Dysaphis Plantaginea Passerini Research Articles

Effect of intercropping apple trees with basil (Ocimum basilicum) or French marigold (Tagetes patula) on the rosy apple aphid regulation (Dysaphis plantaginea) and the abundance of its natural enemies.

In a global context of pesticide reduction, the sustainable management of aphids is a major challenge in maintaining economically viable fruit production. Intercropping with companion plants (CPs) that emit volatile organic compounds (VOCs) with repellent or attractive properties could be successful in the laboratory. Still, their effects on the orchard have been little documented. We tested in 2018 and 2019 the hypotheses that the introduction of basil or French marigold, decreases the populations of Dysaphis plantaginea Passerini, the rosy apple aphid (RAA) and increases the abundance of its natural enemies (NEs) in an apple orchard in the south of France. Laboratory tests confirmed that both CPs altered RAA reproduction performance. In orchards, they attracted more NEs around the pots and at some dates in the aphid colonies near the pots in both years (apart from basil in 2019), without a significant reduction in aphid populations in 2018. In contrast, in 2019, the number and spatial expansion of aphid colonies were significantly lower, close to basil. Further investigation is needed to disentangle the mechanisms explaining the observed effects (e.g., repellent action in autumn, etc.) but the results highlight the potential of CPs to control aphids in orchards and contribute to agroecological production of apple. Thus, this study shows the potential of CPs in a strategy combining aphid repellency and NEs attraction to control aphids in orchards, provided that CP installation lasts over several consecutive years. © 2024 Society of Chemical Industry.

Habitat Modification Alters Food Web Interactions with Focus on Biological Control of Aphids in Apple Orchards

To date, direct interactions between pests and natural enemies are often considered in biocontrol programs. Recently there has been an increase of evidence for the importance of third-party mediated indirect interactions in determining the population dynamics of insects. Predicting the strength of such interactions remains a central challenge in biocontrol assessments. Here, two field experiments were performed in two years to investigate to which extent Dysaphis plantaginea Passerini, Aphis pomi De Geer, and Myzus cerasi Fabricius might indirectly interact through shared natural enemies and ants. We first studied the population dynamics of target insects in isolated orchards of apples and cherries. Secondly, we investigated how the spatial coexistence of aphid-infested cherries can indirectly affect the population dynamics of apple aphids via natural enemies and ants. In the first experiment, nine parasitoid species were recorded on apple and cherry aphids, among them were three species in common. Six predatory families were found on cherry and apple aphids, while only one ant species, Lasius niger L., was found associating with these aphids. In the second experiment, temporal variation in the natural enemy-mediated apparent competition between M. cerasi and apple aphids was found. The cherry aphid is likely to be an important source of natural enemies that attack apple aphids early in the season. Significantly reduced numbers of ants associating with apple aphids in the intercropping habitat were found. Our results emphasize the importance of considering indirect interactions in the designing of pest management strategies.

Flower diet enhances Adalia bipunctata larval development significantly when prey is limited

AbstractPredaceous coccinellids can feed on non‐prey food, but the ecological value of this feeding to maintain a coccinellid population is not well understood. Prey density can vary greatly in the field, whereas non‐prey food sources such as pollen and nectar are more predictable. In the present study, Adalia bipunctata L. (Coleoptera: Coccinellidae) larval performance on pure and mixed diets of a high‐quality non‐prey food with varying amounts of prey was investigated. Rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae), served as prey in the experiment and was given to A. bipunctata larvae either ad libitum as a surplus diet or as a limited diet, the amount of which was selected so that it would limit larval development, according to a pilot study. Flowers of buckwheat, Fagopyrum esculentum L. (Polygonaceae), a high‐value floral diet, served as the non‐prey food. Newly hatched A. bipunctata larvae were reared on each of five diets: (1) flowers only, (2) limited prey only, (3) limited prey plus flowers, (4) surplus prey only, (5) surplus prey plus flowers. Larval survival, developmental time, and adult dry weight were measured. The addition of floral diet had a significant positive impact on A. bipunctata larval survival and development when prey diet was limited, survival ratio was 6× higher and developmental time was 25% shorter. In conclusion, A. bipunctata immature development can benefit from a floral diet supplemented to a prey diet, which indicates that the use of flowers in cropping systems can help to enhance biocontrol services by A. bipunctata.

Does combining Forficula auricularia L. (Dermaptera: Forficulidae) with Harmonia axyridis Pallas (Coleoptera: Coccinellidae) enhance predation of rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae)?

A good knowledge of interactions between natural enemy species is necessary for effective implementation of biological control programmes. This laboratory study aimed at assessing the outcome of intraguild interactions between two generalist predators frequently observed in the colonies of the rosy apple aphid (RAA), Dysaphis plantaginea Passerini (Hemiptera: Aphididae). The level of complementarity between these two species was estimated by the comparison of their individual and combined predation on RAA. Predation by 1st (H1) to 4th (H4) instar larvae of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) and 3rd (F3) and 4th (F4) instar nymphs of Forficula auricularia L. (Dermaptera: Forficulidae) was evaluated for 24 h in Petri dishes using seven different densities (5, 10, 25, 50, 75, 100 and 200) of 3rd instar nymphs of RAA. Both predator species were more voracious as their age increased. The satiation level, i.e. the highest number of consumed RAA, reached on average of 17.8, 36.3, 49.4, 79.6, 62.9 and 84.3 aphids per day for H1, H2, H3, H4, F3 and F4, respectively. In the combined treatments, there was little evidence of intraguild predation. Only 2.9% of H1 and H2 died or disappeared at low RAA densities (≤25 aphids). At the non-limiting RAA density of 200, we observed a slight agonistic interaction with 7.9% less RAA consumption when the two predators were in the same arena than the sum of their individual consumptions. However, this effect was very small and was largely outweighed by the benefits of using these two predators in combination to increase prey consumption. For the other six RAA densities, predators in combination consumed a high proportion (>90%) of RAA. Our results point to the use of combinations of these two predator species, especially of their oldest instars, as promising aphidophagous candidates in early spring against RAA.

Aphid-infested beans divert ant attendance from the rosy apple aphid in apple-bean intercropping

Ecological intensification of cropping systems aims at restoring multi-functionality while supporting current productivity levels. Intercropping is a form of ecological intensification involving ecological processes beneficial to farmers that do not take place in monocultures. Thus, it represents a practical approach to decrease the use of synthetic inputs such as insecticides in cultivated systems. Whereas insecticide reduction via intercropping-facilitated suppression of aphids is reported in literature, the majority of published studies focussed on herbaceous crops. Thus, the effect of intercropping on aphid populations of cultivated trees remains largely unaddressed. In this study we hypothesized that intercropping a specific companion plant within perennial crops would divert ant attendance from an aphid attacking the crop to another aphid feeding on the newly introduced plant, reducing aphid damage on the crop. We tested our hypothesis in the system of apple (Malus domestica Borkhausen), the rosy apple aphid (Dysaphis plantaginea Passerini) and the black garden ant (Lasius niger L.). Bean plants (Vicia faba) with the black bean aphid (Aphis fabae Scopoli) were intercropped within apple trees inoculated with D. plantaginea. We measured ant attendance, aphid development and survival as well as honeydew composition on both plant species through semi-field and field experiments. The majority of ants chose to attend A. fabae over D. plantaginea in the semi-field experiment with potted plants. In the orchard, a larger majority of scouts were scored on A. fabae over D. plantaginea. A higher number of D. plantaginea colonies remained active in the apple control, whilst they were almost eradicated by intercropping. Although chemical analyses of honeydew disclosed differences in the carbohydrate and amino acid profiles between aphid species, the difference in honeydew composition did not explain the preference for A. fabae. Ants did not discriminate between the two honeydew mimics both in laboratory and field bioassays. Our results showed the potential of intercropping apple trees with beans as a method to reduce ant attendance and thus colony survival. We propose that intercropping represents a bottom-up approach towards ecological intensification of perennial crops. Together with other ecosystem-based measures such as habitat management, intercropping should be considered when planning ecosystem redesign to increase biological control of pests.

Spiders (Arachnida: Araneae) in organic apple (Rosaceae) orchards in southeastern France

Abstract The role of spiders (Arachnida: Araneae) in biological control programmes has received less attention than that of insect natural enemies. The aim of this two-year study was to obtain descriptive data on spider spring field population structure and dynamics. The study was carried out in one insecticide-free and four organic apple orchards in southeastern France. Rolls and bands of corrugated cardboard near the ground and shoots infested with Dysaphis plantaginea (Passerini) (Hemiptera: Aphididae) in the tree canopy were used to sample spiders. Thirty-three spider species belonging to 14 families were identified from both sampling methods. Cheiracanthium mildei Koch (Araneae: Cheiracanthiidae) was clearly the predominant arboreal spider species in aphid-infested shoots (>57%). More than half of the spiders recorded in cardboard bands belonged to three species Drassodes pubescens (Thorell) (Araneae: Gnaphosidae), Pseudeuophrys erratica (Walckenaer) (Araneae: Salticidae), and Icius hamatus (Koch) (Araneae: Salticidae). Salticidae (39.9%) and Gnaphosidae (23.4%) families dominated significantly the spider assemblages observed in the cardboard rolls and were present on almost all sampling dates. However, in the two shelter types, the spider abundance curve clearly had a poly-modal shape. This may be due to the sequential arrival of some spider species or their dominance in a certain period of our study.

Influence of the margin vegetation on the conservation of aphid biological control in apple orchards

The influence of three margin strip treatments (wildflower strips, grass strips and spontaneous vegetation) adjacent to apple orchards on the biological control of Dysaphis plantaginea Passerini (Hemiptera: Aphididae) was compared during two consecutive years. The wildflower strips provided the highest amount of floral resources. Within the margin strips, hoverflies responded positively to higher resource provisioning whereas ladybird abundance did not differ between strip treatments. Within the orchards, the presence of parasitoids, hoverflies, and ladybirds in aphid colonies and the predation of sentinel aphids were not significantly affected by the adjacent strip treatments. The number of natural enemies observed in aphid colonies was mainly driven by aphid number. Aphid numbers were higher close to the margin strips suggesting that aphid colonization from orchard edges may counteract the positive effect of wildflower strips on natural enemy abundance and on a reduction of aphid infestation. The results confirm the positive influence of floral resource provisioning by wildflower strips on the conservation of aphid natural enemies, but also suggest that effects of wildflower strips on aphid regulation inside orchards are not very strong compared with spontaneous vegetation naturally occurring in the margins.

Identification of candidate genes at the Dp-fl locus conferring resistance against the rosy apple aphid Dysaphis plantaginea

The cultivated apple is susceptible to several pests including the rosy apple aphid (RAA; Dysaphis plantaginea Passerini), control of which is mainly based on chemical treatments. A few cases of resistance to aphids have been described in apple germplasm resources, laying the basis for the development of new resistant cultivars by breeding. The cultivar ‘Florina’ is resistant to RAA, and recently, the Dp-fl locus responsible for its resistance was mapped on linkage group 8 of the apple genome. In this paper, a chromosome walking approach was performed by using a ‘Florina’ bacterial artificial chromosome (BAC) library. The walking started from the available tightly linked molecular markers flanking the resistance region. Various walking steps were performed in order to identify the minimum tiling path of BAC clones covering the Dp-fl region from both the “resistant” and “susceptible” chromosomes of ‘Florina’. A genomic region of about 279 Kb encompassing the Dp-fl resistance locus was fully sequenced by the PacBio technology. Through the development of new polymorphic markers, the mapping interval around the resistance locus was narrowed down to a physical region of 95 Kb. The annotation of this sequence resulted in the identification of four candidate genes putatively involved in the RAA resistance response.

Alternative to azadirachtin to control Dysaphis plantaginea Passerini (Hemiptera: Aphidae) in organic apple production

The rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphidae), is a major pest of apple trees. In organic apple production, this aphid is commonly controlled by spraying azadirachtin, targeted against fundatrices in spring. However, this is the only active ingredient that has proved effective for the management of this pest in organic production, and therefore it would be desirable to provide other alternatives. In this study, several treatments (pyrethrins, garlic extract, kaolin, potassium salts of fatty acids, and defoliation) applied in autumn to prevent or reduce the presence of winged forms and oviparae in the trees were compared. In addition, applications of paraffin oil and lime sulphur in winter against rosy apple aphid eggs were tested. The trials were carried out in Catalonia (NE of Spain) from 2005 to 2010. The results showed that pyrethrins reduced the presence of rosy apple aphid oviparae but they did not have a knockdown effect. The time of application was crucial since the spring infestation was kept under control only when pyrethrins were sprayed throughout the period when oviparae were in the apple trees. It was demonstrated for the first time that pyrethrins sprayed in autumn can prevent outbreaks of rosy apple aphid and can therefore provide an alternative to azadirachtin. As a result, the rosy apple aphid can be successfully managed in countries where azadirachtin is not approved and the likelihood of development of resistance will be reduced since more than one active ingredient will be available for the control of this pest.

Feasibility and efficacy of a new approach for controlling populations of the rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae) in south-eastern France

ABSTRACTEpisyrphus balteatus De Geer (Diptera: Syrphidae) is one of the most efficient biocontrol agents against Dysaphis plantaginea Passerini (Hemiptera: Aphididae) in apple orchards due to its early arrival. However, releasing flying predators in open orchards may be risky. We thus evaluated the combined effects of biological (early release of syrphids) and physical (Alt'Carpo nets) methods for controlling aphids under orchard conditions assuming that syrphids released under the nets will be able to survive and reproduce. Five experimental treatments containing two rows of trees each were set up in a pesticide-free orchard containing two different apple cultivars. For each cultivar, E. Balteatus adults were released (25, 40 and 90 adults per row) into three treatments, which were covered with nets, and two treatments were maintained free as controls (with and without nets). The releases, mainly in treatment 90, had a small effect on the development of the aphid population compared to netted control trees, especially towards the end of the study period when some of the differences were significant. This study demonstrated that E. balteatus adults can be successfully released under nets since we did observe an accumulation in the offspring of released individuals, mainly in treatments 40 and 90.

Individual and combined effects of the generalist Forficula auricularia and the specialist Episyrphus balteatus on Dysaphis plantaginea – are two predators better than one?

AbstractThe interactions between specialist and generalist natural enemies could affect the success of biological pest control, especially in augmentation programmes. The aim of this laboratory study was to quantitate the individual and combined effects of the generalist predator Forficula auricularia L. (Dermaptera: Forficulidae) and the specialist Episyrphus balteatus De Geer (Diptera: Syrphidae) on the population growth of the rosy apple aphid (RAA), Dysaphis plantaginea Passerini (Hemiptera: Aphididae). The experiment was carried out using apple seedlings with five levels of initial RAA infestation. In most cases, both predator species (alone and in combination) were able to reduce RAA densities or to keep them at their initial level. This suppression effect was greater when RAA densities were low and resulted in near‐complete mortality of the RAA colony after 4–6 days. Without predators, RAA population size almost doubled within 10 days, whereas with predators, RAA population size was reduced by about 20 (alone) and 50% (in combination). Although RAA numbers in the two‐predators treatment were ca. 81% of RAA numbers in the one‐predator treatment for pooled numbers across dates and densities, the difference between the two treatments was not significant. Some predator mortality occurred with first and second instars of the syrphid larvae and only at the two lowest initial RAA infestation levels. This mortality may be explained by inadequate food supply, intraguild predation (IGP) (in 13.3% of the possible cases), or both. However, the incidence of IGP under natural conditions could be even less frequent, as both predators were never observed on the same leaf.

The feasibility and efficacy of early-season releases of a generalist predator (Forficula auricularia L.) to control populations of the RAA (Dysaphis plantaginea Passerini) in Southeastern France.

Augmentative biological control is not commonly used in commercial orchards. We used an exclusion system to evaluate the potential of early-season releases of the European earwig (Forficula auricularia L., Dermaptera: Forficulidae) for control of the rosy apple aphid (Dysaphis plantaginea Passerini, Hemiptera: Aphididae) in the spring of 2009 in two pesticide-free apple orchards. In order to conduct this experiment we successfully reared earwigs with a high survival rate of nymphs (more than 96%) which may have commercial application. There were three treatments in the study: (i) a 'release treatment' where we confined the released earwigs in the canopy by using a barrier system; (ii) an 'exclusion treatment' where we blocked free access of earwigs into the canopy using the same barrier system; and (iii) a 'control treatment' that represented the natural situation. Contrary to expectations, earwig releases did not reduce D. plantaginea populations. In general, the abundance of natural enemies and their groups did not differ significantly among treatments, except for earwigs. We observed that the exclusion systems we used successfully kept both earwigs and ants away from tree canopies; total numbers on trees in the 'exclusion treatment' were significantly lower than on the other two treatments. Due to the complexity and difficulty of evaluating augmentative releases of natural enemies in open orchard conditions, we conclude that new technical approaches to control site conditions are needed when conducting such studies.

Effect of management strategies on arthropod communities in the colonies of rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae) in south-eastern France

Apple orchardists are encouraged to adopt pest control strategies with less pesticide use and thus less harmful environmental impacts. In this study, we compared the possible effects of organic, integrated pest management (IPM), and conventional protection strategies on the rosy apple aphid-ant-natural enemy communities in 12 apple orchards in south-eastern France in 2008 and 2009. The organic orchards had the smallest aphid populations and the most diverse and abundant natural enemy populations compared with the other orchards. More diverse and abundant natural enemy populations were observed in IPM compared with conventional orchards. In 2009, the aphid abundance in IPM orchards was, however, significantly higher than in conventional orchards. No significant differences in ant densities were observed among protection strategies in 2008, but in 2009, these densities were significantly higher in conventional compared with organic orchards. Three predator groups were the most common: Coccinellidae, Forficulidae, and Syrphidae. These were significantly more abundant in organic orchards than in the other orchards, except in 2008 when there was no significant difference in syrphid and earwig abundance between organic and IPM orchards. Parasitoids were significantly more abundant in organic orchards in 2009 but not in 2008. The smaller number of aphids in organic orchards appears to results from the absence of toxic insecticides and thus to increased natural enemies compared with other orchards. Our findings emphasize the importance of no or less intensive synthetic pesticide usage for the conservation of natural enemies biodiversity and biological control of rosy apple aphid in apple orchards.

Can artificial nectaries outcompete aphids in ant-aphid mutualism? Applying artificial sugar sources for ants to support better biological control of rosy apple aphid, Dysaphis plantaginea Passerini in apple orchards

The rosy apple aphid, Dysaphis plantaginea Passerini, is a serious pest in apple orchards. It establishes close facultative mutualistic relationships with ants. An experiment manipulating the presence of the common black ant, Lasius niger (L.), in colonies of D. plantaginea in the canopy of apple trees by provision of ant-feeders (artificial nectaries) containing sucrose solution as an alternative sugar source were conducted in apple orchards in the United Kingdom and Hungary to test if this method can regulate densities of D. plantaginea below the threshold for economic damage through enhancing the activity of its natural enemies. Apple trees with physical ant-exclusion (sticky barriers) and without any treatment were used as controls.Ant-feeding with sucrose solution, in a similar way to physical ant exclusion, effectively reduced the numbers of ants tending D. plantaginea colonies and it consequently resulted in a reduction in D. plantaginea populations in both studies. In spite of marked differences in natural enemy abundance and composition found in UK and Hungary, both treatments caused significant increases in natural enemy (e.g. Dermaptera, Heteroptera, Coccinellidae, Syrphidae) pressure on D. plantaginea. Our results show that supplementary sugar feeding of ants is a successful method for supporting biocontrol of rosy apple aphid through enhancing the effectiveness of its natural enemies. This new biocontrol approach to control aphids in apple orchards is likely to substantially reduce the need for aphicide sprays in orchards and is compatible with organic pest control. The implications of these results for supporting better biological control of aphids in apple orchards are discussed.

Sugar feeding of the common black ant, Lasius niger (L.), as a possible indirect method for reducing aphid populations on apple by disturbing ant-aphid mutualism

The rosy apple aphid, Dysaphis plantaginea Passerini, and the green apple aphid, Aphis pomi De Geer, are serious pests of apple and are commonly found together as pests in apple orchards. Both species establish mutualistic relationships with ants.Two experiments manipulating the presence of the common black ant, Lasius niger (L.), visiting aphid colonies by ant-exclusion with sticky barriers, or ant-feeding with honey as an alternative sugar source, were conducted, one in an apple orchard in the United Kingdom and one in an apple orchard in Hungary to test if these methods can reduce aphid infestations on apple trees.The exclusion of ants reduced D. plantaginea and A. pomi populations in both experiments. It caused significant increases in natural enemy pressure on both aphid species in the experiment in the UK and on A. pomi in the experiment in Hungary.Ant-feeding with honey reduced the numbers of ants tending D. plantaginea colonies, and it consequently resulted in a reduction in D. plantaginea populations in both experiments. The supplementary feeding of ants was more effective in reducing D. plantaginea than A. pomi. This was probably due to the greater intensity of ant attendance on A. pomi than on D. plantaginea colonies when both species were present together.Our results showed that supplementary sugar feeding of ants is a successful method for supporting biocontrol of apple aphids through enhancing the effectiveness of their natural enemies. However, the species of aphid targeted and the design and position of the feeder could affect the efficacy of this biocontrol method.

Biology of rosy apple aphid, Dysaphis plantaginea Passerini (Homoptera: Aphididae), on its summer hosts in eastern Washington

In surveys of apple-production areas east of the Cascade Mountains of Washington, broadleaf plantain, Plantago major Linnaeus (Plantaginaceae) was common throughout while narrowleaf plantain, P. lanceolata Linnaeus, was most common south of Orondo, Douglas County (47.7° latitude). Rosy apple aphid was the most common aphid on these two herbaceous plants; however, colonies were scarce, on only 19% of broadleaf and 11% of narrowleaf plantain samples. Colonies were also generally small, fewer than 25 individuals. Adult rosy apple aphid was collected on plantain from late May through October. Adults reached their highest levels in July before declining in August. Colonies increased again in September and October. Relatively few predators (mainly syrphids) and parasitoids (two species of Aphidius) were found on plantain. On apple, the most common predators were the mirid Campylomma verbasci (Meyer-Dür), earwigs, coccinellids, cecidomyiids and syrphids; the most common primary parasitoid was Lysiphlebus testaceipes (Cresson). Secondary or hyperparasitoids consistently outnumbered the primary parasitoids. Plantains growing outside of orchards but within 1 km of apple trees had the highest incidence of RAA infestation. The potential for management of RAA on its summer hosts is discussed.

The role of natural enemies on the population dynamics of the rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae) in organic apple orchards in south-eastern France

Efficient pest control using conservation strategies requires sound knowledge of the dynamics of the pest and its natural enemies (NE). But the role of natural regulation under natural conditions is not easy to prove. The rosy apple aphid (RAA) Dysaphis plantaginea is the most detrimental aphid in organic apple orchards. Our aim was to determine whether and to which point the abundance and composition of arthropod communities associated with aphid colonies affects RAA population dynamics. The present study, based on weekly observations of marked and infested apple shoots was carried out from April to June in 2008 and 2009 in one experimental insecticide-free apple orchard and four organic commercial orchards located in south-eastern France. NE populations were the most diverse (7.3 taxonomic groups for 50 shoots) and abundant (1.44 individuals per shoot) in the experimental orchard compared to organic orchards (3.8 groups for 50 shoots and 0.7 individuals per shoot). The large RAA populations per shoot (more by 1.7-fold) observed in two of the five orchards were presumably related to a lower number of NE (less by 1.9-fold) and a high abundance of ants (more by 6.2-fold). Among the main NE groups, syrphids arrived first, followed by coccinellids and earwigs. Parasitism rates, mainly due to Ephedrus sp. (Braconidae), were between 0.66% and 6.93%. Based on their precocity and abundance, syrphids appeared to be the most efficient group of NE under the study conditions. By surveying the same shoots weekly we could demonstrate that RAA population dynamics were strongly affected by the presence of NE. This predatory effect was however not sufficient to prevent damage to the apple trees. New management practices aimed at favoring natural regulation, especially augmentative approaches, need to be developed.

Role of ants in structuring the aphid community on apple

1. The aphids Dysaphis plantaginea Passerini, Aphis spp. (Aphis pomi De Geer and Aphis spiraecola Patch), and Eriosoma lanigerum Hausmann are commonly found together in apple orchards. Ants establish a mutualistic relationship with the myrmecophilous aphids D. plantaginea and Aphis spp. but not with E. lanigerum.2. Field surveys and one experiment manipulating the presence of ants and the aphid species were conducted to test the hypothesis that ants play a role in structuring the community of these aphids on apple.3. Ants tended D. plantaginea and Aphis spp. but not E. lanigerum colonies. In the field, D. plantaginea performed better in the presence of ants while no effect was observed in Aphis spp. Contrarily, populations of Aphis spp. in the manipulative experiment performed better in the presence of ants while no differences were observed for D. plantaginea. Such differences between field and manipulative conditions could be related to thermal tolerance, phenology, and life cycles. In contrast, populations of E. lanigerum were reduced in the presence of ants.4. Ants also had a significant negative effect on the abundance of natural enemies, which could partially explain the benefits to the tended aphids. However, while ants did not provide a benefit to Aphis spp. when it was reared alone, in the presence of other species ant attendance increased Aphis abundance by 256% and simultaneously reduced E. lanigerum abundance by 63%. Therefore, ants benefited Aphis by reducing competition with other aphid species, which involves a different mechanism, explaining the benefit of ant attendance. Considering all the aphid species together, ants had a net positive effect on aphid abundance, which was consequently considered harmful for the plant.5. Our results highlighted the role that ants play in structuring apple aphid communities and give support to the observed pattern that ants can benefit tended aphids while simultaneously reducing the abundance of untended herbivores.

Tolerance of some scab-resistant apple cultivars to the rosy apple aphid, Dysaphis plantaginea

Rosy apple aphid (RAA), Dysaphis plantaginea Passerini (Homoptera: Aphididae), is a major apple pest that is normally controlled by insecticide sprays. The use of tolerant cultivars to reduce damage of this aphid would contribute to a non-chemical crop protection. This study evaluated the susceptibility of nine scab-resistant apple cultivars (‘Dayton’, ‘Freedom’, ‘Galarina’, ‘GoldRush’, ‘Jonafree’, ‘Liberty’, ‘Priscilla’, ‘Redfree’ and ‘Williams’ Pride’) to RAA. Greenhouse trials and field observations were conducted for 2 years. Significant differences were observed among cultivars in aphid abundance and damage level 21 days after an infestation in the greenhouse. ‘GoldRush’ and ‘Galarina’ did not show typical leaf-rolls induced by RAA and were considered tolerant to this aphid species. Some cultivars showed low susceptibility while the cultivars ‘Jonafree’ and ‘Redfree’ turned out to be highly susceptible. Aphid abundance and damage levels were positively correlated. Field surveys confirmed greenhouse results. Growing cultivars resistant to scab and tolerant or only slightly susceptible to RAA would reduce pesticide use and increase opportunities for sustainable apple production.

Colonization of apple orchards by predators of Dysaphis plantaginea: sequential arrival, response to prey abundance and consequences for biological control

Episyrphus balteatus (DeGeer) (Diptera: Syrphidae), Adalia bipunctata (L.) (Coleoptera: Coccinellidae) and Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) are the three most abundant natural enemies of Dysaphis plantaginea Passerini (Homoptera: Aphididae) in Asturian (NW Spain) apple orchards. They attack this aphid in sequence: E. balteatus arrived first, followed by A. bipunctata and then by A. aphidimyza. The cecidomyiids arrived too late to have a regulating effect. The syrphids laid an average of 2.3 ± 1.7 eggs per aphid colony and the coccinellids 18.4 ± 9.9 regardless of the degree of the infestation rates of the apple shoots. This value corresponds to the size of an egg batch laid by one female. Therefore, these aphid predators did not respond numerically to the abundance of the pest. The results of this study indicate that natural populations of syrphids and ladybird beetles are unable to control D. plantaginea, and therefore a more complex strategy than waiting for natural enemies is required.