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 Summary

The 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.

Abstract

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.

Tunnel entries and a killing agent uncover the importance of fly retention in Drosophila suzukii traps

BACKGROUND

Spotted wing drosophila (SWD), Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is a pest of stone and small fruits causing considerable economic losses. Current management strategies rely primarily on calendar-based spraying, owing to the poor relationship between monitoring data and damage levels, and the lack of success of mass-trapping tools. The aim of this study was to evaluate different trap models for SWD, with an emphasis on their fly-retention capacity. To this end, we examined and quantified the added value of two fly-retaining trap features; tunnel entries to impede escape and an insecticide-coated inner surface as a killing agent.

RESULTS

An insecticide-coated inner surface resulted in significantly higher trap retention after 24 h in the laboratory (4.9- to 7.4-fold greater, depending on trap type) compared to a noncoated trap. Trapping efficacy was significantly improved in field trials by such a killing agent in the trap (1.2- to 4.5-fold greater). Tunnel entries significantly improved trap retention in the laboratory and field (by 1.5-fold).

CONCLUSION

The outcomes of this study clearly reveal the substantial impact of the fly-retention capacity of SWD traps on their overall capture performances. It was demonstrated for the first time that an insecticide-coated inner surface as a killing agent significantly improves trap efficacy for SWD. This finding can readily be implemented in any trap model to improve monitoring and mass trapping of SWD. Also tunnel entries were shown to have a significant influence on the fly retention and, hence, substantially enhance trapping efficacy.

Anthonomus spilotus (Coleoptera: Curculionidae): new to the Belgian fauna

Short notes have no abstract.

Entomopathogenic nematodes as biocontrol agents of insect pests in orchards

Abstract

Entomopathogenic nematodes (EPNs) are increasingly being used as biological control of insect pests due to their successful biocontrol activity against various economically important insect pests. Despite the growing success of EPNs, their effective use in orchards remains rather scarce. The principal limiting factors for the practical implementation of EPNs in Integrated Pest Management (IPM) programmes in orchards are their reduced control activity and persistence due to low-temperature regimes and desiccation, in particularly when applied against aboveground pest stages. However, recent advances in formulation technology, application strategy (with emphasis on improved persistence of the applied EPNs) and gradually acquired knowledge on optimal implementation strategies already have extended - and in the future most likely will further expand - the practical adoption of EPNs in pest management programmes in orchards. A successful implementation of EPNs in orchards requires that their usage fits into an IPM strategy. Interactions between EPNs and other biological or chemical control agents can be synergistic, additive or antagonistic, depending on the specific chemical and biological agents, as well as their rates and timing and host species. In this article, the most important aspects and features of EPN applications in orchards are reviewed.

Validation of Individual-Based Markov-Like Stochastic Process Model of Insect Behavior and a "Virtual Farm" Concept for Enhancement of Site-Specific IPM

The paper reports application of a Markov-like stochastic process agent-based model and a "virtual farm" concept for enhancement of site-specific Integrated Pest Management. Conceptually, the model represents a "bottom-up ethological" approach and emulates behavior of the "primary IPM actors"-large cohorts of individual insects-within seasonally changing mosaics of spatiotemporally complex faming landscape, under the challenge of the local IPM actions. Algorithms of the proprietary PESTonFARM model were adjusted to reflect behavior and ecology of R. cerasi. Model parametrization was based on compiled published information about R. cerasi and the results of auxiliary on-farm experiments. The experiments were conducted on sweet cherry farms located in Austria, Germany, and Belgium. For each farm, a customized model-module was prepared, reflecting its spatiotemporal features. Historical data about pest monitoring, IPM treatments and fruit infestation were used to specify the model assumptions and calibrate it further. Finally, for each of the farms, virtual IPM experiments were simulated and the model-generated results were compared with the results of the real experiments conducted on the same farms. Implications of the findings for broader applicability of the model and the "virtual farm" approach-were discussed.

SIDE-EFFECTS OF COMMONLY USED CROP PROTECTION PRODUCTS IN PEAR ON TWO BENEFICIAL MIRIDAE BUGS

Anthocoris nemoralis, Anthocoris nemorum and Orius spp. are not the only beneficial predatory bugs inhabiting pear orchards in Belgium. Quite often, the Miridae bugs Heterotoma spp. and Pilophorus spp. can be found during spring and summer in these orchards, thereby feeding on several pests such as psyllids, aphids, spider mites, ... . Side-effects are usually assessed on Anthocoris and Orius spp., but due to the potential importance of Miridae bugs in pest reduction, we tested some commonly used crop protection products used in pear cultivation on Heterotoma planicornis and Pilophorus perplexus (residue-based tests in petri-dishes). One day after treatment, mortalities already could be observed for some products. Seven days after treatment, abamectin, deltamethrin and thiacloprid were considered the most toxic products as stated by the IOBC classification. This outcome was then analysed with regard to different treatment schedules, providing insights in potential side-effects on crop protection treatments on the composition of beneficial fauna in pear orchards.

POPULATION DYNAMICS OF DROSOPHILA SUZUKII (DIPTERA: DROSOPHILIDAE) IN BELGIUM IN 2013

The vinegar fly Drosophila suzukii (Matsumura) (Diptera Drosophilidae), spotted wing drosophila, is a new invasive fruit pest that recently became established in Europe. Unlike other fruit flies that typically only infest overripe and rotten fruit, D. suzukii females oviposit in ripe fruit leading to considerable economic losses of fruit during production. In 2011 and 2012 D. suzukii was detected at several places in Belgium. In 2013, a large-scale monitoring in frame of the project "FLY ALERT" (FOD) was executed using traps with liquid attractant (apple cider vinegar) at more than 100 locations across Belgium during the whole fruit growing season. At 16 locations we also compared the efficacy of a 'bottle type' trap with a 'cup type' trap. The results show that D. suzukii has expanded its distribution in Belgium. Remarkably, in 2013 as well as in 2012 the first detections were made only in the second part of the growing season (August) and the populations reached their peak only at the very end of the season (November). In the bottle type trap the first flies were caught 2-3 weeks earlier than in the cup type trap. In addition, also the population peaks were on average 1 week earlier when monitored with the bottle trap compared to when monitored with the cup trap. In 2014, after an exceptional mild winter adult D. suzukii flies were continuously detected throughout the winter and early spring. The implications of these findings for the phenology of D. suzukii in the Northwest climate region of Europe are discussed.

BIOLOGY AND CONTROL OF THE APPLE MEALYBUG PHENACOCCUS ACERIS (SIGNORET) IN BELGIUM

Although in general very rare, some outbreaks of the apple mealybug Phenococcus aceris (Signoret) (Hemiptera: Pseudococcidae) were reported in the Belgian fruit growing area recently. This insect is known to be geographically widespread, to have a broad host range and to infest apple trees. Damage at harvest is considerable when sooty molds, a consequence of the pest's honeydew production, cover the fruits. Indirect damage of an infection is caused in cherry cultivation through transmission of the Little cherry virus (LChV2). Efficacy trials were executed in infested apple orchards in the Belgian fruit growing area and the life cycle of the pest on apple was studied more into detail. Apple mealybugs are univoltine, overwinter as 2nd instar nymphs inside a white cocoon on the tree (under the bark, in crevices) and leave their overwintering site in early spring (mid March). On sunny days the nymphs become active, move around and attach to start feeding (mid April). After a final moult into the adult form, females lay eggs in a cocoon-like white structure (from flowering on). Following hatching (end May), massive numbers of young nymphs spread out on the underside of the leaves (mid June) where they feed through suction. In order to manage this pest the efficacy of several plant protection products was tested in two infested apple orchards. Results indicated that mortality was high after an application of compounds belonging to the neonicotinoid insecticides. Different application timings and control strategies are possible, with active nymphs being the most vulnerable life stage. The observed degree of parasitation in our trial orchards also indicates a biological control contribution of parasitic wasps that should be taken into account. A decent IPM-strategy based on our results solved the problem in both apple orchards.

Preliminary results on the ability of pentatomidae to transfer fire blight Erwinia amylovora under controlled conditions

With their piercing-sucking mouthparts stink bugs (Heteroptera: Pentatomidae), a major pest in especially organic orchards, create wounds in fruit of pear trees. As Erwinia amylovora (Burrill, Winslow et al.), a wide spread bacterial disease affecting many rosaceous plants including pome fruit trees and hawthorn, enters through openings in flowers, leaves, shoots and fruit, feeding punctures caused by these bugs might be inoculated with Erwinia bacteria. In order to investigate the ability of the bugs Pentotoma rufipes L. and Polomena prasina L. to transmit fire blight, insects were caught in an organically managed orchard without fire blight, brought into contact with artificially inoculated immature pear fruit/slices and transferred to healthy, mechanically wounded pear fruit/slices. After an incubation period potential transmission of bacteria was examined by evaluation of symptom expression (necrosis, ooze production). To assess the presence of bacteria on the exoskeleton of the tested bugs, all bugs were forced to walk on a semiselective nutrient agar medium. In another experiment the viability of Ea on the exoskeleton was tested -after previous contact with ooze- through washing and plating of the wash water. All experiments were conducted under optimal climatological conditions and according to quarantine standards. Results demonstrated the ability of stink bugs to transfer E. amylovora to fruit and the viability of bacteria on stink bugs externally - both under lab conditions.

Control of sawflies in apple and pear in Belgium

In the Belgian fruit growing area, sawflies are generally common but minor pests in pome fruit. Though, intensity and frequency of sawfly damage in apple and pear is increasing the last years in IPM and especially in organic orchards. The main species are apple sawfly (Hoplocampa testudinea Klug) and pear sawfly (Hoplocaompa brevis Klug) and recently also pear shoot sawfly (Janus compressus Fabricius). Here we report efficacy results on all three sawfly species fromtrial of three consecutive years (2011, 2012, and 2013). Flights and embryonic development were monitored and small plot efficacy trials were executed. Control of apple sawfly was complete (97.6% Abbott -trial 2011) when thiacloprid at 120 g/ha LWA was applied at the moment embryos are visible in the sawfly eggs. In 2012, a trial was executed on pear sawfly. Applications with thiacloprid were executed when the embryo was visible in the pear sawfly eggs and earlier at the start of egg laying. At both application timings, 100% Abbott efficacy was reached. A number of other active ingredients were tested at the moment embryos are visible in the sawfly eggs and very interesting efficacy results were reached for thiofanate-methyl, indoxacarb, spinosad, pyrethrins + piperonyl butoxide (PBO) and acetamiprid. In 2013, a preflowering application with pyrethrins + PBO reached the highest control against this pest. The most effective active ingredients of the pear sawfly trial were applied also in a trial on pear shoot sawfly. Efficacies were low or lacking, except for thiacloprid. Thiacloprid is in pear growing in Belgium only registered before flowering and after harvest. Therefore further research is needed to test the effect of earlier applications against this pest. This is a valuable efficacy study on occasionally occurring pests that are able to cause considerable economic losses.

Optimal profit of the parasitation by Aphelinus mali in an IPM complementary strategy for the control of Eriosoma lanigerum

During summer the parasitoid Aphelinus mali may certainly reduce the infestation of woolly apple aphid (Eriosoma lanigerum), but studies on the single interaction rarely indicate sufficient biological control in the period May-June. In this period chemical control by spirotetramat or pirimicarb remains indispensable in order to anticipate on dense migration waves and subsequent colonization of extension shoots by E. lanigerum. The limited parasitation by A. mali around flowering is linked with a delayed emergence from diapause and with a slower reproduction rate than its host. In 2010 and 2011 the first adult flights monitored on yellow sticky traps corresponded perfectly with the currently used prediction models for A. mali. Further accurate monitoring all along the season enabled also to determine a well defined endo-parasitic phase of A. mali occurring after the small peak observed around flowering. During this endo-parasitic phase A. mali larvae reside inside their mummified host. Compounds with higher acute toxicity on A. mali adults, like chloronicotinyl insecticides (CNI's), are preferably positioned here. Selectivity in the time can then be claimed. Respecting this principle, the further parasitation potential of A. mali in summer is not hampered. Preservation of the first peak of flights of A. mali in the pre-flowering period is essential for an exponential flight increase. This is essential for the parasitation of E. lanigerum in summer, which constitutes a valuable complement in the integrated control strategy.