W3008: Integrated Onion Pest and Disease Management

(Multistate Research Project)

Status: Active


Onion, Allium cepa L., is the third most consumed vegetable in the U.S., behind tomato and potato. The per capita consumption of onions in the U.S. 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 USD/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 U.S. and is valued over $100 million/year. Onion is grown on 125,000 acres across at least 20 states with a majority produced in California, Colorado, Georgia, New Mexico, New York, Oregon, Texas and Washington.

The need as indicated by stakeholders. Onion crops are damaged by a similar spectrum of pests and pathogens throughout the U.S. For example, onion thrips, Thrips tabaci Lindeman, damages onion by feeding on leaves that significantly reduces onion bulb yield and quality (30 to 50%) (Fournier et al. 1995). Onion thrips also is notorious for developing resistance to insecticides (Shelton et al. 2003, 2006; Allen et al. 2005) and spreading plant pathogens like Iris yellow spot virus (IYSV), which also reduces bulb yield and quality as well as seed production (Gent et al. 2004 & 2006, du Toit and Pelter 2005). There are multiple fungal and bacterial pathogens that can cause onion yield losses in the field and in storage facilities throughout the U.S. (Schwartz and Mohan 2005). Each disease can cause up to 25 to 100% crop loss. The most important fungal diseases include Stemphylium leaf blight (SLB), Stemphylium vesicarium, purple blotch (PB), Alternaria porri, downy mildew (DM), Peronospora destructor, black mold, Aspergillis niger, Botrytis leaf blight (BLB)/ blast and neck rot, Botrytis species, powdery mildew, Leveillula taurica, 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 sp., and Enterobacter bulb decay, Enterobacter cloacae. Over the past several years, growers in some regions have abandoned onion production because of losses due to problems caused by one or more of these organisms. Consequently, stakeholders have identified onion thrips, IYSV and these fungal and bacterial pathogens as significant threats to sustainability of the U.S. onion industry http://www.ipmcenters.org/pmsp/pdf/USonionPMSP.pdf).

The importance of the work, and what the consequences are if it is not done. The work proposed is critical for solving the most important pest and disease problems facing the US onion industry. We are not aware of other public or private entities that will be as organized across state borders to solve these problems as the W3008 group, particularly given the successful foundation set by the preceding multistate projects (W1008: Biology and Management of Iris yellow spot virus (IYSV) and Thrips in Onions from 2005-2010, and W2008: Biology and Management of Iris yellow spot virus (IYSV), Other Diseases and Thrips in Onions from 2011-2016). We anticipate that results from this research and extension effort will continue to contribute significantly to science and agriculture as we communicate new knowledge about the biology, ecology and management of these pests and pathogens through peer-reviewed publications, presentations at professional meetings, field days, and web-based resources for stakeholders. Consequences of not addressing these significant issues include further reductions in US onion acreage due to limited ability to manage the pest and diseases mentioned above, reduced profits as a result of decreased bulb yields, reduced quantities and/or qualities of onion seed produced, and greater pesticide and fertilizer inputs, as well as potential environmental and human health concerns associated with greater fertilizer and pesticide use.

The technical feasibility of the research. Participants of this Project will include researchers at institutions that have the resources, laboratories, land for research and personnel required to conduct the studies described herein. Project objectives are designed to include short-term, medium-term, and longer-term research studies that should reasonably be completed within the 5-year duration of this proposed project.

The advantages for doing the work as a multistate effort. The principal advantage of doing this work as a multistate effort is that this proposal builds on two previous, highly successful multistate projects (W1008 from 2005 to 2010, and W2008 from 2011 to 2016). We anticipate that participants of our proposed project will continue to include most of those who are leaders in their respective areas of onion breeding, horticulture, entomology, plant pathology, virology and microbiology. Past participants have included public and private researchers, extension professionals, onion growers and seed industry personnel throughout the US who have formed productive collaborations. Many of the problems affecting onion production occur in most regions in the US, so our project brings together those with similar interests in solving the issues. The proposed research is synergized by interactions this group has developed over the past 11 years, which we anticipate will continue.

What the likely impacts will be from successfully completing the work. 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 other pests and diseases, 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 use should reduce watershed pollution caused by nutrient runoff or leaching, and will 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.

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