Brief Summary of Minutes of Annual Meeting

See attached minutes.

The meeting was called to order at 10 am with state reports presented over ~90 minutes by participating members representing Georgia (by Ron Gitaitis), Colorado (by Mike Uchanski), New Mexico (by Chris Cramer), New York (by Christy Hoepting), Utah (by Dan Drost), Washington (by Tim Waters), and Wisconsin (by Mike Havey). Refer to the details covered in four pages of the minutes of the annual meeting for information from each state related to onion research and extension activities.

2017 Executive Committee of the proposed W3008:

Chair: Lindsey du Toit, Washington State University, responsible for chairing the 2017 W3008 annual meeting.

Vice-Chair: Christy Hoepting, Cornell University, responsible for writing/submitting the 2017 annual report.

Secretary: Beth Gugino, Pennsylvania State University, was voted in by members and is responsible for writing/submitting the annual meeting minutes.

Secetary-Elect: Bhabesh Dutta, University of Georiga.

Past-Chair: Tim Waters, Washington State University.

The location of the 2017 W3008 meeting was discussed, with preference for a more central location that is efficient for members across the USA to fly in/out. Chicago was recommended because of central location and ready access to airport hotels. Mary Hausbeck suggested having the meeting immediately preceding or after the Great Lakes Expo in Grand Rapids, MI in early Dec., as there is an onion session at this conference that many of our project members attend or have attended, and we could invite onion stakeholders from the conference to participate in the annual meeting. The Executive Committee was asked to reach a decision. [Subsequent to the annual meeting, a decision was reached to work with Mary Hausbeck and Ben Werling to have the W3008 annual meeting on Monday, Dec. 4^th, preceding the Great Lakes Expo (5^th - 7^th Dec.) in Grand Rapids, MI. Lindsey will work with Mary and Ben on a room reservation, accommodation options, etc.]

Proposal for W3008: Brian Nault led the writing of a proposal to extend the W2008 to the W3008, following expiration of the W2008 in 2017, with the new title “W3008: Integrated Onion Pest and Disease Management”. The following revised objectives are in the proposal, submitted to Steve Loring on 10 Dec. 2016 (submission deadline is January 15, 2017), along with a list of organizations that will be engaged by the W3008 project and a letter from Wayne Mininger on behalf of the National Onion Association, supporting the project:

• Evaluate onion germplasm for resistance or tolerance to key pathogens and insect pests;
• Investigate the biology, ecology and management of onion thrips and other pests;
• Investigate the biology, epidemiology and management of onion diseases; and
• Facilitate discussions among W3008 participants and onion stakeholders that will advance onion pest and disease management.

NOTE: Following this meeting, Steve Loring entered the objectives into the NIMSS system and requested everyone interested in participating in W3008 sign up by completing the Appendix E for the proposal. Steve noted the W2008 project will need an impact statement to tell the story of this 5-year project at the national level. Steve offered to take the lead using impact statements from previous annual reports, and will contact this group if needed. Multistate project proposals will be reviewed in spring 2017, with a call for additional information and a decision made in June/July. Steve Loring suggested compiling a list of potential reviewers for the W3008. Howard Schwartz can be recommended.

Federal award nomination for outstanding multistate projects:  Steve Loring will submit a nomination of the W2008 for a federal award for an outstanding multistate project. Feedback from a previous nomination for this award will be considered in developing the nomination.

Alliumnet and Onion ipmPIPE websites: These websites do not appear to have been updated since Howard Schwartz retired. Mark Uchanski offered to follow up to see if these websites can be changed to become static or whether they should be removed. Mark also will check with NOA to see if the W1008 to W3008 annual reports may be housed on the NOA website. Lindsey enquired about the possibility of moving some resources to established, maintained websites, e.g., the Pacific Northwest Vegetable Extension Group (PNW VEG) website at (http://mtvernon.wsu.edu/path_team/vegpath_team.htm) with sections on onion diseases, pests, and other problems, as well as IPM resources: e.g. http://mtvernon.wsu.edu/path_team/onion.htm and http://mtvernon.wsu.edu/path_team/ipmResources.htm#onion

W2008 Annual Report: Lindsey du Toit requested states submit their annual reports to her by 23^rd Dec. 2016 so she can compile the overall 2016 annual report and get it submitted before January 10^th, after which she’ll be traveling overseas (the deadline is January 15^th).

Onion Federal Grant Proposals:

The group discussed submitting a new USDA Specialty Crops Research Initiative (SCRI) onion proposal, pending the outcome of the USDA SCRI grant proposal submitted by Hanu Pappu, Mike Havey, Brian Nault, and Chris Cramer on thrips, IYSV, and white rot in 2016. Lindsey du Toit offered to lead a USDA SCRI grant proposal on onion diseases to be submitted in Nov. 2017, covering bacterial diseases, pink root, Stemphylium leaf blight, and other diseases. Members were asked to let Lindsey know if they are interested in participating in the proposal, and diseases on which they would like to help write the proposal.

The meeting adjourned at 2:08 pm

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

Colorado – More than 40 cultivars were evaluated for thrips tolerance and horticultural traits in replicated trials in northern and southern Colorado. Several high yielding varieties had appreciable tolerances to thrips. The cv. Yosemite had the fewest number of thrips/plant at two locations in northern Colorado. Several widely-grown varieties were evaluated for total metabolite content. Samples from University-sponsored trials in northern Colorado, southern Colorado, and the Columbia Basin of central Washington showed compositional differences based on variety and environment.

New Mexico – Through economic analysis, a hypothetical 10, 25, and 50% reduction in onion bulb size from one market grade to another caused by onion thrips and Iris yellow spot (IYS) was estimated to cause a 4, 10, and 20% reduction, respectively, in marketable bulb yield; and 4, 10, and 21% reduction, respectively, in gross returns. For the US onion industry, the loss could be as large as $210 million/year. Cultivars resistant to thrips and/or IYS exhibit less or no reduction in bulb size when challenged by these pests. If the onion germplasm developed by the New Mexico onion breeding program for resistance to either/both pests can reduce one insecticide application for control of thrips, an estimated $56 to $91/acre could be saved depending on the insecticide applied. Nationally, savings could reach $13 million/year.

New York – The incidence and severity of IYS were evaluated for 3 cultivars with increasing susceptibility to onion thrips, Avalon, Delgado and Bradley. Cultivars were sprayed weekly with insecticides, sprayed when thrips densities reached a threshold of 1 larva/leaf, or not sprayed with insecticides. All cultivars had 100% IYS incidence by harvest, but severity of IYS was greater in non-treated vs. treated plots from Jul. through early Aug., by which time all plots reached 100% incidence. IYS incidence and severity in plots sprayed weekly were similar to those sprayed based on the action threshold.

Utah - Thirty Spanish onion cultivars were assessed for productivity and maturity, and rated for IYS. IYS symptom expression in commercial fields was very low. While all varieties showed IYS, IYS in the variety evaluations did not appear to impact bulb yield. Summer conditions were favorable for plant growth, and growers reported excellent yields with IYS appearing very late. More work on the relation between IYS incidence and bulb storage is needed.

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

Colorado - A 2014 survey of growers’ fields in Utah and Colorado showed that soil potassium (K) levels correlated with IYS symptom expression and IYSV incidence. A 2015 trial showed that increasing soil K from 170 to 350 ppm doubled the percentage of symptomatic plants, and increased available soil micronutrients, especially manganese (Mn). Many growers’ fields have >400 ppm K. In 2016, a field trial was conducted to identify if soil type, soil texture, and fertilizer type might influence the efficacy of using K and other nutrients to manage IYSV, by evaluating the effects of two K fertilizers and three application rates on the relationship with IYS, IYSV incidence, and onion thrips. As the rate of application of K fertilizer increased to 750 g/10 ft row, IYS severity and incidence of plants with IYSV (ELISA) increased; however, non-treated control plots had the greatest incidence of IYSV. The efficacy of Minecto-Pro insecticide in an integrated foliar management program was compared to the grower standard program with Movento (Bayer). Minecto-Pro gave comparable thrips control to the standard program.

Georgia - Losses caused by IYSV in Georgia were negligible in the 2016 Vidalia onion crop. In most years, conditions are is too cool for IYSV to cause significant damage in short-day onion crops grown from September to May in southeastern Georgia.

Idaho - Natural infection of Allium fistulosum, green or bunching onion, by IYSV was confirmed in Idaho. Foliar symptoms included elliptical to irregular, straw-colored, chlorotic lesions there were mostly elongate and irregular-shaped. The N-gene sequence was 99% identical to that of an IYSV isolate from Washington (KF263486.1).

New York - Early-season management of onion thrips is most effective with foliar applications of Movento. However, the number of applications (1 vs. 2) and action threshold (0.2 vs. 1 thrips/leaf) required to optimize control are unknown. Among four application frequency x action threshold combinations evaluated, two applications of Movento, the first at 1 thrips/leaf and the second a week later, reduced infestation the most and for the longest. Movento will continue to be recommended when thrips populations reach 1/leaf.

Minecto Pro (abamectin + cyantraniliprole) was highly effective against onion thrips as a foliar spray at 7 or 10 fl oz/acre. Efficacy of Minecto Pro was similar to Exirel (cyantraniliprole) at 13.5 fl oz/acre, but better numerically than Agri-Mek (abamectin) at 3.5 fl oz/acre. Minecto Pro and Radiant (spinetoram) at 8 fl oz/acre provided equivalent thrips control. Minecto Pro should be available to NY growers in 2017.

The ability to rescue onion crops from severe onion thrips infestation was evaluated using Exirel (13.5 and 20.5 fl oz/acre) and Radiant (6 fl oz and 10 fl oz/acre). Two population levels (4.3 and 9.1 thrips/leaf) were established, at which time each of four insecticide product x rate treatments were applied and followed with a second application a week later. Thrips infestations were controlled effectively with all four treatments when applications were made at 4.3 thrips/leaf. In contrast, only the high rate of Radiant reduced thrips populations when treatments were applied at 9.1 thrips/leaf. This is useful information for growers who encounter severe thrips infestations.

A laboratory bioassay was used to assess sensitivity of 6 onion thrips populations in NY to Radiant, of which 1 (from a farm near Sodus, NY) was more susceptible than the others. Other populations were less susceptible and had greater variability in susceptibility to Radiant, suggesting the populations contain susceptible and resistant individuals. Research is needed to determine why some thrips populations are more susceptible, and the mechanism(s) of resistance.

Combinations of N fertilizer and insecticide were evaluated for thrips control in onion 3 cultivars differing in susceptibility to thrips. Nitrogen was applied at planting at 60, 90, and 125 lbs/acre. Insecticide regimes included a weekly spray program (standard), a program based on 1 larva/leaf (action threshold), and non-treated plots. Regardless of cultivar, N had no effect on larval thrips densities or bulb yields. Across cultivars, the standard and action threshold programs provided equivalent thrips control and reduced the population 60-81% compared to control plots. Standard and action threshold program plots had similar yields and yielded 10-54% greater than control plots. However, the action threshold program averaged 33-50% fewer insecticide applications than the standard program. Results indicated growers can reduce the number of insecticide applications and N rate at planting without compromising yield or thrips control within the range of treatments evaluated.

Oregon – Onion thrips and IYSV management were evaluated in field trials with 36 insecticide regimes. Product recommendations included using Movento at the start of programs. However, when management needs to begin by May, delaying use of Movento by 1-2 weeks can improve management of peak thrips populations at the end of June and early July.

Utah – Onion thrips and IYSV were evaluated in a N-by-crop rotation trial from Jun. to Sep. Thrips densities (averaged across treatments) were low in Jun. (10/plant), moderate in Jul. (45/plant), and high in late Aug. (102/plant). Onion plants grown with low N (140 lb/A) had fewer thrips/plant than plants grown with high N (330 lb/A). Onion yields were similar in low and high N plots. IYSV was detected in early Aug. and increased dramatically thereafter. IYS incidence by late Aug. was very high with some fields at 60%. Sustainable production occurs when crop inputs (variety selection, plant nutrition, irrigation management, and pest control), onion thrips, and IYSV are managed properly. Growers in Utah reported little difficulty controlling thrips and noted IYS severity varied greatly from low to moderately high incidence in 2016. Growers are using Utah State Univ. research on improving N levels, doing a better job of keeping field borders weed-free, and changing crop rotation practices to better manage thrips numbers and IYSV.

Washington - Field plots (cv. Calibra) were established in Pasco, WA, with drip irrigation and standard grower practices, excluding thrips treatments on 9 May 2016 with two double-rows/44-inch-wide bed. Lorsban 15G (chlorpyriphos) was applied at planting and incorporated (3.7 oz./1,000-ft-row). Foliar applications were made with a tractor-mounted plot sprayer at 30 gpa and 25 psi. Sprinkler chemigation applications were made with a trailer-mounted sprayer in 0.1-inches water/application with in-line injection of insecticide. Thrips pressure was low, with no significant reduction in thrips populations with overhead chemigation of Minecto Pro, Exirel, or Agrimek. There was a numeric decrease in thrips populations with Minecto Pro and Exirel, but not with Agrimek. Foliar Radiant applications were superior to other treatments. Foliar applications of Minecto Pro and Agrimek were numerically, not statistically, better than chemigated applications. In a separate experiment, Radiant and Lannate significantly reduced thrips numbers by chemigation compared to check plots. AzaDirect applied by drip chemigation was not effective. Warrior did not provide control of thrips. Radiant was the most effective insecticide by foliar application. Movento, Exirel, Minecto Pro, Agrimek, and Lannate all provided control better than check and Warrior plots, but were not as effective as Radiant.

Thrips collected weekly by deploying yellow sticky traps in three pairs of onion seed crops and bulb crops (<1 mile apart/pair) are being evaluated for thrips species and IYSV infection (PCR assays). IYSV was present in many of the Thrips tabaci samples. The data should clarify when thrips and IYSV moved from biennial seed crops to annual bulb crops, and out of bulb crops in the fall. To date, >95% of the thrips were T. tabaci.

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

Colorado - A 2-year study to investigate efficacy of symbiotic arbuscular mycorrhizal fungi (AMF) in onions was completed. The objectives were to determine if AMF were present in four commercial onion fields under two irrigation regimes, and if application of AMF at planting could have a positive effect on bulb yield and quality, and reduce soilborne disease problems. MYKE Pro Specialty Crop P (Premier Tech) was used at 3.2 viable spores/seed and placed in planter seed boxes for application in March of 2015 and 2016 at $36/acre. Stand counts were less in AMF-treated plots at three of four locations. The inoculant powder could have displaced seed in the planter cups, reducing plant populations. There was less pink root in MYKE Pro-treated plots at two of four locations compared to check plots; however, pink root severity was lower in check plots at a third location compared to MYKE Pro plots. There was no significant difference between MYKE Pro-treated or non-treated plots in bulb size or marketable yield at all locations. No economic advantage was seen to using MYKE Pro at planting. The lack of consistency in MYKE Pro efficacy on pink root suppression and onion yield could have been influenced by high levels of soil P and/or fungicide-treated seed that can inhibit AMF root colonization.

 In 2016, efficacy of the bio-pesticide Melocon, applied at 4 lb/A prior to planting, on plant parasitic nematodes in commercially grown onions was investigated. There were no differences in onion stands, nematode and thrips populations, pink root severity, and bulb size or marketable yield for Melocon vs. check plots. Limited rainfall and irrigation early in the season possibly limited nematode/Melocon interactions, and severe pink root infection could have displaced nematode feeding and/or infection of onion roots, masking potential Melocon activity.

Georgia – In the past, center rot (Pantoea ananatis) has been observed after seeding (~Sep. 1) of onion beds until the end of October. In 2015, center rot progressed in onion transplants until the end of Dec., extending the window of occurrence by 8 weeks. This effect was likely due to higher than normal temperatures. Mean monthly high temperature in Nov. and Dec. were not significantly different from the mean monthly high in Mar., and the mean monthly lows were greater in Nov. and Dec. 2015 than the 5-year mean monthly low in Mar., when center rot typically begins developing again. Studies on genetic diversity of P. ananatis indicated two broad groups of the pathogen. One is diverse in terms of sources from which the bacterium was isolated (weeds, seeds, thrips, and diseased onion plants). The other was isolated predominately from diseased onion plants or seed. A host range study on five members of the Alliaceae indicated onion was susceptible to all strains of P. ananatis tested. Strains were less virulent on leek, but virulent strains tended to be more virulent on leek than other hosts tested. Epiphytic populations of P. ananatis studied on leaves of Florida pusley (Richardia scabra) under wet-dry periods of various durations indicated the bacterium survives best during periods of prolonged leaf wetness at 21°C. The weed might serve as a primary source of inoculum for center rot epidemics in Georgia. In another study, several sweet onion varieties were used to assess effects of timing of infection. Varieties 1518 and 1407 had lower incidence of bulb rot compared to Pirate, Sweet Harvest, and Granex. Bulbs were more susceptible to infection when inoculation occurred at bulb initiation vs. at first leaf senescence or bulb swelling.

A transcriptome analysis was conducted on bulbs with different copper:iron (Cu:Fe) ratios as this was reported to affect onion resistance/susceptibility to sour skin (Burkholderia cepacia). In general, mRNA transcripts involved in the systemic acquired resistance (SAR) pathway were up-regulated in bulbs with a high Cu:Fe, whereas only one mRNA transcript was up-regulated in bulbs with a low Cu:Fe. In contrast, all mRNA transcripts were down-regulated in bulbs with a low Cu:Fe and none was down-regulated in bulbs with a high Cu:Fe. Affected mRNA transcripts included B2, bark storage protein, phototropin 1A, serine/threonine kinases, snakin-2, pathogenesis related protein 1 (PR1), and other proteins associated with SAR. In addition, an effect of cropping history not related to nutrient composition of the bulb was observed. Onion bulbs harvested from areas previously seeded to pearl millet tended to have more mRNA transcripts related to SAR up-regulation than bulbs in soil with other rotation crops.

New Mexico - Seeds of original, intermediate, and advanced Fusarium basal rot (FBR)-selected populations and resistant and susceptible check cultivars were evaluated for resistance to FBR. The resistant and susceptible entries exhibited high FBR severity and incidence. With the high rate of disease development, many selected populations did not perform well in terms of FBR severity and incidence. Selections from resistant and susceptible checks exhibited reduced disease severity and incidence compared to original populations. Inoculation of 3 x 10⁵ spores/ml of Fusarium oxysporum f. sp. cepae on a cut basal plate was very effective at causing FBR in most bulbs. Selections were made for FBR-resistant bulbs using this method. In separate studies, a reduction in FBR severity and incidence was observed when inoculum concentration was reduced to 3 x 10³ spores/ml. If the basal plate was not cut prior to inoculation, FBR incidence and severity were minimal compared to cut bulbs. Additional modifications to inoculation and incubation procedures will be made to mimic natural infection. In addition, seed produced from FBR-resistant selections made in 2015 from 33 germplasm lines will be used for further evaluations to ascertain progress for resistance to FBR.

New York - New York research has shown that Bravo (chlorothalonil) provides best control of Botrytis leaf blight (BLB). However, other Cornell University studies showed that, when chlorothalonil was co-applied with the insecticides Movento (spirotetromat), Agri-Mek (abamectin), and Radiant (spinetoram), control of onion thrips was reduced by 12-35%. In 2016, Bravo (3 pt/A) and Bravo (1.5 pt/A) + Scala (pyrimethanil, 9 fl oz/A) provided the best control of BLB with 84 and 81% control, respectively. However, Merivon (fluapyroxad + pyraclostrobin, 9 fl oz/A), Inspire Super (16 fl oz/A) + Rovral (1 pt/A), and Scala (9 fl oz) + Rovral (1 pt/A) were equivalent to these treatments with 85, 81, and 80% BLB control, respectively. With the exception of Quadris Top (difenaconazole + azoxystrobin), fungicides that are also effective against Stemphylium leaf blight (SLB), including Merivon (85% control), Luna Tranquility (fluopyram + pyrimethanil; 75% control), Inspire Super (difenoconazole + cyprodinil; 69.5% control), and Fontelis (penthiopyrad; 66% control) provided significant control of BLB compared with control plots. For reducing SLB progression and preventing leaf dieback, Inspire Super + Rovral performed as well as the best fungicides (Merivon, Luna Tranquility and Fontelis), while Rovral + Scala was less effective. Results will be used to make fungicide recommendations to control BLB and SLB effectively without compromising efficacy of insecticide applications targeting thrips.

SLB incidence was rated using a 5-point scale (0-4), and SLB severity rated using a 7-point scale (0-6). To determine a total SLB disease score, these ratings were used in combination with estimated % leaf dieback, number of green leaves/plant, and % green foliage/plot. In plots treated with insecticides to control onion thrips, but not treated with fungicides, there was a 20-29% (significant) reduction in disease score compared with nontreated plots, indicating that thrips control is important for reducing SLB damage. In SLB Trial 1, SLB damage was best controlled using Luna Tranquility at 12 or 16 fl oz/A. SLB progression was reduced equivalently with Viathon (phosphorous acid + tebuconazole), Inspire Super, and Merivon. Aprovia Top (difenoconazole + benzovindiflupyr) significantly reduced SLB severity and kept plants healthy compared with the control plots, but numerically was not as effective as Viathon. SLB severity in plots treated with Thyme Guard (thyme oil) was not significantly different from the control plots. In SLB Trial #2, SLB control was evaluated over 7 weeks using combinations of fungicides and foliar applications of N and micronutrients.  Fungicides included Inspire Super, Luna Tranquility and Merivon, while the nitrogen and micronutrient product was ENC Elemax (Helena Chemical). Co-applications of fungicides and ENC Elemax were made during weeks 1-3 (front-loaded), weeks 3-5 (middle-loaded), weeks 5-7 (end-loaded), every other week (half), or every third week (1/3). None of the ENC Elemax foliar treatments improved SLB control or plant health beyond the fungicide program alone. In SLB Trial #3, timing of fungicides for SLB control were evaluated. Luna Tranquility was applied weekly for seven weeks starting at early bulbing, and compared with front-, middle and end-loaded program (as for SLB Trial #2), front + middle loaded (weeks 1-6), middle + end loaded (weeks 3-7), and an extended program (weeks 1-9) when two additional sprays were made after lodging. Fungicide applications towards the end of the season (end-loaded, middle + end loaded), season long, and season-long + after lodging had less SLB disease progression and severity than front-loaded and middle-loaded programs. The results indicated that highly effective fungicides should be used later in the season to control SLB. Use of SLB fungicides prior to bulbing was not evaluated.

Oregon – A major portion of the Food Safety Modernization Act’s Produce Safety Rule focuses on the microbiological quality of irrigation water. Multi-year studies on the effect of contaminated irrigation water on the relative fate of generic Escherichia coli in water, in soil, and on onions during growth, curing, harvesting, and storage were completed. Drip or furrow irrigation did not appear to pose a significant risk for E. coli contamination of dry bulb onions. E. coli rapidly died-off in the soil and on onion exteriors in the field. Plastic containers did not provide added food safety value compared with wooden boxes for storage of dry bulb onions. Chlorine dioxide showed promise to remediate microbial contamination of water used in drip irrigation, if needed for compliance with water quality standards.

Pennsylvania – Annual losses to bacterial diseases can range from 5-40% in PA onion crops. During 2016, efforts continued to be directed towards developing research-based management strategies for less harvest and post-harvest losses to center rot. Two replicated field trials evaluated the effect of N application timing and rate on center rot incidence and marketable yield, as preliminary data suggested applying total crop N prior to onion bulbing increased yield and reduced bacterial disease incidence. Also, low lying areas in heavily manured fields had up to 83% bacterial bulb decay incidence at harvest. A positive, quadratic relationship was found between percent foliar N at bulbing and center rot incidence at harvest. In addition, an interaction existed between N rate and application timing (half vs. full season applications) but trends were variable based on location. This may have been due to very high disease pressure at one location, suggesting a disease threshold above which augmenting N applications may not benefit disease management. Currently, there are no known public onion breeding programs targeting center rot, nor have there been many trials to evaluate susceptibility of commercial cultivars. To address this, 13 onion cultivars were evaluated in two trials for center rot susceptibility, marketability, and select horticultural characteristics. The only cultivar with lower disease incidence and severity and comparable yields to the grower standard cv. Candy was Spanish Medallion. The next step will be to evaluate this cultivar on commercial farms under diverse field settings to assess the potential to be in the Pennsylvania “Simply Sweet” program. Based on in-vitro and laboratory transplant assays, hydrogen dioxide, hydrogen peroxide with mono- and di-potassium salts of phosphorus acid, copper sulfate pentahydrate, and streptomycin sulfate were effective at reducing epiphytic bacterial populations from the surface of onion transplants. These could be important tools for reducing sources of inoculum. Many of the treatments evaluated are labeled for use in onion crops in PA; therefore, minimal adjustments would be needed to product labels to encompass pre-plant applications.

Washington - Onion stunting caused by Rhizoctonia spp. is an important soilborne disease on sandy soils in the Columbia Basin of Washington and northcentral Oregon where cereal winter cover crops are planted the previous fall to prevent wind erosion of soil. The cover crop is killed with a herbicide shortly before or after onion seeding in spring. The dead cereal plants protect onion seedlings against sand-blasting, but the cover crop provides a bridge for Rhizoctonia spp. on dead cereal roots to colonize onion roots, causing onion stunting. To determine the effect of herbicide application to reduce this green bridge, three glyphosate application timing intervals preceding onion planting were evaluated. As the interval between herbicide application and onion planting increased from 3 to 27 days, the number of patches of stunted onion plants decreased by ≥55%, total area of stunted patches decreased by 54-63%, and patch severity decreased by 59-65%. Increasing the interval between herbicide application to the cover crop and onion planting is a practical strategy to avoid onion stunting.

The effects of four commercial AMF products on onion growth were evaluated in a growth chamber trial for onion root colonization by AMF, and shoot height and dry weight: i) BioTerra Plus (Plant Health LLC); ii) MycoApply Ultrafine Endo (Mycorrhizal Applications, Inc.); iii) Mykos Gold Granular (Reforestation Technologies Inc.); and iv) MykePro Granular (PremierTech Horticulture). Onions in soil amended with Mykos Gold Granular were taller, had greater shoot dry weight, were colonized extensively by AMF (82.2%), and had significantly greater foliar K, total N, Mg, S, Fe, and B compared to plants in control soil without AMF treatment. Mykos Gold Granular was the only product that consistently improved onion growth and AMF root colonization, warranting evaluation under field conditions. Additional trials with AMF products as seed treatments, with or without fungicide seed treatments, revealed that the liquid formulation of Mykos Gold did not lead to onion root colonization by AMF. Fungicide seed treatments commonly used by onion growers can inhibit AMF colonization of roots. In 2016, five onion trials were completed in grower-cooperator fields in the Columbia Basin to evaluate the potential use of AMF inoculants in direct-seeded onion crops for enhancing production by increasing P use efficiency, reducing severity of soilborne pathogens, and promoting onion growth. Results to date indicate AMF treatments generally did not improve stand, bulb yield, pink root control, or foliar nutrient content significantly. However, high levels of P in the fields may have negated potential benefits of AMF. Trials are planned to evaluate potential impacts of soil P levels on AMF colonization of onion roots to assess the importance of modifying soil fertility practices in order to benefit from AMF inoculants.

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

Colorado – Outputs of this work were presented at multiple meetings in Colorado and out-of-state. The information will be used by Colorado and national onion industries, growers, seed company breeders and pathologists, and integrated pest management specialists to select more effective management strategies including promotion of varieties less susceptible to thrips.

Georgia - The annual meeting of the National Onion Assoc. and biennial meeting of the National Allium Research Conf. were in Savannah, GA on 30 Nov. – 3 Dec. 2016, and attended by >300 people associated with the onion industry, including growers and other stakeholders. There were 53 oral paper and poster presentations and a tour of the Vidalia onion industry.

New York - Onion growers from around New York who had an opportunity to follow the Cornell Onion Thrips Management Program stated they: 1) found action thresholds to be useful, 2) reduced the number of insecticide sprays targeting thrips by 2 to 3/field, 3) saved an average  $50/acre, 4) had excellent thrips control, 5) maintained high bulb yields, and 6) did not appear to have difficulty controlling thrips with Radiant. About 75% of onion growers in NY adopted all or part of the program, saving about $350,000/year. In the hot and dry 2016 season, 10 growers participated in the Cornell Cooperative Extension Vegetable Program Onion Research Scouting Program (collaboration with Cornell Onion Thrips Management Program) and saw that BLB and downy mildew (DM) pressure were very low and, thus, gained confidence to follow the recommendations to skip fungicide applications for these diseases. The farmers reduced fungicide sprays by 83 and 74% to an average of 1.3 and 3.7 times for BLB and DM, respectively, and total costs by 58% to only $50/acre. Results were presented at meetings throughout NY and beyond.

Oregon – In a new area-wide monitoring program, Treasure Valley growers received weekly reports of thrips abundance and IYSV incidence collected from commercial fields throughout the valley. This information enabled growers to better assess risks of thrips and IYSV in their growing regions.

Pennsylvania – Research results were disseminated at local and regional vegetable grower meetings in-state and internationally. Results were also disseminated throughout the season through one-on-one interactions with growers.

Utah – Utah State University, in cooperation with the Utah Onion Assoc., hosted: Annual winter onion meetings (54 attended) in Feb. 2016 in Brigham City, UT; and a summer field tour (52 attended) in Aug. 2016. Two presentations were made at the joint NOA/NARC meetings describing Utah based onion research, and the Utah State report given at the W2008 meeting on 1-3 Dec. in Savannah, GA.

Washington – The Washington State Univ. Onion Field Day in 2016 was attended by~100 growers and other stakeholders who viewed replicate plots of 50 cultivars, with presentations made by researchers. In Feb. 2016, onion bulbs in storage were evaluated for 55 cultivars from the 2015 WSU Onion Cultivar Trial to assess storage quality and diseases. Numerous presentations were given in 2016 (see Publication and Field Days below), and many onion samples diagnosed with accompanying management recommendations.

(See attached file for complete listing of abstracts, reports, and presentations.)

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.

Bartolo, M.E., and K.J. Tanabe. 2015. Onion variety trial. Pp. 16-18 in: Arkansas Valley Res. Center 2010 Reports, CO State Univ. Ag. Expt. Station Tech. Rep. TR15-11.

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