Greenhouse Growers Research Articles

Improved control of Trialeurodes vaporariorum using mixture combinations of entomopathogenic fungi and the chemical insecticide spiromesifen

Greenhouse whitefly (Trialeurodes vaporariorum) is a major global pest, causing direct damage to plants and transmitting viral plant diseases. Management of T. vaporariorum is problematic because of widespread pesticide resistance, and many greenhouse growers rely on biological control agents to regulate T. vaporariorum populations. However, these are often slow and vary in efficacy, leading to subsequent application of chemical insecticides when pest populations exceed threshold levels. Combining chemical and biological pesticides has great potential but can result in different outcomes, from positive to negative interactions. In this study, we evaluated co-applications of the entomopathogenic fungi (EPF) Beauveria bassiana and Cordyceps farinosa and the chemical insecticide spiromesifen in laboratory bioassays. Complex interactions between the EPFs and insecticide were described using an ecotoxicological mixtures model, the MixTox analysis. Depending on the EPF and chemical concentrations applied, mixtures resulted in additivity, synergism, or antagonism in terms of total whitefly mortality. Combinations of B. bassiana and spiromesifen, compared to single treatments, increased the rate of kill by 5 days. Results indicate the potential for combined applications of EPF and spiromesifen as an effective integrated pest management strategy and demonstrate the applicability of the MixTox model to describe complex mixture interactions.

Daily Light Integral, but Not the Photoperiod, Influences the Time to Flower and Finished Quality of Dianthus Specialty Cut Flowers

Because of the burgeoning year-round demand, greenhouse growers across the United States are increasingly becoming interested in producing specialty cut flowers for local and regional markets. However, outdoor or high tunnel production is not possible year-round in northern latitudes because of low temperatures and radiation intensities experienced during the winter and early spring. Additionally, natural short days in these seasons can limit which photoperiodic crops can be grown. Thus, our objectives were to quantify the influence of the photoperiod and daily light integral (DLI) on greenhouse-grown dianthus ‘Amazon Neon Cherry’ and ‘Amazon Rose Magic’ (Dianthus barbatus interspecific) cut flowers during the young plant and finishing stages. Seeds of both cultivars were sown under 9-, 10-, 11-, 12-, 13-, 15-, or 16-hour photoperiods and a DLI of either ≈5 or 10 mol⋅m−2⋅d−1. After 4 weeks, seedlings from several young-plant photoperiods were distributed across 11-, 12-, 13-, 14-, 15-, or 16-hour photoperiods or a 4-hour night interruption (NI) under a DLI of either ≈5 (low) or 14 (moderate) mol⋅m−2⋅d−1 for finishing. The young plant photoperiod generally had a statistical, but not commercial, influence on development and finished cut flower quality, whereas a 16-h finishing photoperiod marginally hastened development compared with an 11-hour finishing photoperiod. Additionally, stems were 11 to 13 cm longer when finished under the 16-hour photoperiod compared with those finished under the 11-hour photoperiod. Day length minimally influenced the time to flower and harvest, indicating a day-neutral flowering response. However, plants finished under a moderate DLI reached visible flower bud and were harvestable 9 to 10 days earlier than those finished under a low DLI. Additionally, ≈99% of cut flowers finished under a moderate DLI were harvestable, whereas only up to 32% and 57% of dianthus ‘Amazon Rose Magic’ and ‘Amazon Neon Cherry’, respectively, finished under a low DLI were harvestable. Although finished stem lengths were comparable between DLI treatments, cut flower stems were up to 29.6% thicker under a moderate DLI. These findings indicate that high-quality greenhouse-grown dianthus ‘Amazon Neon Cherry’ and ‘Amazon Rose Magic’ cut flowers can be produced when grown under any photoperiod between 9 and 16 hours for 4 weeks (during the young plant stage) and finished under any photoperiod between 11 and 16 hours or a 4-hour NI during finishing. If longer stems are desired, then plants can be finished under a 16-hour photoperiod. Young plants should be grown under a moderate DLI ≥10 mol⋅m−2⋅d−1 to promote biomass accumulation and reduce the young plant crop time. Additionally, plants should be finished under a moderate DLI ≥14 mol⋅m−2⋅d−1 to reduce crop time and increase stem thickness and yield.

Resistance to Seven Site-Specific Fungicides in Botrytis cinerea from Greenhouse-Grown Ornamentals.

The fungal pathogen Botrytis cinerea is a notorious problem on many floriculture greenhouse hosts including petunia, geranium, and poinsettia; these key crops contribute to the $6.43 billion U.S. ornamental industry. While growers use cultural strategies to reduce relative humidity and free moisture to limit Botrytis blight, fungicides remain a primary component of control programs. Isolates (n = 386) of B. cinerea sampled from symptomatic petunia, geranium, and poinsettia in Michigan greenhouses from 2018 to 2021 were screened for resistance to eight fungicides belonging to seven Fungicide Resistance Action Committee (FRAC) groups. Single-spored isolates were subjected to a germination-based assay using previously defined discriminatory doses of each fungicide. Resistance was detected to thiophanate-methyl (FRAC 1; 94%), pyraclostrobin (FRAC 11; 80%), boscalid (FRAC 7; 67%), iprodione (FRAC 2; 65%), fenhexamid (FRAC 17; 38%), cyprodinil (FRAC 9; 38%), fludioxonil (FRAC 12; 21%), and fluopyram (FRAC 7; 13%). Most isolates (63.5%) were resistant to at least four FRAC groups, with 8.7% of all isolates demonstrating resistance to all seven FRAC groups tested. Resistance frequencies for each fungicide were similar among crops, production regions, and growing cycles but varied significantly for each greenhouse. Phenotypic diversity was high, as indicated by the 48 different fungicide resistance profiles observed. High frequencies of resistance to multiple fungicides in B. cinerea populations from floriculture hosts highlight the importance of sustainable and alternative disease management practices for greenhouse growers.

Sugarcane Bagasse Is an Effective Soilless Substrate Amendment in Quick-turn Osteospermum Production

Many greenhouse growers rely on peat-based soilless substrates to produce salable crops in a relatively short period of time. Peat-based substrate suppliers often incorporate additional organic materials such as wood fiber to extend peat supplies. Given the relative success of wood-based substrates, growing interest in other fiber materials such as sugarcane bagasse may provide similar benefits for substrate processers. The objective of this research was to evaluate substrate properties and the productivity of a short-term floriculture crop, Osteospermum ‘Bright Lights Purple’, in a commercially available peat-based substrate (PL) that has been amended with either commercially available wood fiber [Hydrafiber (HF)] or an aged sugarcane bagasse fiber (SCB). Thus, substrates consisting of PL amended with 15% or 30% HF or SCB were developed. Plants were fertigated weekly at rates of 100, 200, or 300 ppm N, respectively. Crop growth and fertility dynamics were assessed. Substrate shrinkage was greatest in the 30% bagasse blend but had minimal impact given the 2-month crop cycle. The incorporation of 15% and 30% SCB and HF produced slight changes in pH over a 9-week growth period, with HF generally raising pH and SCB generally lowering pH compared with the 100% PL, showing promise for bagasse in managing substrate pH where irrigation water has high pH and/or alkalinity. Substrate EC was initially reduced by blending SCB and, to a lesser extent, HF, but differences ceased to exist by the end of the experiment. Chlorophyll and blooms were abundant in all substrates and fertigation rates. Regardless of fertigation rate, 30% HF had the lowest growth index and shoot dry mass, and 30% SCB had the lowest root dry mass, although differences were not visually apparent. Foliar N concentrations were greatest in plants grown in the PL and SCB substrates and lowest in HF blends. Overall, growth and dry mass differences were minimal across substrate treatment and fertigation rate, and all plants were marketable with statistically similar shelf life. In conclusion, this research indicates the potential of using SCB as a substrate amendment for short-term crop systems in a similar manner as wood fiber.

Experimental evaluation of three different dehumidifiers for greenhouses in cold regions

Selecting a dehumidifier is not easy for greenhouse growers because of its high capital and operation cost and new emerging technologies, besides selection variations with crop species, local weather climate, and greenhouse sizes. The technical performance evaluation of various dehumidification technologies in commercial-scale greenhouse settings and their comparative results can give growers the new information needed to select the best dehumidifier. In this study, the field performance of a newly developed state point liquid desiccant (SPLD) dehumidifier is compared with two other commercial dehumidification technologies; direct contact liquid desiccant (DCLD) dehumidifier, and heat recovery ventilator (HRV), in ornamental (rose) and tomato greenhouses. Under the test condition, among the three dehumidifiers, the HRV unit had the highest calculated moisture removal rate (MRR) of 189.1 kg hr-1, the lowest moisture removal cost of 0.022 $ kg−1, and the lowest electricity consumption (0.02 kWh kg−1 of moisture removal). The highest electrical consumption was found in the SPLD unit under the wet mode, with an average of 0.44 kWh kg−1. However, the SPLD-wet mode was the most efficient regarding net energy consumption (0.53 kWh kg−1). The DCLD showed a moderate performance on electrical energy (0.15 kWh kg−1) and net energy consumption (0.775 kWh kg−1) with good indoor humidity control. The SPLD unit under dry mode was similar to the HRV unit regarding moisture removal cost (0.026 $ kg−1) and electricity consumption (0.046 kWh kg−1). The comparative results of this study indicate that a single dehumidification technique cannot be both technically effective and economically cost-saving year-round. Thus, combining a low-cost technology, such as ventilation or a heat exchanger, and an internal dehumidification technology will be the most practical and feasible in cold regions.

A theoretical comparison of nursery and greenhouse growers’ water conservation and water treatment technology adoption in the United States

A theoretical comparison of nursery and greenhouse growers’ water conservation and water treatment technology adoption in the United States

Spectrum of low-intensity screw-in horticultural light-emitting diode lamps influences time to flower and finished quality of long-day ornamental species

Bedding plants with a long-day (LD) flowering requirement constitute a substantial portion of annuals and perennials produced in the United States for spring sales. However, greenhouse production often occurs when the day length is naturally short and not conducive for flower induction of LD plants (LDPs). Thus, growers must create artificial LDs through day-extension, cyclic, or night-interruption (NI) lighting to promote flowering of LDPs. Many low-intensity, screw-in horticultural light-emitting diode (LED) lamps are now commercially available, though their emission spectra vary. Therefore, the objective of our study was to quantify the influence of various commercially available low-intensity screw-in horticultural LED lamps on the flowering and growth responses of LDPs. We grew several obligate and facultative LD annuals under either a 9-h truncated short-day (SD), or a 9-h SD with NI lighting from 2200 to 0200 hr each day. NI treatments consisted of Feit 9-W Non-Dimmable Plant Grow Lights (Feit), General Electric (GE) 10-W Arize™ Greenhouse Pro-Photoperiodic LED Lamps (GE), Philips 13-W GreenPower LED flowering lamp 2.0 s (Philips), or TotalGrow ™ 16-W Pure Flowering 200 Lamps (TotalGrow). Philips and GE lamps hastened flowering of all LDPs studied, while TotalGrow lamps promoted or hastened flowering on a genus-specific basis. Flowering was delayed by up to 11 d under Feit lamps and plants developed more nodes and inflorescences at open flower than the other lighting treatments. Generally, the height of plants within genera were similar regardless of the lighting treatment. However, plants grown under TotalGrow lamps had a larger stem length than those grown under the other lighting treatments as they emitted the highest percentage of FR light. Therefore, greenhouse growers should not base their decision solely on the price of lamps.

A new greenhouse energy model for predicting the year-round interior microclimate of a commercial greenhouse in Ontario, Canada

Modelling the energy use and microclimate of a greenhouse can be a valuable tool for commercial growers, making it possible to predict the impact of making changes to greenhouse systems and operation. This allows energy saving scenarios to be identified and can reduce energy use costs. In this study, a lumped capacitance thermal model is developed to simulate the greenhouse interior microclimate based on exterior conditions and operating settings. The current study incorporated many aspects of a complex commercial greenhouse not commonly seen in literature, such as evaporative cooling pads, dehumidification technology, gas burners, energy curtains, supplementary heating and lighting, and forced ventilation. The model was successfully validated at multiple greenhouse sections of a commercial greenhouse during spring, summer, and fall conditions in the southern Ontario climate. Data was collected from the greenhouse from March to November of 2019 at 15-minute intervals. The measured interior temperature and relative humidity data were used to evaluate the accuracy of the model simulations, while other measurements, such as solar radiation, were used as model inputs. The study greenhouse was unique, as potted rose crops were cycled between sections during the growth stage. This made variation in plant properties relatively small during the different seasons. Detailed information on the model methodology was included to improve reader’s understanding. Overall, the model accuracy is comparable or even better when compared to similar models in the literature, proving it is versatile and can be used as a design tool moving forward. In the future, the current model will be used to conduct comparative analyses of a range of different energy-use reduction technologies and operating procedures (including year-round production) to quantify the most economically and practically feasible options specifically for Ontario greenhouse growers.

Impact of Information on Attitudes Regarding Greenhouse Lighting Externality Regulation

AbstractAs food producers face increasing costs, many greenhouse growers are turning to controlled environment agriculture. The use of light-emitting diode (LED) supplemental lighting systems may increase a producer’s profitability, but it also comes with a unique set of externalities. Using an online survey, we found that showing images of light pollution from supplemental LED lighting sources facilitated respondents to want more regulation with state government being the desired regulator. Several significant factors influenced survey respondents’ posttreatment preference outcomes for different levels of regulation and regulators including demographic characteristics as well as initial attitudes toward LED lighting systems before treatment.

Deep Learning to Predict Plant Growth and Yield in Green House Environment

Effective plant growth and yield prediction is an essential task for greenhouse growers and for agriculture in general. Developing models which can effectively model growth and yield can help growers improve the environmental control for better production, match supply and market demand and lower costs. Recent developments in Machine Learning (ML) and, in particular, Deep Learning (DL) can provide powerful new analytical tools. The proposed study utilities ML and DL techniques to predict yield and plant growth on Ficus Benjamin stem growth, in controlled greenhouse environments. We deploy a new deep recurrent neural network (RNN), using the Long Short-Term Memory (LSTM) neuron model, in the prediction formulations. Both the former yield, growth and stem diameter values, as well as the microclimate conditions, are used by the RNN architecture to model the targeted growth parameters. A comparative study is presented, using ML methods, such as support vector regression and random forest regression, utilizing the mean square error criterion, in order to evaluate the performance achieved by the different methods.

Understanding Greenhouse Growers’ Willingness to Use Municipal Recycled Water on Food Crops: The Need for Tailored Outreach Coupled with Deep Engagement to Increase Adoption

Increasing demand on agricultural water resources have caused a greater need for the use of municipal recycled wastewater (MRW) globally. However, in the United States, greenhouse growers have been slow to use it in their greenhouse operations. In this study, we seek to understand the factors that motivate and limit use of MRW among US growers. Using national survey data from 2019 through 2020, we developed a logistic regression model to understand the many factors influencing growers’ willingness to use MRW on food crops. We find that MRW quality is a primary concern and that growers’ willingness to use MRW is shaped by their direct and indirect knowledge of MRW, garnered from their own and others’ experiences using it. Given these findings, improving adoption of MRW requires collective experiential learning opportunities that gather target audiences with educators, policymakers, end users, and local authorities to simultaneously provide hands-on experience tailored to growers’ particular knowledge and concerns with feedback from peers.

Socio-Economic Status, Growing Practices and Marketing Preferences of Greenhouse Growers: The Case of Çarşamba District

Bitkisel üretim, ağırlıklı olarak tarla ve bahçe gibi geleneksel üretim alanlarının yanı sıra örtü altı üretim alanları gibi kontrollü koşullarda da yapılmaktadır. Bu alanlardaki üretimin sürdürülebilirliğinin sağlanması açısından, üreticilerin durumlarının farklı parametrelerle tespit edilmesi önemlidir. Bu araştırma kapsamında Çarşamba ilçesinde örtü altı üretimi yapan üreticilerin sosyo-ekonomik profillerini, örtü altı üreticilik uygulamalarını ve pazarlama tercihlerini ortaya koymak amaçlanmıştır. Araştırmada; tabakalı örnekleme yöntemine göre seçilmiş olan üreticiler ile yüz yüze anket çalışması yapılmış ve üreticilerin ilgili parametreler yönünden durumları tespit edilmiştir. Araştırma sonucu üreticilerin; yaş ortalamasının 53, ailedeki ortalama fert sayısının 5,51, ortalama çiftçilik deneyim sürelerinin 33 yıl ve ortalama örtü altı yetiştiricilik deneyim sürelerinin 16,74 yıl olduğu saptanmıştır. Ayrıca üreticilerin; toprak analizi yaptırmaya mesafeli oldukları, genel olarak çiftlik gübresi kullanmayı tercih ettikleri, kimyasal gübre ve tarımsal mücadele ilaçlarını yaygın biçimde kullandıkları ve sulamada kuyu suyunu ve sulama sistemi olarak da damlama sulama sistemini kullandıkları tespit edilmiştir. İlave olarak üreticilerin; %60,60’ının üretim faaliyeti esnasında girdi kredisi kullandıkları, üretimde kullandıkları fideyi %70,90 piyasadan satın aldıkları ve üretmiş oldukları ürünleri %46,00 haller üzerinden ve %30,80 kendi olanaklarıyla pazarladıkları belirlenmiştir. Sonuç olarak; incelenen parametreler dikkate alındığında, bölgede örtü altı üreticiliği bakımından önemli bir potansiyelin olduğu söylenebilir. Bununla birlikte, bu potansiyelin etkin bir biçimde değerlendirilebilmesi için bilhassa girdi desteğinin artırılması ve pazarlama olanaklarının çeşitlendirilmesine yönelik tarımsal destek faaliyetlerinin artırılması gerektiği kanaatine varılmıştır.

A Supplemental Lighting Control Approach in Controlled Environment Agriculture to Reduce Peak Power Consumption

Global population growth requires efficient food production, especially with food security concerns due to natural resources limitation and climate constraints. Supplemental lighting is an effective means of increasing productivity in greenhouses. However, supplemental lighting electricity cost can be high, and systematic lighting strategies are required to reduce lighting electricity cost. Prior research has focused on minimizing electricity use or cost, while maintaining adequate crop growth. However, in addition to being charged for electricity consumption, US greenhouse growers also pay a demand charge that is based on the peak electricity use during a 15-min period within each billing cycle. This demand charge is in the same order of magnitude as the charge for the used electricity, but has been ignored in prior lighting optimization research. This paper presents a lighting strategy for controlled environments (like greenhouses) equipped with dimmable light-emitting diodes (LEDs) to minimize supplemental lighting electricity cost and peak power consumption of supplemental lighting. Markov-based sunlight prediction is employed to develop a realistic control strategy and improve its efficiency. Moreover, the impact of shifting the time of day during which supplemental lighting is used on peak power consumption is investigated. Compared to a heuristic method, the proposed method illustrates an up to 51% mean peak reduction.

IoT of melon plant continuous diagnostic technique using an open chamber system measurement for photosynthesis and transpiration

Greenhouse growers can utilize techniques to measure the condition of crops, such as growth rate and wilting degree, in addition to environmental information such as temperature, humidity, and solar radiation. These measurements can serve as supplementary data for cultivation management decisions. Among them, photosynthetic rate is a crucial indicator for crop productivity and yield. In this study, we aimed to develop a system that continuously measures the photosynthetic rate, an essential factor in crop biomass production, using an open chamber methodwithin a melon cultivation greenhouse. The measured data is uploaded to thecloud, enabling real-time monitoring of melon photosynthesis throughout the cultivation process. The developed system was implemented at a low cost by utilizing a CO2 sensor, a singleboard microcontroller, and a cloudbased database service. With this system, the net photosynthetic rate and transpiration rate of melon plants could be continuously measured over an extended period and accessed anytime using a PC or smartphone. Additionally, concurrent measurements of melon plant weight and fruit weight allowed for visualizing the plant’s response to environmental factors, including changes in photosynthesis and transpiration rates due to weather conditions.

The Effect of Propagation Substrate on Pythium Root Rot Severity and the Efficacy of Biopesticides

Modern greenhouse crop production utilizes soilless substrates that range from inorganic substrates (Oasis foam and rockwool) to blends of organic substrates (sphagnum peat moss, coconut fiber, bark mulch, wood chips, and wood products). Additionally, greenhouse growers utilize beneficial microorganisms in the form of commercial biopesticides to reduce disease. Few research studies have examined the effect of propagation substrate on the efficacy of commercial biopesticides under greenhouse production conditions. The objective of this study was to evaluate the effect of propagation substrates on commercially available microbial biopesticides (Rootshield WP, Cease, and Regalia) applied during propagation and at transplant for management of Pythium root rot. In this study, cucumber and calibrachoa were used as model crops. Over both cropping systems, plants propagated in Oasis foam had lower root rot compared with plants propagated in coconut coir. Across all biopesticide treatments, cucumber plants propagated in Oasis foam had 52% less root rot compared with plants propagated in coconut coir. In both infested and noninfested calibrachoa plants, plants propagated in Oasis foam had 45 to 67% less disease, and plants propagated in peat had 25 to 40% less disease compared with plants propagated in coconut coir. There was no effect of biopesticide on Pythium root rot severity, except for a reduction seen in calibrachoa plants propagated in coconut coir and treated with Rootshield WP. This research suggests that propagation substrate is important for root disease management.

Photosynthetic Daily Light Integral Influences Growth, Morphology, Physiology, and Quality of Swordfern Cultivars

Boston and Australian swordferns (Nephrolepis sp.) are popular tropical ferns for hanging baskets and containers; however, greenhouse production occurs during times of the year when growers may need to deploy shade or supplemental lighting to manage the growing environment. Our objectives were to quantify the impact of the daily light integral (DLI) on growth, morphology, physiology, and ornamental quality of containerized Nephrolepis species and cultivars, and to establish optimal DLIs for containerized swordferns to assist commercial greenhouse growers with light management strategies during production. Eleven cultivars of Boston swordfern [N. exaltata (L.) Schott Blue Bells, Compacta, Fluffy Ruffles, Gold, Montana, Nevada, Petticoat, Pom Pom, Super, Tiger, and True] and one cultivar of Australian swordfern [N. obliterata (R. Br.) J. Sm. Western Queen] were investigated. Plants were grown for 58 days at 20 °C and placed under one of four different fixed-woven shadecloths providing ≈86%, 62%, 42%, or 26% shade or no shade, thereby establishing mean DLIs of 3.2, 6.4, 10.7, 12.4, and 17.1 mol⋅m−2⋅d−1, respectively. For most cultivars, the growth index, which is an integrated measurement of height and diameter, decreased linearly as the DLI increased from 3.2 to 17.2 mol⋅m−2⋅d−1, resulting in smaller compact plants. Increasing the DLI significantly affected the frond number of each cultivar differently, whereas dry mass generally increased as the DLI increased from 3.2 to 10.7 to 12.4 mol⋅m−2⋅d−1 for most cultivars. For each cultivar, as the DLI increased from 3.2 to 17.1 mol⋅m−2⋅d−1, the chlorophyll concentration index decreased, whereas the hue angle increased and chroma was unaffected. Our results indicate that growers should maintain ≈10 to 12 mol⋅m−2⋅d−1 during greenhouse Nephrolepis production; however, DLIs ≥5.5 mol⋅m−2⋅d−1 and ≤16.5 mol⋅m−2⋅d−1 also improved the quality of some Nephrolepis cultivars.

Subsurface irrigation with ceramic emitters: Optimal working water head improves yield, fruit quality and water productivity of greenhouse tomato

Greenhouses are widely used in Northwest China, especially for tomato, which is the dominant crop. Subsurface irrigation with ceramic emitters (SICE) is a new water-saving technology for continuous low-rate water supply at constant soil moisture. However, a lack of knowledge still existed to define the suitable working water head for SICE to decrease water loss and promote tomato production, fruit quality, and water productivity. In this study, a greenhouse experiment was conducted during spring and autumn cultivation periods under SICE for five working water heads of 0.1 m to 0.5 m with intervals of 0.1 m and subsurface drip irrigation (SDI). The verified HYDRUS-2D model evaluated water balance components and water productivity. A structural equation model (SEM) was developed to determine interactive impacts of SICE and meteorological conditions in greenhouse on tomato yield, fruit quality, and water productivity. The results showed that SICE with a working water head of 0.4 m could be recommended, which created a suitable soil water content of the root zone within 70%–80% of field capacity (FC), resulting in a reduction of water loss from actual evaporation (Ea) and deep percolation (DP) by 12.32% and 21.88% respectively relative to SDI. Fruit weight, yield, water use efficiency (WUE), and irrigation water use efficiency (IWUE) were increased by 8.96%, 8.03%, 19.44%, and 16.05% respectively compared to SDI. Moreover, soluble sugar, organic acid, lycopene, vitamin C, and sugar acid ratio were enhanced by 2.41%, 12.19%, 14.40%, and 2.67% under SICE with the suggested working water head respectively compared with SDI. We recommended that supplemental lighting combined with SICE in autumn cultivation was necessary to ensure tomato production and fruit quality. This study provides an alternative water-saving irrigation method for greenhouse growers to maintain tomato yield and fruit quality in Northwest China.

N and P use efficiencies of basil cultivated in organically fertilized growing media

• Growing media (GM) are the main driver of Basil N- and P- use efficiencies. • Peat provided the best growth conditions under organic fertilization. • Microbial N competition limited basil growth in woody-based GM. • Organic fertilizer localization and PGPR inoculum weakly alleviated N limitation. • Peat will be difficult to replace especially with woody constituents in GM. Sustainable production in soilless cultivation systems may be achieved by using recycled organic materials as constituents of growing media (GM) and as organic fertilizers. Synchronizing nutrient releases from organic fertilizer mineralization with plant needs in containerized production is difficult to manage for greenhouse growers. This is further amplified by the diversification of GM constituents, driving microbial activities. We aimed to evaluate how the plant can adapt its nutrition to different organic fertilization strategies and ensure its growth depending on the GM and organic fertilizer types. Ocimum basilicum L. was grown for 60 days in a greenhouse in pots filled with three different GM: 100% peat (Peat); 70% peat and 30% coir fiber (GM1); and 50% coir pith, 25% composted bark, 25% wood fiber (GM2). Two contrasted organic fertilizers were used (horn and a granular fertilizer), mixed to the GM, localized in the pot, or combined with Bacillus sp. inoculation as plant growth-promoting rhizobacteria (PGPR). Standard mineral fertilization mixed to the GM was also used as a control treatment. We investigated basil growth (height, biomass, leaf area, chlorophyll and flavonol contents) as well as nitrogen (N) and phosphorus (P) use efficiencies, from their uptake by the roots to their allocation to the plant organs. Basil performances were mainly affected by the GM type. Peat provided optimal conditions for plant development. In GM1, basil maximized the utilization of available N and P taken up from the GM and reached the highest biomass production. Basil performances were especially low when it was grown on GM2 because of a strong competition for N between microbes and the roots. The fertilizer type, its localization and PGPR inoculation did not affect basil growth or nutrition in peat; these treatments had only little effect on basil grown on GM1 and GM2, and affected its performances differently depending on the GM type. This study provides evidence that fertilization must be thoughtfully managed depending on the GM in organically fertilized systems.

First Report of Powdery Mildew Caused by Golovinomyces ambrosiae on Cannabis sativa L. (marijuana) in Quebec, Canada.

Marijuana (Cannabis sativa L.) is legal in Canada for medical and recreational purposes and is currently a multi-million-dollar industry. The province of Quebec follows British Columbia and Ontario in production acreage (Government of Canada 2018). During the growing season 2020-2021, five greenhouse growers throughout Quebec reported the presence of signs and symptoms reminiscent of powdery mildew including the presence of white powdery patches on the adaxial sides of leaves of several C. sativa cultivars. From one commercial facility, infected leaves of three cannabis cultivars (Sour Diesel, Orange Krush, and Lemon Sour) were photographed and the fungal mycelium was collected for identification in the laboratory. Fungal mycelium on leaf tissue was white and amphigenous and displayed unbranched hyaline conidiophores ranging from 130 to 275 μm in height (n = 50). Conidiophores arose from the upper surface of hyphal mother cells ranging from 35-70 × 8-13 μm in diameter (n = 25) and formed catenescent conidia. Conidia were broad ellipsoid-ovoid and measured, 24 to 35 × 12 to 19 μm (n = 50), and hyphae ranged from 3-8 μm in diameter (n = 30). Based on previous description (Qiu et al. 2020), the fungus was placed within the Golovinomyces genus. The species identification was confirmed through multi-locus phylogenetic using internal transcribed spacer (ITS), 28S large ribosomal subunit, and chitin synthase I (CHS1) genes amplified as recommended (Qiu et al. 2020), and directly sequenced with amplification primers (Centre Hospitalier de l'Université Laval de Quebec, CA). The three marker sequences shared 100% similarity for all the samples analyzed and were deposited in Genbank under accession numbers: OM131434 (28S), OM131448 (ITS), and OM141118 (CHS1). The phylogenetic analysis of the multi-locus sequences amplified grouped all three Quebec marijuana isolates in the G. ambrosiae accessions, confirming their identification. Pathogenicity was confirmed by transferring conidia onto detached healthy leaves of hop plants (Humulus lupulus) cultivar Northern Brewer kept under greenhouse conditions (28C, 50-60% relative humidity, and 14 h light) via paint brush inoculation. Hop leaves were used as surrogate due to the restricted availability of marijuana leaves. Inoculated leaves were placed in the growth chamber set at 20C, 50-60% relative humidity, and long days conditions as previously suggested (Weldon et al. 2020). The leaves developed powdery mildew colonies after 21 days, and the fungus was confirmed to be G. ambrosiae following morphological characterization and amplification of CHS1. Powdery mildew caused by G. ambrosiae (previous Golovinomyces cichoracearum) has been reported affecting hemp (Cannabis sativa) in New York and Oregon, United Sates (Weldon et al. 2020; Wiseman et al. 2021), and in British Columbia, Canada (Pépin et al. 2018; Punja et al. 2021), and this is the first report of G. ambrosiae causing powdery mildew on marijuana in Quebec. REFERENCES Government of Canada 2018. Online, retrieved January 7, 2021 https://www150.statcan.gc.ca/n1/daily-quotidien/180430/dq180430b-eng.htm Pépin N, Punja ZK, Joly DL. 2018. First report of powdery mildew caused by Golovinomyces cichoracearum sensu lato on Cannabis satia in Canada. Plant Disease. 102(12):2644. Doi: https://doi.org/10.1094/PDIS-04-18-0586-PDN Punja, Z. P. (2021). First report of the powdery mildew pathogen of hops, Podosphaeria macularis, naturally infecting cannabis (Cannabis sativa L., marijuana) plants under field conditions, Canadian Journal of Plant Pathology, Doi: https://doi.org/10.1080/07060661.2021.1960424. Qiu, P.-L., Liu, S.-Y., Bradshaw, M., Rooney-Latham, S., Takamatsu, S., Bulgakov, T. S., Tang, S.-R., Feng, J., Jin, D.-N., Aroge, T., Li, Y., Wang, L.-L., and Braun, U. 2020. Multi-locus phylogeny and taxonomy of an unresolved, heterogeneous species complex within the genus Golovinomyces (Ascomycota, Erysiphales), including G. ambrosiae, G. circumfusus and G. spadiceus. BMC Microbiology. 20:51. Doi : https://doi.org/10.1186/s12866-020-01731-9. Weldon WA, Ullrich MR, Smart LB, Smart CD, Gadoury DM. 2020. Cross-infectivity of powdery mildew isolates originating from hemp (Cannabis sativa) and Japanese hop (Humulus japonicus) in New York. Plant Health Progress. 21(1):47-53. Doi: https://doi.org/10.1094/PHP-09-19-0067-RS Wiseman, M. S., Bates, T. A., Garfinkel, A. R., Ocamb, C. M., and Gent, D. H. 2021. First Report of Powdery Mildew Caused by Golovinomyces ambrosiae on Cannabis sativa in Oregon. Plant Disease 105(9):2733. Doi: https://doi.org/10.1094/PDIS-11-20-2455-PDN.

Effect of Light Intensity on the Growth and Antioxidant Activity of Sweet Basil and Lettuce.

Light and nutrients are among the most important factors for sustained plant production in agriculture. As one of the goals of the European Green Deal strategy is to reduce energy consumption, greenhouse growers focus on high-value crop cultivation with less-energy-demanding growing systems. This study aimed to evaluate the effect of fertilization at different light intensities on the growth of lettuce and basil and the activity of the antioxidant system. Sweet basil (Ocimum basilicum, ‘Opal’) and lettuce (Lactuca sativa, ‘Nikolaj’) were grown in a greenhouse supplementing natural light (~80 µmol m−2 s−1) with lighting at two photon flux densities (150 and 250 µmol m−2 s−1), 16 h photoperiod, and 20/16 °C day/night temperature in May (Lithuania, 55°60′ N, 23°48′ E). In each light regime treatment, half of the plants were grown without additional fertilization; the other half were fertilized twice a week with a complex fertilizer (NPK 3-1-3). The results showed that the antioxidant activity of basil was most affected by 150 µmol m−2 s−1 PPFD lighting and the absence of fertilization. Altered antioxidant activity in lettuce in the presence of 250 µmol m−2 s−1 PPFD additional light intensity and fertilization resulted in higher morphological parameters.