Parasitoid Aphelinus Mali Research Articles

Honeydew Is a Food Source and a Contact Kairomone for Aphelinus mali

Many parasitoids need to feed on sugar sources at the adult stage. Although nectar has been proven to be a source of higher nutritional quality compared to honeydew excreted by phloem feeders, the latter can provide the necessary carbohydrates for parasitoids and increase their longevity, fecundity and host searching time. Honeydew is not only a trophic resource for parasitoids, but it can also constitute an olfactory stimulus involved in host searching. In this study, we combined longevity measurements in the laboratory, olfactometry and feeding history inference of individuals caught in the field to test the hypothesis that honeydew excreted by the aphid Eriosoma lanigerum could serve as a trophic resource for its parasitoid Aphelinus mali as well as a kairomone used by the parasitoid to discover its hosts. Results indicate that honeydew increased longevity of A. mali females if water was provided. Water could be necessary to feed on this food source because of its viscosity and its coating by wax. The presence of honeydew allowed longer stinging events by A. mali on E. lanigerum. However, no preference towards honeydew was observed, when given the choice. The role of honeydew excreted by E. lanigerum on A. mali feeding and searching behavior to increase its efficiency as a biological control agent is discussed.

Exclusion netting affects apple arthropod communities

Exclusion cages can quantitatively demonstrate the value of natural enemies and the biological control services they provide. Currently, in Washington State, enclosing orchards in netting is being evaluated as a pest control method, but these enclosures may also serve as an exclusion cage to natural enemies, thereby disrupting biological control. To test the effects of net enclosures on apple arthropod communities, we conducted a two-year study comparing apple herbivore, predator, and parasitoid densities in caged and uncaged plots (both receiving insecticides) to an untreated check. Effects on the various groups were influenced by size and motility. Densities of larger motile arthropods, including codling moth (Cydia pomonella (L.)), chrysopids, and syrphids, were lower in the caged plots, demonstrating exclusion. Woolly apple aphid (Eriosoma lanigerum (Hausmann)) and its parasitoid Aphelinus mali (Haldeman) densities in the caged plots were over 100-fold greater and 5-fold greater, respectively, than the other treatments. European earwig (Forficula auricularia (L.)), a generalist predator, was more abundant in the caged plots in 2016 but not in 2017. Spider mites were more abundant in the cage treatments for both years, while predatory mites had higher densities in the cages in 2017 only. These outcomes show that net enclosures change the composition of apple arthropod communities through exclusion of certain herbivores and natural enemies. In the case of some pest herbivores (e.g., codling moth), this exclusion is beneficial, but in the case of predators, it is detrimental. This study further demonstrated that exclusion of only part of the natural enemy complex may be sufficient to cause herbivore outbreaks.

Efficacy and Nontarget Effects of Net Exclusion Enclosures on Apple Pest Management.

Management of direct apple pests, such as codling moth, continues to be problematic despite the widespread implementation of behavioral and chemical controls. Apple growers have increased their use of netting to protect fruit from environmental injury, with some structures enclosing the entire orchard. These enclosures represent a new pest management tactic through physical exclusion. We conducted a two-year trial to examine the effects of full exclusion netting on pests and natural enemies of apples. Insect densities and damage in trees under fully enclosed (net) cages were compared with conventionally (insecticide only) treated and untreated plots. Caged plots had 18.1- and 11.4-fold less codling moth damage than the check, and 4.9- and 4.2-fold less damage than the insecticide-only plots in 2016 and 2017, respectively. However, densities of woolly apple aphid and its parasitoid Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) were significantly greater in the caged plots. Densities of earwigs, a typically flightless generalist predator, were not different among treatments, while adults of more mobile flying generalist predators, lacewings and syrphids, were significantly lower in cages compared with uncaged plots. These results demonstrate that although biological control may be partially disrupted, net enclosures have significant potential as a holistic apple management technique.

Towards a Knowledge-Based Decision Support System for Integrated Control of Woolly Apple Aphid, Eriosoma lanigerum, with Maximal Biological Suppression by the Parasitoid Aphelinus mali.

Simple SummaryThe woolly apple aphid Eriosoma lanigerum is an important pest in apple orchards worldwide. At present, effective limitation of woolly aphid populations relies on a good synergy between chemical control treatments and biological suppression by beneficial insects, especially by its main specific natural enemy, the parasitic wasp (parasitoid) Aphelinus mali. In order to reach maximum control levels on woolly apple aphids and avoid negative side effects on A. mali, decision support for the optimal timing and positioning of control treatments is needed. In this study, we developed prediction models that based on the weather conditions (temperature data) can reasonably accurately predict crucial development/activity phases of both insects in the orchard. These prediction models can be utilized to target insecticide sprayings at the most sensitive stage of the pest (woolly apple aphids) and/or to avoid insecticide sprayings with detrimental side effects at the vulnerable stage of the beneficial insect (parasitoid A. mali), as was demonstrated by the outcomes of a field trial in this study.The woolly apple aphid Eriosoma lanigerum (Homoptera: Aphidiae) is an important pest in apple orchards worldwide. Since the withdrawal or restricted use of certain broad-spectrum insecticides, E. lanigerum has become one of the most severe pests in apple growing areas across Western Europe. At present, effective limitation of woolly aphid populations relies on a good synergy between chemical control treatments and biological suppression by beneficial arthropods, especially by its main specific natural enemy, the parasitoid Aphelinus mali (Hymenoptera: Aphelinidae). To develop a knowledge-based decision support system, detailed monitoring data of both species were collected in the field (region of Sint-Truiden, Belgium) for a period of ten years (2010–2020). Aphelinus mali flights were monitored in the field, starting before flowering until the end of the second-generation flight at minimum. The seasonal occurrence of the most important management stages of E. lanigerum, e.g., start of wool production or activity on aerial parts in spring and migration of crawlers from colonies towards flower clusters or shoots, were thoroughly monitored. All obtained data were compared with historical and literature data and analysed in a population dynamics phenological model. Our outcomes showed that the emergence of first-generation A. mali adults (critical for the first parasitation activity and the basis for following A. mali generations in the continuation of the season) can be accurately predicted by the developed model. Hence, this information can be utilized to avoid insecticide sprayings with detrimental side effects at this particular moment as demonstrated by the outcomes of a field trial. In addition, the start of migration of E. lanigerum crawlers towards flower clusters or shoots is accurately predicted by the model. In conclusion, our results demonstrate that the model can be used as decision support system for the optimal timing of control treatments in order to achieve effective control of E. lanigerum with maximal biological suppression by its main natural enemy.

Use of Predators for the Biological control of Eriosoma lanigerum (wooly apple aphids) on apple

Due to increase demand of organic products, biological control methods have gained interest all over the world. Eriosoma lanigerum, commonly known as Wooly apple aphid, is a serious pest of apple. The negative impacts of pesticides on environment and human life make Biological control an important model in the control of the Wooly apple aphid. Some of the biological control agents that have been used in the control of this pest are predators, parasitoids, nectar of flowers etc. The role of the parasitoid Aphelinus mali in the biological control of wooly aphid has been studied by many researchers and found that use of parasitoids Aphelinus mali is not effective when they attack WAA solely in apple orchards. However, efficiency of use of Aphelinus mali in control of WAA is higher when these parasitoids are used along with natural predators (Gontijo, 2011).In recent days, there has been increasing use of predators for the control of aphids. This review focuses on some of the mostly used predators like syrphids, lacewings, earwigs etc. and their role in WAA management. This review focuses on the feeding habits of predators used as biocontrol agents against WAA as well as the occurrence time of these predators before their integration in management practices. Also; this review provides insight into the integration of predators along with other natural enemies for productive control of WAA. This review can be source of information for producers, as well as researchers who are focusing on organic production of apples and integrated wooly aphid management.Int. J. Appl. Sci. Biotechnol. Vol 5(4): 410-414

Predictive thresholds for forecasting the compatibility of Forficula auricularia and Aphelinus mali as biological control agents against woolly apple aphid in apple orchards

The woolly apple aphid (WAA), Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) is a well-known pest of apple orchards world-wide. Several studies have demonstrated variable control of WAA populations by the European earwig, Forficula auricularia (L.) (Dermaptera: Forficulidae) and the WAA parasitoid Aphelinus mali (Halderman) (Hymenoptera: Aphelinidae). We examine whether a beneficial interaction between F. auricularia and A. mali exists and calculate optimal numbers for each species to maintain WAA infestations below acceptable levels. We demonstrate that trees possessing >14 earwigs per trunk trap per week within the first seven weeks post-blossom contained WAA infestations well below acceptable levels. Where these earwig thresholds were not met, a first generation of A.mali greater than 0.5 wasps per tree was required. If these beneficial insect targets were not met, severe WAA infestations occurred. Our findings suggest that if F. auricularia and A. mali numbers exceed these thresholds chemical intervention may not be required.

Field evaluations of the contribution of predators and the parasitoid, Aphelinus mali, to biological control of woolly apple aphid, Eriosoma lanigerum, in Virginia, USA

A series of experiments in Virginia, USA apple orchards evaluated the temporal effects of natural enemies on Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) colonies on potted and mature apple trees. Exclusion cage studies using potted trees resulted in increasing colony numbers on fully caged trees and declining colony numbers or colony extinction on trees exposed to natural enemies. Closer examination of the fate of individual colonies on potted trees produced a similar result and revealed that syrphids oviposited in colonies within two days of tree deployment. Heringia calcarata (Loew) (Diptera: Syrphidae) was the predominant predator and had a greater and more rapid impact on colonies than did the parasitoid Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae). The fate of cohorts of naturally-occurring E. lanigerum colonies on mature trees was examined over two seasons and confirmed that H. calcarata and A. mali were most strongly associated with colony demise.

Complementary suppression of aphids by predators and parasitoids

Biocontrol practitioners have long debated the relative merits of specialist parasitoids versus generalist predators as biological control agents. Predators and parasitoids exhibit a broad array of ecological differences that might lead them to play different, and perhaps complementary, roles in pest suppression. However, predators often feed on parasitoids with the potential to disrupt biological control. We compared suppression of the woolly apple aphid (Eriosoma lanigerum) when attacked solely by the specialist parasitoid Aphelinus mali, to aphid suppression when the parasitoid was joined by a diverse community of generalist predators (primarily earwigs, syrphids, predatory bugs and spiders). In a series of exclusion-cage experiments conducted on apple trees (Malus domestica) placed in the field, we found that the parasitoid alone significantly slowed aphid population growth. However, consistently flat or declining aphid densities were seen only when the parasitoid was paired with the generalist predator guild. This suggested that predators and parasitoid exerted complementary impacts, with the most effective aphid suppression achieved when the two natural enemy classes were present together. Consistent with this observation, percentage aphid parasitism was not consistently reduced in the presence of predators; this implies relatively weak predator–parasitoid interference. Altogether, our results suggest that the conservation of a diverse community of natural enemies, including both predators and parasitoids, is an effective way to strengthen suppression of this, and perhaps other, aphid species.

Evaluating plant volatiles for monitoring natural enemies in apple, pear and walnut orchards

The ability to estimate natural enemy abundance is crucial to the integration of biological control into IPM programs. Traditional sampling approaches for natural enemies are few and most are inefficient, but recent studies suggest attraction of natural enemies to plant volatiles may be a useful proxy for direct sampling. We evaluated various combinations of herbivore-induced plant volatiles and floral volatiles as monitoring tools for natural enemies found in apple, pear, and walnut orchards in California, Oregon, and Washington. In 2010 we used a full factorial experimental designs to evaluate lures for all combinations of acetic acid (AA), acetophenone (AP), phenylacetaldehyde (PAA) and 2-phenylethanol (PE). Of nine natural enemy taxa analyzed, we found syrphid flies responded strongly to PE, but combining AA with PE attenuated trap catch and combining PAA to PE eliminated the activity of PE. Chrysoperla spp. (Chrysopidae) responded strongly to most of the individual compounds and the various interactions between the components allowed multiple ways to achieve roughly the same trap catch. All of the hymenopteran taxa collected responded strongly to PAA, and PAA containing lures were nearly always a component of the top eight lures. A smaller factorial experiment testing all possible combinations of AA, PAA and methyl salicylate (MS) showed that single component AA or MS lures were generally not significantly different than the controls for all taxa tested, but for the hymenopteran taxa, traps baited with MS+PAA performed the best or were not significantly different than the best performing lure. A 2011 trial was conducted to test the influence of the addition of AA and/or MS on previously tested lures. Combining AA or MS with other lures, improved the capture of Chrysoperla spp.; Scaeva pyrastri (L.) (Syrphidae) capture was enhanced when MS was used with PE; and PE was attractive to the three syrphid flies, Chrysoperla spp., and the parasitoid Aphelinus mali (Haldeman) (Aphelinidae). The differential responses to various blends exhibited among taxa show that combinations of plant volatiles can be chosen to increase specificity of attraction to a few taxa or increase the number of species attracted. This flexibility should add to the general value and breadth of use of plant volatile monitoring lures.

Woolly apple aphid Eriosoma lanigerum Hausmann ecology and its relationship with climatic variables and natural enemies in Mediterranean areas.

A multilateral approach that includes both biotic and climatic data was developed to detect the main variables that affect the ecology and population dynamics of woolly apple aphid Eriosoma lanigerum (Hausmann). Crawlers migrated up and down the trunk mainly from spring to autumn and horizontal migration through the canopy was observed from May to August. Winter temperatures did not kill the canopy colonies, and both canopy and root colonies are the source of reinfestations in Mediterranean areas. Thus, control measures should simultaneously address roots and canopy. European earwigs Forficula auricularia (Linnaeus) were found to reduce the survival of overwintering canopy colonies up to June, and this can allow their later control by the parasitoid Aphelinus mali (Haldeman) from summer to fall. Preliminary models to predict canopy infestations were developed.

Estimating Gene Flow between Refuges and Crops: A Case Study of the Biological Control of Eriosoma lanigerum by Aphelinus mali in Apple Orchards

Parasitoid disturbance populations in agroecosystems can be maintained through the provision of habitat refuges with host resources. However, specialized herbivores that feed on different host plants have been shown to form host-specialized races. Parasitoids may subsequently specialize on these herbivore host races and therefore prefer parasitizing insects from the refuge, avoiding foraging on the crop. Evidence is therefore required that parasitoids are able to move between the refuge and the crop and that the refuge is a source of parasitoids, without being an important source of herbivore pests. A North-South transect trough the Chilean Central Valley was sampled, including apple orchards and surrounding Pyracantha coccinea (M. Roem) (Rosales: Rosacea) hedges that were host of Eriosoma lanigerum (Hemiptera: Aphididae), a globally important aphid pest of cultivated apples. At each orchard, aphid colonies were collected and taken back to the laboratory to sample the emerging hymenopteran parasitoid Aphelinus mali (Hymenoptera: Aphelinidae). Aphid and parasitoid individuals were genotyped using species-specific microsatellite loci and genetic variability was assessed. By studying genetic variation, natural geographic barriers of the aphid pest became evident and some evidence for incipient host-plant specialization was found. However, this had no effect on the population-genetic features of its most important parasitoid. In conclusion, the lack of genetic differentiation among the parasitoids suggests the existence of a single large and panmictic population, which could parasite aphids on apple orchards and on P. coccinea hedges. The latter could thus comprise a suitable and putative refuge for parasitoids, which could be used to increase the effectiveness of biological control. Moreover, the strong geographical differentiation of the aphid suggests local reinfestations occur mainly from other apple orchards with only low reinfestation from P. cocinnea hedges. Finally, we propose that the putative refuge could act as a source of parasitoids without being a major source of aphids.

Toxicity of pesticides to <i>Aphelinus mali</i> the parasitoid of woolly apple aphid

The parasitoid Aphelinus mali controls woolly apple aphid (WAA; Eriosoma lanigerum) in New Zealand apple orchards The effects of seven pesticides on A mali exposed to residues on filter paper were assessed in a laboratory bioassay immediately postapplication Spinosad at label rate was moderately to highly toxic but other compounds and lower rates of spinosad had no detrimental effects on A mali Another bioassay incorporating field application and exposure to aged residues on leaves determined the toxicity of carbaryl diazinon indoxacarb and lime sulphur Carbaryl had the greatest residual toxicity to A mali on harvested leaves causing 85 mortality 21 days after application declining to 40 by 28 days In contrast diazinon initially caused high mortality but residues were not toxic 15 days after application while indoxyacarb and lime sulphur were not toxic Minimising the use of pesticides toxic to A mali should benefit the sustainable management of WAA in apple orchards

Biological control of woolly apple aphid, Eriosoma lanigerum (Hausmann), during transition to integrated fruit production for pipfruit in Central Otago, New Zealand

Woolly apple aphid (WAA), Eriosoma lanigerum (Hausmann), and its natural enemies were monitored from 1994 to 2000 on apples at Clyde, Central Otago, New Zealand during the transition from conventional fruit production (CFP), which used broad spectrum insecticides, to integrated fruit production (IFP), which was based on selective insecticides. Populations were compared in orchard blocks under three management regimes: CFP; transition to IFP; and a biological fruit production (BFP) programme which complied with BioGro® organic certification. WAA remained at very low levels in the CFP programme, because of insecticides, and in the BFP programme, primarily because of natural enemies. Transition to IFP was accompanied by a surge in WAA and a slow colonization by natural enemies which took at least four years to reduce the aphid population to acceptable levels. The principal natural enemy that achieved this was the parasitoid Aphelinus mali (Haldemann), assisted by predators whose contribution remained obscure, including the brown lacewing Micromus tasmaniae (Walker) and the European earwig Forficula auricularia L. A single annual application of lufenuron within the IFP programme was not detrimental to any of these natural enemies, although further research is needed to confirm its lack of impact on the lacewing. Lufenuron reduced arboreal predator diversity, as measured by the Shannon-Wiener index, and this was in part due to decline in the populations of the generalist predator Orius vicinus (Ribaut) and the coccinellid mite predator Stethorus bifidus Kapur. Pirimicarb was an effective selective aphicide for integration with the action of the natural enemies of WAA, but a substitute is required, as its use is no longer permitted on export crops. The implications of these findings for the management of WAA in IFP are discussed.

Comparison of a Canadian and a Dutch strain of the parasitoid Aphelinus mali (Hald) (Hym., Aphelinidae) for control of woolly apple aphid Eriosoma lanigerum (Haussmann) (Hom., Aphididae) in the Netherlands: a simulation approach

Woolly apple aphid, Eriosoma lanigerum is one of the important apple pests in the Netherlands. Weather conditions and natural enemies determine whether woolly apple aphid (WAA) will reach pest status. WAA may escape control by natural enemies and therefore it must be controlled using chemical insecticides. To prevent unnecessary applications of insecticides and to promote biological and natural control of WAA more knowledge is needed about the role of natural enemies, weather and their effects on the development of WAA populations. The monophagous parasitoid Aphelinus mali (Hald.) has been introduced into most of apple growing areas to control WAA, but success is variable and depends on climatological conditions. In the Netherlands the level of parasitization is often too low, especially after warm winters. The biological control potential of a strain of A. mali from Nova Scotia (Canada) was compared with a Dutch strain by simulating population growth of both WAA and the Dutch and Canadian strain of the parasitoid for three different years The results indicate that the Canadian strain would perform in general better than the Dutch strain under Dutch weather conditions.

Susceptibility of the woolly apple aphid parasitoid,Aphelinus mali (Hym.: Aphelinidae), to common pesticides used in apple orchards in Israel

The effects of one acaricide (cyhexatin), two fungicides (penconazole and sulfur), and six insecticides (azinphos-methyl, chlorpyrifos, imidacloprid, pirimicarb, triazamate and vamidothion) on the adult stage of the parasitoidAphelinus mali (Haldeman), a parasite of the woolly apple aphidEriosoma lanigerum (Hausmann), were investigated under laboratory conditions. Chlorpyrifos (an organophosphorus insecticide-OP) was found to be highly toxic to the adult wasps. Vamidothion (OP) was more toxic to the parasitoid than azinphos-methyl (OP). On the other hand, both chlorpyrifos and azinphos-methyl were found to be harmless to the immature stages of the parasitoid in a test conducted under semi-field conditions. Of the other insecticides, imidacloprid was more toxic to the adult parasitoid than pirimicarb and triazamate. Neither cyhexatin nor penconazole had a considerable toxic effect upon the parasitoid. In contrast, sulfur was found to be moderately toxic to the parasitoid under laboratory conditions, as well as in a field survey in which we followed populations ofE. lanigerum andA. mali parasitization in sulfur-treated plots, and in a plot treated withAmpelomyces quisqualis Ces., a fungus antagonist to powdery mildew. The implications of these results to IPM programs of apple orchards in Israel are discussed