Scholarly Works, Virginia Agricultural Experiment Station

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https://hdl.handle.net/10919/24309

VAES faculty are located at 11 Agricultural Research and Extension Centers in Virginia and three colleges at Virginia Tech (CALS, CNRE, and VMRCVM).

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Transcriptome Profiling of a Salt Excluder Hybrid Grapevine Rootstock ‘Ruggeri’ throughout Salinity
Gajjar, Pranavkumar; Ismail, Ahmed; Islam, Tabibul; Moniruzzaman, Md; Darwish, Ahmed G.; Dawood, Ahmed S.; Mohamed, Ahmed G.; Haikal, Amr M.; El-Saady, Abdelkareem M.; El-Kereamy, Ashraf; Sherif, Sherif M.; Abazinge, Michael D.; Kambiranda, Devaiah; El-Sharkawy, Islam (MDPI, 2024-03-14)
Salinity is one of the substantial threats to plant productivity and could be escorted by other stresses such as heat and drought. It impairs critical biological processes, such as photosynthesis, energy, and water/nutrient acquisition, ultimately leading to cell death when stress intensity becomes uncured. Therefore, plants deploy several proper processes to overcome such hostile circumstances. Grapevine is one of the most important crops worldwide that is relatively salt-tolerant and preferentially cultivated in hot and semi-arid areas. One of the most applicable strategies for sustainable viticulture is using salt-tolerant rootstock such as Ruggeri (RUG). The rootstock showed efficient capacity of photosynthesis, ROS detoxification, and carbohydrate accumulation under salinity. The current study utilized the transcriptome profiling approach to identify the molecular events of RUG throughout a regime of salt stress followed by a recovery procedure. The data showed progressive changes in the transcriptome profiling throughout salinity, underpinning the involvement of a large number of genes in transcriptional reprogramming during stress. Our results established a considerable enrichment of the biological process GO-terms related to salinity adaptation, such as signaling, hormones, photosynthesis, carbohydrates, and ROS homeostasis. Among the battery of molecular/cellular responses launched upon salinity, ROS homeostasis plays the central role of salt adaptation.
Effects of Grosmannia clavigera and Leptographium longiclavatum on Western White Pine Seedlings and the Fungicidal Activity of Alamo®, Arbotect®, and TREE-äge®
Wyka, Stephen A.; Doccola, Joseph J.; Strom, Brian L.; Smith, Sheri L.; McPherson, Douglas W.; Acimovic, Srdan; Klepzig, Kier D. (International Society of Arboriculture, 2016-03-15)
Bark beetles carry a number of associated organisms that are transferred to the host tree upon attack that are thought to play a role in tree decline. To assess the pathogenicity to western white pine (WWP; Pinus monticola) of fungi carried by the mountain pine beetle (MPB; Dendroctonus ponderosae), and to evaluate the potential for systemic prophylactic treatments for reducing fungal impacts, experiments were conducted with WWP seedlings to meet three objectives: 1) evaluate pathogenicity of two MPB-associated blue-stain fungi; 2) evaluate phytotoxicity of tree injection products; 3) evaluate the anti-fungal activity of tree injection products, in vitro and in vivo, toward the associated blue-staining fungi. To evaluate pathogenicity, seedlings were inoculated with Grosmannia clavigera or Leptographium longiclavatum, common fungal associates of MPB. Seedling mortality at four months after inoculation was 50% with L. longiclavatum and 90% with G. clavigera, both significantly higher than controls and thereby demonstrating pathogenicity. Phytotoxic effects of TREE-äge®, Alamo®, and Arbotect® were evaluated by stem injection; no phytotoxic effects were observed. Anti-fungal properties of the same three products were evaluated in vitro against G. clavigera, where Alamo was most active. Co-inoculation of G. clavigera and L. longiclavatum into seedlings after a stem injection of Alamo showed significantly less mortality and lesion formation than either species alone. Results support the hypothesis that MPB blue-stain associates, particularly G. clavigera, promote death of WWP when attacked by MPB. These findings suggest that the administration of a fungicide with insecticide for tree protection against bark beetles may be advantageous.
Eutypa Dieback and ESCA - Trunk Necrosis and Dieback Diseases of Grapevines in Serbia
Acimovic, Srdan; Delibašić, Goran; Schilder, Annemiek; Tanovic, Brankica (University of Novi Sad, Serbia, 2008-12-22)
Erwinia amylovora in Vojvodina and Measures of Control
Balaž, Jelica S.; Keserović, Zoran; Acimovic, Srdan; Nikolic, Zorica; Mažić, Jelena (University of Novi Sad, Serbia, 2009-02-10)
Cultural characteristics of Eutypa lata and one unknown isolate on different nutrient media
Acimovic, Srdan; Delibašić, Goran (University of Kragujevac, Serbia, 2005-08)
Improved Canker Processing and Viability Droplet Digital PCR Allow Detection of Erwinia amylovora Viable Nonculturable Cells in Apple Bark
Dhar, Bidhan Chandra; Delgado Santander, Ricardo; Aćimović, Srđan G. (MDPI, 2024-02-12)
The bacterium Erwinia amylovora causes fire blight and continues to threaten global commercial apple and pear production. Conventional microbiology techniques cannot accurately determine the presence of live pathogen cells in fire blight cankers. Several factors may prevent E. amylovora from growing on solid culture media, including competing microbiota and the release of bacterial-growth-inhibitory compounds by plant material during sample processing. We previously developed a canker processing methodology and a chip-based viability digital PCR (v-dPCR) assay using propidium monoazide (PMA) to bypass these obstacles. However, sample analysis was still time-consuming and physically demanding. In this work, we improved the previous protocol using an automatic tissue homogenizer and transferred the chip-based v-dPCR to the BioRad QX200 droplet dPCR (ddPCR) platform. The improved sample processing method allowed the simultaneous, fast, and effortless processing of up to six samples. Moreover, the transferred v-ddPCR protocol was compatible with the same PMA treatment and showed a similar dynamic range, from 7.2 × 10² to 7.6 × 10⁷ cells mL⁻¹, as the previous v-dPCR. Finally, the improved protocol allowed, for the first time, the detection of E. amylovora viable but nonculturable (VBNC) cells in cankers and bark tissues surrounding cankers. Our v-ddPCR assay will enable new ways to evaluate resistant pome fruit tree germplasm, further dissect the E. amylovora life cycle, and elucidate E. amylovora physiology, epidemiology, and new options for canker management.
Pre-Harvest Corn Grain Moisture Estimation Using Aerial Multispectral Imagery and Machine Learning Techniques
Jjagwe, Pius; Chandel, Abhilash K.; Langston, David B. (MDPI, 2023-12-18)
Corn grain moisture (CGM) is critical to estimate grain maturity status and schedule harvest. Traditional methods for determining CGM range from manual scouting, destructive laboratory analyses, and weather-based dry down estimates. Such methods are either time consuming, expensive, spatially inaccurate, or subjective, therefore they are prone to errors or limitations. Realizing that precision harvest management could be critical for extracting the maximum crop value, this study evaluates the estimation of CGM at a pre-harvest stage using high-resolution (1.3 cm/pixel) multispectral imagery and machine learning techniques. Aerial imagery data were collected in the 2022 cropping season over 116 experimental corn planted plots. A total of 24 vegetation indices (VIs) were derived from imagery data along with reflectance (REF) information in the blue, green, red, red-edge, and near-infrared imaging spectrum that was initially evaluated for inter-correlations as well as subject to principal component analysis (PCA). VIs including the Green Normalized Difference Index (GNDVI), Green Chlorophyll Index (GCI), Infrared Percentage Vegetation Index (IPVI), Simple Ratio Index (SR), Normalized Difference Red-Edge Index (NDRE), and Visible Atmospherically Resistant Index (VARI) had the highest correlations with CGM (r: 0.68–0.80). Next, two state-of-the-art statistical and four machine learning (ML) models (Stepwise Linear Regression (SLR), Partial Least Squares Regression (PLSR), Artificial Neural Network (ANN), Support Vector Machine (SVM), Random Forest (RF), and K-nearest neighbor (KNN)), and their 120 derivates (six ML models × two input groups (REFs and REFs+VIs) × 10 train–test data split ratios (starting 50:50)) were formulated and evaluated for CGM estimation. The CGM estimation accuracy was impacted by the ML model and train-test data split ratio. However, the impact was not significant for the input groups. For validation over the train and entire dataset, RF performed the best at a 95:5 split ratio, and REFs+VIs as the input variables (r_train: 0.97, rRMSE_train: 1.17%, r_entire: 0.95, rRMSE_entire: 1.37%). However, when validated for the test dataset, an increase in the train–test split ratio decreased the performances of the other ML models where SVM performed the best at a 50:50 split ratio (r = 0.70, rRMSE = 2.58%) and with REFs+VIs as the input variables. The 95:5 train–test ratio showed the best performance across all the models, which may be a suitable ratio for relatively smaller or medium-sized datasets. RF was identified to be the most stable and consistent ML model (r: 0.95, rRMSE: 1.37%). Findings in the study indicate that the integration of aerial remote sensing and ML-based data-run techniques could be useful for reliably predicting CGM at the pre-harvest stage, and developing precision corn harvest scheduling and management strategies for the growers.
Using Aerial Spectral Indices to Determine Fertility Rate and Timing in Winter Wheat
Oakes, Joseph; Balota, Maria; Cazenave, Alexandre-Brice; Thomason, Wade (MDPI, 2024-01-03)
Tiller density is indicative of the overall health of winter wheat (Triticum aestivum L.) and is used to determine in-season nitrogen (N) application. If tiller density exceeds 538 tillers per m² at GS 25, then an N application at that stage is not needed, only at GS 30. However, it is often difficult to obtain an accurate representation of tiller density across an entire field. Normalized difference vegetative index (NDVI) and normalized difference red edge (NDRE) have been significantly correlated with tiller density when collected from the ground. With the advent of unmanned aerial vehicles (UAVs) and their ability to collect NDVI and NDRE from the air, this study was established to examine the relationship between NDVI, NDRE, and tiller density, and to verify whether N could be applied based on these two indices. From 2018 to 2020, research trials were established across Virginia to develop a model describing the relationship between aerial NDVI, aerial NDRE, and tiller density counted on the ground, in small plots. In 2021, the model was used to apply N in small plots at two locations, where the obtained grain yield was the same whether N was applied based on tiller density, NDVI, or NDRE. From 2022 to 2023, the model was applied at six locations across the state on large scale growers’ fields to compare the amount of GS 25 N recommended by tiller density, NDVI, and NDRE. At three locations, NDVI and NDRE recommended the same N rates as the tiller density method, while at two locations, NDVI and NDRE recommended less N than tiller density. At one location, NDVI and NDRE recommended more N than tiller density. However, across all six locations, there was no difference in grain yield whether N was applied based on tiller density, NDVI, or NDRE. This study indicated that UAV-based NDVI and NDRE are excellent proxies for tiller density determination, and can be used to accurately and economically apply N at GS 25 in winter wheat production.
An Economic Evaluation of Alternative Methods to Manage Fire Blight in Apple Production
Rickard, Bradley J.; Acimovic, Srdan; Fazio, Gennaro; Silver, Casey (NYSHS, 2023-04-01)
Our research examined the economic implications of managing fire blight in apple production by using susceptible rootstocks or resistant rootstocks with and without protective sprays. Our results indicate that use Geneva® rootstocks across all incidence levels of fire blight considered gave superior economic outcomes compared to susceptible rootstocks or tree insurance for fire blight.
The identity of Neocnemodon calcarata (Loew) (Diptera: Syrphidae), a specialized flower fly predator of woolly apple aphid
Bergh, J. Christopher; Marek, Paul E.; Short, Brent D.; Skevington, Jeffrey H.; Thompson, F. Christian (2023-03-05)
The names and identities of the specialized flower fly predators of the Woolly Apple Aphid, Eriosoma lanigerum (Hausmann, 1802) are fixed. These predators, Neocnemodon calcarata (Loew, 1866) and Neocnemodon vitripennis (Meigen, 1822), are important biological control agents as they prey on both arboreal and root colonies of the aphid. A lectotype is designated for Pipiza calcarata Loew, 1866, and type notes of N. calcarata and N. vitripennis are provided.
Testing Novel Seed Treatments and Soil-Applied Insecticides Against Wireworm in Corn, 2023
Bekelja, Kyle; Malone, Sean (Oxford University Press, 2024-01)
A Novel Insecticide, Isocycloseram, Shows Promise as an Alternative to Chlorpyrifos Against a Direct Pest of Peanut
Bekelja, Kyle; Malone, Sean; Mascarenhas, Victor; Taylor, Sally V. (2024-01)
Larvae of the southern corn rootworm (SCR) Diabrotica undecimpunctata howardi Barber (Coleoptera: Chrysomelidae) are primary pests of peanut in the Virginia-Carolina region of the United States, and are relatively sporadic pests in southern states such as Georgia, Alabama, and Florida. Peanuts have strict quality standards which, when they are not met, crop value is diminished by more than 65%. Management of direct pests like SCR is therefore crucial to maintaining the economic viability of the crop. The soil-dwelling nature of SCR larvae complicates management due to difficulties associated with monitoring and predicting infestations. Non-chemical management options are limited in this system; preventative insecticide applications are the most reliable management strategy for at-risk fields. Chlorpyrifos was the standard product for larval SCR management in peanut until its registration was revoked in 2022, leaving no effective chemical management option for larvae. We tested a novel insecticide, isocycloseram, for its ability to reduce pod scarring, pod penetration, and non-SCR pod damage in field studies conducted in Suffolk, Virginia in 2020 – 2022. Overall injury was low in 2020 and 2022, and in 2022 there was not a significant effect of treatment. In 2021, two simulated chemigation applications of isocycloseram in July significantly reduced pod scarring and overall pod injury relative to chlorpyrifos and the untreated control. Our results suggest that isocycloseram may become an effective option for managing SCR in peanut, although more work is needed to understand the mechanisms by which it is effective as a soil-applied insecticide.
Cover crop termination options and application of remote sensing for evaluating termination efficiency
Kumar, Vipin; Singh, Vijay; Flessner, Michael L.; Haymaker, Joseph; Reiter, Mark S.; Mirsky, Steven B. (Public Library of Science, 2023-04-20)
Efficient termination of cover crops is an important component of cover crop management. Information on termination efficiency can help in devising management plans but estimating herbicide efficacy is a tedious task and potential remote sensing technologies and vegetative indices (VIs) have not been explored for this purpose. This study was designed to evaluate potential herbicide options for the termination of wheat (Triticum aestivum L.), cereal rye (Secale cereale L.), hairy vetch (Vicia villosa Roth.), and rapeseed (Brassica napus L.), and to correlate different VIs with visible termination efficiency. Nine herbicides and one roller-crimping treatment were applied to each cover crop. Among different herbicides used, glyphosate, glyphosate + glufosinate, paraquat, and paraquat + metribuzin provided more than 95% termination for both wheat and cereal rye 28 days after treatment (DAT). For hairy vetch, 2,4-D + glufosinate and glyphosate + glufosinate, resulted in 99 and 98% termination efficiency, respectively, followed by 2,4-D + glyphosate and paraquat with 92% termination efficiency 28 DAT. No herbicide provided more than 90% termination of rapeseed and highest control was provided by paraquat (86%), 2,4-D + glufosinate (85%), and 2,4-D + glyphosate (85%). Roller-crimping (without herbicide application) did not provide effective termination of any cover crop with 41, 61, 49, and 43% termination for wheat, cereal rye, hairy vetch, and rapeseed, respectively. Among the VIs, Green Leaf Index had the highest Pearson correlation coefficient for wheat (r = -0.786, p = <0.0001) and cereal rye (r = -0.804, p = <0.0001) with visible termination efficiency rating. Whereas for rapeseed, the Normalized Difference Vegetation Index (NDVI) had the highest correlation coefficient (r = -0.655, p = <0.0001). The study highlighted the need for tankmixing 2,4-D or glufosinate with glyphosate for termination instead of blanket application of glyphosate alone for all crops including rapeseed and other broadleaf cover crops.
Enhancement of phenolics extraction from red algae (Kappaphycus spp.) using solid-state fermentation
Norakma, M. N.; Zaibunnisa, A. H.; Wan Razarinah, W. A. R.; Zarei, Mohammad; Sobah, A.; Hamid, N.; Astuti, P. D. (Rynnye Lyan Resources, 2023-11-11)
The effects of solid-state fermentation (SSF) on microbial growth contribute to the bio-enrichment and availability of phenolic compounds in different varieties of Kappaphycus spp. red algae through the action of hydrolytic enzymes produced are investigated. Three different red algae samples were used; K. striatum var. green flower (GF), K. alvarezii var. white giant (WG) and K. alvarezii var. purple giant (PG). SSF was performed using A. oryzae for 0 to 6 days at 30°C. Results obtained demonstrated that the highest (p<0.05) extraction of phenolics (10.022 mg GAE/g and 14.90 mg CE/g), and antioxidant properties (72.47% activity of DPPH radical scavenging and 18.23 mM/g FRAP value respectively) was obtained for GF sample at day 4 of fermentation. Cellulase, β-glucosidase, and xylanase were found to be responsible for enhancing phenolics and antioxidant activity of WG and GF varieties by releasing bound phenolics. However, for the PG sample, β-glucosidase showed a significant relationship with TPC and antioxidant activity.
Insects as Valuable Sources of Protein and Peptides: Production, Functional Properties, and Challenges
Hasnan, Fatin Fayuni Binti; Feng, Yiming; Sun, Taozhu; Parraga, Katheryn; Schwarz, Michael; Zarei, Mohammad (MDPI, 2023-11-24)
As the global population approaches 10 billion by 2050, the critical need to ensure food security becomes increasingly pronounced. In response to the urgent problems posed by global population growth, our study adds to the growing body of knowledge in the field of alternative proteins, entomophagy, insect-based bioactive proteolysates, and peptides. It also provides novel insights with essential outcomes for guaranteeing a safe and sustainable food supply in the face of rising global population demands. These results offer insightful information to researchers and policymakers tackling the intricate relationship between population expansion and food supplies. Unfortunately, conventional agricultural practices are proving insufficient in meeting these demands. Pursuing alternative proteins and eco-friendly food production methods has gained urgency, embracing plant-based proteins, cultivated meat, fermentation, and precision agriculture. In this context, insect farming emerges as a promising strategy to upcycle agri-food waste into nutritious protein and fat, meeting diverse nutritional needs sustainably. A thorough analysis was conducted to evaluate the viability of insect farming, investigate insect nutrition, and review the techniques and functional properties of protein isolation. A review of peptide generation from insects was conducted, covering issues related to hydrolysate production, protein extraction, and peptide identification. The study addresses the nutritional value and global entomophagy habits to elucidate the potential of insects as sources of peptides and protein. This inquiry covers protein and hydrolysate production, highlighting techniques and bioactive peptides. Functional properties of insect proteins’ solubility, emulsification, foaming, gelation, water-holding, and oil absorption are investigated. Furthermore, sensory aspects of insect-fortified foods as well as challenges, including Halal and Kosher considerations, are explored across applications. Our review underscores insects’ promise as sustainable protein and peptide contributors, offering recommendations for further research to unlock their full potential.
New Insights in the Detection and Management of Anthracnose Diseases in Strawberries
Aljawasim, Baker D.; Samtani, Jayesh B.; Rahman, Mahfuzur (MDPI, 2023-10-27)
Anthracnose diseases, caused by Colletotrichum spp., are considered to be among the most destructive diseases that have a significant impact on the global production of strawberries. These diseases alone can cause up to 70% yield loss in North America. Colletotrichum spp. causes several disease symptoms on strawberry plants, including root, fruit, and crown rot, lesions on petioles and runners, and irregular black spots on the leaf. In many cases, a lower level of infection on foliage remains non-symptomatic (quiescent), posing a challenge to growers as these plants can be a significant source of inoculum for the fruiting field. Reliable detection methods for quiescent infection should play an important role in preventing infected plants’ entry into the production system or guiding growers to take appropriate preventative measures to control the disease. This review aims to examine both conventional and emerging approaches for detecting anthracnose disease in the early stages of the disease cycle, with a focus on newly emerging techniques such as remote sensing, especially using unmanned aerial vehicles (UAV) equipped with multispectral sensors. Further, we focused on the acutatum species complex, including the latest taxonomy, the complex life cycle, and the epidemiology of the disease. Additionally, we highlighted the extensive spectrum of management techniques against anthracnose diseases on strawberries and their challenges, with a special focus on new emerging sustainable management techniques that can be utilized in organic strawberry systems.
A NitroPure Nitrocellulose Membrane-Based Grapevine Virus Sampling Kit: Development and Deployment to Survey Japanese Vineyards and Nurseries
Nita, Mizuho; Jones, Taylor; McHenry, Diana; Bush, Elizabeth; Oliver, Charlotte; Kawaguchi, Akira; Nita, Akiko; Katori, Miyuki (MDPI, 2023-10-17)
We developed a NitroPure Nitrocellulose (NPN) membrane-based method for sampling and storing grapevine sap for grapevine virus detection. We devised an efficient nucleic acid extraction method for the NPN membrane, resulting in 100% amplification success for grapevine leafroll-associated virus 2 (GLRaV2) and 3 (GLRaV3), grapevine rupestris stem pitting-associated virus (GRSPaV), grapevine virus A, grapevine virus B, and grapevine red blotch virus (GRBV). This method also allowed the storage of recoverable nucleic acid for 18 months at room temperature. We created a sampling kit to survey GLRaV2, GLRaV3, and GRBV in Japanese vineyards. We tested the kits in the field in 2018 and then conducted mail-in surveys in 2020–2021. The results showed a substantial prevalence of GLRaV3, with 48.5% of 132 sampled vines being positive. On the other hand, only 3% of samples tested positive for GLRaV2 and none for GRBV.
Fruit Quality of Several Strawberry Cultivars during the Harvest Season under High Tunnel and Open Field Environments
Patel, Hiral; Taghavi, Toktam; Samtani, Jayesh B. (MDPI, 2023-09-28)
Parameters such as titratable acids (TA), total soluble solids (TSS), and their ratio (TSS/TA) are critical in determining strawberry fruit quality and the value of new cultivars. Ten strawberry cultivars were evaluated in two environments (open field and high tunnel) in the city of Virginia Beach. The objective was to evaluate the fruit quality characteristics (total soluble solids, titratable acidity TA, and total anthocyanin content) of newer strawberry cultivars grown in the annual hill plasticulture systems in coastal Virginia climatic conditions. Another objective was to measure the correlation between TA and a new digital meter (pocket acidity meter; PAM). Fruits were harvested weekly and TSS was measured using a refractometer. Acidity was measured using the pocket acidity meter and titratable acidity by a single sample titrimeter. Genetics significantly affected total anthocyanin content, TSS, TA, and acidity. The effect of the environments (high tunnel and open field) was not significant on TSS but significant on total anthocyanin content, TA, and acidity. “Flavorfest” had the highest and “Sweet Ann” the lowest anthocyanin content, TSS, and TA among the cultivars. The acidity (PAM data) showed a different level of correlation than TA, with a higher correlation for the open field than the high tunnel. On average, when outliers were removed, there was a regression of TA = 2.22(PAM) + 0.49 between the two data sets, with R² = 0.47.
Plant Density Recommendations and Plant Nutrient Status for High Tunnel Tomatoes in Virginia
Torres-Quezada, Emmanuel; Gandini-Taveras, Ricardo José (MDPI, 2023-09-22)
Open-field tomatoes in Virginia are traditionally planted in a single row with 2 ft (0.60 m) of in-row spacing, resulting in a plant density of 4356 plants per acre (10,890 plants/ha). However, there has been increasing interest among small and medium-sized farmers in high tunnel production. In order to be profitable, farmers must maximize their yield per unit area and take advantage of the potential benefits of producing under high tunnels. A common approach under greenhouse conditions is to increase the planting density to enhance yield per area. However, high tunnel farmers often extrapolate open-field practices to their high tunnels as they believe both systems are closer related together than to greenhouse production. In those cases, high tunnel farmers could potentially be neglecting yield increases due to their planting density selection. Additionally, irrigation and fertilization management (fertigation) under high tunnels tend to be more efficient than open-field systems, as the frequency of application is increased with a lower volume per application. A higher efficiency of fertigation could alter plant yield responses, especially under traditional planting-density systems. Hence, this study aimed to identify the effect of high planting density on high tunnel tomatoes and their nutrient status on the Eastern Shore of Virginia. The experiment was established on a completely randomized block design with four replications, with 20 ft (6.09 m) experimental plots. We evaluated the combination of two in-row distances and single and double planting rows, with treatments consisting of 2 ft of in-row distance in a single row (4356 plants/acre—current open-field recommendation), 1.5 ft (0.45 m) of in-row distance in a single row (5808 plants/acre [14,520 plants/ha]), 2 ft of in-row distance in a double row (8712 plants/acre [21,780 plants/ha]), and 1.5 ft of in-row distance in a double row (11,616 plants/acre [29,040 plants/ha]). Summer-grown tomatoes produced on the Eastern Shore of Virginia under high tunnel conditions should be planted with 2 ft of in-row spacing and with a single row of plants per planting bed. Increasing the plant density or modifying the current recommended plant distribution could result in yield losses per plant between 32% and 46% and substantial increases in production costs compared with the traditional planting density. Throughout all treatments, tomato plants did not show deficient nutrient status. We hypothesized that irrigation water and pollination were the limiting factors that promoted a decrease in yield per plant for the high-density treatments.
Surveying North American Specialty Crop Growers' Current Use of Soilless Substrates and Future Research and Education Needs
Fields, Jeb S.; Owen, James S.; Lamm, Alexa; Altland, James; Jackson, Brian; Oki, Lorence; Samtani, Jayesh B.; Zheng, Youbin; Criscione, Kristopher S. (MDPI, 2023-08-31)
Many specialty crop growers are transitioning high-value crops from in-ground production to soilless culture due to the diminishing availability of fumigants, increasing pest pressure, extreme weather, and the need for flexible production practices. The objective of this study was to determine the research and educational needs of specialty crop growers who are transitioning to soilless substrates. North American growers were surveyed using an online instrument that incorporated Likert-type statement matrices, open-ended questions, and demographic questions. Additionally, two virtually led focus groups were conducted to further expand upon the quantitative findings with descriptive data. Respondents indicated the most important factors in considering whether to adopt soilless substrates were improving, managing, and reducing overall plant quality, disease management, and crop loss, respectively. The most important research needs were understanding the effects of substrates on crop quality and uniformity, fertilizer management, and economic costs and benefits/return on investment. In both the grower survey and focus groups, crop quality and uniformity were among the highest-scored responses. Food safety, disease and pest management, consumer perception, substrate disposal-related issues, transportation, and return-on-investment were also identified as important factors when considering soilless substrates.

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