INTEGRATED ONION PEST AND DISEASE MANAGEMENT

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1014401
• Multistate No.: W-3008
• Project Start Date: Oct 30, 2017
• Project End Date: Sep 30, 2022
• Program Code: [(N/A)]- (N/A)

Recipient Organization
PENNSYLVANIA STATE UNIVERSITY
208 MUELLER LABORATORY
UNIVERSITY PARK,PA 16802

Performing Department
Plant Pathology & Environmental Microbiology

Non Technical Summary
Onion, Allium cepa, is the third most consumed vegetable in the US, behind tomato and potato. The per capita consumption of onion in the US is about 20 pounds per year, which has increased 70% over the past 20 years (https://www.onions-usa.org/all-about-onions/consumption). Onion is also one of the most economically important specialty crops with a farm-gate value of nearly $1 billion per year (https://www.nass.usda.gov/Publications/Ag_Statistics/2015/Chapter04.pdf) and over $70 million in added value after processing. In addition, over 20% of the world's onion seed is produced in the US and is valued at over $100 million per year. Onion is grown on 125,000 acres across at least 20 states with a majority produced in California, Idaho-Eastern Oregon and Washington in the west and Georgia and New York in the east (https://www.onions-usa.org/all-about-onions/where-how-onions-are-grown).Onion crops are damaged by a similar spectrum of pests and pathogens throughout the US. For example, onion thrips, Thrips tabaci, damages onion plants by feeding on leaves. The damage can reduce onion bulb yield and quality by up to 30 to 50% (Fournier et al. 1995). Onion thrips also is notorious for developing resistance to insecticides (Shelton et al. 2003, 2006; McIntyre Allen et al. 2005) and spreading pathogens like Iris yellow spot virus that also can reduce bulb yield and quality as well as seed production (Gent et al. 2004, 2006; du Toit and Pelter 2005; Bag et al. 2015). Multiple fungal and bacterial pathogens can cause onion yield losses in the field and in storage facilities throughout the U.S. (Schwartz and Mohan 2008). Each disease can cause up to 25 to 100% crop loss. The most important fungal diseases include Stemphylium leaf blight (caused by Stemphylium vesicarium), purple blotch (Alternaria porri), downy mildew (Peronospora destructor), black mold (Aspergillis niger), Botrytis leaf blight (Botrytis squamosa) and neck rot (Botrytis species), powdery mildew (Leveillula taurica), Fusarium basal rot (Fusarium oxysporum f. sp. cepae) and white rot (Sclerotium cepivorum). The most important bacterial diseases include sour skin (Burkholderia cepacia), slippery skin (Burkholderia gladioli pv. Alliicola), center rot (Pantoea ananatis and P. agglomerans), leaf streak (Pseudomonas viridiflava), soft rot (Pectobacterium carotovorum and Dickeya spp.), and Enterobacter bulb decay (Enterobacter cloacae). Growers continue to abandon onion production in some regions because one or more of these organisms have caused catastrophic losses. Consequently, they have identified these pathogens and pest as major threats to the sustainability of their industry (http://www.ipmcenters.org/pmsp/pdf/USonionPMSP.pdf). We propose to address these concerns through the following objectives:Evaluate onion germplasm for resistance to pathogens and insects.Investigate the biology, ecology and management of onion thrips and other pests.Investigate the biology, epidemiology and management of onion plant pathogens.Facilitate discussions between W3008 participants and onion industry stakeholders that will advance onion pest and disease management.This project is expected to have positive impacts on the economy, environment and society. The cost of onion production should be reduced through implementation of new management tactics that utilize new onion cultivars with greater resistance to thrips, IYSV and FBR, and reduced inputs such as pesticides and fertilizers. More judicious use of reduced-risk insecticides and fungicides, action threshold-based pesticide application programs, and optimal pesticide and fertilizer application techniques and strategies that mitigate insecticide and fungicide resistance risks will contribute directly to improved environmental stewardship and sustainability. Reduced fertilizer inputs should reduce watershed pollution caused by nutrient runoff or leaching, and reduce production costs. Society will benefit from the training of graduate and undergraduate students working with faculty on this project, preparing the next generation of researchers, extension specialists and agricultural professionals who will shape the future of production agriculture.

Animal Health Component

100%

Research Effort Categories

Basic

(N/A)

Applied

100%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
212	1451	1160	50%
216	1451	1160	50%

Knowledge Area
212 - Pathogens and Nematodes Affecting Plants; 216 - Integrated Pest Management Systems;

Subject Of Investigation
1451 - Onion, garlic, leek, shallot;

Field Of Science
1160 - Pathology;

Keywords

onion

disease

integrated pest management

Goals / Objectives
Investigate the biology, epidemiology and management of onion plant pathogens. Facilitate discussions between W3008 participants and onion industry stakeholders that will advance onion pest and disease management.

Project Methods
Objective 3. Investigate the biology, epidemiology and management of onion plant pathogens. Onion disease research planned for the 5-year duration of W3008 includes research and extension activities in California, Georgia, Michigan, New York, Oregon, Pennsylvania, Washington and other collaborating states/countries.Bacterial pathogens. Management of bacterial pathogens requires an integrated approach that focuses on understanding the potential sources of bacteria (seed, transplants, soil, weeds and crop debris), their etiology and epidemiology, as well the impact of combinations of management practices to reduce losses. Efforts to reduce epiphytic bacterial populations associated with transplants through the application of pre-plant treatments will continue, as well as screening cultivars to identify reduced susceptibility.Bacterial pathogens that cause center rot, Pantoea ananatis and P. agglomerans, are major problems in onion, especially in the eastern US. In Pennsylvania, replicated research trials will be conducted to evaluate the impact of timing and rate of nitrogen application on percent nitrogen in foliage and center rot incidence at harvest. Harvest timing recommendations will be fine-tuned based on visual symptom thresholds that growers can use as a guideline to help minimize bacterial movement from the leaves into the bulb.Objective 4. Facilitate discussions between W3008 participants and onion industry stakeholders that will advance onion pest and disease management. We intend to expand membership in W3008 by broadening the scope of our objectives and connecting with more stakeholders in the national onion industry. A concerted effort will be made to inform the onion industry about upcoming W3008 annual meetings via trade magazines, email, internet promotions, and a new and improved version of the www.alliumnet.com web site. Our goal is to communicate current research results and identify research priorities of the US onion industry. We have maximized our interactions with the US onion industry by having joint meetings among W2008, NARC and NOA. More details about communicating information about this project are described in the Outreach Plan.

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:Current and future onion growers in Pennsylvania and in other onion growing regions will benefit from the research conducted as part of this project. Smaller scale growers sell primarily sweet onions through local produce auctions and direct markets. These lucrative markets pay $1.00/lb or more for jumbo and colossal sized bulbs. Reducing losses associated with bacterial diseases of onion through education and the development of an integrated pest management program will aid in sustaining and building the fresh market onion industry in Pennsylvania. The general public will also benefit from having affordable high-quality locally-grown onions available. In addition, annual regional project meetings will provide the opportunity to network and share research and extension efforts. When possible, these meetings will be held in conjunction with the National Allium Research Conference and National Onion Association to engage with more Allium researchers and industry stakeholders. Changes/Problems:Several field trials evaluating onion bacterial disease management practices were postponed until 2021 due to COVID-restrictions especially limiting research early in the pandemic. These trials would have been planted in mid-April 2020. The decision was made to focus onconducting the commercial field sampling and processing as a part of an Specialty Crop Research Initiative (SCRI) grant funded to Washington State University in 2019 given significant labor restrictions. Regarding opportunities for training and professional development, COVID-19 international travel and visa restrictions havedelayed the arrival of a new PhD student who will be working on this project until spring 2021. What opportunities for training and professional development has the project provided?Two presentations, one in-person for a grower stakeholder audience and one webinar training for PA Department of Agriculture(PDA) Inspectors were delivered to, in part, increase knowledge about the identification and/or management of bacterial diseases of onion. COVID-19 international travel and visa restrictions delayed the arrival of a new PhD student who will be working on this onion bacterial disease project until spring 2021. How have the results been disseminated to communities of interest?Research results were disseminated through one-on-one interactions with growers as well as winter meetings with vegetable growers and training update for PDA inspectors. See the lists under presentations and other products. What do you plan to do during the next reporting period to accomplish the goals?Objective 1 (multistate objective 3): A second year of sampling and isolating bacteria from symptomatic onions from commercial fields in Pennsylvania (CB1)and New York is planned. This will build the bacterial collection both regionally and selected isolatewill be deposited in a national collection at University of Georgia (UGA). In addition, a series of replicated field trials will be conducted to evaluate the effect of irrigation and fertility practices on disease incidence and severity in the field and post-harvest as well as a product efficacy trial focusing on copper-based products and a trial to evaluate the timing of onion topping at harvest on bulb disease severity post-harvest. Objective 2 (multistate objective 4): The next W3008 regional project meeting was originally scheduled to be held in conjunction with the Southeast Regional Fruit and Vegetable Conference; however, it will now be held virtually in conjunction with the onion bacterial disease SCRI meeting and possibly the National Allium Research Conference in early 2021. As appropriate, project results will be disseminated in the Penn State Extension Vegetable Gazette Newsletter and other online and hardcopy publications as well as at summer twilight meetings and the 2022 Mid-Atlantic Fruit and Vegetable Convention and in one-on-one communications with growers.

Impacts
What was accomplished under these goals? Objective 1 (multistate objective 3): During the 2020 production season, tenwhole onion plantsamples with characteristic center rot bacterial disease symptoms were collected from each of fivefields in Centre, Clinton, and Lancaster Co., PA at two time points during the season (8 to 9 leaf stage and at harvest). From each plant, isolations were made onto onion extract media (OEM) and nutrient agar and up to six unique bacterial colonies were selected from each media at 24 and 48 hr following plating. A total of approximately 600 bacterial isolates have been collected from PA fields and are in -80C storage awaiting 16S DNA sequencing for bacterial genera identification and pathogenicity testing using a red onion scale clearing assay as well as whole plant foliar assay if needed. Samples were also collected from NY onion fields and processed in a similar manner under an Animal and Plant Health Inspection Service (APHIS) 526 permit.

Publications

• Type: Conference Papers and Presentations Status: Other Year Published: 2020 Citation: Gugino, B.K. Integrated disease management with emphasis on cucurbits, tomatoes, and onions. Beginning Vegetable Growers Meeting Series, Lewisburg, PA. 29 February 2020.
• Type: Conference Papers and Presentations Status: Other Year Published: 2020 Citation: Gugino, B.K. Vegetable (bacterial) disease update. Pennsylvania Department of Agriculture Inspector Training. Webinar. 27 April 2020.

Progress 10/01/18 to 09/30/19

Outputs
Target Audience:Current and future onion growers in Pennsylvania and in other onion growing regions will benefit from the research conducted as part of this project. Smaller scale growers sell primarily sweet onions through local produce auctions and direct markets. These lucrative markets pay $1.00/lb or more for jumbo and colossal sized bulbs. Reducing losses associated with bacterial diseases of onion through education and the development of an integrated pest management program will aid in sustaining and building the fresh market onion industry in Pennsylvania. The general public will also benefit from having affordable high-quality locally-grown onions available. In addition, annual regional project meetings will provide the opportunity to network and share research and extension efforts. When possible, these meetings will be held in conjunction with the National Allium Research Conference and National Onion Association to engage with more Allium researchers and industry stakeholders. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?Research results were disseminated through one-on-one interactions with growers as well as participation in the 2019 International Allium Convention in Madison, WI in July. What do you plan to do during the next reporting period to accomplish the goals?A subset of the W3008 project team led by Dr. Lindsay du Toit received an SCRI grant in 2019 to further the research being conducted on bacterial diseases of onion. This effort will further leverage the impact of the W3008 project.

Impacts
What was accomplished under these goals? During the 2019 production season, two onion center rot trials were conducted. One was in partnership with IR-4 to evaluate the performance of 14 commercial as well as experimental products for the management of center rot of onion caused by Pantoea agglomerans and P. ananatis (considered a pest problem without a solution by IR-4). The treatments plus a non-treated control were evaluated in a randomized complete block design with four replicates. Applications were initiated prior to toothpick inoculation of the pathogens. Data on disease severity as well as harvest data were collected. A subset of marketable onions from each treatment has been placed in storage for evaluation in mid- to late October. The data collected to-date is in the process of being analyzed. A second replicated multi-factorial center rot (P. agglomerans and P. ananatis) research trial was established in partnership with the Pennsylvania Vegetable Growers Association to evaluate several bacterial inoculation methods (three methods) and inoculation timing (three plant growth stages). The goal being to identify a consistent inoculation method and time to inoculate the plants to achieve uniform disease distribution throughout plots in the field. Data on disease severity as well as harvest data were collected and are in the process of being analyzed.

Publications

• Type: Conference Papers and Presentations Status: Accepted Year Published: 2019 Citation: W2008/W3008 Pennsylvania State Report. W2008/W3008 Multi-State Regional Project Meeting, Madison, WI. (July 24, 2019).

Progress 10/30/17 to 09/30/18

Outputs
Target Audience:Current and future onion growers in Pennsylvania and in other onion growing regions will benefit from the research conducted as part of this project. Smaller scale growers sell primarily sweet onions through local produce auctions and direct markets. These lucrative markets pay $1.00/lb or more for jumbo and colossal sized bulbs. Reducing losses associated with bacterial diseases of onion through education and the development of an integrated pest management program will aid in sustaining and building the fresh market onion industry in Pennsylvania. The general public will also benefit from having affordable high-quality locally-grown onions available. In addition, annual regional project meetings will provide the opportunity to network and share research and extension efforts. When possible, these meetings will be held in conjunction with the National Allium Research Conference and National Onion Association to engage with more Allium researchers and industry stakeholders. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Two undergraduate summer research assistants had the opportunity to learn about sweet onion production in Pennsylvania. They aided in the maintenance and harvest of an onion plot being maintained at the Russell E. Larson Agricultural Research Center in Centre Co., PA. During harvest they had the opportunity to observe symptoms of center rot of onion along with the foliar fungal diseases purple blotch and Stemphylium leaf blight. Results of the research conducted to-date and current management recommendations were also shared as part of a broader exposure to vegetable diseases and their management. In addition, the project leader had the opportunity to tour the new onion packing facility recently built in Clinton, Co., PA to service the primarily Anabaptist onion (and butternut squash) growers in central PA who are part of the Lancaster Vegetable Cooperative and market their sweet onions as part of the Simply Sweet Onion program. How have the results been disseminated to communities of interest?The research results have disseminated at several vegetable grower meetings that took place during the 2017-18 project year. Locally, results were also disseminated throughout the season through one-on-one meetings with growers either in person or via telephone conversations. What do you plan to do during the next reporting period to accomplish the goals?It is anticipated that the inoculation methodology and timing trial will be repeated in the upcoming year and research results and management recommendations will continue to be disseminated through traditional and electronic means. In addition, planning is underway to resubmit a Specialty Crop Research Initiative grant that will leverage the regional/national efforts of this multi-state project to address bacterial diseases of onion.

Impacts
What was accomplished under these goals? In the first year of this project, emphasis was placed on disseminating results from the previous W2008 regional project at a number of local winter grower meetings and summer pest and disease walks in support of objective 4. A total of five presentations reaching over 490 participants were given that included at least impart the identification and management of bacterial diseases of onion. In addition, a replicated multi-factorial center rot research trial was established to evaluate several bacterial inoculation methods (three methods) and inoculation timing (three plant growth stages) in support of objective 3. The goal was to identify a consistent inoculation method and time to inoculate the plants to achieve uniform disease distribution throughout the plots. This in turn would reduce variability in disease pressure across the trial and facilitate the more standardized evaluation of management tactics which could then be employed in multiple onion growing regions across the U.S. Unfortunately, the trial was terminated prematurely due to the extreme wet weather in the central and eastern parts of Pennsylvania this past season.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: Pfeufer, E.E. and B.K. Gugino. Environmental management factors associated with bacterial diseases of onion in Pennsylvania. Plant Disease. doi.org/10.1094/PDIS-11-17-1703-RE