Preceding crop affects soybean aphid abundance and predator–prey dynamics in soybean

Crop rotations alter the soil environment and physiology of the subsequent crop in ways that may affect the abundance of herbivores and their natural enemies. Soybean aphids are a consistent pest of soybean throughout North America, but little work has focused on how preceding crops may affect pest–predator dynamics. In a replicated experiment over three years, we examined how two preceding crops (spring wheat or an oat/pea mixture) affected seasonal soybean aphid pressure and the ratio of aphids to their predator community. Peak aphid populations were reduced by 40% and 75% in years 1 and 2 by planting spring wheat before soybeans (relative to the oat–pea mixture). Aphid densities were unaffected by preceding crop in the third year of study (aphids were at threshold in this year). Predators responded positively to aphid population increases and were unaffected by preceding crops. Additional research on how crop rotations can be used as a tool to manage soybean aphids warrants further attention.     

Effects of a simple plant morphological mutation on the arthropod community and the impacts of predators on a principal insect herbivore

Plant features that enhance predator effectiveness can be considered extrinsic-resistance factors because they result in reduced insect herbivory. In this paper we test the hypothesis that reduced epicuticular wax (EW) in Pisum sativum L. is an extrinsic-resistance factor contributing to field resistance to Acyrthosiphon pisum (Harris). We monitored pea aphid populations in the field on reduced EW and normal EW near isolines of peas for two seasons and confirmed that aphid populations are lower on reduced EW peas than on normal EW peas. We also monitored predators within the canopies of the two pea lines to discover community level patterns in response to differences in EW. We found that while predator numbers were similar between the two lines, there were more syrphids on the normal EW peas, and a trend towards more coccinellids on reduced EW peas. We tested the impact of predators on pea aphids on the two EW lines by monitoring their population levels in cages that excluded predators, and in cages that allowed predators to enter. We found that pea aphid populations were similar on the two EW lines when predators were excluded. When predators were allowed access to the plants, pea aphid populations were reduced more on reduced EW peas than on normal EW peas. We also examined the intrinsic resistance to aphids in reduced EW peas with laboratory dual-choice tests comparing aphid response to reduced EW and normal EW peas, and found that walking, apterous aphids displayed no preference for one pea line over the other. Bioassays to measure growth and fecundity of the pea aphid on the two EW types in the greenhouse and in the field showed that intrinsic rate of increase, and other life table parameters, were not different for aphids on the two lines. Together these results support the hypothesis that reduced EW in peas is a predator-dependent extrinsic resistance factor. Genetically reducing EW bloom in peas and other waxy crop plants might improve the effectiveness of arthropod natural enemies of insect pests. More generally, the results show that a subtle change in plant morphology can substantially influence the impact of predators on insect herbivore populations. The benefit of extrinsic resistance to herbivory conferred by reduced EW may balance any benefits of a prominent EW bloom, thereby sustaining EW polymorphisms in some natural plant populations.     

Risk assessment for non-crop hosts of pea enation mosaic virus and the aphid vector Acyrthosiphon pisum

1. Viral insect-borne plant pathogens have devastating impacts in agroecosystems. Vector-borne pathogens are often transmitted by generalist insects that move between non-crop and crop hosts. Insect vectors can have wide diet breadths, but it is often unknown which hosts serve as pathogen reservoirs and which non-crop host harbours the highest density of vectors.
2. In the Pacific Northwest USA, the pea aphid (Acyrthosiphon pisum) is a key virus vector in pulse crops. Despite pea aphid having a large number of potential non-crop plant hosts occuring in the region, no reservoir has yet been identified for the economically-costly pathogen Pea Enation Mosaic Virus (PEMV).
3. We addressed these issues by linking field surveys of an aphid vector and plant virus with statistical models to develop risk assessments for common non-crop legumes; in 2018, we completed a 65-site survey where aphids were surveyed in weedy legumes within and outside dry pea fields.
4. We quantified the abundance of pea aphids on 17 hosts, and plant tissue was tested for PEMV. Relatively high densities of A. pisum were found in habitats dominated by hairy vetch (Vicia villosa), which was the only legume other than cultivated dry pea where PEMV was detected.
5. Our results indicate that V. villosa is a key alternative host for PEMV, and that pest management practices in this region should consider the distribution and abundance of this weedy host in viral disease mitigation efforts for pulses.

     

Effects of hydrophilic and hydrophobic kaolin-based particle films on pea aphid (Homoptera: Aphididae) and its entomopathogen Pandora neoaphidis (Entomophthorales: Entomophthoraceae)

Hydrophobic and hydrophilic kaolin-based particle films are effective for control of insect pests in certain agricultural crops. How these products interact with potential biological control agents is not well documented. This study was conducted to evaluate the effects of the hydrophobic (M96-018) and hydrophilic (Surround WP) kaolin-based particle films (Engelhard Corporation, Iselin, NJ) on pea aphid, Acyrthosiphon pisum (Harris), on peas (Pisum spp.), and on the fungal aphid pathogen Pandora neoaphidis (Remaudière and Hennebert) Humber. Over two field seasons (2001 and 2002) in northern Idaho, applications of M96-018 significantly reduced the rate of pea aphid increase on pea, but Surround WP, tested only in 2001, did not reduce aphid population growth rate. Neither particle film treatment was as effective as a standard application of esfenvalerate (DuPont Asana). In the laboratory, particle films suppressed pea aphid populations by up to 30%. M96-018 seemed to have some repellent activity based on aphid distributions after treating plants. When applied along with P. neoaphidis conidia, M96-018 but not Surround WP caused higher percentage of infection mortality of pea aphids by P. neoaphidis than occurred on controls treated only with P. neoaphidis conidia. P. neoaphidis conidia deposited on glass slides coated with M96-018, produced more germ tubes and secondary conidia than those deposited on untreated glass slides or slides treated with Surround WP. This result suggests that greater infection of pea aphids on plants treated with M96-018 is in part a result of a direct enhancement of fungal germination by the particle film.     

Is there an associational resistance of winter pea–durum wheat intercrops towards Acyrthosiphon pisum Harris?

Acyrthosiphon pisum Harris (Aphididae: Hemiptera), the pea aphid, is an important pest in organic farming systems. In this work, the objective was to gather empirical field data on the associational resistance of durum wheat–winter pea intercrops towards the pea aphid, compared with pure stands of winter pea. Our results showed that intercropping winter pea with durum wheat significantly decreased A. pisum abundance in all the situations. Moreover, it was systematically observed that pea grew bigger in pure than in intercropped stands but after considering pea dry mass as a covariate, it appeared that the durum wheat–winter pea intercrop was still significantly less attacked by pea aphids than the sole crop. Intercrop sowing designs had an incidence on infestation levels: substitutive diversification systems of different types are more effective in decreasing the level of aphid infestation than does the additive system. In addition, substitutive row intercrop is significantly less infested than substitutive mixture. These results suggest that a mechanism related to the resource concentration hypothesis may explain the associational resistance of the IC of durum wheat–winter pea towards A. pisum.     

Temporal habitat variability and the maintenance of sex in host populations of the pea aphid

The evolutionary maintenance of sex, despite competition from asexual reproduction, has long intrigued the evolutionary biologists owing to its numerous apparent short-term costs. In aphids, winter climate is expected to determine the maintenance of sexual lineages in the high latitude zones owing to their exclusive ability to produce frost-resistant eggs. However, diverse reproductive modes may coexist at a local scale where climatic influence is counteracted by microgeographical factors. In this study, we tested the influence of local habitat characteristics on regional coexistence of reproductive modes in the pea aphid, Acyrthosiphon pisum. In the laboratory, the induction of sexual morph production of many pea aphid genotypes from the local fields of annual (pea and faba bean) and perennial (alfalfa and red clover) crops in Western France indicated that A. pisum lineages from annual crops had a significantly higher investment in sexual reproduction than A. pisum lineages from the perennial hosts. We propose that temporal habitat variability exerts a selective pressure to maintain the sexual reproduction in A. pisum. The ecological and evolutionary consequences of the association between the mode of reproduction and the host population on gene flow restriction and on ecological specialization are discussed.     

Leaf surface wax and plant morphology of peas influence insect density

Insect predators and parasitoids adhere better, forage more effectively, and take more aphid prey on pea plants (Pisum sativum L.) (Leguminosae) with mutations that reduce the crystalline wax bloom on the plant surface. To assess the agronomic potential of this trait for pest management, abundance of pea aphids (Acyrthosiphon pisum L.) (Homoptera: Aphididae) and coccinellid predators, and percent parasitism of the aphids were evaluated on pea lines differing in wax bloom and plant architecture over two field seasons. Three pairs of pea lines were evaluated, each pair with a different architecture and differing within the pair in the amount of surface wax bloom (reduced or normal). The trials included plots treated with a narrow spectrum insecticide (pymetrozine) to reduce aphid populations and untreated controls. Reduced wax peas had significantly fewer aphids per plant in 2002 but not in 2003. Total natural enemy abundance was greater on reduced wax than on normal wax pea lines in both years of the study. Pymetrozine reduced aphid densities significantly in both years. Among the four pea lines evaluated for yield, seed yield per plant was affected by plant morphology and insecticide treatment. Yield was greatest on semileafless plants and on pymetrozine sprayed plots in both years. Yield of the reduced wax line in the semileafless background was similar to or exceeded yield in its normal wax sister line, suggesting that this morphological type was best for an agronomically viable reduced wax phenotype. Pea weevil (Bruchus pisorum L.) (Coleoptera: Bruchidae) damage to seed was overall more frequent on seeds from reduced wax varieties than from normal wax varieties. The results illustrate the trade‐offs associated with a reduced wax trait in peas but also show that certain combinations of reduced wax and gross morphology lead to reduced pea aphid populations and yields similar to those of normal wax peas.     

Plant waxy bloom on peas affects infection of pea aphids by Pandora neoaphidis

This study examined the effects of the surface wax bloom of pea plants, Pisum sativum, on infection of pea aphids, Acyrthosiphon pisum, by the fungal pathogen Pandora neoaphidis. In prior field surveys, a higher proportion of P. neoaphidis-killed pea aphids (cadavers) had been observed on a pea line with reduced wax bloom, as compared with a sister line with normal surface wax bloom. Laboratory bioassays were conducted in order to examine the mechanisms. After plants of each line infested with aphids were exposed to similar densities of conidia, the rate of accumulation of cadavers on the reduced wax line was significantly greater than on the normal wax bloom line; at the end of the experiment (13d), the proportion of aphid cadavers on the reduced wax line was approximately four times that on the normal wax bloom line. When plants were exposed to conidia first and then infested with aphids, the rate of accumulation of cadavers was slightly but significantly greater on the reduced wax line, and infection at the end of the experiment (16d) did not differ between the lines. When aphids were exposed first and then released onto the plants, no differences in the proportion of aphid cadavers were observed between the pea lines. Greater infection of pea aphid on reduced wax peas appears to depend upon plants being exposed to inoculum while aphids are settled in typical feeding positions on the plant. Additional experiments demonstrated increased adhesion and germination by P. neoaphidis conidia to leaf surfaces of the reduced wax line as compared with normal wax line, and this could help explain the higher infection rate by P. neoaphidis on the reduced wax line. In bioassays using surface waxes extracted from the two lines, there was no effect of wax source on germination of P. neoaphidis conidia.     

Host-based divergence in populations of the pea aphid: insights from nuclear markers and the prevalence of facultative symbionts

In North America, the pea aphid Acyrthosiphon pisum encompasses ecologically and genetically distinct host races that offer an ideal biological system for studies on sympatric speciation. In addition to its obligate symbiont Buchnera, pea aphids harbour several facultative and phylogenetically distant symbionts. We explored the relationships between host races of A. pisum and their symbiotic microbiota to gain insights into the historical process of ecological specialization and symbiotic acquisition in this aphid. We used allozyme and microsatellite markers to analyse the extent of genetic differentiation between populations of A. pisum on pea, alfalfa and clover in France. In parallel, we examined: (i) the distribution of four facultative symbionts; and (ii) the genetic variation in the Buchnera genome across host-associated populations of A. pisum. Our study clearly demonstrates that populations of A. pisum on pea, clover and alfalfa in France are genetically divergent, which indicates that they constitute distinct host races. We also found a very strong association between host races of A. pisum and their symbiotic microbiota. We stress the need for phylogeographic studies to shed light on the process of host-race formation and acquisition of facultative symbionts in A. pisum. We also question the effects of these symbionts on aphid host fitness, including their role in adaptation to a host plant.     

Facultative symbionts are associated with host plant specialization in pea aphid populations

The pea aphid, Acyrthosiphon pisum, shows significant reproductive isolation and host plant specialization between populations on alfalfa and clover in New York. We examine whether specialization is seen in pea aphids in California, and whether fitness on alternative host plants is associated with the presence of bacterial symbionts. We measured the fitness of alfalfa- and clover-derived aphids on both types of plants and found no evidence for specialization when all aphid lineages were considered simultaneously. We then screened all aphids for the presence of four facultative bacterial symbionts: PAR, PASS, PABS and PAUS. Aphids with PAUS were host-plant specialized, having twice as many offspring as other aphids on clover, and dying on alfalfa. Other aphids showed no evidence of specialization. Additionally, aphids with PABS had 50% more offspring than aphids with PASS when on alfalfa. Thus, specialist and generalist aphid lineages coexist, and specialization is symbiont associated. Further work will resolve whether PAUS is directly responsible for this variation in fitness or whether PAUS is incidentally associated with host-plant specialized aphid lineages.     

Seasonal incidence of aphid,Amphorophora ampullata Bukton (Homoptera: Aphididae) on fern,Hypolepis polypodioides (Blume) Hook (Hypolepidaceae) from Western Himalaya

Seasonal incidence of aphid, Amphorophora ampullata on Hypolepis polypodioides was recorded throughout the year from November 2012 to November 2013 at weekly interval. Peak incidence of aphid was recorded during third week of November 2012 (25.94 ± 2.39 aphids/pinna), later the aphid population gradually decreased from December 2012 onwards and reached below threshold level during the last week of January (0.1 ± 0 aphids/pinna). The aphid population starts building up again from first week of February 2013 (1.6 ± 0.13 aphids/pinna) and attained its peak in the last week of August (32.17 ± 1.22 aphids/pinna) then decreased gradually in the first week of September (20.82 ± 4.70 aphids/pinna). Aphid densities again increased gradually from second week of September (21.62 ± 3.02 aphids/pinna) to November 2013 and reached maximum aphid densities during November (56.55 ± 4.34 aphids/pinna). Among weather parameters, aphid population showed significant positive correlation with relative humidity during morning hours.     

Role of host nutrition in symbiont regulation: impact of dietary nitrogen on proliferation of obligate and facultative bacterial endosymbionts of the pea aphid Acyrthosiphon pisum

The impact of host nutrition on symbiont regulation in the pea aphid Acyrthosiphon pisum was investigated. The population density of the obligate symbiont Buchnera aphidicola positively correlated with dietary nitrogen levels. In contrast, the population density of the facultative symbiont Serratia symbiotica increased in aphids reared on low-nitrogen diets, indicating distinct regulatory mechanisms in the same insect host.     

EVOLUTION OF AN APHID-PARASITOID INTERACTION: VARIATION IN RESISTANCE TO PARASITISM AMONG APHID POPULATIONS SPECIALIZED ON DIFFERENT PLANTS

The evolution of associations between herbivorous insects and their parasitoids is likely to be influenced by the relationship between the herbivore and its host plants. If populations of specialized herbivorous insects are structured by their host plants such that populations on different hosts are genetically differentiated, then the traits affecting insect-parasitoid interactions may exhibit an associated structure. The pea aphid (Acyrthosiphon pisum) is a herbivorous insect species comprised of genetically distinct groups that are specialized on different host plants (Via 1991a, 1994). Here, we examine how the genetic differentiation of pea aphid populations on different host plants affects their interaction with a parasitoid wasp, Aphidius ervi. We performed four experiments. (1) By exposing pea aphids from both alfalfa and clover to parasitoids from both crops, we demonstrate that pea aphid populations that are specialized on alfalfa are successfully parasitized less often than are populations specialized on clover. This difference in parasitism rate does not depend upon whether the wasps were collected from alfalfa or clover fields. (2) When we controlled for potential differences in aphid and parasitoid behavior between the two host plants and ensured that aphids were attacked, we found that pea aphids from alfalfa were still parasitized less often than pea aphids from clover. Thus, the difference in parasitism rates is not due to behavior of either aphids or wasps, but appears to be a physiologically based difference in resistance to parasitism. (3) Replicates of pea aphid clones reared on their own host plant and on a common host plant, fava bean, exhibited the same pattern of resistance as above. Thus, there do not appear to be nutritional or secondary chemical effects on the level of physiological resistance in the aphids due to feeding on clover or alfalfa, and therefore the difference in resistance on the two crops appears to be genetically based. (4) We assayed for genetic variation in resistance among individual pea aphid clones collected from clover fields and found no detectable genetic variation for resistance to parasitism within two populations sampled from clover. This is in contrast to Henter and Via's (1995) report of abundant genetic variation in resistance to this parasitoid within a pea aphid population on alfalfa. Low levels of genetic variation may be one factor that constrains the evolution of resistance to parasitism in the populations of pea aphids from clover, leading them to remain more susceptible than populations of the same species from alfalfa.     

Facultative symbiont infections affect aphid reproduction

Some bacterial symbionts alter their hosts reproduction through various mechanisms that enhance their transmission in the host population. In addition to its obligatory symbiont Buchnera aphidicola, the pea aphid Acyrthosiphon pisum harbors several facultative symbionts influencing several aspects of host ecology. Aphids reproduce by cyclical parthenogenesis whereby clonal and sexual reproduction alternate within the annual life cycle. Many species, including the pea aphid, also show variation in their reproductive mode at the population level, with some lineages reproducing by cyclical parthenogenesis and others by permanent parthenogenesis. While the role of facultative symbionts has been well studied during the parthenogenetic phase of their aphid hosts, very little is known on their possible influence during the sexual phase. Here we investigated whether facultative symbionts modulate the capacity to produce sexual forms in various genetic backgrounds of the pea aphid with controlled symbiont composition and also in different aphid genotypes from natural populations with previously characterized infection status and reproductive mode. We found that most facultative symbionts exhibited detrimental effects on their hosts fitness under sex-inducing conditions in comparison with the reference lines. We also showed that the loss of sexual phase in permanently parthenogenetic lineages of A. pisum was not explained by facultative symbionts. Finally, we demonstrated that Spiroplasma infection annihilated the production of males in the host progeny by inducing a male-killing phenotype, an unexpected result for organisms such as aphids that reproduce primarily through clonal reproduction.     

Partitioning of Symbiotic Bacteria between Generations of an Insect: a Quantitative Study of a Buchnera sp. in the Pea Aphid (Acyrthosiphon pisum) Reared at Different Temperatures

The population of symbiotic Buchnera bacteria in parthenogenetic females of the pea aphid Acyrthosiphon pisum was determined by quantitative hybridization of a DNA probe (groESL) to aphid homogenates. The aphids bore 1 x 10(sup7) to 2 x 10(sup7) bacterial cells per mg (fresh weight). In teneral aphids (i.e., aphids that had moulted to adulthood but that had not initiated reproduction), >75% of the bacteria were in the embryos, and the density of bacteria in the embryos was consistently greater than that in the maternal tissues. The bacterial density in teneral aphids increased from 1.3 x 10(sup7) to 2.0 x 10(sup7) cells mg (fresh weight) of aphids(sup-1) with temperature between 15 and 25(deg)C. This variation could be attributed to a temperature-dependent increase in both the density of bacteria in the embryos and embryo content of the aphids.     

Host plant age and population development of a cereal aphid, Metopolophium dirhodum (Hemiptera: Aphididae)

The sudden decline following the peak in population abundance of aphids on crops of small grain cereals is attributed to the joint effect of natural enemies and plant senescence. To distinguish between these causes, a four year experiment was established in which the numbers of Metopolophium dirhodum (Walker) infesting spring wheat plots sown from April to June at c. 14 day intervals were determined. Aphid abundance in replicates sown at successive dates peaked within a period of 5-9 days (106-171 day degrees above a base temperature of 0 degrees C) although their sowing dates varied by 62-97 days (727-1106 day degrees). At the time of the aphid population peaks, plants in the different sowings differed in age (11-99 days), developmental stage (stage 15-65 on the Zadoks scale), leaf nitrogen content and shoot mass. Maximum abundance of M. dirhodum decreased with sowing date because the time available for its population increase was shorter on late than early sowings. The abundance of M. dirhodum on spring wheat was similar to its abundance on winter wheat. After reaching peak abundance, aphids declined in numbers within 3-7 days. The effect of host plant ageing on the M. dirhodumdecline thus appeared small. Natural enemies (largely mycoses), and timing of alata production may have contributed to the aphid decline.     

The host plant range of the pea aphid subspecies Acyrthosiphon pisum ssp. destructor (Johnson) (Hom., Aphididae)

Abstract:  In order to establish the host range of the pea aphid subspecies, Acyrthosiphon pisum ssp. destructor , and hence from which plant species pea crops are likely to become infested, the performance of this aphid on different leguminous plants was assessed. The plant species used were: Lotus uliginosus , Medicago sativa , Melilotus officinalis , Ononis repens , Sarothamnus scoparius , Trifolium hybridum , Trifolium pratense , Trifolium repens , Vicia cracca and Vicia faba . Vicia faba and Trifolium hybridum were the plants on which aphids reached the greatest size, took the least time to reach maturity, and experienced the lowest mortality. The time taken for the aphids to develop to maturity was negatively correlated with adult size, whereas survival to maturity was positively correlated with adult size. The host preference of the aphids was also assessed. The plant species selected as hosts by alatae were those on which their offspring performed best.     

Farm‐scale assessment of movement patterns and colonization dynamics of the grain aphid in arable crops and hedgerows

1 Integrated management of crop pests requires the identification of the appropriate spatial scale at which colonization processes occurs. We assessed, by coupling demographic and genetic methods, the relative contribution of local and transient migrants of the grain aphid Sitobion avenae to wheat field colonization in spring. 2 We examined, during two consecutive years, the daily colonization of wheat by aphid migrants and compared this with daily aphid flight monitored by a local 12.2‐m suction trap. The genetic profiles of aphids landing on crops were compared with those of both flying aphids caught by the suction trap and local populations from arable crops and hedgerows. 3 In the first year, we observed: (i) a strong correlation between aphids colonizing the crop and those moving within the crop and a close genetic similarity between aphids from these samples and (ii) a high level of genetic differentiation between these aphids and populations from local cereals and field margins. In the second year, the number of migrants recorded on the wheat was three‐fold higher than in the previous year, and less correlated with that recorded by the suction trap. This was associated with a lack of genetic differentiation between all samples. 4 This variation in the colonization processes resulted mainly in an abrupt increase in abundance of genotypes from local over‐wintering sites in 2004. This suggests that, despite the long range dispersal potential of the grain aphid, outbreak risks could be mainly determined at a local scale, encouraging the design of relatively small management units.     

The significance of a facultative bacterium to natural populations of the pea aphid Acyrthosiphon pisum

Abstract. 1.  Laboratory studies have implicated various accessory bacteria of aphids as important determinants of aphid performance, especially on certain plant species and under certain thermal regimes. One of these accessory bacteria is PABS (also known as T-type), which is distributed widely but is not universal in natural populations of the pea aphid Acyrthosiphon pisum in the U.K.
2.  To explore the impact of PABS on the performance of A. pisum , the nymphal development time and fecundity of aphids collected directly from natural populations and caged on the host plant Vicia faba in the field were quantified. Over 4 consecutive months June–September 1999, the performance of PABS-positive and PABS-negative aphids did not differ significantly.
3.  Deterministic modelling of the performance data showed that the variation in simulated population increase of PABS-positive and PABS-negative aphids would overlap substantially.
4.  Analysis of aphids colonising five host plants ( Lathyrus odoratus , Medicago sativa , Pisum sativum , Trifolium pratense , Vicia faba ) between April and September 2000 and 2001, identified no robust differences between the distribution of PABS-positive and PABS-negative aphids on different plants and with season or temperature.
5.  It is concluded that PABS is not an important factor shaping the performance or plant range of A. pisum under the field conditions tested. Reasons for the discrepancies between this study and laboratory-based studies are considered.     

Relative importance of long‐term changes in climate and land‐use on the phenology and abundance of legume crop specialist and generalist aphids

Abstract Insect populations are prone to respond to global changes through shifts in phenology, distribution and abundance. However, global changes cover several factors such as climate and land-use, the relative importance of these being largely unknown. Here, we aim at disentangling the effects of climate, land-use, and geographical drivers on aphid abundance and phenology in France, at a regional scale and over the last 40 years. We used aerial data obtained from suction traps between 1978 and 2015 on five aphid species varying in their degree of specialization to legumes, along with climate, legume crop area and geographical data. Effects of environmental and geographical variables on aphid annual abundance and spring migration dates were analyzed using generalized linear mixed models. We found that within the last four decades, aphids have advanced their spring migration by a month, mostly due to the increase in temperature early in the year, and their abundance decreased by half on average, presumably in response to a combination of factors. The influence of legume crop area decreased with the degree of specialization of the aphid species to such crops. The effect of geographical variation was high even when controlling for environmental variables, suggesting that many other spatially structured processes act on aphid population characteristics. Multifactorial analyses helped to partition the effects of different global change drivers. Climate and land-use changes have strong effects on aphid populations, with important implications for future agriculture. Additionally, trait-based response variation could have major consequences at the community scale.