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Natalie Bumgarner, Sheri Dorn, Esther McGinnis, Pam Bennett, Ellen Bauske, Sarada Krishnan and Lucy Bradley

Many fields of research converge to assess the impact of plants on human health, well-being, and nutrition. However, even with a recent history of horticulturists contributing to human–plant interaction work, much of the current research is conducted outside the context of horticulture and specifically outside of consumer horticulture (CH). To connect CH to research being conducted by other disciplines that explore the role of plants in improving human quality of life, a workshop was held on 1 Aug. 2018 in Washington, DC, at the American Society for Horticultural Science (ASHS) annual conference. The workshop focused on current food science, nutrition, and crop-breeding efforts to enhance nutrition and flavor, and human health and well-being research related to nature and plant interactions in an increasingly urban population. Following these presentations regarding potential research linkages and collaboration opportunities, a facilitated discussion identified ways to improve future CH research and foster collaborative work. Action items identified included connecting research and vocabulary to help cultivate an interest in plants in younger generations; supporting awareness of collaborative opportunities with health, nutrition, urban planning, and public health practitioners; ensuring CH is known to administrators; and taking responsibility for initiating communication with colleagues in these areas.

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Anthony L. Witcher, Fulya Baysal-Gurel, Eugene K. Blythe and Donna C. Fare

Flowering dogwood (Cornus florida) is a valuable nursery product typically produced as a field-grown crop. Container-grown flowering dogwood can grow much faster than field-grown plants, thus shortening the production cycle, yet unacceptable crop loss and reduced quality continue to be major issues with container-grown plants. The objective of this research was to evaluate the effects of container size and shade duration on growth of flowering dogwood cultivars Cherokee Brave™ and Cherokee Princess from bare-root liners. In 2015, bare-root liners were transplanted to 23-L (no. 7) containers and placed under shade for 0 months (full sun), 2 months (sun4/shade2), 4 months (sun2/shade4), or 6 months (full shade) during the growing season. In 2016, one-half of the plants remained in no. 7 containers and the other half were transplanted to 50-L (no. 15) containers and assigned to the same four shade treatments. In 2015, plant height was greatest with full shade for both cultivars, whereas stem diameter and shoot dry weight (SDW) were greatest in full shade for Cherokee Brave™. In 2016, both cultivars in no. 15 containers had greater plant height, stem diameter, root dry weight (RDW), and SDW. Full shade resulted in the greatest height, stem diameter, RDW, and SDW for Cherokee Brave™, and improved overall growth for ‘Cherokee Princess’. However, vigorous growth due to container size and shade exposure increased the severity of powdery mildew (Erysiphe pulchra) in both years. Substrate leachate nutrient concentration (nitrate nitrogen and phosphate) was greater in no. 15 containers but shade duration had no effect.

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Sueyde Fernandes de Oliveira Braghin, Simone C. Mello, Jéssika Angelotti-Mendonça, Keigo Minami and Yuncong C. Li

Fertilizer management is an essential step in the production process, as it allows the plant to use its productive capacity to the fullest extent possible. Researchers have tested maximum nutrient use with reduced losses to the environment aiming to increase productivity with fewer environmental impacts. This study compared the effects of controlled-release fertilizers (CRFs) with water-soluble fertilizer (WSF) and clear water (control) on the growth and nutrient uptake of croton (Codiaeum variegatum L.) and nitrogen leaching. The experiment was conducted with three replications and six treatments: two rates (1.5 g and 3.0 g per liter of substrate) of two CRFs [Osmocote Plus (15% N, 3.93% P, and 9.96% K) and Basacote (15% N, 3.49% P, and 9.96% K)], WSF, and clean water as control. All CRFs were applied before planting and WSF was supplied as nutrient solution through automated moisture sensor activated irrigation system. Plant growth (number of leaves, leaf area, stem height, root volume, and shoot and root dry weights) and total nutrient contents in the leaf tissue were evaluated every 30 days. Electrical conductivity (EC), pH, nitrate, ammonium, and total nitrogen contents were measured in the leached solution. Indeed, results showed that CRFs at a low rate provided similar development and quality of croton plants compared with WSF. Plant growth indicators were similar until 90 days after transplanting (DAT). After that, at 150 DAT, the highest values to number of leaves and leaf area occurred with WSF and with the lowest CRF rate as compared with the other treatments and control. The highest root volume was found with the WSF, which resulted in larger roots compared with the other treatments. These results showed WSF can be replaced by CRFs at low rates on croton growth. Moreover, according to the visual scale, the best treatments were WSF and Basacote at the low rate, where plants were bright, with multicolored leaves with prominent orange shades. However, CRFs maintained pH and EC within the recommended range for the growth of croton and reduced the nitrogen leaching from the pots.

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Xunzhong Zhang, Mike Goatley, Jamie Conner, Megan Wilkins, Inna Teshler, Jun Liu, Michael Fefer and Wenzi Ckurshumova

Plant-based pigments have been used as substances to improve crop yield and quality, but the mechanisms of their action on plant growth and stress tolerance are not well understood. The objective of this study was to investigate effects of two formulations of plant-based copper chlorophyllin (Cu-Chl) with and without synthetic paraffinic oil. These formulations, referred to as B18-0074 and B18-0075, were applied as a soil drench plus foliar or a foliar-only application. We investigated their impact on physiological responses of tomato plants under prolonged drought stress conditions. In addition, we examined photosynthetic impacts associated with the application of Cu-Chl formulations. B18-0074 increased leaf photosynthetic rate (Pn) by 8.8% with soil plus foliar application and 18.6% with foliar application relative to the control under drought stress at day 21. Similarly, B18-0075 increased Pn by 16.9% with soil plus foliar application and 24.6% with foliar application relative to the control under drought stress at day 21. The application of the two Cu-Chl–containing products increased leaf antioxidant enzyme catalase (CAT) and ascorbate peroxidase (APX) activity, as well as glutathione (GSH) content. The two products also increased leaf soluble sugars and proline content, indicating improvement of osmotic adjustment. Soil plus foliar and foliar application only of B18-0075 increased root biomass but did not consistently affect plant shoot growth. The results of this study suggest that application of Cu-Chl in combination with synthetic paraffinic oil may improve photosynthetic function, osmotic adjustment, antioxidant defense capacity, and root growth of tomato plant grown under drought stress conditions.

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Fan-Hsuan Yang, David R. Bryla and Bernadine C. Strik

Over-canopy sprinkler systems are used to cool northern highbush blueberry (Vaccinium corymbosum L.) fields and maintain fruit quality in the northwestern United States, but more information is needed to determine exactly when cooling is needed. The objective of this study was to identify the critical temperatures for heat damage to berries and for effective evaporative cooling. An initial study conducted in western Oregon in a mature planting of late-season ‘Elliott’ blueberry revealed that heat damage was typically observed within 1 to 3 days after an extreme heat event. Fruit damage, including softening, shriveling, and necrosis, occurred during both green and blue stages of development and was found primarily on sun-exposed berries, which on hot, sunny days (>35 °C) were 7 to 11 °C warmer than the ambient air temperature. A subsequent study was conducted to determine whether the critical temperature for heat damage differed between the green and blue fruit stages. In this case, ‘Aurora’ was compared with ‘Elliott’ blueberry. Berries were heated using a chamber-free convective unit and were exposed for up to 4 hours to berry temperatures of 42, 44, 46, and 48 °C. When the berries were green, significant damage was visible at each temperature within 1.5 to 2 hours in ‘Aurora’ and 3 to 3.5 hours in ‘Elliott’. Damage of green berries increased with time and temperature, and after 4 hours, ranged from 17% to 59% of the total berry number in the cluster in ‘Aurora’ and 10% to 24% in ‘Elliott’. Fruit damage at the blue stage was less than at the green stage and was only significant at 46 and 48 °C (within 3.5 to 2 hours, respectively) in ‘Aurora’ and at 48 °C (within 2 hours) in ‘Elliott’. Wax and cutin layers thickened on the berries as they progressed from green to blue, which perhaps increased their tolerance to heat at later stages of development. Based on these results, northern highbush blueberry fields should be cooled at air temperatures >32 °C during the green stages of fruit development and >35 °C during ripening.

Open access

Christopher D. Ryan, J. Bryan Unruh, Kevin E. Kenworthy, Alexa J. Lamm, John E. Erickson and Laurie E. Trenholm

Every county and municipality in Florida can adopt its own unique ordinance regulating the fertilization of lawns and landscapes. With increased concern for eutrophication to state waterbodies, many have chosen to implement seasonal fertilizer restrictive periods prohibiting the application of nitrogen and phosphorus fertilizers, typically during the rainy summer months. These fertilizer “blackout” policies have been the subject of controversy among environmental activists, university scientists, and policy decision makers, with their efficacy being called into question. A Foucauldian discourse analysis was undertaken to trace the dynamics of the controversy, and survey research was conducted with Florida residents and with Florida decision makers to compare their lawncare maintenance practices, sentiments surrounding turfgrass, their trust in landscape science, as well as their awareness of policy in the city or county in which they reside. Differences were found between the two populations in terms of how many respondents fertilized, used automated irrigation systems and hand-pulled weeds. Although both populations had very neutral sentiments around turfgrass with no significant differences, Florida decision-maker respondents had a higher mean response for trust in landscape science. Only 32% of Florida resident respondents were able to accurately identify if their city or county had a blackout ordinance, compared with 81% of decision-maker respondents. Increasing civic science may be the best way for reducing this discrepancy, while also giving power to citizens in environmental policy adoption.

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Kathleen G. Haynes, Lincoln Zotarelli, Christian T. Christensen and Stephanie Walker

Consumer demand for specialty market potatoes has been growing. Cultivated South American diploid potatoes possess great variation for skin and flesh colors, shape, and taste. A long-day adapted population of Solanum tuberosum groups Phureja and Stenotomum (phu-stn) was evaluated for characteristics associated with the type known as papa criolla or papa amarilla in South America. Tubers have intense yellow flesh and may be fried or roasted and eaten whole. A U.S. northern location (Maine), representative of a seed growing region, and two southern locations (Florida and New Mexico), representative of potato growing regions near large Hispanic populations, evaluated yellow-fleshed clones selected within a phu-stn population. Agreement between selectors at two locations was greater than 50%. Tuber skin color and shape were highly correlated between locations; flesh color and tuber dormancy moderately so; eye depth had low correlation between locations; and appearance and skin texture had low or no correlation between locations. Tuber dormancy was generally short, but a few longer dormant clones were identified. There were significant differences among clones for yields, with the highest yields occurring in Maine. More intense evaluations are planned for a subset of these clones before possible release as new varieties. Future breeding efforts will be undertaken to lengthen tuber dormancy in this population.

Open access

Lijia Shi, Jinghui Wang, Zhifeng Gao, Xin Zhao, Francesco Di Gioia, Haichao Guo, Jason Hong, Monica Ozores-Hampton and Erin Rosskopf

With the phase-out of methyl bromide due to its impact on ozone depletion, research has focused on developing alternative chemical and biologically based soil disinfestation methods. Anaerobic soil disinfestation (ASD) was developed to control plant-parasitic nematodes, weeds, and soilborne pathogens. However, whether farmers will adopt ASD methods on a large scale is unknown. This study evaluates the economic viability of using ASD in open-field, fresh-market tomato (Solanum lycopersicum) production, drawing on data from field experiments conducted in 2015 in Immokalee, FL, and Citra, FL. The experiment included three treatments: chemical soil fumigation (CSF), ASD1 [the standard ASD treatment with 1482 gal/acre molasses and 9 tons/acre composted poultry litter (CPL)], and ASD0.5 (the reduced rate ASD treatment with 741 gal/acre molasses and 4.5 tons/acre CPL). Results from the economic analysis show that ASD treatments require higher labor costs than CSF regarding land preparation and treatment application. However, yields from ASD treatments are higher than those resulting from CSF, and the improvement in yield was enough to offset the increased labor costs. Relative to CSF, ASD0.5, and ASD1 achieved additional net returns of $630.38/acre and $2770.13/acre, respectively, in Immokalee, FL. However, due to unexpected conditions unrelated to soil treatments, the net return of ASD1 was lower than that of CSF in Citra, FL. Breakeven analysis indicates that ASD treatments would remain favorable even with an increase in the molasses price. However, when the tomato price is low, ASD could potentially lose its advantage over CSF.

Open access

Wenlei Guo, Li Feng, Dandan Wu, Chun Zhang and Xingshan Tian

Widespread herbicide-resistant weeds and severe insect pest infestations pose a challenge to the preplant pest management (PPPM) strategy currently in use in leaf vegetable fields in southern China. The aim of this study was to develop a new weed and insect control method for use before planting leaf vegetables in southern China. Two flaming machines (a tractor mounted and a trolley flaming machine) were designed, and their efficacies for the control of insect and weed pests were evaluated and compared in two field trials. With liquefied petroleum gas (LPG) at 101 kg·ha−1, flaming machines reduced plant numbers by 86.7% to 98.8% 2 days after treatment (DAT), which was equal to or higher than the reduction after application of paraquat at 900 g·ha−1. Some weed species, especially awnless barnyard grass (Echinochloa colona) and goosegrass (Eleusine indica), regrew at 7 DAT, resulting in a decrease in control efficacy. Flaming machines also reduced the number of diamondback moth (Plutella xylostella) larvae by 83.0% to 88.2% and the number of adult striped flea beetles (Phyllotreta striolata) by 64.9% to 80.9%. This is the first report on flaming treatment in China to show that this method is a promising alternative to chemical pesticides for PPPM in leaf vegetable fields.