Brief Summary of Minutes of Annual Meeting

Call to Order, Welcome, Business of the Day, Thank You

The meeting was called to order by Dan Drost, Utah State University, who organized the meeting. Dan welcomed everyone to the meeting, and thanked the sponsors of the meeting – Utah Onion Association, Western SARE, National Onion Association, and the Pacific Northwest Vegetable Association.

New W2008 Administrator and Working Group Update

Steve Loring was introduced as the new Administrative Advisor to W2008. He is based at New Mexico State University. Steve noted that this group needs to prepare our annual report within 30 days of this meeting (Jan. 10, 2016).

W2008 meeting with the National Onion Association (NOA) and National Allium Research Conference (NARC)

The next W2008 meeting will take place in conjunction with the NOA/NARC meeting in Savannah, GA on Nov. 30-Dec. 3, 2016. Appreciation was expressed to Ron Gitaitis for agreeing to organize the NARC meeting.

Oral State Reports:

California (given by Bob Ehn):

Production: Yields are down from 0.5 to 1.0 ton per acre in both onions and garlic. Because of the drought, growers were forced to rely upon ground water to supplement the minimal surface water allocations. As the season progressed, salt content in ground water increased with much higher levels of selenium and boron. Boron toxicity was evident in several onion fields in the Central Valley. The warm winter of 2014/2015, with reduced chilling hours/lack of cold exposure on the fall planted garlic, caused reduced bulb size. Some brooming (vegetative growth from developing cloves) was observed. Thunderstorms in late May in the Central Valley damaged some harvested onions, and garlic that were dug and windrowed experienced staining that forced fresh market fields to be rendered to dehydrators.

Pests/diseases: Thrips populations were low throughout the year in the desert, Central Valley, and northern Tulelake areas. There were reports of IYSV in the desert areas of southern California. Infected onion transplants in a nearby field that were being grown for seed seem to have been the origin of the virus, with surrounding dehydrator onion fields showing IYS symptoms on fields near the onion transplants. Only two white rot strikes were reported in the Central Valley this year. A combination of high soil temperatures and bulb development were not conducive to sclerotia infection and reproduction of the fungus. Much of the onion and garlic was grown outside of the normal production areas as processors and handlers had to source fields with reliable ground water sources. Downy mildew pressure was very severe in desert onion crops this year as above-average rainfall occurred during the growing season. Because of early summer rains and warm temperatures in the Central Valley, conditions for garlic rust infection periods were favorable, and fields were treated several times to get adequate control. Seed corn maggot/onion maggot: Severe pressure, primarily from seed corn maggot, was noted in the Tulelake area of northern California. Seed treatments with spinosad have given excellent control in the past - far superior to in-furrow treatment with chlorpyrifos. This year, the seed treatments did not provide adequate control, and in-furrow chlorpyrifos treatment was significantly better. We think the method by which seed was treated may have caused the product to wash off the seed and, thus, did not protect the seed.  

Georgia report (given by Ron Gitaitis):

There was an unusual amount of Botrytis leaf blight in some onions in early March. The overriding factor was that in the majority of these fields in which it was observed, there was a delay in the application of an SDHI product like Pristine, Fontelis, or Endura. Most organic fields suffered drastically from these infections as well. There was also some crop loss due to hail damage and heavy winds that laid down some foliage prematurely. There were a fair number of fields with onions experiencing some type of tip die-back. At the time it seemed that each field had something different going on (low pH, excessive Goal injury, etc.); however, they were spread over a multi-county area. Nothing was ever cultured from these onions at the UGA Plant Disease Clinic. There was a fairly severe outbreak of center rot in approximately 900 acres of onions grown in southern Georgia and northern Florida (outside of the defined Vidalia onion zone as defined by the marketing order). This outbreak occurred on new ground as well as on land previously used to produce onions. County agents made the observation that most of the onions were planted behind corn. There also was an unusual outbreak of center rot caused by Pantoea ananatis in the heart of the Vidalia onion-growing region (Toombs and Tattnall Counties). Particularly hard hit were the bulbs from the middle maturity group. Furthermore, those infections were somewhat unusual for center rot in that typical necrosis of upper leaves was absent. Instead, there generally was a reddish-colored leaf in the neck of the bulbs observed at grading, but it obviously did not originate from a dying leaf in the top foliage. A few millimeters below the discoloration in the neck, a very small area of grayish, gummy tissues developed. This discoloration and texture remained restricted and did not spread in to the rest of the bulb. It was speculated that physiological conditions initiated the syndrome resulting in secondary colonization by P. ananatis. One observation in that regard was that the middle maturity group experienced unusually high temperatures at a critical phase of bulbing when nutrients were being relocated from foliage to bulb. It was speculated that high temperatures at that critical period, in combination with P. ananatis, may have caused the unusual symptoms. Finally, there is a substantial amount of seedling blight caused by Pantoea ananatis in the seedbeds that are now being transplanted for the 2016 crop. It will be interesting to see if this plays out in to having increased center rot problems this spring.

Oregon Treasure Valley (report given by Clint Shock):

There have been a lot of heat units in the Treasure Valley this past season, and very little irrigation water. The season started very early. Record heat units were recorded in the 2014 season and again in the 2015 season. Onion bulbs aren’t finishing completely. The predominant symptom Clint has seen is not the dry scale reported by Lindsey, Tim, and Stuart (see below), but incomplete top end of the fleshy scales. Some cultivars seem worse affected than others, but it’s not clear if there’s a cultivar trend because of many confounding factors. They’re also seeing more bacterial bulb rots associated with this, and Fusarium proliferatum infection of these symptomatic bulbs has been very spotty. They don’t know what’s causing the dry upper end of all the fleshy scales. Some growers have shortened their rotations a lot, which may be contributing to problems. Thrips and IYSV were less severe than usual, despite the heat stress, because most growers have implemented good management programs.

Washington (report given by Lindsey du Toit and Tim Waters):

It was a very warm season in Washington State with high temperatures early in the season and extended periods of heat stress (22 days >100^oF in the Tri-Cities area, and the warmest temperature of 113^oF was recorded in late June). As a result, crops matured 2 to 3 weeks earlier than normal, and thrips numbers were very high early during the cropping cycle. Thrips damage was quite severe in some crops, as was IYSV incidence in some bulb crops in relatively close proximity to onion seed crops. In some fields, the early maturity resulted in smaller-than-normal bulb size and, therefore, lower-than-average yields. There was also significant damage from internal dry scale, a physiological response that appears to be triggered by extended periods of heat stress, and often is accompanied by secondary colonization of the collapsed, internal fleshy scales by bacteria and/or fungi. Some entire onion crops and bulb lots in storage were abandoned as the affected bulbs could not be culled effectively (symptoms are almost entirely internal). Fall temperatures were also warm, making good curing conditions in most onion crops. A few crops received late rain after undercutting and/or windrowing, which will likely result in decreased storage quality. Black mold incidence (exterior of bulbs) was at significant levels in some fields due to warm temperatures. The warm fall also resulted in significant damage to fall-planted, overwintering crops from onion leafminer. Normally, cool fall temperatures reduce their activity, but not this season. Some overwintering bulb crops were also damaged by fall armyworm and had to be treated for this pest. Overall, a rough year for onions in central Washington and there is concern about how bulbs will fare in storage.

Discussion ensued about heat stress and some of the other problems growers have been experiencing in the Pacific Northwest with some of the growers present at the meeting. One grower stated that onion seed alone costs ~$600/acre.

New Mexico (report by Mark Uchanski):

New Mexico onion growers have not reported problems with IYSV this season. They’ve had typical thrips and pink root pressure. Conditions have been moderate and slightly cooler than normal, with normal precipitation. Yields are OK. It’s been a good season overall.

Mark stated he would like to put the W2008 nomination in again for the Western Association of Agricultural Experiment Station Award. Seed the Open Discussion items below.

New York (report given by Christy Hoepting):

New York onion growers experienced a very dry start to the season (May), but June was very wet and some growers lost onion stands. It was a moderate season overall with consistent rains that resulted in good yields in general. Thrips were relatively well controlled as a result. There were a few outbreaks of downy mildew and Stemphylium leaf blight. Bulb rots were at average levels. In some grower-cooperator, bacterial rot field trials, soil fumigation with chloropicrin had no significant effect on soil populations of the three main onion bacterial bulb rot pathogens (Burkholderia cepacia, Enterobacter ludwigii, and Pantoea ananatis) or on the incidence of bulb rots at harvest. Applications of TerraClean likewise had no significant effect on the numbers of these bacteria in the soil or bulb rots at harvest. Applications of a vermicompost extract (‘worm poop tea’ as Christy’s daughter called it) had no significant effect on bulb rots when applied as a drench, but dipping transplant seedlings in the extract prior to transplanting reduced the incidence of bacterial rot by about 50%. One grower made weekly applications of ‘pool chlorine’ to half of a field of onions at a rate of 1 gal of product/1,000 gal tank of water (Steve Beer didn’t know the chlorine concentration of the product, but estimated the chlorine application was at ~100 ppm). The incidence of bulb rot at harvest was reduced 60% compared to the non-treated half of the field, and the grower estimated a 22% increase in bulb yield. The treated part of the field lodged 2 weeks later than the non-treated part of the field.

Clint Shock discussed the recommended use of chlorine dioxide rather than other forms of chlorine. Bill Dean noted that some growers in the Columbia Basin who use pivot-irrigation routinely apply chlorine at 1 gal/hour (~1 ppm chlorine) using a 12.5% a.i. commercial product to clean irrigation water and equipment (sometimes at every irrigation).

Seven onion cultivars were evaluated by Brian Nault’s program for onion thrips resistance in New York.  Six of the seven cultivars were short-day onions bred for southern production areas, while the other cultivar was bred for intermediate-day growing conditions. Unfortunately, the short-day cultivars did not grow well under western New York’s environmental conditions, and generally produced small plants and unmarketable bulbs; thrips resistance could not be assessed accurately. The intermediate-day cultivar showed signs of partial thrips resistance, but bulb yields were significantly less than standard cultivars for the region. Nonetheless, this intermediate-day onion cultivar shows promise for future thrips-resistance breeding projects.

Utah (report given by Dan Drost):

2015 has been a good year overall for Utah onion growers. 2015 was one of the hottest seasons on record and yet there were no days in Utah >100^oF, which was surprising. The record heat was largely a result of warm nights. Overall bulb yields and quality were good. Thrips were not excessive. IYSV came late into most fields (about the time of lifting), so there was little effect on yield. Dan has WSARE funding for a multi-year project looking at field border management for thrips and IYSV (see Focused Talks below).

Focused Talks

Presentations were given from 10 am to ~3 pm (excluding the lunch hour) on focused topics, as detailed in the meeting program (contact individual presenters to request copies of their presentations):

1. Progress in managing leaf diseases of onion in New York, featuring Stemphylium leaf blight - Christy Hoepting (Cornell University Cooperative Extension)
2. How fertility can affect sour skin severity and the expression of proteins associated with the plant systemic acquired resistance (SAR) pathway - Ron Gitaitis (Univ. of Georgia)
3. White rot management in garlic and onions and California’s “Water Woes” - Bob Ehn (CA Garlic and Onion Research Board)
4. Determining the presence of endophytic pathogenic bacteria in non-symptomatic onion necks or bulbs - Steve Beer (Cornell Univ.)
5. Onion internal dry scale: An emerging problem associated with climate change in the Pacific Northwest? - Lindsey du Toit (Washington State Univ.)
6. Systems Drivers for Managing Thrips/IYSV: Rotations, Borders and Nutrition Influences - Dan Drost (Utah State Univ.)
7. Controlling Insects Impacting Columbia Basin Onion Producers - Tim Waters (Washington State Univ.)
8. Onion insect pest management in onion with insecticides – the challenges ahead - Brian Nault (Cornell Univ.)

Open Discussion – Other Research Needs, Issues, Future Focus

• September 30, 2017 is when the current W2008 expires:
  • We need to write a new W3008 proposal in 2016, to be submitted before the W2008 expires.
  • The group agreed we should consider a new title that it not focused as intensely on thrips/IYSV because of the large success in managing these problems in onion and the emergence of other major issues for onion growers across the USA. An example of a suggested title is “Integrated Onion Pest and Disease Management” (with added terms such as “frontlines” or “solutions”).
  • A subcommittee of volunteers was formed to write this document: Brian Nault, Dan Drost, Hanu Pappu, and Lindsey du Toit.
• There is a need for a standing NARC planning committee to streamline the planning and succession process. This will be discussed in Savannah, GA in 2016
• Mark stated he would like to put the W-2008 nomination in again for the Western Association of Agricultural Experiment Stations Award. Steve Loring indicated the due date in the Directors’ Office is February 28, 2016.
• Brian Nault thanked Dan Drost and the Utah Onion Association for organizing this meeting in Salt Lake City.

Election of new W2008 secretary for 2016

Christy Hoepting from Cornell University kindly agreed to be the next Secretary. Officers for 2016:

Past Chair: Mark Uchanski

Chair: Tim Waters

Vice Chair: Lindsey du Toit

Secretary: Christy Hoepting

History of W1008/W2008 meetings for a historical perspective, compiled by Mark Uchanski and Chris Cramer:

2019: Internat. Soc. Edible Alliaceae with NOA, NARC, and W3008 in Madison, WI - summer

2016: NARC + NOA combined with W2008 in Savannah, GA

2015: W2008 in Salt Lake City, UT

2014: NARC + NOA and W2008 in Scottsdale, AZ

2013: W2008 in Denver, CO

2012: NARC and W2008 in Las Cruces, NM

2011: W1008/W2008 in Las Cruces, NM

2010: NARC and W1008 in Reno, NV

2009: W1008 + NOA in San Antonio, TX - Dec.

2008: W1008 in Denver, CO - Jan; NARC and W1008 in Savannah, GA - Dec.

2007: W1008 in Denver, CO - Jan.

2015 Attendees:

Objective 1. Evaluate onion germplasm for greater levels of tolerance to Iris yellow spot virus (IYSV), other pathogens and thrips.

Colorado (T. Gourd)-

Two onion variety trial sites were set up at Sakata Farms locations along the Front Range of Colorado. The Howard Farm averaged only 6.2 thrips per onion plant, and the Zaiss location averaged 14.8 thrips per plant. This low thrips pressure could explain why very little Iris Yellow Spot Virus (IYSV) was observed at either location in 2015.

New Mexico (C. Cramer) – In the previous year, germplasm lines were identified that possessed a reduced number of thrips per plant or less severe IYS disease symptoms than most entries. Seed productions of these lines were necessary to have ample seed quantities for distribution in the future. A total of 56 germplasm lines were regenerated using a total of 123 different crossing cages.

Original, intermediate, and advanced FBR-selected populations and one resistant and one susceptible check were evaluated for resistance to FBR. Both the resistant and susceptible check entries exhibited a high level of disease severity and incidence. With the high rate of disease development throughout the study, many of the selected populations did not perform well in terms of disease severity and incidence. The inoculation method of 3 x 105 sporesml-1 of FOC placed on a cut basal plate was very effective at causing disease in most bulbs. Selections were made for FBR-resistant bulbs using this method. In addition, seed was produced of FBR-resistant selections made in 2014. Seed was produced from a total of 22 different germplasm lines associated with this project. This will be used for evaluations to ascertain additional progress made for resistance to FBR.

New York (B. Nault, S. Beer, S. Pethybridge & C. Hoepting) – Seven onion cultivars were evaluated for onion thrips resistance in New York. The short-day onion cultivars did not grow well under New York’s environmental conditions and generally produced small plants and bulbs; thrips resistance could not be accurately assessed. The intermediate-day onion cultivar showed signs of partial thrips resistance, but bulb yields were significantly smaller than standard cultivars. Nonetheless, this intermediate-day onion cultivar shows promise for future thrips-resistance breeding projects.

OREGON - (S. Reitz, C. Shock, E. Feibert, A. Rivera, & M. Saunders) Early maturity and full season onion variety trials were conducted in 2015. The trials were grown under drip irrigation. All varieties were evaluated for their yield, maturity and susceptibility to thrips damage and IYSV. Varieties had significant differences in IYSV in 2015.

Thrips populations and IYSV incidence were compared among four experimental breeding lines from Chris Cramer, NMSU, and three commercial cultivars. The experimental lines tended to have lower populations of thrips and IYSV severity than the commercial cultivars.

Utah (D. Drost) - Twenty-nine (29) commercially available Spanish onion cultivars were assessed for productivity, maturity and rated for IYSV. While symptom expression of IYSV in 2015 was very low, all varieties evaluated showed visual evidence of IYSV under field conditions. IYSV had little impact on onion bulb yield as summer conditions were favorable for plant growth and IYSV incidence occurred very late in the season. More work on the relation between IYSV incidence and storage is needed.

Washington (T. Waters, L. J. du Toit, H. R. Pappu & C. Wohleb) - Onion genotypes (n = 35) were evaluated for resistance to stunting caused by Rhizoctonia solani anastomosis group (AG) 8 in a growth chamber at 15 ^oC. The trial was repeated. Resistance was defined as a lack of significant difference in plant height, root length, and/or total dry biomass between inoculated and non-inoculated plants of the same genotype. Of the 35 genotypes evaluated, 3, 16, and 3 demonstrated partial resistance to R. solani AG 8 for plant height, root length, and total biomass, respectively. Plant height, root length, and biomass of PX07713218 were not affected by the fungus in either trial; and R14885, R14888, and SN307 displayed partial resistance in both trials for two of the three onion growth parameters measured, and in one of the two trials for the third parameter. These four genotypes could be used in onion breeding programs to develop cultivars partially resistant to stunting caused by R. solani AG 8.

Objective 2. Investigate thrips biology and IYSV epidemiology to improve management strategies.

New York (B. Nault, S. Beer, S. Pethybridge & C. Hoepting)- Co-applications of insecticides with either a non-ionic surfactant (Induce), a methylated seed oil (MSO), a mineral oil (JMS Stylet oil) or an organosilicone (Silwet L-77) were more effective for managing onion thrips than when insecticides were used alone. None of co-application treatments exacerbated the incidence of foliar diseases such as botrytis leaf blight, downy mildew, Stemphyllium leaf blight and purple blotch.

Early-season management of onion thrips continues to be most effective beginning with Movento compared with other products like Radiant.

A new product, Minecto Pro, which includes a combination of abamectin and cyantranilprole, was effective in managing onion thrips. The efficacy of Minecto Pro was similar to Exirel (cyantraniliprole), but numerically better than Agri-Mek.

Based on historical levels of onion thrips control using Radiant (spinetoram) in New York, there is a downward trend in the level of control over the past decade suggesting that resistance to spinetoram may be developing in onion thrips populations.

OREGON - (S. Reitz, C. Shock, E. Feibert, & M. Saunders)Two insecticide rotation trials were conducted to evaluate the effectiveness of various insecticides in managing thrips and IYSV. One trial included all foliar applied insecticides, and another trial featured insecticides applied through drip irrigation and by ground application. Movento and Agri-mek were effective in early season thrips management. Using moderately efficacious insecticides, such as azadirachtin at the beginning of a spray program, has been encouraging. This use pattern allows applications of Movento to be made later in the season so that Radiant remains the most effective insecticide for mid to late season thrips management.

Programs with drip applied products performed as well as foliar applied products. Drip applications may reduce grower expenses by reducing overall application costs.

Utah (D. Alston, D. Drost & C. Nischwitz) – Onion thrips and IYSV were evaluated in field and research trials from June until September. Thrips densities on plants were very low in June (10/plant), increased to moderate levels in July (36/plant) and were quite high in late August (92/plant) as the onions began to mature. There was no difference in thrips numbers between the different nitrogen levels in 2015. A likely reason is that all onion plots sampled in 2015 followed three previous years of alfalfa and one year of onion production. Alfalfa may have increased soil nitrogen levels thus negating differences between high and low nitrogen application rates. IYSV levels increased throughout the summer but did not impact productivity.

Sustainable production occurs when inputs, onion thrips, and IYSV are properly managed. Growers in Utah report little difficulty with thrips and IYSV severity was low in 2015. Growers are using USU research findings on lowering nitrogen input levels, working harder to keep field border weed free, and exploring the use of alternative crop rotations to help manage thrips numbers and IYSV incidence.

Selected weeds growing next to onion fields were sampled for IYSV and thrips in the 2015. Weeds found with thrips (adults, nymphs and eggs) include bindweed, flixweed, sowthistle, common mallow, and foxtail barley. Identification of IYSV hosts that can serve as a green-bridge from year-to-year is critical to target, treat, and remove plants with IYSV growing near onions..

Washington (T. Waters, L. J. du Toit, H. R. Pappu & C. Wohleb) -Field plots of onion in Pasco, WA and grown using drip irrigation. Plots were established in a randomized complete block design with 4 replications. Foliar applications were made with a CO₂ pressurized sprayer. Sprinkler chemigation applications were made with a trailer-mounted research sprayer applying and drip applications were made by injecting insecticides into individual drip lines. Efficacy was evaluated four or five days after each application by counting the number of immature and adult thrips per plant on 10 individual plants per plot. At the end of the growing season, onion yield and size were evaluated.

Using insecticides that are effective at controlling thrips increases yield and size class of dry bulb onions. Radiant and Lannate were found to be the most effective products while Movento, Verimark/Exirel and AgriMek provided good suppression of onion thrips. We also found that Radiant was more effective in the early season compared to Movento. Chemigation was an effective way to apply Lannate, Exirel and Radiant. Verimark was also effective when applied via drip injection.

Acibenzolar-S-Methyl (ASM) is a functional analog of salicylic acid (SA) that activates local and systemic acquired resistance (SAR) responses in plants against a wide variety of pathogens. To explore the possibility of utilizing SAR as a control option, we first used two different hosts of IYSV, Datura stramonium and Nicotiana benthamiana, to study the ability of ASM in triggering SAR against IYSV infection. Quantitative descriptors based on both symptom expression and relative levels of IYSV nucleoprotein and viral small RNA were developed and used to determine the SAR in ASM- and buffer-treated plants. A significant reduction in virus levels in ASM-treated plants was noticed by ELISA and PCR. The level of SAR response was also assessed by measuring the IYSV lesion size and number on the inoculated leaves of ASM-treated plants. ASM-treated plants showed reduced symptoms compared to buffer-treated plants. This study could be useful in potentially developing novel SAR-based options for virus management.

Objective 3. Investigate the biology, ecology and epidemiology of other pathogens to improve management strategies.

Colorado (T. Gourd)-

An evaluation of Mycorrhizal Fungi on Commercially Grown Onions in Colorado was conducted during the 2015. The objectives of this study were to use large scale on-farm test to demonstrate efficacy of MYKE Pro Specialty Crop P endomycorrhizal inoculant. The active ingredient is Glomus spp. We evaluated for enhanced seedling growth, increased pathogen resistance/protection of onions and increased onion yield (quality and quantity).

• The bottom line was no economic advantage was seen using a planter box application of MYKE Pro Specialty Crop P endomycorrhizal inoculant at two farm locations in 2015

Georgia (R. Gitaitis, B. Dutta, D. Riley, R. Srinivasan, & A. Watson-Selph) –

Previously developed regression models consisting of concentrations of cations and cation ratios accurately predicted sour skin severity. In 2015 these models were used to identify healthy bulbs that had the highest and lowest levels of sour skin. RNA was extracted and used for transcriptomic analysis. Many proteins were expressed at significantly higher levels in bulbs with a higher copper to iron ratio which was also associated with reduced sour skin levels. Increased levels of important proteins that particularly have known functions in the systemic acquired resistance (SAR) pathway in plants, included: >5,000 fold increase in universal stress protein A (USPA is very similar to Pto which is known to convey resistance in tomato); > 4700 fold increase in B2 protein (increases hydrogen peroxide levels, a precursor for salicylic acid); > 900 fold increase in enhanced disease resistance protein (EDR1 is involved in a MAP kinase cascade that regulates salicylic acid dependent defense responses); and > 3900 fold increase in glutaredoxin (known to interact with non-expressor pathogenesis-related protein 1 (NPR1) which has a feedback control of salicylic acid production). The most important example of an elevated protein level of a SAR-connected protein in bulbs with a higher copper to iron ratio was a > 5000 fold increase in the expression of pathogenesis-related protein 1 (PR1). PR1 is known to be regulated through the salicylic acid pathway and is a plant resistance protein whose production is regulated by NPR1. The PR1 protein identified had 85% similarity with PR1 from garlic.

Field studies indicated that titanium dioxide nanoparticles doped with zinc, acibenzolar-S-methyl and cupric hydroxide had little effect on center rot. When the same treatments were evaluated in for postharvest rots due to sour skin caused by B. cepacia, cupric hydroxide applied weekly significantly reduced postharvest levels of sour skin. Evaluating acibenzolar-S-methyl in combination with different nutrients found that lowest levels of sour skin occurred in all treatments receiving gypsum. Onions with the highest levels of sour skin had all been treated with acibenzolar-S-methyl in combination with either iron, copper, manganese or zinc chelates. The highest level of sour skin occurred with the treatment of copper, calcium chloride, magnesium sulfate and acibenzolar-S-methyl and was significantly different from copper, calcium chloride and magnesium sulfate without acibenzolar-S-methyl indicating a possible negative interaction with the plant resistance inducing compound.

A paper was published in the J. Econ. Entomol. entitled “Thrips Settling, Oviposition and IYSV Distribution on Onion Foliage”. Results from studies confirmed that distribution of thrips adults, nymphs, and eggs were skewed toward the base of the plant. The settling distributions of thrips adults and nymphs differed slightly from the egg distribution. In a field study, the results suggested that adults of different species appear to segregate along leaf length. Finally, thrips oviposition on 2-cm segments and Iris yellow spot virus positive leaf segments were quantified in the field, irrespective of thrips species. Both variables demonstrated a very similar pattern of bias toward the base of the plant and were significantly correlated.

Idaho (B. Schroeder)- The impact of curing temperature and duration on the development of storage rot caused by the bacterial pathogens Pantoea ananatis, Pantoea agglomerans, and Pantoea allii on onion bulbs was completed. As with previous studies, it was determined that curing onion bulbs with cooler temperatures for a longer duration will reduce the amount of rot caused by these pathogens if the bulbs were infected prior to storage.

A DNA macroarray was developed for the detection of fungal and bacterial plant pathogens (26+) capable of causing onion bulb rot in storage. The DNA macroarray for the fungal pathogens was just evaluated for sensitivity and it appears to be able to detect ng levels of the pathogen present in a sample. It was determined that the DNA macroarray is able to detect the presence of Fusarium proliferatum in asymptomatic onion bulbs prior to curing. The DNA macroarray is being used to obtain pathogen incidence data to correlate with disease incidence in storage. A macroarray that readily detects latent infections by bulb rot pathogens will enable stakeholders to make informed storage management decisions.

New York (B. Nault, S. Beer, S. Pethybridge & C. Hoepting)- Bacterial Diseases of Onion Emphasis was placed on three bacterial pathogens, Burkholderia cepacia, Enterobacter cloacae and Pantoea ananati, known to cause great losses to New York onion growers. Plants were collected biweekly during the later two-thirds of the growing season from one grower in each of the three major onion-growing areas of New York State and analyzed to determine the degree of bacterial infection, infestation and susceptibility to the three bacterial pathogens.

Very little infection was detected visually in any samples until the last two collections, a few weeks prior to harvest of the crop. Infestation of bulbs varied depending on the pathogen and the location from which the plants were collected. Overall, pathogenic bacteria were isolated and identified from (4 to 24%) of symptomatic bulbs of growing plants. This suggested the hypothesis that the degree of infestation with pathogenic bacteria may indicate the extent of decay at harvest or following storage.

Generally, plants were susceptible to infection following inoculation with P. ananatis or B. cepacia at any age tested. Only 1 of 9 of the inoculated plants became symptomatic after prolonged incubation following inoculation with E. cloacae at the 6-leaf stage of growth.

In controlled inoculation and environment studies conducted in the laboratory, conditions were discovered that were conducive to the initiation and development of infection of growing onion plants that had reached the “bulbing” stage when inoculated with pure cultures of B. cepacia.

We evaluated four materials that may reduce bacterial rot. None of the materials had been tested rigorously previously for the control of bacterial rot of onions. The materials were: 1. Chloropicrin, 2. vermicompost extract, 3. TerraClear®5, and “Pool Chlorine”.

Research plots were set up in 3 onion-producing regions of NY. At harvest bulbs were collected and each was cut and examined closely for evidence of bacterial decay. Based on these analyses, we concluded that the Chloropicrin fumigation did not affect rot, but vermicompost extract and TerraClear®5 both reduced the percentage of rot somewhat. Treatment with sodium hypochlorite not only reduced the percentage of rot, but yields in the treated plots were substantially increased. Clearly, additional testing of the three promising materials is in order.

Fungal Diseases of Onion Onion production in NY is affected by a complex of foliar fungal diseases including downy mildew (Peronospora destructor), Stemphylium leaf blight (SLB; Stemphylium vesicarium) and purple blotch (Alternaria porri). The objectives of this research were to quantify the prevalence and incidence of foliar diseases and determine the symptoms associated with each of the pathogens in the ‘target spot’ complex of onion. Stemphylium vesicarium was the most prevalent fungus associated with foliar disease in NY. The isolation frequency of S. vesicarium was not significantly affected by production type and was not significantly different in conventional and organic fields. Moreover, the frequency of the teleomorph of S. vesicarium, Pleospora allii was significantly higher in conventional fields than organic production. This may indicate that factors that are prevalent in conventional fields may be inducing the production of the teleomorph. The high frequency of S. vesicarium from foliar disease was irrespective of symptom type but most commonly with an asymmetric, necrotic lesion. In conventional fields, there was a low prevalence and incidence of Peronospora destructor, and Botrytis spp. The isolation frequency of Alternaria porri and A. alternata was significantly higher in organic than conventional production. These findings suggest the fungicides being used within conventional production are efficacious for the control of purple blotch, downy mildew and Botrytis spp.

In 2015, a replicated field trial evaluated the relative efficacy of currently registered and perspective fungicides for control of SLB. It was a randomized complete block design with 18 treatments and 5 replicates. An untreated control with no pesticide applications and an untreated with only onion thrips and downy mildew maintenance sprays were included.

A final SLB score was determined within each plot from six disease and plant health assessments from Aug-5 to Aug-30. A higher SLB score indicated more severe disease. All fungicide treatments had significantly lower SLB scores than the untreated (score 345), which was significantly lower than the untreated check with maintenance sprays (score 303). Maximum disease control was obtained with Luna Tranquility, Merivon, Inspire Super and Fontelis. Plots receiving fungicides belonging to FRAC 11 were not significantly different than the maintained untreated. Products with only FRAC 3 active ingredients and only FRAC 7 active ingredients provided significantly poorer disease control than Luna Tranquility, but not significantly different from Inspire Super or Fontelis, and between each other. The only product with just FRAC 9 was Scala, which provided mediocre control. SLB control was significantly improved when Scala was premixed with fluopyram (7) within Luna Tranquility. Another premix product with FRAC 9 was Switch, which performed similarly to Scala. Disease control in plots receiving Omega and Gavel were not significantly different to those receiving Scala and Switch.

In conclusion, Luna Tranquility was the most efficacious fungicide for controlling SLB in onions and this was attributed to the presence of fluopyram (7). Generally, products belonging to FRAC groups 3 and 7 provided the best control of SLB. The lack of efficacy from strobilurin products is concerning and the subject of further studies.

OREGON - (S. Reitz, C. Shock, E. Feibert, A. Rivera, & M. Saunders)

In anticipation of the rules in the Food Safety Modernization ACT, research on onion production in relation to food safety continued in 2015 to compare the roles of wooden and plastic storage containers on contamination of onion bulbs with generic Escherichia coli, the FDA indicator for potential microbial contamination. E. coli levels of onions grown in furrow-irrigated plots using surface irrigation water with enhanced E. coli levels and harvested into old wooden boxes and sterilized plastic crates were compared with E. coli levels of onions grown under drip irrigation. After 6 weeks in storage, onions were prepared for shipment through removal of loose skin, roots and soil. Regardless of irrigation source, neither onions stored in plastic nor in wooden containers had detectable E. coli on the bulb exteriors or interiors. These results are consistent with our previous trials and indicate that storage container material does not affect the likelihood of E. coli contamination of dry bulb onions.

We repeated field studies to evaluate if surface irrigation systems reusing water may deliver bacteria to onions. We tested the potential for furrow irrigation using canal water with moderate or high levels of E. coli contamination and drip irrigation using canal water and well water free of E. coli to deliver E. coli to onion bulbs. The four irrigation systems applied water to onion. Water was sampled hourly for E. coli and the lateral movement of E. coli in the soil solution was tracked by soil samples. Onions were sampled for E. coli contamination. Consistent with previous results, furrow irrigation delivered E. coli to the soil immediately adjacent to the onion bulbs. E. coli movement under drip irrigation was mostly confined to near the drip tape and very little reached the onion bulbs, indicating that drip irrigation did not directly deliver E. coli to onions.

In Oregon, surface irrigation water is commonly used for drip irrigation. We evaluated the use of chlorine dioxide to reduce bacterial loads in surface irrigation water. Growers often routinely use injections of chlorine dioxide at the end of irrigation cycles to control the growth of algae in drip irrigation lines. The current rates of chlorine dioxide for drip line maintenance (3 ppm) virtually eliminate E. coli.

Pennsylvania (B. Gugino) – In PA and NY, annual losses from bacteria range from 5 to 40%. However, these losses are variable, between fields and within the same field; in many cases the full extent of disease losses is not evident until harvest or after post-harvest storage. During 2015, efforts were directed towards the development of targeted research-based management strategies for reducing harvest and post-harvest losses due to bacterial bulb rots described below.

A replicated field trial evaluated the effect of nitrogen application timing and rate on onion bacterial disease incidence and marketable yield. The trial was a split plot randomized complete block design with nitrogen application timing as the whole plot and application rate as the sub-plot. Preliminary data analysis indicates that marketable yields were most influenced by disease pressure (inoculated vs not inoculated), the nitrogen rate (more nitrogen increased yields) rather than the timing of application.

Host resistance is one of the most important tools available for disease management. Identification of less susceptible cultivars that meet the marketing program criteria would provide growers with another management tool. A field trial was conducted to evaluate the susceptibility of ten onion cultivars to center rot. Each plot was subdivided and two alternate 20 ft rows were toothpick inoculated with a bacterial suspension containing a mix of three isolates of Pantoea ananatis and P. agglomerans, the two causal pathogens of center rot. Significant differences in yield between the cultivars were observed with cv. Great Western and Expression being the highest yielding and Sedona, BGS 300F1 Blush and Aruba being the lowest yielding. Cv. Aruba with the lowest yields also had the highest incidence of bacterial bulb rot at harvest as well as foliar disease symptoms during the season.

Washington (T. Waters, L. J. du Toit, H. R. Pappu & C. Wohleb)

Onion pink root Serenade Soil trial (L.J. du Toit): A field trial was completed to evaluate Serenade Soil for management of onion pink root in a drip-irrigated, certified organic, onion bulb crop of the cv. Merenge in a commercial crop. Replicate plots of each of two Serenade Soil treatments were compared with control plots in each of two trial sites at the same field, one trial site with severe pink root pressure compared to the other site as a result of 2- vs. 4-year rotations out of onion, respectively. Serenade Soil treatments were applied after planting in a band over each double-row using a CO₂-pressurized backpack sprayer on 3 April. A second application of Serenade Soil was made on 24 April, and a third application on 22 May. In both trials, onion stands were significantly less in plots treated with Serenade Soil once or three times compared to control plots. The incidence of bulbs with pink root symptoms averaged 56.7% in the site with a 4-year rotation out of onions, compared to 100% pink root in the site with a 2-year rotation. In both trials, application of Serenade Soil once at 4 qt/acre or three times at 3-week intervals at 2 qt/acre/application did not reduce the incidence or severity of pink root.

Onion stunting caused by Rhizoctonia spp.: (L.J. du Toit): Onion stunting is an important soilborne disease on very sandy soils in the Columbia Basin. Isolates of Rhizoctonia spp. were obtained from soil and onion plant samples collected from inside and outside patches of stunted plants in 29 fields. Based on sequence analysis of the internal transcribed spacer (ITS) rDNA region, 13 anastomosis groups (AGs) or subspecies were detected. The most frequent was Waitea circinata var. circinata (25%), followed by Rhizoctonia solani AG 3 (17%), R. solani AG 4 (14%), Ceratobasidium sp. AG A (10%), R. solani AG 8 (7%), Ceratobasidium sp. AG K (6%), R. solani AG 2-1 (6%), W. circinata var. zeae (6%), R. solani AG 5 (4%), Ceratobasidium sp. AG G (2%), R. solani AG 11 (2%), and R. solani AG 1-1B and AG 10 (each <1%). However, the distribution of AGs and subspecies varied depending on whether soil or onion plant samples were collected within or adjacent to patches of stunted onion plants. In an attempt to predict the risk of onion stunting prior to planting, DNA concentrations of AG 2-1, AG 3, AG 4, and AG 8 were quantified from bulk soil samples from nine fields. Pre-plant DNA concentrations did not correlate significantly with the amount of stunting observed during the growing season. In contrast, the frequency of isolation and DNA concentration of R. solani AG 8 detected in soil sampled during the growing season were greater from inside patches of stunted onion plants than from adjacent healthy areas of one but not for another onion crop. AG 2-1, AG 3, and AG 4 DNA concentrations did not differ significantly in soil sampled inside vs. outside stunted patches in the fields sampled in either year. Relationships between the number of bulbs harvested or bulb weight vs. severity of stunting were defined using correlation and regression analyses for six onion cultivars. Onion stunting reduced the average marketable bulb yield by 25 to 60% within stunted patches of the six cultivars. Stunting did not reduce onion plant stand but consistently reduced bulb size, and yield.

Objective 4. Facilitate interaction and information transfer between W2008 participants, the onion industry and other stakeholders.

Colorado (T. Gourd)-

The Northern Colorado Onion Variety Trials Field Tour was held on Friday, September 4.

Idaho (B. Schroeder)- The University of Idaho Plant Pathology laboratory has provided diagnostic services to the onion stakeholders throughout 2015 using the DNA macroarray and detected Fusarium proliferatum a fungal pathogen.

New York (B. Nault, S. Beer, S. Pethybridge & C. Hoepting)- As a result of onion growers’ following the Cornell-recommended IPM program for thrips, effective management of onion thrips was achieved with nearly 2 fewer insecticide applications. This reduction in insecticide use translated into an average savings of $50 per acre in insecticide costs. We estimated that 75% of the onion growers in New York have adopted this program, thereby saving these growers approximately $375,000 in 2015.

Oregon - (S. Reitz, C. Shock, E. Feibert, & M. Saunders)-The Oregon project has continued to transfer information pertinent to IYSV and thrips biology and management to growers, other onion industry parties, and the public through numerous meetings, field days, workshops, publications, and the internet. The Malheur Experiment Station hosted field days on July 8 and August 25 and a stop on the NOA tour on July 17. Results have also been presented at the Idaho-Malheur County Onion Growers Association Meeting, Pacific Northwest Vegetable Association Meeting, and the Treasure Valley Irrigation Conference.

Pennsylvania (B. Gugino) – In Pennsylvania the research results were disseminated at several local and regional vegetable grower meetings/conferences both in-state and out-of-state throughout 2015. Results were also disseminated throughout the season through one-on-one with the growers. We continued to disseminate the Diagnostic Pocket Series as well as the Onion Health Management and Production bulletin to interested growers and other stakeholders and wrote an article for the grower publication Onion World.

Utah (D. Alston, D. Drost & C. Nischwitz) – USU hosted; winter onion meetings (56 attended) in February 2015 in Brigham City, UT; a summer field tour (52 attended) in August 2015; and Drost gave two presentations on Utah’s systems approach to managing onion thrips and IYSV to the onion industry (220 attended) of Idaho, Oregon and Washington in November 2015 (see dissemination section). Two presentations were made at the W2008: Biology and Management of Iris Yellow Spot Virus, Other Diseases, and Thrips in Onions Regional Meetings on Dec 10 in Salt Lake City describing Utah based research findings.

Washington (T. Waters, L. J. du Toit, H. R. Pappu & C. Wohleb) In Washington, results from the thrips insecticide efficacy results were shared at the WSU Onion Field Day, several grower meetings, and by a written report. Using the most effective insecticides improve their yields and reduce the incidence of IYSV, therefore improving yield, quality, and profitability of producers. An impact report by Washington State University (http://ext100.wsu.edu/impact/improving-insect-management-in-dry-bulb-onions-in-the-columbia-basin/) cites the importance of this work and how widely adopted these practices are by Washington Onion Producers

Alston, D. G., 2015. Growing cover crops for pest management. Utah Pests News, Utah State University Extension, 9(Fall). http://utahpests.usu.edu/files/uploads/UtahPests-Newsletter-fall15.pdf

Asselin, J.E., J.M. Bonasera, and S.V. Beer. 2016. PCR Primers for detection of Pantoea ananatis, Burkholderia spp., and Enterobacter sp. from onion. Plant Disease. 100: 1-11.

Asselin, J. E., J.M. Bonasera, and S.V. Beer. 2015. New York bacterial rot research update: Critical factors. Onion World 31(3):20-23.

Buckland, K., Alston, D. G., Reeve, J., Nischwitz, C., & Drost, D. T. Trap crops in onion to reduce onion thrips and Iris yellow spot virus: Environmental Entomology/Entomological Society of America. (Submitted).

du Toit, L.J. and Derie, M.L. 2015. 2014 Onion pink root Serenade Soil efficacy trial, Connell, WA. Research report submitted to Bayer CropScience, Feb. 2015. 4 pp.

du Toit, L.J., Waters, T., and Reitz, S. 2016. Internal dry scale and associated bulb rots of onion. Extension Bulletin PNW 686. In press.

du Toit, L.J., Waters, T., and Reitz, S. 2015. Internal dry scale and associated bulb rots: Bane of the 2014 Pacific Northwest onion season. Onion World May/June 2015:4-7.

Gill, H.K., H. Garg, A.K. Gill, J.L. Gillett-Kaufman, and B.A. Nault. 2015. Onion thrips (Thysanoptera: Thripidae) biology, ecology, and management in onion production systems. J. Integ. Pest Mngmt. 6(1): 6. DOI: 10.1093/jipm/pmv006.

Gugino, B.K. and E.E. Pfeufer. 2015. Bacterial disease management of onion. 2015 Mid-Atlantic Fruit and Vegetable Convention Proceedings, Pennsylvania Vegetable Growers Association, Richfield, PA. pp. 79-81.

Hoepting, C.A. 2015. New top performing pesticides now registered in onions in New York. March 1, 2015 Veg Edge, 11(3): 136-145.

Hoepting, C.A. 2015. Onion thrips breaking spray threshold in upland transplanted onion.  May 27, 2015, 2015 Veg Edge, 11(7): 9-10.

Hoepting, C.A. 2015. The conflicts of simultaneous control of onion thrips and Botrytis leaf blight in onions. June 17, 2015 Veg Edge, 11(10): 6-7.

Hoepting, C.A. 2015. Management of Summer Leaf Diseases in Onion: Target Spot Diseases. July 1, 2015, 2015 Veg Edge, 11(13): 6-7.

Hoepting, C.A. and B.A. Nault. 2015. Strategic Management of Onion Thrips in Onions. July 15, 2015, 2015 Veg Edge, 11(14): 4.

Hoepting, C.A. 2015. Causes of Outer and Inner Leaf Dieback in Onions. July 22, 2015, 2015 Veg Edge, 11(15): 5.

Hoepting, C.A. 2015. Scouting Tips for Identifying Downy Mildew in Onions. July 29, 2015, 2015 Veg Edge, 11(16): 5.

Hoepting, C.A. 2015. Managing Downy Mildew of Onion: Control of target Spot Diseases is Critical. August 5, 2015, 2015 Veg Edge, 11(17): 4-5.

Hoepting, C.A. 2015. Iris Yellow Spot Virus of Onion. August 12, 2015, 2015 Veg Edge, 11(18): 3.

Hoepting, C.A. 2015. Using Ridomil to Manage Downy Mildew in Onion. August 12, 2015, 2015 Veg Edge, 11(18): 6.

Hoepting, C.A. 2015. Managing Stemphylium leaf blight and downy mildew. Onion World, 31(7): 34-37.

Maughan, T., D. Drost and N. Allen. 2015. Vegetable Irrigation: Onion. Utah State University Cooperative Extension Bulletin. http://digitalcommons.usu.edu/extension_curall/723/

Nault, B.A. 2015. Onion thrips management: Crisis averted? What’s next?, 4 pgs. Empire State Producers EXPO. January 22, 2015. Syracuse, NY.             http://www.hort.cornell.edu/expo/proceedings/2015/onions/Thrips%20management%20crises%20averted.pdf

Nault, B.A. 2015. Onion maggot and onion thrips management in onion. Onion World 31(2):   16-19.

Pappu, H.R. 2015. Thrips-transmitted Iris yellow spot virus – A threat to onion sustainability. Agricultural Research Journal 52: 10-12

Pfeufer, E., C. Hoepting, and B. Gugino. 2015. Advances in managing onion bacterial diseases in the Northeastern U.S. Onion World 31(6): 22-27.

Rinehold, J., Bell, N., Waters, T.D., & McGrath, D. 2015. Vegetable Insect Pests. In Craig Hollingsworth (Eds.), 2015 Pacific Northwest Insect Management Handbook Corvallis, OR: Oregon State University.

Sharma-Poudyal, D., Paulitz, T.C., and du Toit, L.J. 2015. Evaluation of onion genotypes for resistance to stunting caused by Rhizoctonia solani AG 8. HortScience 50:551-554.

Sharma-Poudyal, D., Paulitz, T.C., and du Toit, L.J. 2015. Stunted patches in onion bulb crops in Oregon and Washington: Etiology and yield loss. Plant Disease 99:648-658.

Sharma-Poudyal, D., Paulitz, T.C., and du Toit, L.J. 2016. Timing of glyphosate applications to wheat cover crops to reduce onion stunting caused by Rhizoctonia solani. Plant Disease 100: accepted Nov. 2015 pending minor revisions, revised & re-submitted Dec. 2015. PDIS-10-15-1234-RE

Shock, C.C., E.B.G. Feibert, A. Rivera, L.D. Saunders. 2015. Response of onion yield, grade,   and financial return to plant population and irrigation system. HortScience 50(9):1312-1318.

Shock, C.C., J.M. Pinto, E.B.G. Feibert, and C.B. Shock. 2015. Optimal irrigation criteria for drip irrigated onions. Growing Produce. March 24, 2015.

Smith, E.A. 2016. Patters of dispersal activity of onion thrips, Thrips tabaci Lindeman, in onion ecosystems. Cornell University, PhD. Dissertation. Pp. 131.

Smith, E.A., M. Fuchs, E.J. Shields, and B.A. Nault. 2015. Long-distance dispersal potential for onion thrips (Thysanoptera: Thripidae) and Iris yellow spot virus (Bunyaviridae: Tospovirus) in an onion ecosystem. Environ. Entomol. 44(4): 921-930. DOI: 10.1093/ee/nvv072.

Vahling-Armstrong, C., Dung, J.K.S., Humann, J.L., and Schroeder, B. K. 2015. Effects of postharvest onion curing parameters on bulb rot caused by Pantoea agglomerans, Pantoea ananatis and Pantoea allii in storage. Plant Pathology, http://onlinelibrary.wiley.com/doi/10.1111/ppa.12438/epdf

Tripathi, D., G. Raikhy, and H.R. Pappu (2015). Movement and nucleocapsid proteins coded by two tospovirus species interact through multiple binding regions in mixed infections. Virology 478:143-53. doi: 10.1016/j.virol.2015.01.009

Tripathi, D., G. Raikhy, R. Dietzgen, M. Goodin, and H.R. Pappu (2015). In vivo Localization of Iris yellow spot virus (Bunyaviridae: Tospovirus)-encoded Proteins and Identification of Interacting Regions of Nucleocapsid and Movement Proteins. PLoS ONE 10(3): e0118973. doi:10.1371/journal.pone.0118973

Tripathi, D., and H.R. Pappu (2015). Evaluation of Acibenzolar-S-Methyl-Induced Resistance against Iris yellow spot tospovirus. European J. Plant Pathology 142:855–864. DOI 10.1007/s10658-015-0657-0 E.

Waters, T.D. and Skoczylas, J.C. 2015. Thrips Control in Dry Bulb Onions in Washington State, 2012. Arthropod Management Tests. Report #E70.

Waters, T.D. and Skoczylas, J.C. 2015. Thrips Control in Dry Bulb Onions in Washington State, 2014. Arthropod Management Tests. Report #E72.

Waters, T.D. and Skoczylas, J.C. 2015. Thrips Control on Dry Bulb Onions Using Overhead Chemigation of Insecticides, 2014. Arthropod Management Tests. Report #E71.

Wohleb, C.H. and Waters T.D. Yield, Quality, and Storage Characteristics of Onion Cultivars in the Columbia Basin of Washington. HortTech. Submitted.

Zaid, A.M., J.E. Asselin, and S.V. Beer. 2016. Detection of Burkholderia cepacia in onion planting materials and onion seeds. Chapter 22 in M. Fatmi and N. W. Schaad, eds. APS Manual on Detection of Plant Pathogenic Bacteria in Seed and Planting Material. 2nd Ed. APS Press. St. Paul, MN. (In Press).