Insect production is generally a monoculture where insects are kept in an enclosed environment with a stable climate to maximise production. To maintain these conditions air treatment is necessary, which results in high operational costs. Combining insect rearing with hydroponic greenhouse cultivation (HGC) of fruit vegetables might offer an opportunity for cost reduction. Fruit vegetables generally require more elevated air temperature, while leaving enough space under the substrate supporting gutters to allow insect rearing. In this study the feasibility of combining both production systems was evaluated with mealworms ( Tenebrio molitor ) and cucumber HGC serving as model species. The influence of the greenhouse climate was assessed by rearing mealworms simultaneous at two locations (a climate room and a cucumber HGC). Furthermore, pruning waste and aesthetically declined fruits could serve as a feed for insects. This was tested by comparing 4 different wet feeds (whole and mashed cucumber pruning, tomatoes and agar-agar). Larval growth was monitored and at harvest the mealworm yield was compared among treatments. Mealworm growth in the greenhouse was on average 8.1% slower than growth in a climate room even though the average ambient temperature in the greenhouse was lower and more variable (22.1±3.30 °C standard deviation compared to 27.0±0.34 °C). Moreover, the results showed that the tested HGC residues can be used as wet feed given that mashed cucumber pruning gave similar results as agar-agar (control) and tomatoes even outperformed the control significantly in terms of growth. ‘Entomoponics’ is introduced as the name for the combination of insect production and HGC of vegetables as a way to create added value in unused heated space inside a greenhouse and valorise greenhouse residues.

Didymella bryoniae (synonym Stagonosporopsis cucurbitacearum) is a necrotrophic fungus which can cause internal and external fruit rot in cucurbits. Infection of living material occurs by mycelium growth starting from dying material or by infection via the flower. This results in important production losses due to rotten and malformed fruits. A set of control measures has been evaluated, which resulted in an advice to the growers based on a combination of both preventative and curative measures. Out of 12 fungicides and six biocontrol organisms tested for their effectiveness against D. bryoniae in a semi-commercial crop, four chemical crop protection products showed a good result. These treatments are, however, a temporary solution. Differences in plant infections depend mainly on cultivation methods, plant morphology, fruit charge and climate. Moisture plays an important role. Climate and infection data of 6 growers show that problems occur when the humidity deficit is low. This finding was confirmed in a greenhouse trial. In addition, irrigation should be reduced in the evening and the night. It was demonstrated that air circulation has a limited but positive influence in preventing infections and inhibiting fungal growth. The results of these trials were combined in an integrated control strategy for D. bryoniae in cucumber.

Insufficient pollination, resulting from low pollen availability, leads to dark and pointy, non-marketable fruits. It is a major cause of economic losses during spring zucchini production in Flanders, where hormonal sprays are not authorized. As the differentiation of flower primordia into male flowers is being favored by summer conditions, low daily temperatures are one of the key limiting factors regarding pollen production. This research aimed to determine an optimal heating strategy for early season production. During spring 2016 and 2018, field trials were conducted to determine the minimal temperature required to prevent a shortage of male flowers. In 2016, a flat temperature regime (DIF=0 degrees C) was compared to a positive DIF of 6 degrees C at two research stations; in one location the daily temperature (DT) was set at 13 degrees C, in the other at 17 degrees C. An average daily temperature (ADT) below 14 degrees C during the first month after planting resulted in plants with a flower sex ratio male:female (FSR) below 1:9 for nearly two months. This ratio is considered to be the minimal threshold for zucchini setting. At 17 degrees C, FSR stayed above this threshold and less pointy fruits were harvested. Installing a positive DIF had no effect on FSR and is preferred over a DIF=0 degrees C heating regime because of its lower energy consumption. In 2018, ADT was decreased from 17 to 15 degrees C after one month cultivation, leading to a slight drop in sex ratio and a relative short period lacking male flowers. The highest fruit quality was seen at the highest ADTs tested. Prevention of male flower insufficiency requires at least an ADT above 15 degrees C.

Male flower shortage is a major reason of insufficient pollination in zucchini (Cucurbita pepo L.), leading to pointy fruits that rot quickly in the post-harvest phase.Harvesting pollen grains early in the season, when male flowers are abundant, followed by storage and subsequent manual pollination, could be a solution, provided that high pollen viability is maintained.Therefore, insight in parameters affecting pollen viability during anthesis and under storage are needed to advice growers on the most successful pollination strategy.Pollen viability was determined using Fluorescein Diacetate (FDA) and digital image analysis performed with Image J.Under practice conditions, viability started to diminish three hours after anthesis.At flower closing, only 60% of pollen grains remained viable and the next morning no more than 10%.In order to assess the impact of storage on pollen viability, pollen grains were subjected to different relative humidities and storage times.Stored at 20°C and 80% RH or lower for four hours, at least 90% of the pollen turned out to be non-viable.At 20°C and 90%, RH pollen viability remained above 50% for eight hours.When female flowers were pollinated with stored pollen (five days or longer), none of the fruits set sufficiently to be marketable, while fresh harvested pollen resulted in 90% marketable fruits.Therefore, pollen should be harvested and applied on the stigma within three hours after anthesis in order to ensure good fruit setting.Pollen could not be stored longer than eight hours without severe loss of viability or pollinating capacity.

Lamb's lettuce (Valerianella locusta L.) is occasionally stored by the growers before delivering to the vegetable auctions in anticipation of better prices. The aim of this experiment was to optimize the storage methods that can be used at the level of the grower. Plants from commercial growers were stored at 1 and 4 degrees C. Half of the storage boxes at each temperature were wrapped in shrink-film. At 5, 7, 14 and 21 days after storage the plant quality was determined by a panel of experts. Withering of the plants was higher without wrapping. Wrapping combined with higher temperatures reduced withering but favoured leaf rot. However, the plants that were wrapped and stored at 1 degrees C still met the requirements of the retail after 21 days. Withholding the wrapping application until plant temperature has reached the temperature set point could optimize the storage quality because the wrapping slows down the cooling process. Nevertheless, storage by the grower beyond two weeks is not advised. Yellowing of the leaves becomes an issue and as this process accelerates with higher temperatures, problems could occur further down the distribution chain.

An adequate irrigation schedule is necessary to optimize water-use efficiency, prevent nutrient leaching and maintain optimal growing conditions in soil-bound lettuce production. As Flemish growers base their strategy mainly on experience and basic soil sampling, the implementation of a decision support system (DSS) could improve their irrigation management. We simplified an already adapted Penman-Monteith model for calculation of actual water demand of lettuce crops, by reducing the amount of essential input variables from five to three namely irradiation (Rs), ambient temperature (Ta) and relative humidity (RH). Data collection was facilitated using the climate computer or a custom developed sensor module. To promote implementation in practice, a user-friendly web application was developed. The irrigation management decision support tool (IMDST), referring to the combination of sensor module and web-application, was introduced in 12 Flemish greenhouses. Four growers validated the tool in 16 plantings, comparing model irrigation (MI) with their personal irrigation (PI) strategy. In half of them, no differences in irrigation amount nor crop yield were observed. In four, heavier crops were obtained following MI and in two lighter crops. In only one planting, MI yielded water savings of more than 10%, without adverse effects on yield. In two other plantings, MI required at least 10% more water compared to PI, without providing any gain in yield or quality. The remaining eight growers applied the tool as DSS in over 30 plantings divided over different seasons. The use of the IMDST in those plantings revealed that for light soil textures, like sand, the model generally advised less water than growers normally would apply. On loamy soils, growers rapidly gained confidence in the tool, as calculations closely resembled their own strategy. By deploying the IMDST on professional horticultural production sites, growers acquired hands-on experience and learned how the tool contributes to a smarter, more sustainable, irrigation management. Growers confirmed usefulness of the IMDST, providing that recommendations should be interpreted according to PI strategies.

HomePlant DiseaseVol. 102, No. 5First Report of Fusarium oxysporum f. sp. lactucae Race 4 on Lettuce in Belgium PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Fusarium oxysporum f. sp. lactucae Race 4 on Lettuce in BelgiumJ. Claerbout, S. Venneman, I. Vandevelde, A. Decombel, P. Bleyaert, A. Volckaert, J. Neukermans, and M. HöfteJ. ClaerboutSearch for more papers by this author, S. VennemanSearch for more papers by this author, I. VandeveldeSearch for more papers by this author, A. DecombelSearch for more papers by this author, P. BleyaertSearch for more papers by this author, A. VolckaertSearch for more papers by this author, J. NeukermansSearch for more papers by this author, and M. Höfte†Corresponding author: M. Höfte; E-mail: E-mail Address: monica.hofte@ugent.beSearch for more papers by this authorAffiliationsAuthors and Affiliations J. Claerbout , Department of Plants and Crops, Laboratory of Phytopathology, Ghent University, 9000 Gent, Belgium S. Venneman I. Vandevelde , PSKW (Proefstation voor de groenteteelt), 2860 Sint-Katelijne-Waver, Belgium A. Decombel P. Bleyaert , Inagro vzw, 8800 Rumbeke-Beitem, Belgium A. Volckaert J. Neukermans , PCG (Provinciaal Proefcentrum voor de Groenteteelt Oost-Vlaanderen vzw), 9770 Kruishoutem, Belgium M. Höfte † , Department of Plants and Crops, Laboratory of Phytopathology, Ghent University, 9000 Gent, Belgium. Published Online:16 Mar 2018https://doi.org/10.1094/PDIS-10-17-1627-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In Belgium, lettuce (Lactuca sativa L.) is an important crop that is mainly grown in soil in glasshouses. During autumn 2015, wilting symptoms on butterhead lettuce ‘Halewyn’ (Rijk Zwaan, the Netherlands) and an unknown cultivar were observed in two different commercial glasshouses in the Province of Antwerp, Belgium. The disease incidence was around 10 and 20%, respectively, with a disease severity of 9 and 18%. Since 2015 the disease has spread very fast; already 15% of the glasshouse lettuce production area in Flanders (northern part of Belgium) is infested. Dwarf growth and yellowing of the outer leaves were noticed on affected plants, followed by complete wilting and death. The vascular tissue showed a brown to red discoloration. Affected root and leaf tissues were surface-sterilized with 1% NaOCl for 30 s and washed three times with sterile water. The plant tissues were cut into 1 cm2 pieces and plated on potato dextrose agar amended with streptomycin sulfate (100 mg/liter) and incubated at room temperature (19 to 22°C). Consistently dense fungal colonies with pale cream to purplish mycelia grew out of the plant tissues. Microconidia, macroconidia, and chlamydospores typical for Fusarium oxysporum were observed. Microconidia from isolates Fus1.01 and Fus1.02, coming from the two different glasshouses, measured respectively 5.99 to 8.64 (mean 6.98) × 2.75 to 4.39 (mean 3.32) µm and 6.75 to 11.50 (mean 8.42) × 2.75 to 4.59 (mean 3.61) µm. Chlamydospores were terminal and intercalary, rough walled, and measured 6.86 to 10.72 (mean 8.25) µm for Fus1.01 and 6.13 to 10.80 (mean 8.55) µm for Fus1.02. Macroconidia were straight to slightly curved with three septa and measured 24.49 to 31.27 (mean 27.27) × 2.93 to 4.42 (mean 3.84) µm for Fus1.01 and 20.91 to 26.09 (mean 22.58) × 3.42 to 4.70 (mean 3.98) µm for Fus1.02. Subsequently, DNA from single-spore cultures (Fus1.01 and Fus1.02) was extracted using the Invisorb Spin Plant Mini Kit (Stratec Molecular). The translation elongation factor 1-α (EF1-α) gene was amplified using primers EF1/EF2 (O’Donnell et al. 1998) and sequenced in both directions by LGC Genomics (Berlin) using Sanger sequencing technology. The EF1-α sequences of both isolates showed 100% similarity with the EF1-α sequence of F. oxysporum f. sp. lactucae strain S1 (accession no. DQ837657) (Mbofung et al. 2007) and were deposited (MG599512 and MG599513). By using specific primers FPUF and FPUR (Gilardi et al. 2016), we could show that both isolates belong to race 4. Moreover, pathogenicity tests with three different lettuce cultivars (‘Costa Rica No. 4’, ‘Banchu Red Fire’, and ‘Romana Romabella 30 CN’) provided by Rijk Zwaan (the Netherlands) were conducted to confirm the positive result with the primers FPUF and FPUR and to complete Koch’s postulates. Roots of 2-week-old lettuce plants were dipped in a 5 × 105 spores/ml suspension, and five plants per cultivar were used. The experiment was carried out twice. Inoculated lettuce seedlings were planted in 100 g of steamed potting substrate and were maintained in a climate room at 24°C. In both experiments, wilting was observed after 4 weeks for the cultivars Costa Rica No. 4 and Romana Romabella 30 CN, but no symptoms could be seen on the cultivar Banchu Red Fire. F. oxysporum was consistently reisolated from all inoculated cultivars. These results are consistent with pathogenicity tests carried out before with two isolates of F. oxysporum f. sp. lactucae race 4 from the Netherlands (Gilardi et al. 2016) and indicate that this new race is also the causal agent of Fusarium wilt on lettuce in Belgium. This report shows that race 4 is spreading fast and imposes a serious risk to other lettuce production areas in Europe.References:Gilardi, G., et al. 2016. Plant Pathol. 66:677. https://doi.org/10.1111/ppa.12616 Crossref, ISI, Google ScholarMbofung, G. Y., et al. 2007. Phytopathology 97:87. https://doi.org/10.1094/PHYTO-97-0087 Link, ISI, Google ScholarO’Donnell, K., et al. 1998. Proc. Natl. Acad. Sci. U.S.A. 95:2044. https://doi.org/10.1073/pnas.95.5.2044 Crossref, ISI, Google ScholarDetailsFiguresLiterature CitedRelated Vol. 102, No. 5 May 2018SubscribeISSN:0191-2917e-ISSN:1943-7692 Metrics Article History Issue Date: 20 Apr 2018Published: 16 Mar 2018First Look: 22 Dec 2017Accepted: 19 Dec 2017 Page: 1037 Information© 2018 The American Phytopathological SocietyFundingVLAIOGrant/Award Number: 140984Cited byFusarium isolates from Belgium causing wilt in lettuce show genetic and pathogenic diversity16 November 2022 | Plant Pathology, Vol. 97Discovery and fine mapping of a novel resistance locus to Fusarium wilt race 2 in lettuce (Lactuca sativa L.)29 July 2022 | Euphytica, Vol. 218, No. 8Marulda solgunluğa neden olan Fusarium oxysporum f. sp. lactucae etmenine karşı Metarhizium anisoplae’nın biyokontrol potansiyelinin belirlenmesi31 March 2022 | European Journal of Science and TechnologyFusarium oxysporum f.sp. lactucaeCABI Compendium, Vol. CABI CompendiumGenetic Resistance of Lactuca spp. against Fusarium oxysporum f. sp. lactucae Race 1HortScience, Vol. 56, No. 12Low temperatures favour Fusarium wilt development by race 4 of Fusarium oxysporum f. sp. lactucae12 May 2021 | Journal of Plant Pathology, Vol. 103, No. 3Development of PCR-based marker for resistance to Fusarium wilt race 2 in lettuce (Lactuca sativa L.)31 May 2021 | Euphytica, Vol. 217, No. 6The Population of Fusarium oxysporum f. sp. lactucae in California and ArizonaKelley R. Paugh and Thomas R. Gordon13 April 2020 | Plant Disease, Vol. 104, No. 6First report of damping-off disease caused by Fusarium oxysporum in Pinus massoniana in China4 February 2020 | Journal of Plant Diseases and Protection, Vol. 127, No. 3Emerging soilborne pathogens and trends in their managementActa Horticulturae, No. 1270Preventative treatments in nursery with different biocontrol agents and potassium phosphite salt to control Fusarium wilt agents of lettuce and rocketActa Horticulturae, No. 1270Seed and Propagative Material18 March 2020IPM for Protecting Leafy Vegetables Under Greenhouses18 March 2020First Report of Fusarium oxysporum f. sp. lactucae Race 4 on Lettuce in ItalyG. Gilardi, A. Garibaldi, S. Matic, M. T. Senatore, S. Pipponzi, A. Prodi, and M. L. Gullino12 August 2019 | Plant Disease, Vol. 103, No. 10Ready-to-Eat Salad Crops: A Plant Pathogen’s HeavenMaria Lodovica Gullino, Giovanna Gilardi, and Angelo Garibaldi25 July 2019 | Plant Disease, Vol. 103, No. 9

In this highly urbanized world, there is a growing demand to supply fresh food into the cities. Urban farming can deliver an answer, but experience is still limited. At the same time, greenhouse horticulturalists face important challenges, such as availability of space and energy costs. To address these challenges, Inagro is building an 8000-m(2) research greenhouse, Agrotopia, on the rooftop of a warehouse of REO Veiling, agricultural auction market. Integrated in the city of Roeselare (Belgium), the greenhouse will use resources from the city environment such as energy and water. The greenhouse aims to be energy neutral by exchanging residual heat and electricity with REO Veiling. A 6000-m(2) cultivation area to grow vegetables soilless, will allow to develop and demonstrate best practices for hydroponic systems. One compartment will be equipped for multilayer indoor growing with artificial lighting. A 12-m high vertical compartment will allow to explore the potential of growing vegetables along high walls and maximize cultivation area. Specific attention will be paid to minimize energy use by applying the Dutch concept of "Next Generation Growing" and comparing different types of energy screens. Other research topics will include integrated pest management, reuse of nutrient waste solutions, use of low-grade heat from the city waste incinerator, possible applications for non-harvestable plant tissues, etc. The greenhouse will also serve as a living lab to exchange knowledge and develop innovations through co-creation, involving all relevant stakeholders in the innovation process. Technology developers will have the opportunity to engage in this co-creation process or to demonstrate their latest innovations in an exhibition room. Agrotopia will deliver both an inspiring research environment, resulting in innovative solutions for high technological greenhouse horticulture and urban farming, and an explicit example of urban vegetable production.

Lamb's lettuce (Valerianella locusta L.) that is presented to the market is not always freshly harvested. The product can be stored for up to 28 days and is indistinguishable from fresh material by the human eye. However, due to the prior storage period, the shelf-life potential is limited, and this leads to losses in distribution and a lower quality for the consumer. This work aims to develop a rapid and non-destructive methodology using visible/near-infrared (Vis/NIR) reflectance spectroscopy to quantify the postharvest age. Vis/NIR reflectance spectra were linked to the time in storage by partial least-squares regression (PLS). Two variable selection techniques, genetic algorithms PLS and Monte Carlo uninformative variable elimination PLS, were combined to improve the accuracy and robustness of the prediction model while decreasing the number of wavelengths used. The final model used only 10% of the original wavelength variables, while the root mean squared error of cross validation decreased from 6.0 to 3.6 days. The final model was tested using two external test sets and had a maximum root mean squared error of prediction of 3.7 days. Therefore, it was concluded that Vis/NIR reflectance spectroscopy can be a valid, rapid and non-destructive method for identifying and quantifying the postharvest age of lamb's lettuce.

Although growers seem to be able to control the incidence of tipburn in soilgrown lettuce (Lactuca spp.), this physiological disorder causes substantial yield losses in hydroponics (up to 50%). Tipburn is generally considered to be a calcium deficiency related disorder, but literature exhibits apparently contradictory findings, because the research always focused on the effects of the environment on the occurrence of tipburn, whereas the plant physiological aspects were seldom included. Therefore, there is a strong need for a plant physiological interpretation of the tipburn disorder, which correlates the different environmental effects to the plant physiological processes. In this study, we present the use of plant sensors to assess the plant physiological response to its environment with respect to the incidence of tipburn. As such, stem diameter and leaf thickness were continuously monitored, because variations in these variables are strongly related to variations in the plant water relations, turgor pressure and growth rate. Leaf thickness measurements were combined with a mechanistic model to detect periods of water deficits or abrupt changes in turgor pressure. This approach could additionally help to monitor root pressure and investigate the hypothesis that root pressure has beneficial effects on the supply of calcium to slowly transpiring leaves. As such, growth rate, supply of calcium to low transpiring leaves and abrupt variations in turgor pressure, all of which are associated with tipburn, could be instantly visualised by these plant sensors and consequently identify environmental drivers for tipburn.