affected.

110 citations


Journal ArticleDOI
P. W. Miles1, J. J. Oertli1
TL;DR: The hypothesis is advanced that a redox system controls oxidation rates during the responses of plants to attack by sucking insects, and that soluble antioxidants, such as ascorbate and glutathione, enhance the effectiveness of the plant's defensive system.
Abstract: The hypothesis is advanced that a redox system controls oxidation rates during the responses of plants to attack by sucking insects, that soluble antioxidants, such as ascorbate and glutathione, enhance the effectiveness of the plant's defensive system, and that oxidising enzymes in the saliva of aphids (and other phytophagous sucking insects) serve to counter it. Plants typically respond to wounding, including that caused by sucking insects, by mobilising and oxidising phenolic compounds. The initial phenolic monomers, and especially the monomeric o-quinones to which many give rise on oxidation, are generally deterrent to insects. Their final oxidation products, however, are polymers and phenol-protein conjugates, which are non-toxic, but serve to seal off damaged cells. It is suggested that effective defence by the plant requires oxidation of phenolics at a controlled rate that maintains a deterrent titre of the monomers, while allowing a well ordered deposition of sealants. It is also suggested that the salivary oxidases of the insects hasten oxidation in the affected tissues, thereby decreasing concentrations of monomeric phenols and quinones. It is further suggested that sedentary species may also thereby disorganise the sealing off of affected tissues. A kinetic model is developed to show that inclusion of a reductive cycle in the sequential oxidation of phenolics increases the steady state concentrations of monomeric phenols for a given throughput. Conversely, an increase in oxidation rates diminishes the titre of monomers for the same throughput. In initial biological tests of the hypothesis, infiltration of stems of lucerne cultivars with ascorbate or glutathione reduced the reproductive rate of spotted alfalfa aphid, Therioaphis trifolii maculata (Buckton), and of blue-green aphid, Acyrthosiphon kondo Shinji, feeding thereon. Intrinsically non-deterrent concentrations of ascorbate synergised the deterrence of the plant phenolics chlorogenic acid and catechin to the apple aphid, Aphis pomi (de Geer), and the spotted alfalfa aphid, T. t. maculata, respectively.

107 citations


Journal ArticleDOI
TL;DR: Under field conditions, NSO and NSE treatments were as effective as the botanical insecticide pyrethrum for control of aphids on pepper and strawberry, but ineffective for the control of Aphids on lettuce.
Abstract: Laboratory and field trials with formulated neem seed oil (NSO) and neem seed extract (NSE) demonstrated that these materials are effective aphicides. NSO sprays to intact plants in the laboratory resulted in significant reductions in numbers of green peach aphids, Myzus persicae (Sulzer), on peppers and rutabagas; currant-lettuce aphids, Nasonovia ribisnigri (Mosley), on lettuce; and strawberry aphids, Chaetosiphon fragaefolii (Cockerell), on strawberry. NSO reduced aphid numbers in a dose-dependent manner, with estimated concentrations for a 50% reduction in aphid populations (EC50) ranging from 0.2 to 1.4%. Under field conditions, NSO and NSE treatments were as effective as the botanical insecticide pyrethrum for control of aphids on pepper and strawberry, but ineffective for the control of aphids on lettuce. The effectiveness of neem appears to be influenced by the host plant, the aphid species, and weather conditions.


Journal Article
TL;DR: By refraining from laying eggs in aphid colonies already exploited by predators and those that are shortly to decline in abundance when the aphids disperse, these predators are able to forage in a way that is consistent with the predictions of optimal foraging theory.
Abstract: Coccinellids and syrphids that feed on aphids and coccids face the same problem: an unstable food supply. Their eggs and larvae face cannibalism and/or starvation if the aphid colony they attack declines in abundance before they mature. Optimal foraging theory predicts that such predators should lay a few eggs early in the development of an aphid colony. Studies on two species of coccinellid and one species of syrphid revealed that they do respond to the quality as well as the abundance of their prey. By refraining from laying eggs in aphid colonies already exploited by predators and those that are shortly to decline in abundance when the aphids disperse, these predators are able to forage in a way that is consistent with the predictions of optimal foraging theory.

Journal ArticleDOI
TL;DR: Transmission tests between different species of aphids using PVY∘-infected pepper and tobacco as source plants indicated that M. persicae was the most efficient vector, followed by Aphis gossypii Glover and Acyrthosiphon pisum Harris.
Abstract: Transmission of Potato Virus Y (PVY) by several aphid vectors was studied under laboratory and greenhouse conditions to determine vector propensity on sweet pepper ( Capsicum annum L.) plants. Laboratory experiments were conducted with three PVY strains: pepper-PVY pathotype φ (PVYφ) and potato-PVY (ordinary strain, PVY∘, and necrotic-type strain, PVYN). Pepper (‘Yolo Wonder’), tobacco ( Nicotiana tabacum L., ‘xhanthi nc’), and potato ( Solanum tuberosum L., ‘Bintje’) were used as virus sources or test plants, or both. Results showed that both pepper-PVY and potato-PVY strains were transmissible by Myzus persicae Sulzer to pepper plants, although potato-PVY∘ and – PVYN are less efficiently transmitted than PVY∘. Transmission tests between different species of aphids using PVY∘-infected pepper and tobacco as source plants indicated that M. persicae was the most efficient vector, followed by Aphis gossypii Glover and Acyrthosiphon pisum Harris. Aphis fabae Scopoli also was capable of transmitting PVY∘, but with much less efficiency. Greenhouse experiments designed to evaluate the dispersion (secondary spread) of PVY by alatae aphids indicated that M. persicae transmitted the virus at the highest rate. Aphis fabae and Aphis gossypii also were able to spread PVY efficiently under test conditions. Previous works indicated that non-colonizer species, principally in the genus Aphis , have much higher alate activity in open field conditions (higher landing rate) than M. persicae . Therefore, much of the natural spread of virus may be by species that are not commonly found feeding on pepper crops.

Journal ArticleDOI
TL;DR: The life-cycle of A. svalbardicum is well suited to exploit higher summer temperatures, and the annual success of local populations are sensitive to small changes in temperature, suggests that the aphid is living at the limits of its thermal range at Ny Ålesund based on its summer thermal budget requirements.
Abstract: A manipulation experiment was carried out on a field population of the aphid Acyrthosiphon svalbardicum near Ny Alesund, on the high arctic island of Spitsbergen, using cloches to raise temperature. An average rise in temperature of 2.8 deg. C over the summer season markedly advanced the phenology of both the host plant Dryas octopetala and the aphid. Advanced aphid phenology, with concomitant increases in reproductive output and survival, and successful completion of the life-cycle led to an eleven-fold increase in the number of overwintering eggs. Thermal budget requirements in day degrees above 0°C were calculated for key life-cycle stages of the aphid. Temperature data from Ny Alesund over the past 23 years were used to calculate thermal budgets for the field site over the same period and these were compared with the requirements of the aphid. Each estimated thermal budget was then adjusted to simulate the effect of a +2, +4, and −2deg. C change in average temperature on aphid performance. This retrospective analysis (i) confirms that the life-cycle of A. svalbardicum is well suited to exploit higher summer temperatures, (ii) indicates that the annual success of local populations are sensitive to small changes in temperature and (iii) suggests that the aphid is living at the limits of its thermal range at Ny Alesund based on its summer thermal budget requirements.

Journal ArticleDOI
TL;DR: A significant positive relationship between the numbers of eggs per aphid and weed density was detected during June in the second year of the study, and the implications of the implementation of a modified herbicide regime in the headlands of cereal fields for the biological control of cereal aphids by syrphid larvae is discussed.
Abstract: SUMMARY The abundance and species composition of syrphid adults in herbicide-treated and untreated headlands was recorded in a replicated within-field experiment conducted over a two-year period. The highest numbers of the most abundant syrphid species, Episyrphus balteatus, were recorded in the untreated headland strips. Analysis of the behaviour of the adult flies showed that they were retained in the untreated strips because they were foraging on the flowering non-crop plants. The distribution of syrphid eggs between herbicide treated and untreated headland replicates was examined. A significant positive relationship between the numbers of eggs per aphid and weed density was detected during June in the second year of the study. This is in part attributed to the tendency of Melanostoma females to oviposit on non-crop plants. The implications of the implementation of a modified herbicide regime in the headlands of cereal fields for the biological control of cereal aphids by syrphid larvae is discussed.

Journal ArticleDOI
TL;DR: A simulation model is used to investigate how many hosts the parasitoid should infect per colony to maximize the long-term average rate of producing eclosing offspring and the optimal number of aphids to infect within a colony decreases with a decreases in the colony size, with an increase in the average number of perparasitoid visits, and with a decrease in travel time between aphid colonies.
Abstract: Using an aphid-parasitoid-hyperparasitoid system as an example, we study the optimal oviposition strategy of a parasitoid whose offspring are subject to attack by hyperparasitoids. We assume that hyperparasitoids, which search aphid colonies for aphids that have been infected by parasitoids, decide to leave a colony when they have searched some fixed number of aphids consecutively without finding an infected one. We use a simulation model to investigate how many hosts the parasitoid should infect per colony to maximize the long-term average rate of producing eclosing offspring. We consider three different variables and deal with them one at a time: (1) N = the number of aphids in a colony, (2) H = the average number of perparasitoids visiting each colony, and (3) τ = the parasitoid travel time between colonies. The optimal number of aphids to infect in a colony is sometimes much less than the total number of aphids available. The optimal number of aphids to infect within a colony decreases with a decrease...

Journal ArticleDOI
TL;DR: The observation of only low levels of entomophthoralean fungal infection in the nonirrigated fields suggests that reliable use of these natural control agents against aphids in the semiarid West will require manipulation of environmental conditions through irrigation.
Abstract: Colorado has experienced high levels of Russian wheat aphid, Diuraphis noxia (Kurdjumov), damage and is considered an important site for release of biocontrol agents. In June 1990, field surveys were initiated to provide baseline data on the identity and prevalence of existing aphid pathogens, parasites, and predators. Sampling was conducted in spring-planted grain in irrigated and dry-land fields near Fort Collins and Akron. D. noxia was the most abundant aphid; populations were high in both irrigated and dry-land fields. Parasite prevalence was low <5%) in all fields. D. noxia was the most frequently parasitized aphid, and the most common parasite was Diaeretiella rapae (M'Intosh). Syrphid fly larvae were the only predators consistently found feeding on aphids within the D. noxia –damaged (rolled) leaves. However, syrphid populations were low, <0.3 larvae per aphid-infested tiller. The ineffectiveness of the existing complex of parasites and predators in suppressing D. noxia populations underscores the need for introductions of more efficient biocontrol agents. Pathogenic fungi were active in nearly all fields; three species were found. In irrigated fields, Entomophthora chromaphidis Burger & Swain was the most common pathogen during the spring, with peak prevalence of 13% on 22 June. Pandora (= Erynia ) neoaphidis (Remaudiere & Hennebert) was not detected until late June, but it rapidly reached epizootic levels (44% infection by 18 July). Highest prevalence (20%) of Conidiobolus obscurus (Hall & Dunn) coincided with that of P. neoaphidis . Prevalence of fungal pathogens in dry-land fields did not exceed 2.5%. The observation of only low levels of entomophthoralean fungal infection in the nonirrigated fields suggests that reliable use of these natural control agents against aphids in the semiarid West will require manipulation of environmental conditions through irrigation.

Journal ArticleDOI
TL;DR: In studies of insect‐host plant interaction it is often suggested that insects preferentially colonize host plants on which their fitness is maximized (a positive covariance of preference and performance), but this suggestion stems from the assumption that natural selection has driven the system toward optimal use of resources.
Abstract: . 1. In studies of insect-host plant interaction it is often suggested that insects preferentially colonize host plants (or sites within plants) on which their fitness is maximized (a positive covariance of preference and performance). This suggestion stems from the assumption that natural selection has driven the system toward optimal use of resources. 2. Our study of the galling aphid Smynthurodes betae Westw. demonstrates that the distribution of galls on leaves is not due to preference, and can be altered by manipulating the aphid arrival time or the shoot growth rate. 3. We found no correlation between gall density and performance (aphid clone size) at different positions along the shoot. 4. Because leaves on the growing shoot are not equally responsive to aphid stimulation, the colonizers have no choice but to settle on leaves that are at the right stage when they arrive. 5. S.betae colonizers did not discriminate between shoots of their host and a congeneric non-host, on which their fitness is invariably zero. 6. Synchronization between galler and host plant phenologies seems to be the key to the observed distribution of galls on the tree. The data give no support to the preference-performance hypothesis.

Journal ArticleDOI
TL;DR: Strains of the aphid Aphis gossypii, taken from cucumber in UK glasshouses were tested for resistance to pirimicarb, diazinon and heptenophos, and host plant preference tests showed that all strains (including stock cultures) tested could readily breed on cotton.
Abstract: Summary Strains of the aphid Aphis gossypii, taken from cucumber in UK glasshouses were tested for resistance to pirimicarb, diazinon and heptenophos. Compared to a susceptible strain, resistance factors to diazinon of up to 659 were found in populations collected between 1987 and 1989. Compared to the same susceptible strain, diazinon-resistant populations also showed a reduced response to heptenophos. All field populations tested against pirimicarb were resistant. Host plant preference tests showed that all strains (including stock cultures) tested could readily breed on cotton. However strains originally collected from chrysanthemum did not transfer to cucumber and likewise strains from cucumber would not colonise chrysanthemum. Polyacrylamide gel electrophoresis of four of the aphid strains showed differences in migration rates and intensity of staining of esterase bands. Intensity of staining was correlated with the degree of diazinon resistance.

Journal ArticleDOI
TL;DR: All 6 aphids show a variety of overwintering strategies, and Aphis fabae, Acyrthosiphon pisum and Myzus persicae are serious pests of Vicia, Pisum and Solanum species respectively.
Abstract: The overwintering strategies of 6 aphid pests of arable crops are discussed. Three, Sitobion avenae, Rhopalosiphum padi and Metopolophium dirhodum are important pests of cereals world-wide. The other three, Aphis fabae, Acyrthosiphon pisum and Myzus persicae are serious pests of Vicia, Pisum and Solanum species respectively. All 6 aphids show a variety of overwintering strategies. A. fabae, M. dirhodum and R. padi are mainly host-alternating (heteroecious) holocyclic species; A. pisum and S. avenae are single host (autoecious) holocyclic species. Myzus persicae is mainly anholocyclic and autoecious although it can be holocyclic and heteroecious. The degree to which each aphid specialises in a particular mode of overwintering is discussed. The amount of mortality likely to be experienced by eggs (70 %) and viviparae (up to 100 %) is compared and contrasted. Natural enemies are the major factor causing egg mortality and low temperatures are the greatest single cause of mortality affecting the viviparae. Systems predicting aphid numbers on summer crops, based on winter populations of aphids are described and assessed as to their accuracy. Zusammenfassung Zur Uberwinterung von sechs Ackerland-Aphiden. Ein Uberblick unter besonderer Berucksichtigung des Pest-Managements Es werden die Uberwinterungsstrategien von 6 Ackerland-Aphiden dargestellt und erortert. Drei Arten: Sitobion avenae, Rhopalosiphum padi und Metopolophium dirhodum, sind weltweit wichtige Getreideschadlinge. Die anderen drei: Aphis fabae, Acyrthosiphon pisum und Myzus persicae sind bedeutende Schadlinge an Vicia, Pisum und Solanum. Alle 6 Blattlausarten zeigen eine Variabilitat in ihrer Uberwinterungsstrategie. A. fabae, M. dirhodum und R. padi sind wirtswechselnd (heterozisch) und holozyklisch. A. pisum und S. avenae sind nicht wirtswechselnd (autozisch) und holozyklisch. M. persicae ist hauptsachlich anholozyklisch und autozisch, obwohl sie auch holozyklisch und heterozisch auftreten kann. Der Grad, bis zu welchem sich jede Aphidenart in ihrer Uberwinterung spezialisiert hat, wird diskutiert. Die Mortalitat, gemessen bei Eiern (bis 70%) und Viviparen (bis 100%) werden verglichen. Naturliche Feinde bilden die Haupt-Mortalitatsfaktoren bei den Eiern, tiefe Temperaturen jene bei den Viviparen. Es werden Systeme beschrieben und erortert, die an Hand der Uberwinterungs-population eine Vorhersage des Aphidenauftretens auf den Sommerwirten erlauben.

Journal ArticleDOI
TL;DR: The presence of spiders significantly caused between 34 and 58% reduction in aphid population development on wheat plants compared to the Aphid population in the absence of spiders.
Abstract: Laboratory experiments were performed to determine the potential of dominant spider species in winter wheat in Germany,Erigone atra (Blackwall),Lepthyphantes tenuis (Blackwall) andPardosa agrestis (Westring) adults and youngs, in suppressing the population ofRhopalosiphum padi (L.) on wheat plants and their functional response to different aphid densities. The presence of spiders significantly caused between 34 and 58% reduction in aphid population development on wheat plants compared to the aphid population in the absence of spiders. The functional response curves for these spiders as predators ofR. padi seem to descrive a typical type II functional response with the prey consumed increasing to a plateau as aphid densities increased. Prey killed without eating was linear on prey density.

Journal ArticleDOI
TL;DR: Females were larger than males although the degree of sexual size dimorphism declined with increased host size, and development time from oviposition to adult eclosion varied non-linearly with the host instar at parasitization, and was shortest in first and fourth nymphal instars.
Abstract: We tested the hypothesis that the pattern of development and growth of a generalist parasitoid wasp varies in different hosts. We reared Ephedras californicus Baker (Hymenoptera: Aphidiidae), a solitary parasitoid of aphids, under controlled laboratory conditions on five kinds of hosts: nymphal instar 1 (24 h old), 2 (42 h), 3 (96 h), and 4 (144 h) of apterous virginoparae of Acyrthosiphon pisum (Harris), and nymphal instar 1 (24 h) of Macrosiphum creelii Davis (Homoptera: Aphididae). Parasitoid dry mass increased with the host instar at parasitization. Females were larger than males although the degree of sexual size dimorphism declined with increased host size. Development time from oviposition to adult eclosion varied non-linearly with the host instar at parasitization, and was shortest in first and fourth nymphal instars. Parasitoids developing in M. creelii gained more mass in less time than their counterparts developing in A. pisum of the same initial size. In low-quality hosts, parasitoids apparently trade off increased development time for a gain in adult mass. A possible explanation of sexual size dimorphism in E. californicus is that large females may be able to overcome aphid defensive behaviours better than small ones.

Journal ArticleDOI
TL;DR: The results of this analysis support the hypothesis, that the marked seasonal changes in the total quantity of amino acids in sycamore leaves and intraspecific competition for this resource, through its effect on adult weight, shape the seasonal cycle in the reproductive activity of the Sycamore aphid.
Abstract: The hypothesis that seasonal changes in sycamore aphid,Drepanosiphum platanoidis (Schr), recruitment are determined by changes in food quality and aphid population density was tested There was no clear association between the reproductive activity of the sycamore aphid and the seasonal changes in specific amino acids or groups of amino acids in extracts of sycamore,Acer pseudoplatanus L, leaves Seasonal changes in reproductive activity tracked the changes in total amino acids of the leaf tissue of the host, but with a short time delay High numbers of adult aphids appeared to depress reproductive activity A regression analysis of the results revealed that total amino acids the previous week and current numbers of adult aphids significantly affected sycamore aphid reproductive activity The results of this analysis support the above hypothesis, that the marked seasonal changes in the total quantity of amino acids in sycamore leaves and intraspecific competition for this resource, through its effect on adult weight, shape the seasonal cycle in the reproductive activity of the sycamore aphid

Journal ArticleDOI
TL;DR: It is pointed out the possibility that the prokaryotes under intracellular conditions have been subject to some common evolutionary pressures, and as a result, have come to resemble cell organelles.
Abstract: All aphids harbor symbiotrophic prokaryotes (“primary symbionts”) in a specialized-abdominal cell, the bacteriocyte. Chaperonin 60 (Cpn60, symbionin) and chaperonin 10 (Cpn10), which are high and low molecular weight heatshock proteins, were sought in tissues of more than 60 aphid species. The endosymbionts were compared immunologically and histologically. It was demonstrated that (1) there are two types of aphids in terms of the endosymbiotic system: some with only primary symbionts and others with, in addition, secondary symbionts; (2) the primary symbionts of various aphids are quite similar in morphology whereas the secondary symbionts vary; and (3) irrespective of the aphid species, Cpn60 is abundant in both the primary and secondary symbionts, while Cpn10 is abundant in the secondary symbionts but present in small amounts in the primary ones. Based on these results, we suggest that the primary symbionts have been derived from a prokaryote that was acquired by the common ancestor of aphids whereas the secondary symbionts have been acquired by various aphids independently after divergence of the aphid species. In addition, we point out the possibility that the prokaryotes under intracellular conditions have been subject to some common evolutionary pressures, and as a result, have come to resemble cell organelles.

Journal ArticleDOI
TL;DR: The aphidiid waspLysiphlebus cardui parasitizes in ant-attendedAphis fabae cirsiiacanthoidis colonies without causing aggressive behavior in the antLasius niger, and chemical stimuli on the cuticle are major cues for the ants to distinguish between the parasitoids.
Abstract: The aphidiid waspLysiphlebus cardui parasitizes in ant-attendedAphis fabae cirsiiacanthoidis colonies without causing aggressive behavior in the antLasius niger. By contrast,Trioxys angelicae, another aphidiid parasitoid of aphids, is rapidly recognized and vigorously attacked by the ants.L. niger workers also responded differently to dead individuals ofL. cardui andT. angelicae. DeadL. cardui parasitoids were often ignored when encountered byL. niger, whereas deadT. angelicae individuals were immediately grasped by ants that discovered them. However, hexane-washed parasitoids caused a similar reaction pattern in the ants, in that both aphidiid species were tolerated in the aphid colony. Lure experiments demonstrated that chemical stimuli on the cuticle are major cues for the ants to distinguish between the parasitoids. The hexane extract ofL. cardui transferred to washed individuals ofT. angelicae resulted in ant responses characteristic towardsL. cardui, andL. niger workers displayed the typical removal pattern they normally showed towardsT. angelicae whenT. angelicae extract was applied toL. cardui individuals. Both parasitoid species treated with the hexane extract ofA. fabae cirsiiacanthoidis were similarily treated by the ants as were aphid control individuals. The suggestion that the aphidiid waspL. cardui uses chemical mimicry is discussed.

Journal ArticleDOI
TL;DR: Development, fecundity, and longevity of the predator, Orius insidiosus (Say) (Heteroptera: Anthocoridae), when reared on greenbug, cotton aphid, or eggs of tobacco budworm with green beans or water were examined.
Abstract: Development, fecundity, and longevity of the predator, Orius insidiosus (Say) (Heteroptera: Anthocoridae), when reared on greenbug [Schizaphis graminum (Rondani)], cotton aphid (Aphis gossypii Glover), or eggs of tobacco budworm [Heliothis virescens (F.)] with green beans or water were examined. Developmental time was shortest when predators were reared on H. virescens eggs and beans and longest when reared on cotton aphids and water. Predators were most fecund when fed H. virescens eggs. The inclusion of beans in the nymphal diet further enhanced fecundity when fed eggs. Longevity of both females and males was significantly shorter when reared on aphids than on eggs. Beans in the nymphal diet enhanced longevity of female predators only in combination with budworm eggs. Female O. insidiosus were largest when reared on H. virescens eggs. Addition of green beans in aphid treatments resulted in increased size of O. insidiosus when compared to aphids and free water.

Journal ArticleDOI
01 Jul 1993-Ecology
TL;DR: In this paper, a comparative experimental analysis of larval behavior in two sympatric pre-dacious sister-species (Chrysopa quadripunctata, a generalist, and C. slossonae, a specialist on the woolly alder aphid) was conducted during four discrete developmental periods.
Abstract: To examine pathways in the evolution of prey specialization in insects, we conducted a comparative experimental analysis of larval behavior in two sympatric pre- dacious sister-species (Chrysopa quadripunctata, a generalist, and C. slossonae, a specialist on the woolly alder aphid). Responses of the larvae to food (Myzus persicae) and cam- ouflaging material (waxy secretions from woolly alder aphids or exuviae from M. persicae) were quantified during four discrete developmental periods. Our analysis revealed species- specific, ontogenetic, and environmentally induced variation in larval defensive and feeding behavior. The pattern of interspecific variation indicates that larval behavior could have subserved two processes in the evolution of prey specialization in the sister-species' pro- genitor: establishment on a specific prey and adaptation to the prey. First, the presence of the woolly alder aphid's secretions results in generalist larvae camouflaging themselves to a degree that rivals that of the specialist. Such phenotypic plasticity could have promoted the progenitor's initial adoption of the ant-tended woolly alder aphid as prey and its wool as a source of camouflaging material. Second, quantitative differences between the gener- alist's and specialist's behavior indicate that adaptation to the woolly alder aphid did not require the acquisition of novel behavioral traits in the larvae. It involved modifications in the expression of defensive behavior that existed in the generalist ancestor and alterations in the ability to attack and feed on robust prey.

Journal ArticleDOI
TL;DR: Treatment differences in total reproduction were caused by differential mortality rather than differential reproduction rates of individuals, and most (>99%) nymphs produced from infected adults were uninfected.
Abstract: Ten-d-old apterae of Russian wheat aphid, Diuraphis noxia Kurdyumov, (25 per treatment) were inoculated with conidial suspensions (106 conidia per ml) of Beauveria bassiana (Balsamo) Vuillemin, isolate SGBB 8601, or with sterile water, then caged individually on wheat seedlings. Temperature was maintained at 22 ± 3°C, and relative humidity was kept at ≥95% for 24 hand ≈85% subsequently. Each aphid was monitored daily over 14 d for mortality and nymph production. All newborn nymphs and dead adults were removed and plated. The experiment was performed four times. B. bassiana significantly increased aphid mortality (mean mortality due to mycosis, 82%). Over the 14-d period, untreated adults produced significantly more nymphs (37.8 ± 4.5) (mean ± SE) than did Beauveria -treated adults (14.3 ± 1.6). However, the pathogen did not affect nymph production by individual aphids (mean, 3.3 nymphs per d per aphid for both treatments). Thus, treatment differences in total reproduction were caused by differential mortality rather than differential reproduction rates of individuals. Most (>99%) nymphs produced from infected adults were uninfected.

Journal ArticleDOI
TL;DR: Since 1981, field surveys and greenhouse studies have focused on the life cycle and morphs on primary hosts in the genus Rhamnus, the results of which are reported here.
Abstract: The soybean aphid Aphis glycines MATSUMURA is the main sap-sucking pest on soybeans Glycine max In Japan, it is distributed from Hokkaido to Kyushu (Sakai, 1949); abroad, it is found in Korea, China, Taiwan, Thailand, Malay (Paik, 1965), the Phillipines (Takahashi, 1966), and India (Raychaudhuri et al, 1980) In addition to soybeans, wild Glycine species are known to be a secondary host Matsumura reported this aphid species on soybean (1917a) and in the same year recorded that its eggs over-wintered on plants belonging to the wild pea family (1917b) Shindo (1928, 1932) originally identified Kitsunenomago Justicia procumbens and purplish amaranth Amaranthus blitum as primary hosts, but later retracted and reported that the eggs over-winter in the roots of the Japanese chaff flower Acyranthes japonica (1941) However, Sakai (1949, 1950a, b) showed in greenhouse studies that this aphid does not over-winter in the chaff flower, and concluded that the species found on chaff flower was actually Aphis justiciae SHINJI which Shindo (1928) considered to be the same as Aphis glycines While the controversy in Japan about the primary host remained unresolved, in China it was reported by Wang et al (1962) that the eggs over-wintered in the Dahurian buckthorn Rhamnus davurica of the buckthorn family Zhang and Zhong (1982) subsequently established that several of the 15 species in the genus Rhamnus found in China were primary hosts In the reports from China, only the body color and the number of secondary sensilla of the third antennal segment of gynopara were reported, and no mention was made of the morphs on the primary host Since 1981, our field surveys and greenhouse studies have focused on the life cycle and morphs on primary hosts in the genus Rhamnus, the results of which are reported here