Brief Summary of Minutes of Annual Meeting

Objective 1. Evaluate onion germplasm for resistance to pathogens and insects.

New Mexico (Cramer): NMSU breeding lines exhibited a lower Fusarium basal rot (FBR) incidence and severity than a commercial FBR-resistant cultivar. Other NMSU breeding lines exhibited fewer thrips/plant, lower Iris Yellow Spot Virus severity, and greater bulb size than a commercial cultivar. 

New York (Nault, Hoepting, Pethybridge, Hay): Onions with semi-glossy wax leaves and low levels of H-16 ketone have shown partial resistance to onion thrips.  The semi-glossy hybrid, cv. USDA Maia, and a waxy, thrips-susceptible cv., Bradley, were evaluated on two organic farms. Season total thrips densities were similar between the two cultivars, indicating a lack of thrips resistance in USA Maia.  Bacterial bulb rot was 20-40% greater, and marketable bulb yield was 2 to 3 times less in USDA Maia, than in Bradley.  There was no relationship between season total thrips densities and incidences of bacterial bulb rot at harvest.

In 2021, thrips were assessed in an onion variety trial, with an early (Apr 6) and a late (May 4) planting.  There were significant differences in thrips feeding damage among variety, and between insecticide-treated and nontreated, as well as a variety-insecticide interaction (i.e. not all varieties responded the same to insecticide treatment).  Thrips feeding caused 7% to 26% reduction in plant height.  In general, thrips feeding damage increased as days to maturity decreased, but some varieties in each maturity class had more foliar thrips feeding damage than others.  In the nontreated plots, Trailblazer, Braddock and Red Wing appeared more susceptible to thrips damage in the early, main and late maturity classes, respectively.  Crockett (118 days) had the least thrips feeding damage in the trial.

Idaho (Woodhall, Thornton and Schroeder): In fall of 2020, bulbs of 10 yellow onion cultivars and pre-commercial lines were collected and stored(36^oF) . On 24 May and 28 June 2021, samples were removed from storage and evaluated for defects. Seven of the ten onion cultivars and lines reached >90% marketable bulbs on the 24 May. Most non-marketable bulbs were due to internal decay and translucent scale. Caldwell, OLXY14733, and SVNW1526 had a relatively high level of translucent scale (above 8%), while Crockett, Caliber, and OLYS15-50 had less than 2%. Vaquero, the industry standard, had >95% marketable bulbs on 28 June, above the long-term average for this variety.

Utah (Drost, Nischiwitz): Onion germplasm trials were conducted with two growers and evaluated for emergence, plant growth, disease and insect incidence, top down maturity, bulb yield and storage potential. Onion growth was satisfactory and disease and insect pressure was low.

Objective 2. Investigate the biology, ecology and management of onion Thrips and other pests.

Idaho (Woodhall, Thornton and Schroeder): Thrips and IYSV control with a standard foliar insecticide program (Aza/M-pede, Movento, Minecto Pro, Radiant – 2 applications of each) was compared to programs where the Movento foliar applications were substituted with 2 applications of an insecticide from Gowan (GWN-12030) applied via the drip irrigation system.  All insecticide programs reduced thrips populations and IYSV incidence compared to the untreated, and foliar and drip programs provided equal efficacy.  The proportion of ≥3-inch diameter onions was also increased by insecticide programs.

The susceptibility of bulbs from 20 onion cultivars obtained from the OSU Cultivar trial to Fusarium proliferatum was assessed. For each cultivar, 4 replicates of 20 onion bulbs were inoculated with F. proliferatum at harvest and stored for 4 months.  The trial was repeated in two consecutive years.  For evaluation, bulbs were cut down the center and assessed for percent of the surface of the bulb exhibiting rot.  In both years, cultivars Grand Perfection, 16000 and Avalon developed significantly less bulb rot (7.5-12.5%) compared to Montaro, Oloroso, Swale, Vaquero, Tucannon and Sedona (20-23.8%), indicating resistance in some commercially available cultivars.  

New York (Nault, Hoepting, Pethybridge, Hay):  Combinations of fertilizer and insecticide use were evaluated for onion thrips management in 9 commercial onion fields. Thrips populations and marketable bulb yield were not affected by fertilizer treatment. The action-threshold based insecticide program controlled thrips with up to 5 fewer applications (average 2.5 fewer) than spraying weekly, with no difference in yield. Results were similar to previous years.

In a small-plot trial, high rates of isocycloseram (PLINAZOLIN^® technology) and cyantraniliprole provided a commercially acceptable and equivalent level of onion thrips control, and both performed better than the high rate of spinetoram. Foliar applications of PLINAZOLIN^® technology provided a similar and excellent level of allium leafminer (ALM) control in scallions, as Minecto Pro. PLINAZOLIN^® technology seed treatment also exhibited some activity against onion maggot.

The use of spinosyn insecticides, spinetoram and spinosad, for managing allium leafminer infestations in allium crops was optimized in field trials.   Each spinosyn insecticide was applied twice, spaced either one or two weeks apart beginning at various intervals after P. gymnostoma was first detected compared to a weekly spray program. Weekly applications of either insecticide provided ≥ 98% reduction of P. gymnostoma densities in scallions and leeks relative to the untreated control. Spinetoram applied twice, regardless of initial timing and duration between sprays, provided acceptable P. gynostoma control. Spinosad also was effective when applied twice with 85 to 95% reduction in densities relative to the untreated control. Management of P. gymnostoma with spinosyns can be successful with only two applications, but control tended to be best when first applied two to three weeks after initial detection.

Texas (Malla): The relationship between thrips and epicuticular wax profile of 25 germplasm accessions (including 20 from Texas A&M) was assessed. The wax compound 16-Hentriacontanone was negatively correlated (r = -0.34) with thrips per plant in 2018, but not in 2019 (r = 0.08).   Some Texas A&M germplasm entries (e.g. 31034 at Uvalde and 50014 and 50084 at Weslaco) showed tolerance (2 thrips/plant) compared to others (17-45 thrips/plant).

Oregon (Reitz): Onion thrips densities and marketable bulb yield were assessed in response to nitrogen fertilization rates, and insecticides applied either weekly, at an action threshold of 1 thrips larva/leaf, or no insecticide applications. Weekly soil and tissue sampling for nutrients was conducted and nitrogen was applied according to test results for the standard treatment or at 50% of the standard treatment for the reduced nitrogen treatment. Although onion thrips were significantly lower in plots receiving a weekly insecticide application than those following an action-threshold based insecticide program, they were kept below the economic injury level of 2.2 thrips larvae per leaf.  Fertilizer rate had no significant effect on onion thrips densities.

Washington (du Toit, Waters, Pappu): Data was collected on the efficacy of broflanilide to support potential future registration for management of seed-corn maggot (Delia platura), a challenging pest for growers in the PNW.  Broflanilide worked as well as the standard spinosad treatment and offers a potential new tool to manage seedcorn maggot, which is especially important with the recent loss of the use of chloropyrifos insecticide.

The product PQZ and two new yet to be labeled insecticides were compared to a local grower standard (abamectin) for control of onion thrips and IYSV. PQZ was moderately effective at controlling thrips while both numbered compounds controlled thrips as well as abamectin. The development of new active ingredients is integral to continue to control onion thrips which can quickly develop insecticide resistance.

Objective 3. Investigate the biology, epidemiology and management of onion plant pathogens.

California (Putnam, Wilson): The efficacy of fungicides for management of white rot was evaluated.  Tebuconazole applied in-furrow and penthiopyrad banded at cultivation reduced diseased bulb yield by 94% compared to the untreated.  As part of the regional USDA-SCRI Stop the Rot project, bacterial disease samples were collected from throughout California to identify bacterial species.  Bactericides and the influence of irrigation method on the incidence and severity of bacterial diseases in onions was studied. Drip irrigation reduced foliar disease and bulb rot symptoms by more than 90% compared to sprinkler irrigation.  A study in Southern California suggested weather-based fungicide scheduling can reduce fungicide applications required for onion downy mildew control under no to low disease pressure, as could application made prior to, or immediately during, favorable weather conditions.   

Georgia (Dutta, Kvitko): Twelve bactericides and plant defense inducers were evaluated for efficacy against internal bacterial rot of onion. Foliar symptoms were not observed in the field or during harvest. Percent internal bulb rot incidence was significantly lower for all treatments compared with the non-treated check except for treatment with Theia, a bio-fungicide.  Bacteria from symptomatic bulbs with internal rot were confirmed as  P. ananatis.

The effect of digging methods on post-harvest incidence of bacterial bulb rot in onion was evaluated. A significantly higher incidence of internal rot was observed with the straight bed-ridge undercutter compared with the chain digger. An integrated approach that included copper-bactericide, insecticide (thrips control) and herbicide programs considerably reduced center rot incidence in bulb compared to the onion grower’s standard.  Growers can achieve a profit of $880 per acre using the integrated approach identified in this project, equating to a potential profit of $8.8 million if the strategy was used over the entire onion acreage in Georgia (10,000 acres). 

Two distinct secondary metabolite biosynthetic clusters associated with onion pathogenic strains of bacteria were identified, the validated phosphonate cluster (HiVir) and a putative phosphonate biosynthetic cluster (Halophos).  The pepM genes from each cluster (HiVir and Halophos) are required for onion infection by P. stewartii subsp. indologenes and P. allii, but not for millet infection by P. stewartii subsp. indologenes. Conversely, the T3SS was important for millet infection by P. stewartii subsp. indologenes but not onion infection. Induction of the intact Halophos cluster was associated with the accumulation of a necrosis-inducing factor in culture, indicative of a phytotoxin. Seven of the eleven Halophos cluster genes are required for onion necrosis phenotypes. Results indicate a Halophos biosynthetic gene cluster to be associated with onion pathogenicity in strains of P. stewartii subsp. indologenes and P. allii.

Species-specific PCR assays were validated for the detection of P. ananatis, P. agglomerans, P. allii and P. stewartii. Two P. ananatis, one P. allii, one P. agglomerans and three P. stewartii published primers as well as newly developed P. agglomerans PagR primers were evaluated for specificity against 79 Pantoea strains, comprising 15 different species.  Previously described P. ananatis-specific PANA_1008, P. allii-specific allii-leuS, and P. stewartii-specific PANST_rpoB, 3614galE, and DC283galE primers and one newly designed P. agglomerans-specific PagR primer pairs accurately identified these strains to species and, in some cases, sub-species level.  This will facilitate rapid and reliable identification of Pantoea species.

New York (Nault, Hoepting, Pethybridge, Hay):  Management of Stemphylium leaf blight (SLB) has become challenging in NY due to the rapid development of resistance to fungicides despite considerable grower adoption of fungicide resistance management strategies.  The SDH genes of 234 isolates of S. vesicarium were sequenced and 11 mutations identified, which are associated with insensitivity to FRAC 7 fungicides. Currently, the FRAC 3 fungicides are the most effective against SLB in NY. However, in vitro testing has shown a shift towards insensitivity such that disease control can only can be achieved using high rates of combinations of FRAC 3 products (e.g. Viathon + Tilt).  Other studies confirmed volunteer onion as a source of SLB.  However barley, planted between rows as a windbreak for emerging onion seedlings, was not a significant host. 

Idaho (Thornton, Woodhall and Schroeder):  Pink root control from drip applications of Fontelis at the first irrigation followed by a second application 4 weeks later were compared to Velum Prime or Velum Prime followed by Minuet at the same application timings.  All fungicide programs tended to reduce both disease incidence and severity in July and August compared to the untreated.  Reduced pink root was associated with an increased onion yield.  Results confirm those of previous years which showed that Velum Prime and Fontelis applied via drip provide equal suppression of pink root. 

The efficacy of various rotations of foliar-applied Provisto, Pristine, Botran, Zing!, Badge SC and Reason fungicides on incidence of decay of Vaquero yellow sweet Spanish onion bulbs after 5 months in storage was studied.  Fungicides were applied mid-July through mid-August.  Decay incidence averaged 25% in the untreated and none of the fungicide programs reduced decay incidence.

In two consecutive years, cv. Vaquero onion bulbs were inoculated after harvest with Fusarium proliferatum and cured at 25, 30, 35 or 40°C then placed at 5°C (41°F) for long term storage.  Bulbs were cut from stem to basal plate and rated for bulb rot as a percentage of cut bulb surface exhibiting symptoms.  Bulb rot was assessed at 4 and 6 months after inoculation.  For the 2 day curing durations, the bulb rot was not significantly affected by curing temperature (around 30% bulb rot).  With the 2 week curing duration the same was observed, except for the 35°C curing temperature, where more bulb rot was observed at the 4 month storage, compared to 6 month. 

Oregon (Dung, Qian): Formulations of germination stimulants to control onion white rot (Sclerotium cepivorum) were studied.  Garlic oil and diallyl disulfide (DADS) was successfully encapsulated with β-cyclodextrin with greater than 90% recovery. Considerable amounts of DADS and diallyl sulfide (DAS) were detected by gas chromatography-mass spectrometry in soils 27 days post-treatment. Naturally-infested soils treated with DADS, microcapsules of DADS, and microcapsules of garlic oil exhibited 78, 76, and 77% reductions in sclerotia, respectively, compared to non-treated controls. The relative amounts and timing of DADS and DAS detected over time depended on the soil type.

The ability of onion to stimulate sclerotial germination and be used as a trap crop for white rot control was evaluated.  Infested plots were either left fallow or planted to onions which were chemically terminated at the 2-6 true leaf stages. A 24-67% reduction in sclerotia was observed when onions were terminated at the 2nd leaf stage; however, sclerotia counts were similar to fallow plots by the 3rd leaf termination timing and were greater at all subsequent termination timings.  Greenhouse trials showed similar reductions in sclerotia when onions are terminated at the 2-leaf stage.

A garlic field trial evaluated Pyraziflumid applied at 3.1, 4.6, or 6.2 oz/A in-furrow for white rot management. All rates significantly increased stand counts and plant heights and reduced disease severity compared to the control. At harvest, plots treated with Pyraziflumid at 6.2 oz/A had significantly increased marketable yields compared to the non-treated.

Utah (Drost, Nischiwitz): Fertilizer trials showed a trend that high levels of available soil K increased symptom expression of IYSV in infected onions. The percent symptomatic plants more than doubled when soil K in potash treatments increased from 125ppm to 260ppm. However, the results were not statistically significant due to variation within replications. Treatments with potassium sulfate did not increase symptom expression but plants were smaller and less vigorous than with potash treatments. In our trials, soil K affected the uptake of Fe, Mn and Zn which increased with increasing K levels in the plant tissue. However, the mechanism behind the increased IYSV symptoms is unknown.

Washington (du Toit, Waters, Pappu):

Five onion fields were surveyed during the 2021 growing season for symptoms of bacterial diseases and over 75 bacterial strains were obtained (c.f. ~300 strains in the 2020 survey).  Isolates are being identified by DNA sequencing and tested for pathogenicity on onions. Selected strains have been sent to the National Onion Bacterial Strain Collection at UGA for curation and further research on genomics and mechanisms of pathogenicity.

In the 2020 WA trials, copper and other bactericide treatments had no effect on incidence or severity of bacterial bulb rot at harvest or after 5 months of storage. Trials on undercutting, rolling tops, and the timing of topping showed no significant effects on marketable yield or bacterial bulb rots. Trials indicated no benefit to applying ozone or hydrogen peroxide + peroxyacetic acid products to onion bulbs in storage for managing bacterial rots, because the products do not penetrate the dry wrapper scales into the fleshy scales where infections reside. In the 2020 irrigation trials, earlier termination of final irrigation reduced bacterial rot without affecting marketable bulb yield.

To determine the genetic diversity and evolution of IYSV, the complete N gene sequences of 142 IYSV isolates from curated sequence data in GenBank was studied. In silico RFLP analysis, codon-based maximum likelihood studies, genetic differentiation and gene flow within the populations of IYSV genotypes were investigated. Bayesian phylogenetic analysis was carried out to estimate the evolutionary rate. IYSV isolates  grouped into two major genotypes viz., IYSV Netherlands (IYSVNL; 55.63%), IYSV Brazil (IYSVBR; 38.73%) and the rest fell in neither group [IYSV other (IYSVother; 5.63%)]. Genetic diversity tests revealed IYSVother to be more diverse than IYSVNL and IYSVBR. IYSVNL and IYSVBR genotypes are under purifying selection and population expansion, whereas IYSVother showed decreasing population size and hence appear to be under balancing selection. IYSVBR is least differentiated from IYSVother compared to IYSVNL genotypes based on nucleotide diversity. Three putative recombinant events were found in the N gene of IYSV isolates based on RDP analysis. Findings suggest that IYSV continues to evolve using population expansion strategies and the substitution rates are similar to other plant RNA viruses.

Pennsylvania (Gugino) As part of the Stop the Rot SCRI project, 10 whole onion plants samples with bacterial center rot disease symptoms were collected from each of five fields at 8-9 leaf stage and again at harvest. Up to three unique bacterial colonies were selected from isolations from each plant, with 161 bacterial isolates collected and stored (-80°C). Additional samples from NY were also obtained under an APHIS 526 permit for a total of 239 additional isolates. Of the 1501 isolates collected from the field (not post-harvest), 831 were characterized to genus and pathogenicity tested. A total of 46 unique genera were identified but only five (Burkholderia, Enterobacter, Pantoea, Pseudomonas, and Rahnella) contained isolates that were pathogenic based on the red scale assay. This was similar for both PA and NY in 2020 and in 2021.

A bactericide efficacy trial was highly variable in part due to weed pressure, so treatments had no  significant effect on either foliar disease incidence or neck rot (discolored internal neck scales when the onion is topped 2 to 3 inches from the bulb) at harvest. However, the incidence of neck rot was highest in the inoculated controls (20.1%) and lowest in the ManKocide (7.3%) treatment (P=0.328). The untreated uninoculated control had 5.8% neck rot.

A nitrogen rate and timing trial with four rates (0, 50, 105, and 160 lb N/A) at two timings (half and full season) was conducted to evaluate the effect on center rot disease incidence and marketable yield. Nitrogen rate and application timing had no significant effect on the total marketable yield or size class although numerically, the highest rate of nitrogen resulted in the highest total marketable weight. Plots receiving no nitrogen during the season yielded the same as those receiving nitrogen indicating that residual soil nitrogen levels from the previous small grain crop provided enough nitrogen and likely masked any effect of the nitrogen treatments. Unfortunately, there was significant variation between replicates on both the incidence of symptomatic plants and bulbs at harvest .  More disease was observed in the inoculated plots and in those that received the standard grower recommended rate of 105 lb/A.

Objective 4.  Facilitate discussions between W3008 participants and onion industry stakeholders that will advance onion pest and disease management.

New York (Nault, Hoepting, Pethybridge, Hay):   In 2021, 20 commercial onion fields were scouted weekly in four counties.  Incidence and severity of insects and diseases was reported and research-based recommendations provided in weekly scouting reports, including the weekly Elba Muck Donut Hour.  Presentations were made to Oregon Processed Vegetable Commission Annual Meeting,  Syngenta’s North-Atlantic Innovation 2021 Meeting, 69^th Annual Muck Vegetable Growers Conference (Ontario, Canada), W-4168 Multistate Annual Meeting and Empire State Producers Expo 2021.  The ‘2021 Cornell Onion (dry bulb) ‘cheat sheet’ for control of leaf diseases’ was provided on-line. Two articles on foliar disease were published in grower magazine VegEdge.  Guided tours of the SLB fungicide trials were given to growers, crop consultants, and chemical industry representatives.

Texas (Malla): A modified insecticide program was recommended in consultation with Nault and Waters to an onion grower in the Rio Grande Valley who had difficulty controlling thrips. 

Oregon (Reitz, Dung and Shock): Research was presented at the Idaho-Malheur County Onion Growers Meeting, the Pacific Northwest Vegetable Association, and the annual California Garlic and Onion Research Symposium.   Research was published online on the Malheur Experiment Station website  and Central Oregon Agricultural Research and Extension Center website.

Washington (du Toit, Waters, Pappu): The Stop the Rot onion bacterial team reached onion stakeholders through grower meetings, field days, conferences, workshops, the Alliumnet website, industry newsletters, trade publications and extension videos. Growers in each of the onion-growing regions were recruited for participation in field surveys. Stakeholder Advisory Panel members, were engaged with research activities. Panel members represent onion farms, regional onion associations, and major vegetable seed companies (including onion breeders and plant pathologists) from across the U.S., with one international member. Panel members have conducted further outreach to their own networks on behalf of the project.

• A 15-minute extension video was released on bacterial diseases of onion and options for management in the field.
• Articles on the Stop the Rot project in the WSU Onion Alert, circulated to >600 subscribers and in Onion World Magazine.
• Lindsey du Toit’s lab assisted with diagnosis of onion samples and queries from onion growers in the PNW and other states (CA, OR, NV, ID, CO) on disease diagnosis and management.

California (Putnam): The California Garlic and Onion Advisory Board held a one day symposium to update industry representatives and growers on onion research, new product updates, and facilitate discussion on industry research needs and priorities.

Agarwal, G.,  Gitaitis, R.D., and Dutta, B. 2021. Pan-genome of novel Pantoea stewartii subsp. indologenes reveals genes involved in onion pathogenicity and evidence of lateral gene transfer. Microorganisms 9: 1761. https://doi.org/10.3390/ microorganisms9081761

Agarwal, G., Choudhary, D., Stice, S.P., Myers, B.K., Gitaitis, R.D., Venter, S.N., Kvitko, B.H., and Dutta, B. 2021. Pan-genome-wide analysis of Pantoea ananatis identified genes linked to pathogenicity in onion. Frontiers in Microbiology https://doi.org/10.3389/fmicb.2021.684756.

Beck, K. D., Reyes-Corral, C., Rodriguez-Rodriguez, M., May, C., Barnett, R., Thornton, M.K., Bates, A. A., Woodhall, J. W., B. K. Schroeder. 2021. First report of Fusarium proliferatum causing necrotic leaf lesions and bulb rot on storage onion (Allium cepa) in Southern Idaho. Plant Disease: 2021. https://doi.org/10.1094/PDIS-06-20-1399-PDN.

Brown, L., Harrington, S., Harrington, M., Murdock, M. R., Pizolotto C. A., and J. W. Woodhall. 2021. Rhizoctonia solani AG 2-2 IIIB Causing Root Rot of Onion in Idaho. Plant Disease 105:2, 498-498

Cramer, C.S., S. Mandal, S. Sharma, S. Shahabeddin Nourbakhsh, I. Goldman, and I. Guzman. 2021. Recent advances in onion genetic improvement. Agronomy 11:482. https://doi.og/10.3390/agronomy110300482.

Greenway, G., N. Kamal, S. Shahabeddin Nourbakhsh, and C.S. Cramer. 2021. Estimating potential changes in costs and returns from use of a partially onion thrips-resistant cultivar and action-based spray thresholds in Idaho and Eastern Oregon. Southwestern Entomologist. 46:349-356. https://doi.og/10.3958/059.046.0206.

Kamal, Harding, R.S., and B.A. Nault. 2021. Onion Thrips control in onion, 2020. Arthropod Management Tests 46(1): tsab022, https://doi.org/10.1093/amt/tsab022.

Hay, F.S., S. Stricker, B.D. Gossen, M.R. McDonald, D.W. Heck, C.A. Hoepting, S. Sharma, and S.J. and Pethybridge. 2022. Stemphylium leaf blight of onion: A re-emerging threat to onion production in eastern North America. Plant Dis. PDIS-05-21-0903-FE. On Just Published. 8 December 2021. https://doi.org/10.1094/PDIS-05-21-0903-FE.

Hay, F.S., D.W. Heck, S. Sharma, A. Klein, C. Hoepting, and S.J. Pethybridge. 2021. Stemphylium leaf blight of onion. Disease Lesson. The Plant Health Instructor R2 submitted 8 October 2021. In Press.

Hay, F.S., D.W. Heck, A. Klein, S. Sharma, C.A. Hoepting, and S.J. Pethybridge. 2021. Spatiotemporal attributes of Stemphylium leaf blight epidemics and effects of residue management in New York onion fields. Plant Dis. PDIS-07-21-1587-RE. On First Look. 19 November 2021. https://doi.org/10.1094/PDIS-07-21-1587-RE.

Hay, F.S., and S.J. Pethybridge. 2021. Stemphylium leaf blight of onion. Allium Chapter in World Handbook of Vegetables. In Press.

Hoepting, C.A. 2021. Running out of fungicide options for control of Stemphylium leaf blight in onion. Veg Edge, 17(18): 4-5.

Hoepting, C.A. 2021. Onion downy mildew prevention the ‘crutch’ for ‘limping’ SLB fungicides to manage DM-SLB complex. Veg Edge, 17(14): 8-9.

Hoepting, C.A. and Hay, F.S. 2021. Part II: Onion fungicide research updates and new recommendations for control of Botrytis and Stemphylium leaf blights, 2021. Veg Edge, 17(13): 8-9.

Hoepting, C.A. and Hay, F. S. 2021. Part I: Onion fungicide research updates and new recommendations for control of Botrytis and Stemphylium leaf blights, 2021. Veg Edge, 17(12): 8-10.

Iglesias, L.E., R.L. Groves, B. Bradford, R.S. Harding, and B.A. Nault. 2021. Evaluating combinations of bioinsecticides and adjuvants for managing Thrips tabaci (Thysanoptera: Thripidae) in onion production systems. Crop Protection 142 https://doi. org/10.1016/j.cropro.2020.105527.

Iglesias, L.E., M.J. Havey, and B.A. Nault. 2021. Potential for managing onion thrips (Thrips tabaci) in organic onion production systems using multiple IPM tactics. Insects (in press).

Moretti, E.A., A.G. Taylor, K. Wickings, B.A. Nault. 2021. Insights into how spinosad seed treatment protects onion from onion maggot (Diptera: Anthomyiidae). J. Econ. Entomol. doi: 10.1093/jee/toaa332.

Moretti, E.A., K. Wickings, and B.A. Nault. 2021. Environmental factors and crop management that affect Delia antiqua damage in onion fields. Agric. Ecosyst. Environ. 314:  107420.

Nault, B.A., R.K. Sandhi, R.S. Harding, E. Grundberg, and T. Rusinek. 2022. Optimizing spinosyn insecticide applications for allium leafminer (Diptera:  Agromyzidae) management in allium crops. J. Econ. Entomol. https://doi.org/10.1093/jee/toac016.

Regan, K. and B. Nault. 2021. Less is more: Reducing inputs benefits onion production in muck soil. Onion World  37(4): 8-10.

2021. S. Shahabeddin Nourbakhsh, and C.S. Cramer. 2021. Reduced Iris yellow spot symptoms through selection within onion breeding lines. Horticulturae 7:12. https://doi.og/10.3390/horticulturae7060012.

Koirala, S., Zhao, M., Agarwal, G., Stice, S., Gitaitis, R.., Kvitko, B., and Dutta, B. 2021. Identification of two novel pathovars of Pantoea stewartii subsp. indologenes affecting Allium sp. and millets. Phytopathology 111:1509-1519.

Mandal, S. and C.S. Cramer. 2021. Comparing visual and image analysis techniques to quantify Fusarium basal rot severity in mature onion bulbs. Horticulturae 7:156. https://doi.og/10.3390/horticulturae7060156.

Mandal, S. and C.S. Cramer. 2021. Improving Fusarium basal rot resistance of onion cultivars through artificial inoculation and selection of mature bulbs. Horticulturae 7:168. https://doi.og/10.3390/horticulturae7060168.

Mandal, S. and C.S. Cramer. 2021. Screening of USDA onion germplasm for Fusarium basal rot resistance. Horticulturae 7:174. https://doi.og/10.3390/horticulturae7060174.

Shin, G.Y., Smith, A., Coutinho, T.A., Dutta, B., Kvitko, B. 2022. Validation of species-specific PCR assays for the detection of Pantoea ananatis, P. agglomerans, P. allii and P. stewartii. Plant Disease (first look).

Stice, S., Shin, G.Y., Armas, S.D., Koirala, S., Galvan, G.A., Siri, M.I., Severns, P.M., Coutinho, T.A., Dutta, B., and Kvitko, B. 2021. The distribution of onion virulence gene clusters among Pantoea spp. Frontiers in Plant Science https://doi.org/10.3389/fmicb.2021.00184.

Stice, S., Thao, K.K., Khang, C.K., Baltrus, D.A., Dutta, B., and Kvitko, B.H. 2020. Thiosulfinate tolerance is virulence strategy for an atypical bacterial pathogen of onion. Current Biology 30: 1-11. 

Stumpf, S., Leach, L., Srinivasan, R., Coolong, T., Gitaitis, R., and Dutta, B. 2021. Foliar chemical protection against Pantoea ananatis in onion is negated by Thrips feeding.  Phytopathology 111: 258267. 

https://apsjournals.apsnet.org/doi/10.1094/PHYTO-05-20-0163-R

Tabassum, A., S.V. Ramesh, Y. Zhai, R. Iftikhar, C. Olaya, and H.R. Pappu (2021). Viruses without Borders: Global analysis of the population structure, haplotype distribution, and evolutionary pattern of Iris yellow spot virus (Family Tospoviridae, Genus Orthotospovirus). Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2021.633710

Woodhall, J. W., Harrington, M., Keith, S. Oropeza, A., Thornton, M. and B. K. Schroeder. 2020. First report of root rot caused by Pythium myriotylum of onion in Idaho.  Plant Disease 104:9, 2529, https://doi.org/10.1094/PDIS-05-19-0991-PDN

Woodhall, J. W., Harrington, M., Brown, L., Jensen, J. and K. Painter. 2022. Development of a Real-Time Loop-Mediated Isothermal Amplification Assay for Stromatinia cepivora in Response to an Outbreak in Northern Idaho. Plant Health Progress 23:1, 24-27.

Yannuzzi, I. M., E.A. Moretti and B.A. Nault. 2021. Comparison of bioassays used to determine onion thrips (Thysanoptera: Thripidae) susceptibility to spinetoram. J. Econ. Entomol. 114(5): 2236-2240.

Zhao, M., Kvitko, B.H., Gitaitis, R.D., and Dutta, B. 2021. Bacterial streak and bulb rot of onion. Plant Health Instructor  DOI: 10.1094/PHI-E​​-2021-0421-01​.

Zhao, M., Tyson, C., Chen, H.C., Paudel, S., Gitaitis, R., Kvitko, B., and Dutta. B. 2021. Pseudomonas allivorans sp. nov., a plant-pathogenic bacterium isolated from onion leaf in Georgia, USA. Systematic and Applied Microbiology 45 (1):126278. doi: 10.1016/j.syapm.2021.12627

Plant Disease Management Reports:

Belo, T., du Toit, L., Waters, T., Derie, M., and LaHue, G. 2021.  Effects of irrigation frequency and final irrigation timing on onion bacterial diseases in the Columbia Basin of Washington, 2020. PDMR 15:V109 https://doi.org/10.1094/PDMR15

du Toit, L.J., Derie, M.L., Gundersen, B., Waters, T.D., and Darner, J. 2021. Efficacy of bactericides for management of bacterial leaf blight and bulb rots in an onion crop in Pasco, WA, 2020. PDMR 15:V107.  https://doi.org/10.1094/PDMR15

du Toit, L.J., Derie, M. L., and Gundersen, B. 2021. Efficacy of disinfectants applied to onion bulbs in storage for control of bacterial bulb rots, Pasco, WA, 2020-2021. PDMR 15:V102. https://doi.org/10.1094/PDMR15

du Toit, L.J., Derie, M. L., and Gundersen, B. 2021. Efficacy of late-season cultural practices on bacterial leaf blight and bulb rots in an onion bulb crop in Pasco, WA, 2020. PDMR 15:V100. https://doi.org/10.1094/PDMR15

du Toit, L.J., M. L. Derie, B. Gundersen. 2021. Efficacy of disinfectants applied to onion bulbs in storage for control of bacterial bulb rots, Pasco, WA, 2020-2021. PDMR 15.V102.

Dutta, B., and Tyson, C. 2021. Evaluation of harvesting methods on post-harvest incidence of center rot and sour skin in onion, Georgia 2020. PDMR 15:V025.

Dutta, B., and Tyson, C. 2021. Evaluation of digging methods on post-harvest incidence of center rot and sour skin in onion, Georgia 2020. PDMR 15:V026.

Dutta, B. 2021. Evaluation of individual fungicides for downy mildew control in cucumber in Tift County, Georgia, 2020. PDMR 15:V021.

Dutta, B., Tyson, C., Edenfield, J., Williams, Z., Tanner, S., Shirley, A., Reeves, B., and Powell, S. 2021. Evaluation of onion growth stage directed chemical applications and thrips management program on center rot incidence in onion bulbs in Georgia, 2020. PDMR 15:V023.

Dutta, B., Foster, M. J. and Donahoo, W.M. 2021. Evaluation of fungicides to manage Botrytis leaf blight in Georgia, 2020. PDMR 14:V024.

Dutta, B., and Foster, M. J. 2021. Evaluation of bactericides and plant defense inducers to manage center rot of onion in Georgia, 2020. PDMR 15:V027.

Dutta, B., Foster, M. J. and Donahoo, W.M. 2020. Evaluation of fungicides to manage Botrytis leaf blight in onion in Georgia, 2019. PDMR 14:V129.

Hoepting, C.A., Caldwell, S.K., and van der Heide, E.V. 2021. Efficacy of fungicide treatments for control of Botrytis Leaf Blight and Stemphylium leaf blight in onion, Elba, 2020. Plant Disease Management Reports 15: V162.

Hoepting, C.A., Caldwell, S.K., and van der Heide, E.V. 2021. Effect of fungicide application timing on control of Botrytis leaf blight and Stemphylium leaf blight in onion, 2020. Plant Disease Management Reports 15: V163.

Hoepting, C.A., Caldwell, S.K., and van der Heide, E.V. 2021. Efficacy of fungicide treatments for control of Botrytis Leaf Blight and Stemphylium leaf blight in onion, Oswego, 2020. Plant Disease Management Reports 15: V123.

Hoepting, C.A., Caldwell, S.K., and van der Heide, E.V. 2021. Efficacy of fungicide treatments for control of Stemphylium leaf blight in onion, Elba, 2020. Plant Disease Management Reports 15: V155.

Hoepting, C.A., Caldwell, S.K., and van der Heide, E.V. 2021. Efficacy of fungicide combinations for control of Stemphylium leaf blight in onion, Elba, 2020. Plant Disease Management Reports 15: V156.

Hua, K., and Dung, J.K.S.. 2021. Comparison of fungicides for control of white rot on garlic in Oregon, 2019-2020. PDMR 15:V032.

Other Activities

1. Abstracts and Papers at International Professional Meetings

Belo, T., du Toit, L., Waters, T., Derie, M., Schacht, B., & LaHue, G. (2021, 7-10 November). Combating Onion Bacterial Diseases Through Nitrogen Fertility Management [Poster Presentation]. 2021 ASA, CSSA, SSSA International Annual Meeting, Salt Lake City, UT.

MacKay et al. 2021. Combating onion bacterial diseases with pathogenomics tools and enhanced management strategies: Research objectives and preliminary results. Research on Demand presentation for American Phytopathological Society’s annual meeting, Plant Health 2021 Online, 2-6 August 2021.

2. Abstracts and Papers at National Professional Meetings

Heck, D.W., F.S. Hay, A. Klein, C. Sharma, C. Hoepting, and S.J. Pethybridge. 2021. Spatiotemporal dynamics of Stemphylium leaf blight in New York onion fields. APS NE and Potomac Division Meeting (virtual).

Heck, D.W., F.S. Hay, A. Klein, C. Sharma, C. Hoepting, and S.J. Pethybridge. 2021. Spatiotemporal dynamics of Stemphylium leaf blight in New York onion fields. APS Annual Meeting (virtual).

Lai, P.-C., L. Iglesias, and B.A. Nault. 2021. Optimizing onion Thrips management programs in organic onion production. Entomological Society of America Annual Meeting, Denver, CO, November 2, 2021.

Nault, B. A. 2021. Thrips ecology and management. In PIE Member Symposium: Four decades of adapting, advancing and transforming IPM: Honoring the career of Dr. Anthony Shelton. Entomological Society of America Annual Meeting, November 3, 2021, Denver, CO.

Nault, B. A. 2021. Impact of the Lorsban ban in onion in New York. In Symposium: The fate of chlorpyrifos in the US and beyond. Entomological Society of America Pacific Branch Meeting, April 7, 2021. Virtual.

Nourbakhsh, S.S. and C.S. Cramer. 2021. Evaluating onion breeding lines for thrips numbers and plant size when grown using water deficient conditions. HortScience 56: S106.

Qian, Y.P., Dung, J.K.S., Hua, G.K., and Qian, M. 2021.  Encapsulation of garlic oil and diallyl disulfide with β-cyclodextrin for garlic white rot control. American Chemical Society Spring 2021 Meeting. Poster presentation. April 5-30, 2021. Virtual.

Regan, K.H., and B.A. Nault. 2021. Less is more: Evaluating reduced applications of fertilizer and insecticide use for management of onion thrips (Thrips tabaci) on onion. Entomological Society of America Annual Meeting, Denver, CO, November 3, 2021.

Regan, K.H., and B.A. Nault. 2021. Less is more for onion management: Reducing inputs pays off in integrated pest management programs for onion thrips (Thrips tabaci). Entomological Society of America Eastern Branch Meeting, Virtual Format. March 2021.

3. Reports at Grower Meetings and Field Days

Chitturi, A., Feibert, E. B. G., Wieland, K. D., Reitz, S. 2021 Management of Onion Thrips with Threshold-Based Insecticide Applications and Reduced Nitrogen Fertility–2020 (pp. 170-181). Oregon State University https://agsci.oregonstate.edu/mes/station-complete-annual-reports/2020-annual-report.

Drost, D. 2020. Utah Onion Variety Report. Utah Onion Association meeting, Brigham City, UT

Feibert, E. B. G., Reitz, S., Wieland, K. D. 2021. 2020 Onion Variety Trials (pp. 39-61). Oregon State University https://agsci.oregonstate.edu/mes/station-complete-annual-reports/2020-annual-report.

Gugino, B.K. Vegetable pathology program update (included onion bacterial disease projects). Lehigh Valley Vegetable Meeting (webinar). 25 May 2021.

Gugino, B.K. Vegetable field walk (covered onion diseases). Juniata County Vegetable Twilight Meeting. Richfield, PA. 27 July 2021.

Gugino, B.K. Identification and management of common foliar and bulb diseases of onion. Keystone Family Farms Onion Meeting. Madisonburg, PA. 24 January 2022.

Gugino, B.K. Identification and management of common foliar and bulb diseases of onion. 2022 Mid-Atlantic Fruit and Vegetable Convention. Hershey, PA. 1 February 2022.

Hay, F., Heck, D., Hoepting, C., Klein, A., Pethybridge S.J. 2021. Stemphylium leaf blight – Current status of fungicide insensitivity.  Update for W3008 Multistate Project Annual Meeting, February 3, 2021 (by Zoom).

Hoepting, C.A.  2021.  Tour of on-farm Oswego onion fungicide trial, Oswego, NY: August 27, 2021 (11 participants).

Hoepting, C.A.  2021.  Tour of on-farm Elba onion fungicide trials, Elba, NY: August 24, 2021 (9 participants).

Hoepting, C.A.  2021. New onion fungicide recommendations for 2021.  Annual Oswego County Onion Growers Twilight Meeting, Oswego, NY: June 24, 2021 (51 participants).

Hoepting, C.A.  2021. New onion fungicide recommendations for 2021.  Elba Muck Donut Hour, Elba, NY: June 22, 2021 (8 participants).

Hua, K., and Dung, J. 2021. Comparison of Fungicides for Control of White Rot on Garlic in Oregon, 2019-2020. Central Oregon Agricultural Research and Extension Center 2020 Annual Report:17-18. https://agsci.oregonstate.edu/sites/agscid7/files/assets/coarec_annual_report_2020_updated.pdf

Hua, K. and Dung, J. 2021. Use of Alliums as Trap Crops to Reduce White Rot Inoculum in Infested Soils. Central Oregon Agricultural Research and Extension Center 2020 Annual Report:19-20. https://agsci.oregonstate.edu/sites/agscid7/files/assets/coarec_annual_report_2020_updated.pdf

Nault, B.A. 2021. Onion Thrips update and maggot control in a world without Lorsban. Great Lakes Fruit, Vegetable and Farm Market EXPO. Grand Rapids, MI. December 8, 2021. Virtual Speaker, 45 min.

Nault, B.A. 2021. Onion maggot management in the Great Lakes region. Agriculture and Agri-Food Canada’s Pesticide Reduced Risk Webinar for Root Pests of Carrot and Onion. (Ontario, Canada). Virtual. November 30, 2021. Speaker, 25 min.

Nault, B.A. 2021. Update on management tactics for onion insect pests in New York. Sixty-ninth Annual Muck Vegetable Growers Conference (Ontario, Canada). Virtual. April 1, 2021. Speaker, 25 min.

Nault, B.A. 2021. New York vegetable entomology update. Syngenta’s North-Atlantic Innovation 2021 Meeting, March 16, 2021. Virtual. Speaker, 15 min.

Nault, B.A. 2021. Seedcorn maggot biology and management in vegetable crops with an emphasis on seed treatments. Oregon Processed Vegetable Commission Annual Grower Meeting. Virtual. January 25, 2021. Speaker, 40 min.

Nault, B.A. 2021. Past, current and future management of onion maggot using seed treatments. New York State Report for the W-4168 Multistate Annual Meeting, October 15, 2021. Geneva, NY. Speaker, 20 minutes.

Nischwitz, C. 2021. Stop the Rot: Update on Utah’s Survey and Field Trials. Utah Onion Association meeting, Brigham City, UT

Nischwitz, C. 2021. Utah’s Disease Survey and Field Trials. Onion Association Field Day, Ogden, UT

Regan, K. and B. Nault. 2021. Less is more: Reducing inputs pays off in muck onion systems. Cornell Cooperative Extension Presentation, Elba Muck Donut Hour, Elba, NY. 10 August 2021. Co-author, 20 minutes.

Reitz, S. 2021 Monitoring Onion Pests across the Treasure Valley–2020 (pp. 138-144). Oregon State University https://agsci.oregonstate.edu/mes/station-complete-annual-reports/2020-annual-report.

Reitz, S., Feibert, E. B. G., Wieland, K. D. 2021 Effects of Irrigation and Nitrogen Fertility Management on Bulb Rots in Onion–2020 (pp. 158-169). Oregon State University https://agsci.oregonstate.edu/mes/station-complete-annual-reports/2020-annual-report.

Reitz, S., Wieland, K. D., Feibert, E. B. G. 2021 Management of Bacterial Bulb Rots in Onion–2020 (pp. 145-152). Oregon State University https://agsci.oregonstate.edu/mes/station-complete-annual-reports/2020-annual-report.

Schroeder, B. K. 2021. Bacterial Diseases of Onions. Idaho and Eastern Oregon Crop Protection Meeting. Virtual Feb. 2, 2021. 

Schroeder, B. K., Sankaran, S., and Khot, L. FAIMS (Field asymmetric ion mobility spectrometry) Detection of Bulb

Rot Pathogens in Storage. Idaho and Malheur County Onion Growers’ Association 60^th Annual Meeting. Feb. 4, 2020. 

Thornton, M. 2021. Soil-borne diseases. Idaho and Eastern Oregon Onion Crop Protection Meeting, virtual, February 2, 2021.

Thornton, M., N. Olsen, R. Hendricks and L. Woodell. 2021. Pre-harvest bruise factors. AgriNorthwest Agronomy Team Meeting, virtual, February 3, 2021.

Thornton, M. 2021. Pink root and single centers in onions. AgriNorthwest Agronomy Team Meeting, virtual, February 3, 2021.

Thornton, M., R. Portenier, O. Morgan, K. Beck and B. Simerly.  2021.  Long term storage of onion cultivars.   Proc. of the Idaho/Malheur County Onion Growers Meeting. 4pp.

Thornton, M., J. Woodhall, R. Portenier, K. Beck and O. Morgan.  2021.  Pink root control in onions with drip-applied fungicides.   Proc. of the Idaho/Malheur County Onion Growers Meeting. 6pp.

Woodhall, J. Onion disease update, featuring bacterial diseases. 2021. Idaho-Malheur Co. Onion Growers Meeting, Nampa. February 1, 2022

Woodhall J. Stemphylium leaf blight: a re-emerging disease of onions?  U of I, EPPN departmental seminar. 12th April 2021.

Woodhall J. Stop the Rot: Diagnostic and Survey Results. PNW Vegetable Association meeting 2021. 17th November. Kennewick.

Woodhall J. Use of Models and Trapping in Pest Management. PNW Vegetable Association meeting 2021. 18th November. Kennewick.

Woodhall J. Foliar diseases of onion in the Treasure Valley. Onion Crop Protection Meeting. Virtual. February 2nd 2021

4. Newsletter Articles

Cramer, C.S. and I. Guzman. 2021. Breeding for resistance to Iris yellow spot. Onion World. July/August, pp. 10-13.

Drost, D. 2020. Bouncing Back. Onion World Vol. 36(4):6-7. https://onionworld.net/magazine/

Drost, D. 2021. Utah Growers Zoom in on Latest Research. Onion World Vol. 37(4):6-7. https://onionworld.net/magazine/

Drost, D. 2021. Utah State Heads to the Shed and On to Outside. Onion World Vol. 37(7):30-31. https://onionworld.net/magazine/

du Toit, L.J., Waters, T., Derie, M., and Darner, J. 2020. Battling onion bacterial diseases with bactericides. Onion World, December 2020:6-11. https://issuu.com/columbiamediagroup/docs/onion_world_december_2020.

du Toit, L., and Waters, T. 2021. To disinfect or not? Can postharvest applications of disinfectants reduce bacterial bulb rots in storage? Onion World, July/August 2021:6-9. Onion World Magazine July/August 2021

Dutta, B., Grey, T., and Schmidt, J. 2022. Neglecting weeds can lead to late-season disease in organic onions. Specialty Crop News. March 2022.

Dutta, B., DevKumar, G., Kvitko, B.H., and Naikare, H. 2021. Studying Salmonella contamination in onion. Vegetable and Specialty Crop News, August 2021.

Dutta, B. 2021. Onion disease management in Georgia. Vegetable and Specialty Crop News, February 2021.

Dutta, B and Gitaitis, R.D. 2020. Disease quiz II. Onion World Magazine. January 2021.

Dutta, B and Gitaitis, R.D. 2020. Disease quiz I. Onion World Magazine. July 2020.

Gugino, B.K., K. Demchak, and S. Fleischer. 2021 PA Vegetable and Berry Production: Current issues: June 10. Online: https://extension.psu.edu/2021-current-issues-for-pa-vegetable-and-berry-crops-june-10

Gugino, B.K. 2021 Pennsylvania Vegetable Disease Update: June 23 Online: https://extension.psu.edu/2021-pennsylvania-vegetable-disease-update-june-23 

Gugino, B.K., K. Demchak, and S. Fleischer. 2021 PA Vegetable and Berry Production: Current issues: July 6. Online: https://extension.psu.edu/2021-pa-vegetable-and-berry-current-issues-july-6

Gugino, B.K. 2021 Pennsylvania Vegetable Disease Update: July 14 Online: https://extension.psu.edu/2021-pennsylvania-vegetable-disease-update-july-14

Hoepting, C.A.  2021.  2021 Cornell Onion (Dry Bulb) Fungicide Cheat Sheet for Control of Leaf Diseases.  Cornell Cooperative Extension Cornell Vegetable Program. Website: https://rvpadmin.cce.cornell.edu/uploads/doc_982.pdf

Hoepting, C.A.  2021.  Example Onion Fungicide Spray Program for Control of Leaf Diseases in Onion, 2021.  Cornell Cooperative Extension Cornell Vegetable Program. Website: https://rvpadmin.cce.cornell.edu/uploads/doc_984.pdf

Hua, G.H.H. and Dung, J.. 2020. Here Today, Gone Tomorrow: Can Early Terminated Onion Trap Crops Reduce White Rot Infestations? Onion World (November 2020):32-33.

Lameiras, M.M. 2020. UGA researchers discover genes that allow bacteria to resist onion’s natural defenses. CAES News and Events, July 2020.

Mazzone, J.D. and B.K. Gugino. 2021. What have we learned from two decades of onion cultivar research at Penn State? Online: https://extension.psu.edu/what-have-we-learned-from-two-decades-of-onion-cultivar-research-at-penn-state.

Nischwitz, C. 2021. Bacterial Bulb Rot Diseases in Utah. Utah Pests Quarterly. Spring edition. Vol. 15: 11 and 15. (https://extension.usu.edu/pests/files/up-newsletter/2021/UtahPestsNews-spring21.pdf )

Robinson, A. 2020. Fungicide Update for Vegetable Crops. Vegetable and Specialty Crop News, March 2020.

Thompson, C. 2020. Organic Vidalia Onion Industry: Challenges in sour skin management. Onion World Magazine. December 2020.

Thompson, C. 2020. Vidalia onion crop looks ‘favorable’ despite presence of downy mildew disease in localized areas. Vegetable and Specialty Crop  News, April 2020. (edits provided by B. Dutta)

Woodhall JW, Murdock M, Beck K, Thornton . Pink root of onion. University of Idaho Extension press. BUL 1000.

5. Annual Reports

LaHue, G.T., Waters, T., and du Toit, L., 2020. Revisiting nitrogen management recommendations in the context of onion bacterial diseases. Progress report Columbia Basin Onion Research Committee. Submitted 31 October 2020.

6. Internet Resources

Wohleb, C.H., Waters, T.W., du Toit, L.J., and LaHue, G. 2021. Washington State University Extension Onion Alert, 1 September 2021. https://mailchi.mp/wsu/wsu-onion-alert-sept1-2021-1305808?e=72ba613792 

du Toit, Lindsey, MacKay, Heather, Kilgore, Darrell, and Ziegler, Matthew. Combating bacterial diseases of onion: How do we stop the rot? 14.41 min. Posted Dec. 15, 2020. https://youtu.be/VLpZqCrQuPw