Project : USDA ARS

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Research Project: Sustainable Production and Pest Management Practices for Nursery, Greenhouse, and Protected Culture Crops

Location: Application Technology Research

2022 Annual Report

Objectives
1: Develop growth models integrating light, temperature, carbon dioxide, and other environmental factors into decision-support software tools to reduce energy costs or increase yield and quality of ornamental and edible crops grown under controlled environment. 2: Develop nutritional and substrate amendment guidelines that improve crop quality and yield or reduce environmental impacts of food and ornamental plants grown in protected horticulture. 3: Develop new hydroponic and container-culture technologies that improve substrate chemical, physical, or biological properties and reduce nutritional, water, and agrichemical inputs. 4: Identify alternative control agents and develop and/or improve methods and strategies for managing pests (insects, other arthropods, and weeds) in horticultural (food and ornamental) crops through improved knowledge of pest biology, ecology, & behavior in order to reduce pesticide usage.

Approach
Ornamental, nursery, and protected culture crops represent about one-fourth of the farm gate value of all specialty crops, and about 15% of the total value of U.S. crop production (USDA NASS Horticultural Crop Census 2014). Production value of nursery and greenhouse crops was estimated at $19 billion in 2013 (USDA NASS Horticultural Crop Census 2014). This project brings together the expertise of USDA-ARS research scientists with cooperators at other universities to focus on ornamental, nursery, and protected culture research. The project is a science-based, outcome-driven, economically motivated program that is already assisting growers in improving the quality of their food and ornamental crops. This project will continue to further our knowledge base in protected culture crops by: 1) integrating light, temperature, carbon dioxide, and other environmental parameters into growth models that enhance decision support in greenhouses and controlled environments, 2) continue developing silicon and other substrate amendments to enhance crop quality and mitigate biotic and abiotic stress, 3) engineering substrates to improve nutrient and water use efficiency, and 4) developing novel management strategies for insects and weeds that integrate knowledge of pest biology with cultural practices and management tools. This project integrates the mission and expertise of the Application Technology Research Unit with other researchers in disciplines critical to the overall success of the project.

Progress Report
Objective 1: Research continued to investigate plant responses to environmental conditions. In collaboration with the University of Toledo, plant responses to elevated carbon dioxide (CO2) concentration and elevated temperature were investigated. The combination of high CO2 and high temperature caused some plant species to bend their leaves upward. This reduced light capture by the leaves and reduced overall plant growth. This phenomenon occurred across multiple plant families, and appeared more so in species with compound, rather than simple, leaves. Considerable progress has been made on upgrading Virtual Grower software. The lighting section and user interface has been updated with a planned cloud deployment later this year. A new CO2 and lighting control system was developed for greenhouses that is easier to tune and commission than previous daily light integral controllers. Simulations show the algorithm also performs better in terms of energy savings and reducing carbon footprint in multiple contiguous U.S. climates. Objective 2: Silicon uptake by plants (sunflower, geranium, and New Guinea impatiens) did not vary across the substrate pH range recommended for floriculture crops. At very low substrate pH values (<4.5), however, silicon uptake by plants was hampered, likely due to poor root growth in the acidic substrate conditions. In collaboration with the University of Toledo, iron uptake was evaluated in marigold and tomato. Concentrations of iron-uptake proteins (FRO and IRT) in roots increased under iron-limiting conditions in an attempt to mitigate iron deficiency, and decreased under iron-excess conditions in an attempt to minimize iron toxicity, but they were unable to completely mitigate visible symptoms. In a comparison of five tomato genotypes, the iron uptake protein IRT was identified as a potential biomarker that could be useful in identifying genotype tolerance to high or low iron conditions. Anaerobic soil disinfestation trials examining carbon source mixtures and sulfur supplementation were completed and data is currently being summarized and analyzed. Objective 3: In collaboration with Michigan State University, research was completed that identified no growth or physiological differences occurred across economically important ornamental taxa when using raw groundwater or recycled water with trace amounts of pesticides. In collaboration with Ohio State University and Clemson University, data analysis was completed comparing production methods effect on water quality and quantity at commercial nurseries and greenhouses, both runoff during and after an irrigation or storm event and the effect on reservoir used for water storage. In collaboration with Virginia Polytechnical and State University, a metanalysis of storm data across climatological or catchment characteristics determined the effect of dry periods occurring between rain events differs among land use characteristics and impacts event mean concentration less than precipitation depth and duration. In collaboration with Louisiana State University, completed research demonstrated the effectiveness of substrate amendments and stratification (i.e. layering different substrates) to improve water retention and crop survivability when grown under four different irrigation schedules, including single daily application, single application at deficit levels, cyclic application, or cyclic at deficit schedules. Stratified substrates improved crop growth, quality, and yield when compared with plants grown in conventional bark. In collaboration with the University of Florida, research documented the impact of pine bark texture and fertilizer placement on weed establishment and growth in container crops. ARS research showed decreasing weed germination and growth with both increasing the particle size of the top layer, as well as increasing the depth of fertilizer placement in the container. Our research also evaluated pine bark particle size and fertilizer placement in containers that were either irrigated once per day, or irrigated with the same volume of water split into three equal irrigation applications throughout the day (using fixed overhead sprinklers). Irrigating with three smaller irrigation cycles throughout the day kept the container surface wetter for longer periods of time. Applying water in a single application vs. three applications reduced bittercress and oxalis (common weeds) growth by more than 93% across both experiments. Objective 3: Biostimulant experiments for lettuce with Pythium sp., a common hydroponic plant pathogen, have been completed and experiments for tomato with Fusarium oxysporum f.sp. lycopersici, a common tomato wilt pathogen, are currently in progress. Research was slightly delayed due to issues obtaining pathogenic strains of Pythium dissoticum and F. oxysporum f.sp. lycopersici. Good disease pressure was obtained in lettuce-Pythium nutrient film technique (NFT) hydroponics systems, and we observed that addition of yeast extract caused an overgrowth of microbes that clogged pumps and tubing. Objective 4: Field experiments were conducted using a portable ethanol detection device to identify trees emitting stress-related volatiles and at-risk of attack by ambrosia beetles. Time-course emissions of ethanol were monitored from flood-stressed trees in 2022 using a portable device and confirmed using gas chromatography-mass spectrometry. The portable device effectively detected the emission of ethanol from stressed trees, but was not sensitive enough to detect ethanol prior to ambrosia beetles detecting and infesting the stressed trees. The first season of a field experiment was also initiated whereby a trapping grid was used to characterize the dispersal pattern of ambrosia beetles into ornamental nurseries. Weekly captures from the extensive trapping grid deployed from April through October at commercial ornamental nurseries are being processed. Understanding dispersal patterns of exotic ambrosia beetles will maximize detection techniques along with implementing a “push-pull” management tactic, whereby repellents are used to “push” beetles away from valuable crops and attractants are used to “pull” beetles into annihilative traps. Since ambrosia beetles attack trees emitting ethanol, a third season of experiments was conducted to test a proprietary compound for promoting the metabolism of ethanol in trees. Following multiple years of field experiments, root drenches with the proprietary compound decreased ambrosia beetle attacks and colonization of the treated trees. An invention disclosure on this discovery is being finalized for submission in July 2022. RNA was extracted using lab-reared and field-collected ambrosia beetles (Xylosandrus germanus) from selected tissue types. Genes with stable expression were then identified for reference purposes from the various tissue types, including the organ used for carrying spores of their nutritional fungal symbiont to new host trees. Identification of the reference genes is facilitating gene expression studies (e.g., transcriptome analyses) of this organ. In order to identify biological weak points, RNA was extracted from the organ (i.e. mycangium) ambrosia beetles use to transport spores of their nutritional fungal symbiont. The RNA was used to develop a cDNA library to aid in identifying genes involved in the function of the mycangium used for transporting spores. We also attempted to extract RNA from ambrosia beetle antennae to identify an ethanol receptor, but we were unable to collect and isolate enough RNA. As such, research efforts shifted to focus on a transcriptome analysis of the mycangium. To address fungus gnats affecting the production of gourmet oyster mushrooms, sticky traps were sent to producers of food and ornamental crops in controlled environments across the U.S. These efforts will assist with understanding the diversity and seasonal activity of fungus gnats in oyster mushroom production compared to other crops. Results from these efforts will assist with determining if certain species of fungus gnats are unique to oyster mushroom farms. Research was initiated investigating the influence of acetic acid (Ph) on colonization of trees by ambrosia beetles. Preliminary research indicates pH may influence colonization and acetic acid is found in trees producing ethanol. Research related flea beetle attraction to sticky traps of various colors was tested to develop monitoring tools, and two potential chemical attractants. Screening insecticides for control of flea beetles in nursery crops was started. Bioassays using insecticide treated leaves of suitable hosts were run to determine the most effective materials on which to conduct further testing with whole plants. Soybean leaf associated gemygorvirus-1 (SlaGemV-1) is a CRESS-DNA virus classified in the family Genomoviridae, which causes hypovirulence and abolishes sclerotia formation in infected fungal pathogens under the family Sclerotiniaceae. The lack of sclerotia would reduce winter survival and carpogenic germination, and disrupt the disease cycle. To investigate the mechanisms involved in the induction of hypovirulence, RNA-Seq was compared between virus free- and SlaGemV-1-infected Sclerotinia sclerotiorum strain DK3. The cell cycle and DNA replication/repair pathways were investigated and noted to be almost entirely up regulated including a putative cyclin and separase being up regulated 8.3 and 5.2 fold. Transmission Electron Microscopy imaging reveals virus particles collected in large numbers along the inner membrane maintained within vesicles, suggesting endocytosis as the route of horizonal transmission. A quantitative polymerase chain reaction (qPCR) assay was developed for Pyrenochaeta lycopersici, a key root-rotting pathogen in the high tunnels. Final experiments to demonstrate use of this assay for pathogen detection in soil and roots are underway.

Accomplishments
1. Identification of stable reference genes in selected tissues of an ambrosia beetle. To facilitate future studies examining gene expression of a destructive wood-boring insect named the black stem borer, Xylosandrus germanus, ARS researchers in Wooster, Ohio, identified stable genes unaffected by experimental treatments to provide a standard reference for subsequent gene expression studies. Selected tissue types were dissected from laboratory-reared and field-collected ambrosia beetles to evaluate the stability of five reference genes. Two of five genes examined were identified as stable reference genes because their expression was consistent across selected tissue types from X. germnanus. These results will aid in normalizing the expression of target genes during studies of this ambrosia beetle aimed at identifying biological weak points in their association with a fungal symbiont on which the beetles must feed to survive

2. Multi-parameter photosynthesis models to optimize the growth of controlled environment agriculture crops help reduce production costs. In controlled environment agriculture, optimizing the growing environment in greenhouses and indoor farms is key to maximizing plant growth and resource use efficiency. ARS researchers in Wooster, Ohio, developed multi-parameter photosynthetic models for six floriculture species (calibrachoa, geranium, pepper, petunia, sunflower, and verbena) commonly grown in greenhouses. They looked at plant responses to simultaneous changes in light intensity, carbon dioxide concentration (CO2), and temperature. These models can be used by growers to select a set of growing conditions that will provide high plant yields and reduce energy inputs. This will improve resource use efficiency and reduce production costs for controlled environment agriculture producers.

3. New CO2 and lighting control software for greenhouses. Carbon dioxide (CO2) and light are often controlled and supplemented in greenhouse production, although both can be expensive and energy intensive. Resources for precisely controlling these two parameters simultaneously are lacking for most crops. Software was developed by ARS researchers in Toledo, Ohio, for simultaneously controlling CO2 concentration and supplemental light levels in greenhouses. Simulations showed performance improvements over existing CO2 and daily light integral controllers for multiple climates in the contiguous U.S. The software allows growers to reduce carbon footprint, energy consumption, and energy costs, and produce crops with a more consistent size and schedule.

U.S. DEPARTMENT OF AGRICULTURE

Application Technology Research: Wooster, OH