Sustainable Solutions to IYSV on Onion Via Grower-Research Partnerships

Sustainable Solutions to IYSV on Onion Via Grower-Research Partnerships

Summary

The combined effects of variety, irrigation system, irrigation criterion and nitrogen (N) rate on IYSV expression and onion yield and grade were evaluated in 2008 and 2009. N fertilization at 224 kg/ha has consistently failed to improve disease incidence or yield over 112 kg/ha. In 2008, drier irrigation criteria (30 kPa) resulted in more severe IYSV symptoms and lower marketable, colossal and colossal plus super-colossal bulb yield than the wetter irrigation criteria. There were no significant interactions between variety, irrigation criteria and N rate in 2008 or 2009. The 2009 season proved to be helpful in identifying locally-adapted varieties with tolerance to IYSV. Kaolin foliar treatments failed to suppress IYSV and have been dropped by growers.

Objectives/Performance Targets

Maintain onions as a viable part of the PNW family farm crop rotations by reducing the impact of IYSV through the following:

1) Identify onion lines with resistance or tolerance to IYSV.

2) Reduce water stress and heat stress on onions through irrigation systems and irrigation criteria.

3) Determine if added N can help affected onions continue to maintain bulb growth.

4) Synergism among 1-3 above.

5) Reduce heat stress by using foliar kaolin clay at peak heat stress.

6) Demonstrate all useful findings in growers’ fields. Fully and promptly communicate results via word of mouth, field personnel participation, field days, grower meetings, internet, national working group meetings and papers in trade and scientific journals.

The initiatives of our project would be complementary to initiatives of parallel efforts to control onion thrips and isolate over-wintering seed and bulb crops from summer bulb crops.

• Field Day to educate growers on cultural practices to reduce the impact of IYSV on onions

Accomplishments/Milestones

The onion trials were conducted in 2008, 2009 and 2010 as planned. Results from 2008 and 2009 trials have been compiled and distributed to growers and the public. Onions from the 2010 season and stored in the 2010-2011 storage season are being graded and the data will be analyzed, reported and published in the near future. Based on the first two years of the project, preliminary results indicate the following:

1. Based on “on farm” and “on station” trials, onion varieties have been identified that are more and less tolerant to IYSV. The 2009 onion variety trial strongly sorted varieties for IYSV since the infection rate was severe.

2. Irrigation systems and irrigation criteria have been tested as planned. Small increments of water stress on onion were very detrimental to onion yield and grade in the presence of IYSV in 2008. In 2009, the IYSV pressure at the irrigation trial site was less than in 2008, and the effects of water stress were less dramatic. Additional growers are adopting drip irrigation systems and carefully monitoring soil water tension.

3. The growers’ notion that sprinkler irrigation would aid in the reduction of onion thrips has not been substantiated. There seems to be no difference in thrips pressure between irrigation systems.

4. Consistent with the results from 2008, extra N fertilizer in 2009 was not of any benefit to help onions continue growing in the presence of IYSV.

5. No interactions have yet been observed between varieties, water stress and N fertilizer rates.

6. “On farm” attempts to reduce IYSV effects through the application of kaolin clay have not been successful, and growers have stopped trying this option.

7. The project has continued to effectively transfer information pertinent to IYSV and thrips biology to growers, other onion industry parties and the public through numerous meetings, field days, publications and the internet. Results have been effectively communicated by grower and field personnel participation in the project planning and evaluation of results, field days for growers July 14, 2010 and August 29, 2010, grower meetings on February 2, 2010, internet web sites and results being reported in Onion World.

8. An extension brochure was written describing how to optimize onion irrigation scheduling, including how to minimize IYSV through irrigation management. The extension brochure was published in September, 2010. An early version of the extension brochure was published for worldwide distribution in Onion World.

9. A journal article needs to be published that would cover the difference in IYSV symptoms and onion performance with small increments of water stress.

• Certain onion varieties showed fewer IYSV symptoms and less yield reduction due to IYSV
• Successful Onion Irrigation Scheduling SR1097
• Onions maintain with little water stress have few IYSV symptoms

Impacts and Contributions/Outcomes

Damage of IYSV is less pronounced. It is hard to tell if the benefits are related to the current project or fluctuations in weather and thrips populations.

1. More growers are adopting onion varieties with greater tolerance to IYSV. Seed availability is still a limiting factor for these new varieties.

2. Due to better knowledge of the transmission of IYSV, fewer growers are planting overwintering onions. With fewer overwintering onions and better cull onion disposal, growers are breaking the natural green bridge that keeps IYSV pressure high from one production year to the next. Some growers continued to suffer IYSV related yield losses due to overwintering onion bulb or seed fields close to their summer production fields.

3. Increasing numbers of growers are adopting drip irrigation and careful irrigation scheduling. These carefully irrigated onion crops seem to be suffering less from IYSV.

4. More growers are using soft insecticides to control trips early in the season, allowing natural predators to help control thrips, at least at the beginning of the summer. These insecticide use strategies have recently been proven to be effective in replicated field tests.

1. PowerPoint presentations to growers and field personnel

Shock*, C.C. E.B.G. Feibert, L.D. Saunders, L.B. Jensen, S.K. Mohan, R.S. Sampangi, and H. Pappu. 2010. Iris Yellow Spot Virus control through stress reduction. 49th Annual Meeting of the Malheur Onion Growers Association and Idaho Onion Growers Association, 2 February 2010, Ontario, OR.

Shock*, C.C. E.B.G. Feibert, L.D. Saunders, L.B. Jensen, S.K. Mohan, R.S. Sampangi, and H. Pappu. 2010. Onion variety trial report 2009. 49th Annual Meeting of the Malheur Onion Growers Association and Idaho Onion Growers Association, 2 February 2010, Ontario, OR.

Shock*, C.C. and E.B.G. Feibert. 2009. Onion Drip Irrigation, Pacific Northwest Vegetable Association, Kennewick, WA. November 11, 2009.

2. Extension brochures
Shock, C.C., E.B.G. Feibert, L.B. Jensen and J. Klauzer. 2010. Successful onion irrigation scheduling. Oregon State University Extension Service, Corvallis. SR 1097. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/18398/sr1097.pdf?sequence=1

3. Published annual reports
Shock, C. C., E.B.G. Feibert, L.D. Saunders, L.B. Jenson, K. Mohan, R.S. Sampangi, and H. Pappu. 2010. 2009 onion variety trials. Oregon State University Agricultural Experiment Station, 2009 Annual report: 27-37. http://www.cropinfo.net/AnnualReports/2009/OnionVarietyTrials2009.html

Shock, C.C., E.B.G. Feibert, and L.D. Saunders. 2010. Performance of onion varieties in a field with high iris yellow spot virus presence. Oregon State University Agricultural Experiment Station, 2009 Annual report: 38-40. http://www.cropinfo.net/AnnualReports/2009/OnionVarietyPerformanceIYS2009.html

Shock, C. C., E.B.G. Feibert, L.D. Saunders, L.B. Jenson, K. Mohan, R.S. Sampangi, and H. Pappu. 2010. Management of onion cultural practices to control the expression of Iris Yellow Spot Virus. Oregon State University Agricultural Experiment Station, 2009 Annual Report: 47-65. http://www.cropinfo.net/AnnualReports/2009/OnionManagementIrisYellowSpotVirus2009.html

Shock, C.C., E.B.G. Feibert, and J. Taberna. 2010. Effect of harvest timing on onion yield and storability. Oregon State University Agricultural Experiment Station, 2009 Annual Report: 81-91. http://www.cropinfo.net/AnnualReports/2009/OnionHarvestTimeEffects.html

4. Oral presentations to growers at field days, no paper copy:
Shock*, C.C., E.B.G. Feibert*, L.D. Saunders, L.B. Jensen, K.S. Mohan, R. Sampangi, and H. Pappu. 2010. Comparison of irrigation systems and irrigation criteria for onion production under IYSV pressure. Summer Farm Festival and Annual Field Day, OSU Malheur Experiment Station. 13 July 2010. Ontario, OR.

5. Oral presentations and written reports to national working groups:
Shock*, C.C. E.B.G. Feibert, L.D. Saunders, L.B. Jensen, S.K. Mohan, and H. Pappu, and R.S. Sampangi. 2009. Onion stress and its impact on IYSV development. National Onion Association IYSV workshop, San Antonio, TX. December 3, 2009.

Shock, C.C., E.B.G. Feibert, L.D. Saunders, L.B. Jensen. 2010. Oregon 2009 progress on the biology and management of Iris Yellow Spot Virus (IYSV) and thrips in onions. Written report 12 January 2010 to W1008, the national IYSV working group.

• Educating growers on cultural practices to reduce the impact of IYSV on onion
• Educate growers on the control of trips to reduce the impact of IYSV on onion
• Presentation to onion growers associations: Iris Yellow Spot Virus control through stress reduction
• Presentation to onion growers associations: Onion variety trial report 2009

Collaborators: