The question of whether food webs are resource or predation controlled is crucial for the development of sustainable IPM strategies in agriculture. Many IPM studies focus on top–down control, while little is known about bottom–up effects. Here, we unravelled the bottom–up interactions between rosy apple aphid (RAA) Dysaphis plantaginea and 13 apple cultivars in north-eastern Belgium. Population dynamics, apple leaf damage, preference and performance measurements were used to determine the interactions between RAA and apple cultivars. Seasonal abundances and RAA-infested shoots were significantly affected by the cultivar. The cultivars Fuji, Granny Smith, Jonagold and Cripps Pink harboured clearly higher numbers of aphids compared to other cultivars, especially Red Delicious. Regarding leaf damage degree, Fuji was significantly the most impacted, while the lowest damage was recorded on Red Delicious. The potential apparent competition among apple cultivars was evaluated using RAA overlap diagrams. By acting as a potential source of RAA, a particular cultivar can considerably affect other nearby cultivars. In host selection bioassays, significant differences in the choice behaviour of RAA were found in the laboratory for different apple cultivars. Other important findings from the reproduction–offspring performance bioassays revealed that while Fuji stimulated high production of nymphs, their development remained retarded on Fuji, compared to especially Boskoop on which significantly lower numbers of nymphs occurred. Our study provides a promising insight into the importance of studying apple–RAA interactions within an eco-friendly RAA management tactic.

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.

The Asiatic vinegar fly Drosophila suzukii (spotted wing Drosophila, SWD) has recently invaded Europe, and immediately became a key pest of grapes, stone and soft fruits. Unlike other fruit flies that typically infest only overripe and rotten fruit, SWD females oviposit in ripening fruit, leading to considerable economic damage in a broad range of soft-skinned fruits. Here we present recent outcomes from applied research revealing important insights into SWD population dynamics and seasonal changes in odour preferences. Firstly, we demonstrated that the currently widely applied monitoring programs, with traps and liquid attractant based on apple cider vinegar (ACV), provide a distorted picture of the actual SWD population dynamics profile. Use of alternative attractants clearly showed that there is an underestimation of the SWD population development during the main soft and stone fruit production periods (late spring-summer). Secondly, we attempted to unravel the seasonal shifts in preference of the SWD population between fermentation cues (like ACV) and fruit odour. Differences in seasonal odour preferences between winter and summer morphs of SWD were observed in a two-year field experiment. A lab experiment only partially confirmed these findings.

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.

Since the withdrawal of broad spectrum insecticides like carbamates and organophosphates and the restricted use of neonicotinoids, weevils have become an increasing problem in pome fruit in Belgium. In particular, the apple blossom weevil Anthonomus pomorum and the pear bud weevil Anthonomus pyri (syn. A. cinctus or A. piri), that used to be secondary pests, have developed into important pests for many apple and pear growers, respectively. Recently, also the pear blossom weevil Anthonomus spilotus was found to be present in several pear orchards in Belgium, causing considerable damage. Here we present an overview of recent monitoring data, field and laboratory trials, executed in the Belgian fruit growing area near Sint-Truiden. Laboratory trials on A. pyri indicated a high direct contact activity as well as a high indirect residual contact activity of the neonicotinoid insecticides thiacloprid and acetamiprid, while the anthranilic diamide insecticide cyantraniliprole reached only good control activity after exposure of the A. pyri weevils to spray residue on leaves. In a field trial, application of thiacloprid and cyantraliprole targeting the active A. pyri weevils in autumn also resulted in very high control efficacies, leaving opportunities for a successful combination of those insecticides with biological control by the parasitoid Scambus pomorum. This opens perspectives for control strategies in line with sustainable integrated pest management (IPM) principles.

Worldwide monitoring programs of the invasive fruit pest Drosophila suzukii Matsumura (Diptera: Drosophilidae), using fermentation baits like apple cider vinegar (ACV), revealed a counterintuitive period of low trap catches during summer, followed by an autumn peak. In this study, we demonstrate that ACV baited traps indeed provide a distorted image of the D. suzukii population dynamics as it is possible to capture higher numbers during this “low capture period” with synthetic lures. It was hypothesised that the preference of D. suzukii populations for fermentation cues like ACV is most pronounced during autumn, winter and spring, while the flies prefer fresh fruit cues during summer and that this seasonal preference is related to the changing physiology of the flies over the season. To test this hypothesis, the preference between fermentation cues (ACV) and host fruits (strawberries) and the effect of physiology (sex, seasonal morphology and feeding, mating and reproductive status) was investigated both in olfactometer laboratory experiments and a year-round field preference experiment. In olfactometer experiments we demonstrated that protein deprived females, virgin females with a full complement of unfertilised eggs and males show a strong preference for fermentation cues while fully fed reproductive summer morph females generally prefer fruit cues. These findings indicate that D. suzukii is attracted to fermentation volatiles in search of (protein-rich) food and to fruit volatiles in search of oviposition substrates. Winter morph and starved females displayed indiscriminating olfactory behaviour. In the field preference experiment, the hypothesised seasonal shift between fermentation and fruit cues was confirmed. This shift appeared to be highly temperature-related and was similarly observed for summer and winter morphs.

Het project “Praktijkgericht onderzoek en inzet van alternatieve bestrijdingsmiddelen voor de controle van probleemplagen in de biologische pitfruitteelt” had tot doel een bijdrage te leveren aan de teelt- en de bedrijfszekerheid van biologische pitfruitbedrijven. Spruzit (pyrethrinen met synergist piperonylbutoxide (PBO), dat gebruikt werd voor (correctie)behandelingen tegen probleemplagen in de biologische pitfruitteelt is niet meer in de handel sinds januari 2018. Aan de hand van de proeven die in dit project uitgevoerd werden, werd kennis opgedaan met nieuwe middelen tegen meer algemene plagen of met gekende middelen tegen nieuwe plagen. Mogelijk dankzij dit project kunnen een aantal middelen een uitbreiding van hun etiket krijgen. De kennis uit deze proeven voortgevloeid zal via Proefcentrum Fruitteelt continu ter beschikking gesteld worden van de fruittelers en zal als basis dienen voor verdere initiatieven in de zoektocht naar oplossingen voor probleem plagen in de biologische appel- en perenteelt.

Pear sucker remains a major concern of modern pear growing. A successful control of pear sucker relies on the control of both generations: the first generation (G1), which occurs before flowering, and the second generation (G2) occurring during May-June. The action of predatory bugs (Anthocoris spp.) as well as that of other beneficials is very important for the control of subsequent summer generations of the pear sucker, and must be supported by the use of selective insecticides, as soon as the predator populations appear in the orchards. Flupyradifurone applied during pre-flowering period offers a correction spray on the devastating first generation of pear sucker which compromises fruit set, and causes damage on the fruit skin. When applied at pre-flowering, flupyradifurone does not disrupt population dynamics of the Anthocoris population in summer due to the principle of time selectivity. Also for some other beneficial arthropods no harmful effects were observed by flupyradifurone when applied during pre-flowering. Spirotetramat applied on the G2 offers a good control of young and old larvae of Cacopsylla pyri, both on the shoot tips and on cluster leaves in the central part of the tree. Spirotetramat has no impact on Anthocoris spp. (IOBC 1). The long lastingness of spirotetramat in shoot tips is linked with its systemicity towards these growing parts of trees. In the older cluster leaves possibly a switch from sink to source may happen which may cause a decline in the spirotetramat-enol concentration. A directed spray in the central part of the tree guarantees a full control of C. pyri and avoids honeydew and sooty mold staining. On top of that, spirotetramat offers simultaneously control of other pests like Dasineura pyri midges and scales. For pears, spirotetramat offers a multi target control, avoiding the need for other multiple correction sprays.

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.

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.

The grape berry moth, Lobesia botrana, is an important pest of grapes. In Belgium, severe losses of production appeared due to the presence of L. botrona in grapes commercially grown in glasshouses. In 2010 mating disruption became a key pest management tactic in Flemish pip fruit orchards after being tested for several years. In other (European) countries, mating disruption is already applied in grapes but there is no registration in Belgium for use in grapes. Searching for an interesting residue free technique for application in small glasshouses, we evaluated the effect of mating disruption for control of L. botrana under protected conditions (glasshouse trials) during three consecutive years (2010-2012). A prerequisite for successful mating disruption is the treatment of large contiguous areas, as the pheromone product will not remain in sufficient quantities on narrow sites and, moreover, a larger portion of the crop remains at risk from migrating mated females. The glasshouses are rather small, however, we hypothesized that these so called border effects are not present due to the secluded spaces of the glasshouses. Pheromone dispensers were deployed and flights of L botrano moths were monitored (pheromone traps/UV-traps) during the whole time period of the trials. In the mating disrupted glasshouses hardly any moth was caught anymore in pheromone traps, in contrast to UV-traps or catches by pheromone traps in comparable non-mating disrupted glasshouse compartments. This indicates the incapability of the males to localize sex pheromone sources, and hence, the inability of finding females for mating. In line with these flight monitoring data, the nearly absence or strongly decreased L. botrana caused damage symptoms in the mating disrupted glasshouses demonstrates the benefits of the mating disruption technique under protected conditions of grape growing in glasshouses.

Codling moth (Cydia pomonella) is one of the most important pests in apple and pear. In 2010 mating disruption became a key pest management tactic in Flemish pip fruit orchards, largely due to a government subsidy and demonstrating projects aiming to widen the area treated by pheromones as large as possible. As a consequence, the mating disruption strategy was applied at approximately 7.500 ha, or half of the pip fruit area, in 2010 and 2011. The sudden large-scale implementation of this technique changed the codling moth management landscape. Here we present a case study of a commercially managed orchard that suffered from high codling moth pressures for many years, as did the surrounding area. The RAK3 mating disruption system was introduced at this location in 2010, and was continued in 2011. Systematic detailed codling moth flight data for this location are available for many years. In addition, comprehensive data on damage levels of chemically untreated windows spread all over the test orchard in a randomized block design were obtained in successive years, enabling us to thoroughly evaluate the effect of the changed codling moth management strategy. Data from 2011 included damage levels in chemically treated windows when the entire orchard was applied once at the flight peak of Cydia pomonella. In 2009, before introduction of mating disruption, a mean of 8.25 +/- 5.54% of the fruits were infested at harvest when assessed in completely untreated windows. After two years of mating disruption, supported with a full chemical support in 2010, except for the untreated assessment windows, and only one application on the flight peak of 2011, damage was reduced to less than 0.03% at harvest. This is a valuable case study to demonstrate the benefits of the mating disruption approach.

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.

Pome fruit growers around the world are gradually adopting Integrated Fruit Production (IFP). IFP is defined by the IOBC as the economical production of high quality fruit, giving priority to ecologically safer methods, minimising the undesirable side effects and use of agrochemicals, to enhance the safeguards to the environment and human health. Integrated Pest Management (IPM) is central to IFP and strongly depends on the availability of selective insecticides. Spirotetramat (brand name Movento (R)) is a very promising active ingredient belonging to the class of tetramic acid derivatives. It has a two-way systemic action, allowing it to move downwards as well as upwards within the plant in the phloem and in the xylem vessels. From 2002 onwards, numerous GEP and non-GEP field trials with this new compound were performed by pcfruit in apple and pear orchards in Belgium. Trials were all executed according to EPPO guidelines. Based on the outcomes of these trials, spirotetramat was proven to be efficient against a broad range of pests. In addition, spirotetramat was shown to have a good safety profile with respect to a range of beneficial arthropods (e. g., Typhlodromus pyri and Anthocoris sp.). Since the withdrawal of a number of plant protection products and limited use of certain broad-spectrum products according to the IFP-guidelines, the control of pest species such as pear sucker (Cacopsylla pyri) and woolly apple aphid (Eriosoma lanigerum) is very complicated at this time. Hence, the introduction of spirotetramat, with good efficacy against several severe pome fruit pests and good beneficial safety, will appreciably strengthen the currently applied IPM control strategies in IFP.

Since the withdrawal of certain insecticides and the restricted use of some broad-spectrum plant protection products, the woolly apple aphid (Eriosoma lanigerum) has become one of the most severe pests in apple growing areas across western Europe. Their protective wax coating makes them particularly difficult to control. At present, effective limitation of woolly aphid populations relies on a good synergy between chemical control treatments and biological suppression by parasitoids and predators. Optimal control strategies take advantage of a thorough understanding of the life cycle of woolly apple aphids, the timing of their migration waves and their interaction with the environment. Based on monitoring data and research results (side effects trials, field population dynamics of beneficial arthropods) we here present pest management programs that take profit of a maximal natural regulation of E. lanigerum. In addition, the potential implementation of new alternative biological control methods is discussed.

Phytoplasmas are plant pathogenic mollicutes that cause devastating diseases in various crops worldwide. The closely related pome fruit tree phytoplasmas Candidatus Phytoplasma mali and Candidatus Phytoplasma pyri are the causal agents of apple proliferation and pear decline, respectively. They can be transmitted from tree to tree by Psyllidae. As pear suckers (Cacopsylla pyri) are widely considered to be the most important pest in pear orchards, a good control of this insect vector is a key element for limiting the natural spread of pear decline. Efficient control relies on a perfect tuning of treatment schedules, taking into account efficacies of (at preferably) low-impact insecticides and side-(repellent)-effects of alternative products (e.g. kaolin, mineral oils and fungicides), the optimal positioning of these crop protection agents, and the best possible presence of beneficial predators. The department of Zoology of the pcfruit vzw research institute (Belgium) has a long tradition of executing insecticide field trials according to EPPO guidelines. Here, we present an overview of the results of a selection of IPM-compatible insecticides (abamectin, spirotetramat, thiacloprid, spinosad, spirodiclofen), tested in efficacy trials against pear Psylla on different life stages during the last decade. Based on these results and monitoring data of pest and beneficial biology, we additionally propose optimal pear Psylla control schedules which allow to reduce the number of (phytoplasma harbouring) psyllids in integrated systems to a minimum.