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

2021 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. Photosynthetic response curves to light intensity and carbon dioxide (CO2) concentration were developed for tomato cultivars grown in controlled environments. A new research space was designed which will contain four replicated indoor vertical farm rooms on the University of Toledo campus. This will greatly enhance our research capacity and scope when completed in the upcoming year. Engineering lab space is under renovation at the University of Toledo campus and will facilitate construction of a photometer prototype and other controlled environment agriculture (CEA) engineering projects. Objective 2. Longevity of calcium silicate, potassium silicate, steel slag, and rice hulls to supply silicon (Si) was determined to be at least 12 weeks at the rates evaluated in four ornamental crops (lantana, lilac, phlox, and verbena) growing in a soilless substrate. Substrate Si amendments could be considered as slow-release sources of Si for crops with long production cycles. In another study, preliminary results suggest supplying Si in the nutrient solution may improve cut basil postharvest quality and longevity. And lastly, cultivar variability in Si accumulation and distribution continues to be investigated. In sunflower, initial microscopy imaging indicates variation in Si deposition in and around leaf trichomes. Experiments are nearly completed to optimize anaerobic soil disinfestation conditions to manage a widespread soilborne disease complex in high tunnel tomato production. The results will be used to provide improved disease management recommendations to growers and improve tomato productivity through application of anaerobic soil disinfestation. Objective 3: As part of the funded USDA-SCRI planning proposal ‘Ensuring the future success of North American specialty crops through soilless substrate science,‘ and in collaboration with Louisiana State University (LSU), a soilless substrate (i.e. growing media) needs assessment was conducted via survey, interviews, and listening sessions. The input received from CEA crop producers and allied suppliers identified top informational and research needs to ensure a non-hindered, sustainable, and profitable future. USDA-ARS, in collaboration with seven institutions, are in process of engineering, characterizing, and evaluating unique soilless substrates with improved physiochemical properties to increase water and mineral nutrient efficiency and decreased weed occurrence. To further and expand these effort, a USDA-SCRI standard research and extension proposal entitled ‘Soilless Solutions: Formulating long-term sustainable substrates using blueberry and citrus as model crops while establishing a knowledge exchange and interactive community for specialty crop producers‘ was submitted to NIFA. This proposal was comprised of biological, soil, economic and sociology scientists and stakeholders across the specialty crop industry.. Preliminary research in support of these efforts is underway in Wooster, Ohio using blueberry. In collaboration with Clemson University and Ohio State University, a review paper that identifies knowledge gaps of reservoir water quality and design parameters has been accepted by the J. Cleaner Prod. This paper is the basis for the accepted technology transfer publication ‘The Basics of Irrigation Reservoirs for Agriculture’ to soon be published via Land-Grant Press by Clemson Extension. Ongoing research in Ohio and South Carolina will better characterize on-farm water quality of CEA reservoirs and irrigation and storm non-point runoff. Hydroponic systems, including Bato bucket and nutrient film systems, were obtained and set up in a campus greenhouse and successfully used to produce cucumbers, tomatoes, and leafy greens. These systems will be used in future trials to assess plant disease management strategies in hydroponic production. Experiments were conducted and are currently being written for publication that provide new knowledge on how substrate solution located vertically in a container profile is removed via a commonly used extraction procedure called the pour-through procedure. These experiments will change how scientists and growers interpret pour-through results, as well as guide current research on stratified substrates. Objective 4: Field experiments were conducted using a portable ethanol detection device to assist growers, arborists, and researchers with identifying trees emitting stress-related volatiles and at-risk of attack by ambrosia beetles. Time-course emissions of ethanol we monitored from flood-stressed trees using a portable device and confirmed using gas chromatography-mass spectrometry. Analyses are in progress. A third seasonal deployment of a field experiment was conducted to identify an optimal lure release rate of ethanol to maximize trap captures of ambrosia beetles. Lures emitting five different release rates were deployed covering 0.1 g/day to 14 g/day. A release rate of 5 g/day was determined to be ideal for destructive species of exotic ambrosia beetles. This research will assist with maximizing interception tactics. Since ambrosia beetles attack trees emitting ethanol, root drenches of trees with taurine were tested because of the potential for this amino acid to promote the metabolism of ethanol. Trees were pre-treated with taurine and then irrigated with ethanol to promote ambrosia beetle attacks. Taurine treatment did not reduce attacks on trees compared to the untreated controls. Trees are currently being dissected to determine if taurine drenches reduced the colonization success of ambrosia beetles, in support of previous experiments. Analyses are in progress. 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. RNA extracted from these tissues was used to develop a cDNA library, which will aid in characterizing the function of this organ and understanding biological weak points. We also attempted to extract RNA from ambrosia beetle antennae to identify an ethanol receptor, but we were unable to rear enough ambrosia beetles to obtain sufficient concentrations of RNA. We will attempt this research after colony modifications in winter-spring 2021-2022. Research on the effects of flood duration on the ability of ambrosia beetles to colonize tree crops was completed. Research was started with the effects of flood duration on ambrosia beetle colonization tested at three seasonal timings. Research related to testing traps for monitoring flea beetle activity in nurseries was conducted for the second year. Attraction of flea beetles to sticky traps of various colors was tested. Furthermore, two potential olfactory attractants were tested in combination with sticky traps of various colors. There is the potential for a scent-color combination that may improve monitoring for red-headed flea beetles. 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. Experiments have also been conducted to assess the efficacy of entomopathogenic nematodes and the bacteria Bacillus thuringiensis for controlling fungus gnat larvae infesting straw substrates used for growing oyster mushrooms. Experiments determined that treating straw with Bt, but not nematodes, was effective at reducing the emergence of adult fungus gnats. These efforts will assist in developing sustainable management tactics for fungus gnats infesting oyster mushroom farms. A quantitative polymerase chain reaction (qPCR) assay was developed for Pyrenochaeta lycopersici, a key root-rotting pathogen in the high tunnel soilborne disease complex. This pathogen has two distinct genetic types 1 and 2 and the assay can be used to detect and quantify both types. Initial validation steps have been completed for this assay and further validation will be completed to assess P. lycopersici populations in soil and roots. This detection tool can be used for plant disease diagnostics and to develop a better understanding of P. lycopersici biology to improve disease management strategies. Objective 4e: Little is known about the exact host range of widespread genomoviruses. The genome of soybean leaf-associated gemygorvirus-1 (SlaGemV-1) was originally assembled from a metagenomic/metatranscriptomic study without known hosts. SlaGemV-1 was rescued and found that it could infect three important plant pathogenic fungi and Fall armyworm (S. frugiperda, Sf9) insect cells, but not a model nematode, C. elegans, or model plant species. Most importantly, SlaGemV-1 shows promise for inducing hypovirulence of the tested fungal species under family Sclerotiniaceae, including Sclerotinia sclerotiorum (white mold), Botrytis cinerea (gray mold), Monilinia fruticola (stone fruit mommy).

Accomplishments
1. Volatiles emitted from symbiotic fungi for attracting exotic ambrosia beetles. ARS researchers in Wooster, Ohio, identified volatile compounds emitted from the fungal symbiont of an exotic ambrosia beetle using gas chromatography-mass spectrometry. The olfactory response of the exotic ambrosia beetle to the volatile compounds were characterized using an electroantennogram to measure firing of olfactory receptors. Short and long range behavioral responses of the exotic ambrosia beetle were measured in response to the volatile compounds. At short and long ranges, the compounds were not more attractive than the standard attractant (i.e. ethanol) and did not enhance attraction to ethanol. These results reinforced knowledge of ethanol being the primary attractant for certain exotic ambrosia beetles, thereby influencing the direction of future studies.

2. Root silicon accumulation in greenhouse crops. Plants can use silicon to reduce the impacts of stress from weather conditions, nutrient availability, pests, or diseases. Identifying how much silicon a plant takes up and where the plant stores it provides insight to researchers in how silicon protects plants from stress and what processes it regulates. Traditional nomenclature has defined plants as low or high silicon accumulators based solely on leaf silicon concentrations. ARS researchers at Wooster, Ohio, discovered that supplying silicon to petunia (a low silicon accumulator) resulted in higher amounts of silicon in the roots than in the leaves. This suggests tight control of silicon movement from the roots to leaves. It also indicates increased specificity be used by researchers to include both location and concentration when classifying silicon accumulation in plants.

3. Cauliflower mosaic virus inclusion body formation and movement in plant cells. Plant viruses can cause severe crop damage and yield losses. Cauliflower mosaic virus (CaMV) forms specialized compartments called inclusion bodies, which it uses to generate the viral components needed to spread to additional cells during an infection. Understanding inclusion body formation will identify targets researchers can focus on when developing new products to control viral infections. ARS researchers in Toledo, Ohio, in collaboration with the University of Toledo, discovered that small inclusion bodies of CaMV continually move around in a plant cell and likely hitch a ride on actin filaments. Targeted disruption of actin filaments could be a way to control CaMV infection during early and middle stages of infection. They also discovered that large inclusion bodies hijack a host plant’s aggresome pathway for their benefit during the late stages of a CaMV infection. This knowledge is an important first step towards developing new ways to minimize crop damage and yield loss from CaMV.

4. Elevated carbon dioxide and chronic high temperature or drought stress reduce nitrogen uptake in crop plants. The changing climate is predicted to be warmer, drier, and have higher carbon dioxide (CO2) concentrations in future years. Identifying how these environmental conditions may impact nutrient uptake and plant nutrient status has implications on crop yield and quality. ARS researchers in Toledo, Ohio, in collaboration with the University of Toledo, discovered that the combination of elevated CO2 and chronic high temperature stress negatively impacted growth, nitrogen (N) uptake rates, and N transport from roots to the shoot in tomato, and it negatively impacted plant %N and protein content in wheat. Combining elevated CO2 with drought stress reduced plant %N and % phosphorus (P), despite an increase in nutrient uptake transporters in the roots to counteract the stress. Collectively, these studies suggest plant growth, yield, and quality will be negatively impacted by predicted climate scenarios. However, key components in the nutrient uptake and transport pathways are identified that breeders could focus on improving to develop more resilient cultivars well-suited for potential climate conditions.

5. Silicon effects on gene expression during copper toxicity are temporally dynamic. Silicon can be given to plants to help offset a stress, like a nutrient deficiency or toxicity. However, the mechanisms for the beneficial effects observed is unclear. ARS researchers in Toledo, Ohio, in collaboration with the University of Toledo, discovered that disease defense genes are involved in silicon signaling in plants exposed to high levels of copper and they are temporally regulated. The enhancement observed after one week was reduced after three weeks. This decodes one more piece of the puzzle regarding silicon regulation of stress in plants. Additionally, it highlights the importance that researchers are cognizant of the length of time between applying treatments and collecting data, as the effects can change in magnitude over time and impact interpretation of observed results.

6. Ambrosia beetle attacks following short-term flooding less damaging than previously thought. Invasive ambrosia beetles are pests of tree crops including apples and ornamental trees. Invasive ambrosia beetles are pests of tree crops including apples and ornamental trees. Excessive rainfall creates flood events (water saturated soil) that make trees attractive to ambrosia beetles. Ambrosia beetles bore into trees and create galleries in which they raise their offspring. Young trees colonized by ambrosia beetles show signs of damage such as wilting leaves and die-back, or colonized trees die. Currently, nursery growers tend to cull trees with any sign of ambrosia beetle attacks. ARS researchers in Wooster, Ohio, discovered that ambrosia beetles attacked, but were unsuccessful colonizing trees during short-term (3 days) flood events. Trees usually survived the short-term flooding and unsuccessful colonization attempts. These results indicate growers can retain trees attacked during short-term flood events instead of prematurely culling them.

7. Alkaline irrigation water is not detrimental to Controlled Environment Agriculture production of ornamental crops. The popular held belief is that high pH water (i.e. alkaline) that is overhead irrigated at open-air nurseries is detrimental to crop growth resulting in implementation of costly water treatment technology to adjust pH to 5.8 -7.0. ARS researchers in Wooster, Ohio, in collaboration with North Carolina State University and stakeholders in the southeastern U.S., helped disprove the ‘popular belief’ by comparing high pH water to water within recommended ranges for varying durations of exposure to woody ornamental crops. Dry weight of all and gas exchange (photosynthesis and water flux) of woody ornamental shrub (forsythia) was not affected by high pH, low alkalinity (<100 ppm) irrigation water. Findings illustrate that irrigating container plants overhead with high pH, low alkalinity (<100 ppm total alkalinity) source water from ponds did not affect growth enough to warrant investment in an acid injection system for ornamental nursery crop producers simply to lower pH to meet Best Management Practices; however, water treatment should still be considered if sanitizing chemicals to reduce microorganisms.

8. Soilless substrates stratification can increase resource efficiency in Controlled Environment Agriculture (CEA). There has been little novelty in CEA container systems in the last few decades that specifically help address resource efficiency and attempt to speed production to ensure profitability. A need to better engineer soilless substrates was approached from a bioretention perspective allowing researchers to alter chemistry and hydrology throughout the container profile. ARS researchers in Wooster, Ohio, in collaboration with Louisiana State University, demonstrated the impact of a novel method to stack engineered soilless substrates within a container to reduce water and mineral nutrient use by 20% when producing similar or superior quality CEA crops. This preliminary work demonstrates that a low-cost technology such as the soilless substrate (i.e. growing media) can be utilized to reduce use of finite resources, increase potential profitably, and enhance stakeholder environmental stewardship by decreasing non-point source runoff.

9. Less phosphorous fertilizer can be used to produce ornamental crops in Controlled Environment Agriculture (CEA). ARS researchers in Wooster, Ohio, in collaboration with Michigan State University, confirmed that the limiting threshold for woody ornamental crop physiology is below the recommended best management practice of approximately 10 ppm phosphorous as previously demonstrated in soilless substrate and fertilizer formulation research. Different plant species of economically important significance were produced with fertilizer containing varying amounts of phosphorus. This work shows that phosphorus fertilization can be reduced by more than 25% depending on ornamental plant species produced, potentially reducing CEA phosphorus non-point runoff by 50% to 90% without decreasing woody ornamental crop producer’s profitability.

U.S. DEPARTMENT OF AGRICULTURE

Application Technology Research: Wooster, OH