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The European tarnished plant bug, Lygus rugulipennis Poppius, is considered a major pest in chrysanthemum nurseries in The Netherlands. Adults puncture plant's apical meristem, after which the growing point splits and growth is inhibited. Flower buds and flowers can also be severely damaged. Both types of damage result in economic losses for growers. Despite the importance of this pest for chrysanthemum nurseries, there is only very limited information about L. rugulipennis development on chrysanthemum plants, Chrysanthemum × morifolium Ramat., and whether L. rugulipennis can be controlled using trap plants is not known. We investigated whether: (1) L. rugulipennis could develop from egg to adult on the vegetative and flowering stages of chrysanthemum; (2) their performance was enhanced when a supplemental prey source (Ephestia kuehniella Zeller eggs) or another common pest (the green peach aphid, Myzus persicae Sulzer) was present; and (3) there were alternative plant species more attractive than chrysanthemum for use as trap plants for local pest control or monitoring of L. rugulipennis. L. rugulipennis developed on both vegetative and flowering chrysanthemum stages without any additional food source. Nonetheless, when chrysanthemum was supplemented with E. kuehniella eggs, L. rugulipennis achieved the best performance in terms of the number of adults developed and faster developmental time. Interestingly, L. rugulipennis developed faster on chrysanthemum infested with the aphid M. persicae compared to non-infested plants, however, there was no difference in the number of adults developed. In a trap plant experiment with 16 plant species in the vegetative stage, we found that white mustard, Sinapis alba L., was significantly more attractive than chrysanthemum to both adult and nymph L. rugulipennis. Further research is needed to evaluate the potential of S. alba as a trap plant for monitoring L. rugulipennis and how the presence of prey in the crop influences L. rugulipennis.

Several biological control agents of the hemipteran insect families Miridae, Anthocoridae and Pentatomidae, as well as mites of the family Phytoseiidae are known as zoophytophagous predators, a subset of omnivores, which are primarily predaceous but also feed on plants. It has been recently demonstrated that zoophytophagous predators are capable of inducing defenses in plants through their phytophagy. Despite the vast fundamental knowledge on plant defense mechanisms in response to herbivores, our understanding of defense induction by zoophytophagous predators and applied implications is relatively poor. In this review, we present the physiological basis of the defense mechanisms that these predators activate in plants. Current knowledge on zoophytophagous predator-induced plant defenses is summarized by groups and species for the predators of economic importance. Within each group, feeding habits and the effects of their induced-plant defenses on pests and natural enemies are detailed. Also, the ecological implications of how the induction of defenses mediated by zoophytophagous predators can interact with other plant interactors such as beneficial soil microorganisms and plant viruses are addressed. Based on the above, we propose three approaches to exploit zoophytophagous predator-induced defenses in crop protection and to guide future research. These include using predators as vaccination agents, employing biotechnological approaches, as well as applying elicitors to elicit/mimic predator-induced defenses., This work was partly supported by the Spanish Ministry of Science and Innovation through the projects RTA2017-00073-00-00 and PID2020-113234RR-I00. MLP was supported by the Onassis Foundation under the Special Grant and Support Program for Scholars’ Association Members (Grant No. R ZJ 003-2/2019–2020). GM was supported by the Dutch topsector project KV 1509-020. SB is an employee of Koppert Spain, a private company that markets benefcial arthropods. RM works for Biobest Group NV, a private company that markets benefcial arthropods.

Generalist predators are increasingly used in biological pest control for greenhouse crops, as they control multiple pests and persist in crops even when prey is scarce. However, some of these predators may cause plant damage due to their omnivorous feeding behaviour. In many European regions, the omnivorous predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is considered to be a serious tomato pest, regardless of the biological control services it offers, and integrated pest management (IPM) strategies are based instead on Macrolophus pygmaeus (Rambur). However, as N. tenuis may competitively displace M. pygmaeus and cause severe damage, growers often resort to pesticide use, disrupting their biological control practice. In this study, we evaluated the competitive interactions of three mirid predators, Dicyphus errans Wolff, Dicyphus bolivari Lindberg, and Dicyphus cerastii Wagner, with N. tenuis. The results showed that pre-establishment of heterospecific mirid species can successfully suppress N. tenuis in the greenhouse; population growth was reduced by more than 90% compared to plants without competing predators. Further laboratory trials revealed reciprocal intraguild predation between these species in the absence of extraguild prey. Dicyphus adults predated on N. tenuis nymphs, while this was not found for M. pygmaeus. In olfactometer bioassays, N. tenuis females preferred plants previously exposed to heterospecifics but not conspecifics, suggesting that this mirid does not avoid competition. These results suggest that the three Dicyphus species could be interesting candidates for preventive releases in tomato crops due to their ability to effectively suppress N. tenuis population growth.

Proposed treatment processes of OMWW have not been efficient in decreasing its high toxicity or lowering its ecological impact. Bioremediation using microorganisms might be considered an environmentally friendly alternative. In this work, four fungal isolates were tested for their efficacy in lowering the toxicity of OMWW. Results of this work showed that fungal isolates were able to grow on OMWW. However, only one isolate (OMWW2) showed significant lowering in total phenols from 159.27 mg/ml (in controlled untreated water) to 57.75 mg/ml. The treated OMWW was tested on seed gemination of tomato. The results showed 83% germination rates in the presence of treated OMWW compared with 0% rates in nontreated OMWW. The results showed also that OMWW could be used as a supplement fertilizer to the presence of macronutrient and micronutrient. This work provides a promising future treatment OMWW. Further studies are needed to evaluate the possible use of OMWW in horticulture.

It has become clear that omnivorous predators can induce plant defences that affect the performance and host plant choice of herbivores. They are also known to induce the production of plant volatiles that can affect the behaviour of herbivores searching for plants. These volatiles may also affect the searching behaviour of other predators, which was investigated here. The predatory mite Phytoseiulus persimilis preferred plants previously exposed to the omnivorous mirid Macrolophus pygmaeus over clean plants. The mites were equally attracted to plants previously exposed to the omnivore and subsequently infested by spider mites (Tetranychus urticae, prey of the predatory mite and the omnivore) and plants infested with spider mites alone. Moreover, the mites were more attracted to plants infested with prey and subsequently exposed to the omnivore than plants infested with prey but not exposed to the omnivore. The predatory mites were also significantly more attracted to plants on which the omnivores were still present. Experience of the predatory mites with volatiles from plants previously exposed to the omnivore and without prey resulted in a loss of the preference for volatiles emitted by plants exposed to the omnivore. Analysis of the volatiles showed that plant exposure to omnivores induced qualitative and quantitative changes in the volatile blend. Together, these results suggest that omnivorous predators induce the production of plant volatiles that can interfere with the searching behaviour of other predators. The consequences of such interference for biological pest control remain to be investigated.

The effect of sodium accumulation on tomato growth and production was tested in a trial with a crop in stone wool with full recirculation of drain water. Treatments varied from 10 to 25 mmol/l sodium, with two periods of gradual increase, in an 11-month crop. No significant differences were found on yield or quality (shelf life or taste). Blossom End Rot (BER) did not occur. On the basis of the results of this trial, the maximum acceptable level for Na can be increased from 8 to 15 mmol/l. The uptake concentration was linear with the Na concentration in the root environment and is at a reasonable level with approx. 1 mmol/l at 15 mmol/l. From these results it is to be expected that when using rainwater only or water with comparable quality a fully closed cultivation is possible for tomato. Even so this is possible at Na concentrations of less than 1 mmol/l in the water applied. Het effect van natriumophoping op de groei en productie van tomaat werd getest in een proef in steenwol met volledige recirculatie. Behandelingen liepen uiteen van 10 tot 25 mmol/l aan Na, met twee perioden waarin werd gestart met een geleidelijke verhoging, in een teelt van 11 maanden. Er werden geen betrouwbare effecten op de productie of kwaliteit (houdbaarheid of smaak) gevonden. Er trad geen neusrot op. Op grond van de resultaten van deze proef kan de grenswaarde voor spui worden verhoogd van 8 naar 15 mmol/l. De opnameconcentratie was lineair met de aangeboden Na en is met ca 1 mmol/l bij 15 mmol/l Na op een redelijk hoog niveau, waardoor er bij gebruik van alleen regenwater of van water van vergelijkbare kwaliteit geen problemen te verwachten zijn. Op grond van deze resultaten mag worden verwacht dat bij tomaat een volledig gesloten teelt mogelijk is bij een Na concentratie van minder dan 1 mmol/l in het toegepaste water.

Wageningen University and Research Business Unit Greenhouse Horticulture investigated the influence of LED light spectrum, diffuse glass and cultivar on photosynthesis, production, quality, dry matter distribution, resistance and microbiome in the root zone in a winter cultivation with blackberries and raspberries. In addition to the standard light spectrum, there were spectra with extra blue and far-red light. Diffuse glass gave 30% more production with blackberry than clear glass, but with raspberry this effect of the type of glass was the opposite. The influences of cultivar were usually much greater than these of light spectra. Blue light increased resistance to caterpillars. Blackberry had a higher photosynthesis than raspberry, but lower than tomato and strawberry. The light utilization efficiency of blackberry was more than 2.5 times higher than that of raspberry.

In this report, we present an analysis of the consequences of the European authorization policy for plant protection products within the context of the implementation of the Farm to Fork Strategy for Dutch greenhouse horticulture. We analyse European and Dutch crop protection policy and explore the consequences of the expected decrease in the number of approved plant protection products for five crops: tomato, cucumber, gerbera, chrysanthemum and Phalaenopsis. Based on these cases, we make an analysis for the entire greenhouse horticulture sector. Afterwards, we provide an overview of current and future developments in sustainable crop protection methods. Finally, we present conditions that can be imposed on the government, suppliers, buyers, researchers and advisers, and the greenhouse horticulture sector itself, which contribute to a setting in which greenhouse growers are able to continue to make crop protection more sustainable in an economically responsible manner.

Wageningen University and Research Business Unit Greenhouse Horticulture investigated the influence of LED light spectrum, diffuse glass and cultivar on photosynthesis, production, quality, dry matter distribution, resistance and microbiome in the root zone in a winter cultivation with blackberries and raspberries. In addition to the standard light spectrum, there were spectra with extra blue and far-red light. Diffuse glass gave 30% more production with blackberry than clear glass, but with raspberry this effect of the type of glass was the opposite. The influences of cultivar were usually much greater than these of light spectra. Blue light increased resistance to caterpillars. Blackberry had a higher photosynthesis than raspberry, but lower than tomato and strawberry. The light utilization efficiency of blackberry was more than 2.5 times higher than that of raspberry. Door Wageningen University en Research Business Unit Glastuinbouw is in een belichte winterteelt met bramen en frambozen nagegaan wat de invloed was van LED-lichtspectrum, diffusiteit van het kasdek en ras op o.a. fotosynthese, productie, kwaliteit, drogestofverdeling, weerbaarheid en microbioom in de wortelzone. Naast het standaard lichtspectrum, waren er spectra met extra blauw en verrood licht. Diffuus glas gaf bij braam 30% meer productie dan helder glas, maar bij framboos was dit effect van de glassoort juist omgekeerd. De invloeden van het ras waren meestal veel groter dan van de lichtspectra. Blauw licht verhoogde de weerbaarheid tegen rupsen. Braam had een hogere fotosynthese dan framboos, maar lager dan tomaat en aardbei. De lichtbenuttingsefficiëntie van braam was meer dan 2.5 keer zo hoog dan bij framboos.

The effect of sodium accumulation on tomato growth and production was tested in a trial with a crop in stone wool with full recirculation of drain water. Treatments varied from 10 to 25 mmol/l sodium, with two periods of gradual increase, in an 11-month crop. No significant differences were found on yield or quality (shelf life or taste). Blossom End Rot (BER) did not occur. On the basis of the results of this trial, the maximum acceptable level for Na can be increased from 8 to 15 mmol/l. The uptake concentration was linear with the Na concentration in the root environment and is at a reasonable level with approx. 1 mmol/l at 15 mmol/l. From these results it is to be expected that when using rainwater only or water with comparable quality a fully closed cultivation is possible for tomato. Even so this is possible at Na concentrations of less than 1 mmol/l in the water applied.

In this study a greenhouse has been designed for optimal production in the coastal area close to Algiers. Data showed that there are two main options for optimal production of tomatoes and similar products like cucumber. A choice can be made for winter production in a heated greenhouse or summer production with air-conditioning and CO2 injection. The estimated production is fairly similar for both seasons but the costs for summer production are 30% higher. The investment costs for the summer production scenario are higher but running costs are lower, since in summer less additional water and energy are needed for the production. To reduce the use of water and related costs we recommend to grow on substrate, re-circulate the water and collect the rainwater in a water basin. The growth of salad or strawberries might be an alternative for cultivation in early winter or early spring in greenhouses without heating. In deze studie is een optimale kas ontworpen voor gebruik in de kustvlakte rond Algiers. De resultaten gaven aan dat er twee opties zijn voor een optimale productie van een voorbeeld gewas als tomaat. Er is een mogelijkheid om in de winter te telen in een verwarmde kas of in de zomer met behulp van air conditioning in combinatie met CO2 toediening. De opbrengsten van beide systemen zijn vergelijkbaar maar de kosten voor de winterteelt zijn ruim 30% lager. De investeringskosten voor het zomersysteem zijn hoger maar het zomersysteem leidt wel tot een lager (aanvullend) watergebruik en lagere energiekosten. Om water en kosten te besparen wordt geadviseerd om gebruik te maken van substraat, recirculatie van water en de opvang van regenwater in een water bassin. Alternatieve gewassen als sla en aardbei kunnen een optie zijn voor de vroege winter en vroeg voorjaar indien gekozen wordt voor een teelt zonder verwarming

In this study a greenhouse has been designed for optimal production in the coastal area close to Algiers. Data showed that there are two main options for optimal production of tomatoes and similar products like cucumber. A choice can be made for winter production in a heated greenhouse or summer production with air-conditioning and CO2 injection. The estimated production is fairly similar for both seasons but the costs for summer production are 30% higher. The investment costs for the summer production scenario are higher but running costs are lower, since in summer less additional water and energy are needed for the production. To reduce the use of water and related costs we recommend to grow on substrate, re-circulate the water and collect the rainwater in a water basin. The growth of salad or strawberries might be an alternative for cultivation in early winter or early spring in greenhouses without heating.

In this report, we present an analysis of the consequences of the European authorization policy for plant protection products within the context of the implementation of the Farm to Fork Strategy for Dutch greenhouse horticulture. We analyse European and Dutch crop protection policy and explore the consequences of the expected decrease in the number of approved plant protection products for five crops: tomato, cucumber, gerbera, chrysanthemum and Phalaenopsis. Based on these cases, we make an analysis for the entire greenhouse horticulture sector. Afterwards, we provide an overview of current and future developments in sustainable crop protection methods. Finally, we present conditions that can be imposed on the government, suppliers, buyers, researchers and advisers, and the greenhouse horticulture sector itself, which contribute to a setting in which greenhouse growers are able to continue to make crop protection more sustainable in an economically responsible manner. In dit rapport presenteren we een analyse van de gevolgen van het Europese toelatingsbeleid van gewasbeschermingsmiddelen binnen de context van de implementatie van de Farm to Fork Strategie voor de Nederlandse Glastuinbouw. We analyseren het Europese en Nederlandse Gewasbeschermingsmiddelenbeleid, en verkennen de gevolgen van de verwachte afname in het aantal goedgekeurde gewasbeschermingsmiddelen voor vijf gewassen: tomaat, komkommer, gerbera, chrysant en Phalaenopsis. Op basis van deze cases maken we een analyse voor de gehele glastuinbouw. Vervolgens geven we een overzicht van de huidige en toekomstige ontwikkelingen in duurzame gewasbeschermingsmethoden. Ten slotte presenteren we voorwaarden die aan overheid, toeleveranciers, afnemers, onderzoekers en adviseurs, en de glastuinbouw zelf gesteld kunnen worden, die bijdragen aan een setting waarin glastuinders in staat zijn om de gewasbescherming te blijven verduurzamen op een bedrijfseconomisch verantwoorde wijze.

The physiological performance of organisms depends on their environmental context, resulting in performance-response curves along environmental gradients. Parasite performance-response curves are generally expected to be broader than those of their hosts due to shorter generation times and hence faster adaptation. However, certain environmental conditions may limit parasite performance more than that of the host, thereby providing an environmental refuge from disease. Thermal disease refuges have been extensively studied in response to climate warming, but other environmental factors may also provide environmental disease refuges which, in turn, respond to global change. Here, we 1) showcase laboratory and natural examples of refuges from parasites along various environmental gradients, and 2) provide hypotheses on how global environmental change may affect these refuges. We strive to synthesise knowledge on potential environmental disease refuges along different environmental gradients including salinity and nutrients, in both natural and food-production systems. Although scaling up from single host-parasite relationships along one environmental gradient to their interaction outcome in the full complexity of natural environments remains difficult, integrating host and parasite performance-response can serve to formulate testable hypotheses about the variability in parasitism outcomes and the occurrence of environmental disease refuges under current and future environmental conditions. This article is protected by copyright. All rights reserved.

Recirculation of drainage solution reduces the emission of water, nutrients and plant protection products from both substrate-based and water-based growing systems. During cultivation, deviations in nutrient ratios in the root environment may potentially affect yield and quality as well as motivate a grower to discharge the drainage solution. Our objective was to quantify imbalances in nutrient ratios and to assess what part of the nutrient imbalances can be prevented with practical measures. Results: included daily balances for water and individual nutrients, using data from a commercial cherry-tomato grower. The balances showed plant water uptake and uptake of individual nutrients were not strictly correlated. It was also possible to establish individual relations between solar radiation sum and water uptake as well as uptake per individual nutrient. After 200 days of production, an adapted balance was prepared and then used as a model. This model was used to compare various nutrient supply strategies to reduce daily fluctuations in nutrient ratios. Simulations showed the imbalances between supply and uptake could be halved compared with the original grower strategy. This was realized by using a combination of drainage volume percentage, the supply EC and the correlation of the supplied solution EC with solar radiation forecast. The conclusion is that nutrient balances can deliver plant uptake data for water and individual nutrients, which can then be correlated with solar radiation. This can be used to identify and reduce deviations from targeted ratios between nutrients in the supplied solution as well as in the root solution. These conclusions take advantage of information available in practice.

The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), has invaded most Afro-Eurasian countries and is threatening worldwide tomato production. Various strategies have been developed and implemented to manage this pest. Here, we present a timely review on the up-to-date development and practical implementation of integrated pest management (IPM) programs for tomato crops across different world regions infested by T. absoluta. While insecticide resistance is a growing concern, biological control via releasing or conserving arthropod natural enemies and sex pheromone-based biotechnical control are the most successful management practices. Agronomic control-related research is an emerging area where the soil fertilization and/or irrigation, as well as breeding of resistant cultivars, has the potential to enhance IPM effectiveness. Grower survey responses in the native areas (i.e., South America), early-invaded areas (i.e., first report between 2006 and 2012) and newly invaded areas (i.e., first report after 2012) showed that the control programs evolved along with the areas and time since invasion. Growers in the early-invaded areas shifted more rapidly from chemical control to biological control compared to those from the native area. In all concerned regions, the pest control failure risk following chemical insecticide applications and the high cost associated with either biological or biotechnical control methods have been the greatest concerns for growers. The information gathered from the native and/or early-invaded areas may help achieve a more effective management in newly invaded areas. Lastly, researchers are expected to break the bottlenecks of some key issues that would enable lowering application cost of novel biorational alternative management options.

Biofilm formation in irrigation systems can be problematic, as it can cause clogging of drippers or sprinklers and therefore unequal supply of nutrient solution to the crop. In addition to that, a biofilm can be a nesting place for pathogenic microorganisms which diminishes the effect of central irrigation water disinfection. Several commercial products are available to prevent biofilm formation or to remove an existing biofilm, but not all are suited for use in hydroponic cultivation with reuse of drain water, especially in cases in which no drain water can be discharged (goal for Dutch greenhouse horticulture for 2027). An installation and a protocol were developed to test the effectiveness of technologies and strategies suitable for use in zero liquid discharge cultivation systems for prevention of biofilm formation and removal of existing biofilms. The installation consists of three parallel systems and mimics conditions in a tomato greenhouse for temperature, nutrient solution composition, irrigation schedule and system length. Biofilm formation is measured in a biofilm monitor, from which rings of irrigation lines could be sampled and analysed for presence of biomass from living cells. Two chemical treatments (Oxyl-PRO S silver stabilised hydrogen peroxide and in situ produced SureFlow chlorine dioxide) and three physical treatments (electro-magnetic treatment, ultrasound treatment and antibacterial irrigation lines) were tested. The chemical solutions were able to remove existing biofilms and to prevent new biofilm formation, whereas the physical treatments were less effective or did not show any effect at all.

In the Netherlands recirculation of the nutrient solution is statutory required in soilless culture systems. The goal is to achieve a zero liquid discharge, it means no solution with fertilizers, pesticides and/or cleansing products are allowed to be discharged to surface or ground water or the sewage system. It also means that products added to the system should be taken up by the plants or broken down. The objectives of this research were to investigate i) if frequently used cleansing products accumulate in the nutrient solution and may harm growth of the plants, and ii) if the used concentrations of cleansing products were able to eliminate pathogens in the circulating nutrient solution. Gerbera was used as a pilot crop. The research was divided in four steps. As a first step growers and consultants were inquired (1) about the use of cleansing products additional to the traditional disinfection methods. It was followed by laboratory experiments (2) to test a few cleansing products in various concentrations against plant pathogens. A next step was a greenhouse experiment in which gerbera plants were infected with Fusarium oxysporum (3). Finally sampling at commercial farms (4) was performed to investigate if accumulation did really appear. The inquiry showed that nearly all growers were using, additional to UV or heat treatment for disinfection, cleansing products such as hydrogen peroxide, bleach, chlorine dioxide or ECA water. They were mainly used for cleaning of the pipework. From the laboratory experiments it appeared that the concentration to eliminate the pathogen was much higher as the concentration used to clean the pipe work. In the greenhouse experiment two cleansing products (hydrogen peroxide, chlorine dioxide) were added in five concentrations with two replicates and compared with a control. All treatments were infested with F. oxysporum, except for the control. During the short growing cycle there were no symptoms of F. oxysporum at the plants. However, it appeared that the higher the concentration of added cleansing products the worse the state of the plants, decreasing plant growth. Additionally, bleach showed high sodium concentrations, while the iron chelate was broken down by the hydrogen peroxide. Looking to the cleansing products at commercial farms hardly any accumulation could be measured. It was concluded that the low concentrations applied in commercial practice do not accumulate to toxic levels while a side effect of cleansing products against pathogens cannot be expected.

Using proper greenhouse covering materials can provide a suitable environment for plant growth in Saudi Arabia. The effects of three different greenhouse covering materials, clear glass, polycarbonate and diffuse tempered glass were used to evaluate its effect on cucumber productivity, water and energy use efficiency. Results show that either water or light use efficiency was higher in compartments covered with diffused or clear glass than polycarbonate compartment. Inconsequence, fruit yield of cucumber plants/m2 was significantly higher (58%) in clear and diffuse glass greenhouses as opposed to polycarbonate greenhouse. In term of the effect of cultivar or plant density, no significant differences on cucumber yield were found. Using of different covering materials did affect environmental data of greenhouses. Less light was transmitted through polycarbonate cover than clear or diffuse glass. The photosynthesis active radiation (P.A.R.) was 996, 1703, 1690 mol/m2/d, while the electricity consumption was 2.97, 3.44, and 2.88 kWh under polycarbonate, clear glass, and diffuse glass, respectively. Meanwhile, diffuse glass compartment revealed 16% lower of water consumption than other covering materials. In this respect, it could be concluded that using diffuse glass, as a greenhouse cover material, has a strong positive influence on crop productivity under Saudi Arabia climate.

Blattisocius mali (Oudemans) is a candidate predatory mite on some astigmatid mite pests like Tyrophagus putrescentiae (Schrank). In current study, life table parameters of B. mali were comparatively evaluated when fed on mixed life stages, frozen (one day at -20°C) and cold stored (90 days at -20°C and 4°C) eggs of T. putrescentiae. The highest and lowest values of fecundity, total longevity, oviposition period, life span and adult longevity of B. mali were observed when the predator provided with one-day and 90-days frozen eggs (stored at 4°C) of T. putrescentiae, respectively. Moreover, the highest values of net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ) of B. mali were obtained by feeding on one-day frozen eggs (23.94 offspring/individual, 0.332 day-1, 1.39 day-1, respectively), without significant differences from the predators reared on alive mixed stages of T. putrescentiae. However, the lowest values of R0 (1.54 offspring/individual), r (0.058 day-1) and λ (1.06 day-1) were recorded when B. mali was reared on 90-days frozen eggs (stored at 4°C). The results, as first evidence of life-history of B. mali, represent not only the potential of the predator as suitable biological control agent against T. putrescentiae, but also the possibility of its mass production by frozen host stages. Provision of one-day frozen eggs of T. putrescentiae were the best choice for B. mali survival and reproduction with no harmful effects of living stages (direct damage, frass and exuviae) on crop.

Current thinking about circularity and sustainability is used to identify i) recirculation of drainage water, ii) circular fertilisers, and iii) resilience control as growing media related areas with a wider societal meaning. The objectives are to find to which extent circularity can be realized and how growing media and compost research can serve transition to a more circular horticulture. Recirculation of drainage water increases water use efficiency by 50%, nutrient use efficiency by 60% and eliminates the emission of water borne chemical agents. The challenge remains as still 90% of the global area of growing media systems does not yet use available techniques to realize full recirculation. The global use of more circular fertilisers, including plant, animal and human wastes, can stop depletion of natural reserves and diffuse emission of nutrients. It is argued that the combination of irrigation techniques and the use of growing media offer horticulture both opportunity and reasons to lead in the production of circular fertilisers, being either soluble or slow release. Resilient growing media facilitate cultivation without chemical agents, without disinfection before reuse and without continuous disinfection of recirculating water. We identify methodological improvements still needed to safely progress on this road. The importance of growing media based cultivation is put in perspective of the global production of food and ornamentals.

Astigmatid mites can be used as prey for mass rearing of phytoseiid predators, but also as a supplemental food source to support predator populations in crops. Here we evaluated the potential of six species of astigmatid mites (living or frozen) as alternative food for the predatory mite Amblyseius swirskii Athias-Henriot in greenhouse crops. All prey mites tested were suitable for predator oviposition. In general, oviposition was greater when prey mites were reared on dog food with yeast than when they were reared on wheat bran with yeast. Amongst prey items provided as frozen diet, larvae of Thyreophagus entomophagus (Laboulbene), Acarus siro L. and Lepidoglyphus destructor (Schrank) that had been reared on dog food with yeast, resulted in the highest oviposition rates of A. swirskii. T. entomophagus larvae as frozen diet resulted in the shortest preimaginal developmental time of A. swirskii. On chrysanthemum plants, we found that the greatest increase in predator density occurred when living mites of T. entomophagous were used as a food source. This increase was greater than when predators were fed cattail pollen, a commonly used supplemental food. Effects on predators of providing living A. siro and L. destructor, or frozen larvae of T. entomophagous as food, were comparable with provision of pollen. Use of supplemental food in crops can be a risk if it is also consumed by omnivorous pests such as western flower thrips, Frankliniella occidentalis Pergande. However, we showed that both frozen and living mites of T. entomophagous were unsuitable for thrips oviposition. Hence, we believe that provision of prey mite species increases A. swirskii density, supporting biological control of thrips and other pests in greenhouse crops.

Use of peat and coir in horticulture is under pressure because of the negative effects on the environment. Peat harvesting releases CO2 into the atmosphere and changes the wetland ecosystem. Coir production can cause salt pollution in the country of origin as the product has a high salt level and is washed with fresh water before use as a substrate. HydraFiber, a specific wood fiber product was tested as substitute for (part of) peat and coir in professional potting soils. Wood fiber was mixed in 3 volume percentage ratios (30, 40 and 50% v v-1) with peat or coir. Nutrient content and stability were used to calculate appropriate fertiliser levels for each mixture for growth of a begonia crop in an ebb and flood system. Addition of up to 50% v v-1 wood fiber to peat or coir has no negative effect on the rate of development to flowering of a 10 week crop. The ratio of weight/length of the plants is similar for all treatments. Addition of 40% and 50% v v-1 wood fiber to peat reduces water content by 16% v v-1 and increases air content by the same amount in the substrate in the range of -6 to -100 cm pressure head. Addition of wood fiber to coir has a similar effect. A lower average water content in substrate mixes of peat and wood fiber indicates it is more difficult to overirrigate but that it also requires a more precise monitoring of both, water content and nutrient status. It also requires a higher frequency of irrigation and more frequent adaptations of the nutrient level in the water supply. Using wood fiber in percentages from 30 to 50% v v-1 may also require an adaptation in the growing medium used for propagation plugs.

Environmental microbiome 17, 33 (2022). doi:10.1186/s40793-022-00425-1, Published by Springer Nature Switzerland AG, Cham

Over the last decade, LED lighting has gained considerable interest as an energy efficient light source in greenhouse horticulture. Much work on LED lighting is done under controlled conditions in the absence of sun light, whereas the primary application lies in supplementation of low light conditions in winter. A frequently forgotten aspect herein is that spectral composition may also affect the biology of pests and their natural enemies, both directly and indirectly through an impact on induced plant resistance. In this paper, we present results of trials with chrysanthemum and alstroemeria cut flowers which were exposed to lighting regimes with varying contributions of blue, green, red and far-red light. These trials were done under low levels of natural light, mimicking winter conditions. In chrysanthemum, spectra where blue or green were added did not affect stem length, plant dry weight and number of flowers when the percentage of red light remained over 75%. Replacing part of the photosynthetically active radiation (PAR) light by far-red light considerably increased stem length and (in some species) plant dry weight, at the expense of flowering. In alstroemeria, the number of flowers harvested, their length and fresh weight was largest in the treatment with equal shares of blue, green, red and far-red light. In chrysanthemum, the beneficial insect Orius laevigatus was introduced and its egg-laying activity and population development under different lighting strategies was monitored. The number of eggs laid by the first Orius generation was affected by the percentage red light in the spectrum, with the lowest egg number found in plants grown under 95% red. The results for egg-laying by the second Orius generation differed among chrysanthemum cultivars. The implications of this work on lighting strategies for greenhouse horticulture are discussed, both in spectral composition and in timing during the day and the season.

A new parasitoid wasp species, belonging to the genus Stenomacrus (Hymenoptera: Ichneumonidae: Orthocentrinae), was found in several Dutch plant nurseries. Here we describe, illustrate and discuss the biology, morphology and molecular characterisation of Stenomacrus meijeri sp. nov. It was reared from < 24 h old larvae of the fungus gnat Bradysia impatiens (Diptera: Sciaridae).

Astigmatid mites have potential as supplementary prey items to support generalist predator populations in crops. However, applying living prey mites has some disadvantages; if not predated they have the potential to cause crop damage and allergies. In this study, we evaluated various diets based on the astigmatid mite Tyrophagous putrescentiae (Schrank) as a supplemental food source for the predatory mite Amblyseius swirskii Ahias-Henriot. Eggs and larvae of T. putrescentiae were reared on a diet of dog food (rich in proteins and fat) or bran (rich in carbohydrate); they were offered either frozen or alive, and either with or without cattail pollen (Typha angustifolia L.). Oviposition rate of A. swirskii fed with frozen mite larvae reared on dog food was similar to the rate observed when they were fed with cattail pollen or living prey mites, but developmental time of A. swirskii was longer on this frozen diet than on a diet of living prey mites or pollen. Both living and frozen prey mites were, in contrast with cattail pollen, not suitable for oviposition by western flower thrips, Frankliniella occidentalis Pergande. In a greenhouse study, the use of frozen prey mite stages as supplemental food on chrysanthemum plants allowed populations of A. swirskii to establish, but not increase; in contrast, provision of living prey mites and pollen increased A. swirskii populations on plants. Hence, our study shows that living prey mites, but not frozen prey mites, had the greatest potential as a supplemental food source for A. swirskii.

The Dutch authorities established a plan for the reduction of water emissions from the greenhouse sector to become zero by 2027, to enforce the European Union Water Framework Directive. At the end of the cultivation period, a considerable amount of nitrate and phosphate is still present in solution in substrate slabs and in the irrigation system. The left over nutrient solution is generally discharged into the sewage system or surface water. The end of cultivation strategy was developed to use the plant uptake to reduce this nitrate and phosphate in the last 5 weeks of the cultivation period. This reduction should be realised without affecting the production or quality of the last fruits to be harvested. The strategy consisted of a gradual decrease over the last five weeks of the cultivation of nitrate, phosphate and water quantity supplied to the plant. Chloride was used to replace nitrate in the supply water. The anion-shift allowed maintaining a sufficient quantity of cations in the root environment to meet the plant's needs and to avoid production loss. A progressive shift from nitrate-nitrogen to ammonium-nitrogen was realised. The nitrogen-shift acidified the substrate slabs to release precipitated phosphate. A double irrigation cycle at the start of the day was implemented during the strategy to anticipate nutrient accumulation in the root environment. In 2016, the strategy was applied to a sweet-pepper cultivation. The water volume in the substrate slabs was reduced from 6 to 3.5 L m-2. Nitrate quantity was reduced from 109 to 55 mmol m-2. Phosphate quantity was reduced from 0.5 to 0.2 mmol m-2. In 2017, the strategy was applied to a cucumber cultivation. The average water volume was reduced from 8 to 5.3 L m-2. Average nitrate quantity was reduced from 113 to 45 mmol m-2 and average phosphate quantity from 4.5 to 1.65 mmol m-2,.

Water saving is crucial for the survival of agriculture in Saudi Arabia. Natural ground water resources are depleting by the extensive water use for agriculture. At the Estidamah research center in Riyadh water saving technologies for protected horticulture are evaluated in the harsh climatic conditions. Different levels of technology, viz., low, mid and high-tech were evaluated based on water use, energy consumption and production. The low-tech greenhouse is a plastic tunnel greenhouse cooled using a pad and fan system. This type of greenhouse is normally used for year-round production. The mid-tech greenhouse has a glass covering and is also cooled using the pad and fan system though here the amount of ventilation can be regulated using frequency-controlled fans. Finally, the high-tech greenhouse was considered which is a closed greenhouse. The cooling and dehumidification were done using coolers. The center is now in operation for more than two years so the water use over the year for the various types of greenhouse technologies can be evaluated. The water use for cooling in the mid-tech greenhouse is 30% less than what is used in the low-tech greenhouses. The water saving in the high-tech greenhouse is more than 95%.

Growers worldwide often lack means to find the economically soundest order of investing. Authorities face similar problems when deciding which developments to stimulate. For Dutch greenhouse horticulture, models for production, climate, revenue and costs, allow selection of an optimal investment order. This approach was widened into “Adaptive Greenhouse Methodology” which allows evaluation of worldwide climate and greenhouse technology combinations. However, running the models requires expert skills. Our goal was to deliver a simplified software tool, which would allow horticultural suppliers, researchers and growers to autonomously rank alternative investments, for a specific combination of region, greenhouse design and crop. The Investment Order Tool was developed in cooperation with selected horticultural supply companies for the regions Almeria in Spain and the Jordan Valley. In Spain, a flat roofed Parral type greenhouse was compared to an industrial multi-span greenhouse. In Jordan a single tunnel greenhouse was compared to an industrial multi-span greenhouse with passive crop based cooling. The Investment Order Tool uses a one-time run of the Adaptive Greenhouse Methodology based on local information. This data set allows further off-line calculations. All adaptions in greenhouse construction and cultivation system are defined as relative production changes from the local standard. The adaptations are provided with their specific costs and benefits. The investments compared include: reverse osmosis; substrates; nutrient dosing; climate-adapted cultivars; recirculation of drainage water; ventilation capacity; shading screens and thermal screens. The Investment Order Tool informed growers on the investment order with the highest return on investment and the investment order with the lowest demand for capital. Nursery specificity was realized by permitting user defined yield and market price level per month and by defining a first and second class for product quality. It is hoped the Investment Order Tool encourages growers and local authorities to base investment decisions on increasingly solid knowledge.

Modern energy-efficient greenhouses are built on a large scale with glass with anti-reflection treatments to get more sunlight into the greenhouse and thus more solar energy to save fossil fuels and more sunlight for more production. Uncertainty in how a new greenhouse will perform in the next 10 years after construction will lead to reluctance to invest in energy-saving measures and innovation in general. By removing this uncertainty, the sector will be able to invest more confidently in modern energy-efficient greenhouses. After all, if the glass is cleaned incorrectly and part of the light transmission is lost, this has direct consequences for production. The project shows which cleaning agents are safe for AR glasses and which are effective against contamination by chemical or microbiological dirt typically found on greenhouses. Moderne energiezuinige kassen worden op grote schaal gebouwd met glas met anti-reflectie coatings of oppervlaktebehandelingen om zo meer zonlicht in de kas te krijgen en daarmee meer zonne-energie. Dit draagt bij aan de besparing van fossiele brandstoffen en meer licht voor een hogere productie. Onzekerheid in hoe een nieuwe kas de opvolgende 10 jaar na de bouw zal presteren zal leiden tot terughoudendheid bij het investeren in onder andere energiebesparende maatregelen en vernieuwing in het algemeen. Door deze onzekerheid weg te nemen zal de sector met meer vertrouwen kunnen investeren in moderne energiezuinige kassen. Immers als het glas verkeerd wordt schoongemaakt en een deel van de lichttransmissie verloren gaat heeft dit direct gevolgen voor de productie. Het project laat zien welke reinigingsmiddelen veilig zijn voor AR glazen en welke effectief zijn tegen vervuiling door typisch op kassen voorkomend chemisch vuil of microbiologisch vuil.