W4008: Integrated Onion Pest, Disease and Weed Management

(Multistate Research Project)

Status: Active

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SAES-422 Reports

Annual/Termination Reports:

[02/24/2023]

Date of Annual Report: 02/24/2023

Report Information

Annual Meeting Dates: 01/05/2023 - 01/05/2023
Period the Report Covers: 03/01/2022 - 01/05/2023

Participants

Participants Attachment:

W4008 Final Report (2022) Rev 1 02-23-23.pdf

Brief Summary of Minutes

Minutes Attachment:

W4008 Final Report (2022) Rev 1 02-23-23.pdf

Accomplishments

Objective 1. Evaluate onion germplasm for resistance to pathogens and insects.   Georgia: Screened 52 Vidalia cultivars under field conditions for bacterial foliar symptoms and bulbs were screened for the ability of P. ananatis 97-1 strain to induce necrotic lesion on scales. Six varieties (Georgia Boy, Rio Dulce, Emy 55843, Alba Blanca, White Gaspare and Maragogi) displayed significantly lower necrotic lesions compared to others.   California: Analysis of data from Kern variety trial and lab-based assays (bulb assay and scale assay on bulbs from variety trials) is underway.  Preliminary results are that the lab-based assays are not well correlated with the field trial results.   Idaho: In fall of 2021, bulbs of 12 yellow cultivars and pre‐ commercial lines were collected and stored (36°F). On 24 June 2022, samples were evaluated for defects. Only two entries (Crockett and NUN 7212) reached >80% marketable bulbs after 9 months of storage. With few exceptions, translucent scale was the primary defect in bulbs not considered marketable, while internal decay was the second most common defect. Oloroso and Seminis 1526 showed very high levels of translucent scale, while OLX 13-331 and Trident had the highest incidence of internal decay. Vaquero, the industry standard, had ~70% marketable bulbs, below the long‐term average for this cultivar.   Trials at Malheur Agricultural Experiment Station, Oregon State University during 2022, assessed the susceptibility of 16 varieties (12 yellow, four red) to Setophoma terrestris, the causal agent of pink root.  Ten plants were pulled from the discard rows from four replicated plots on two separate dates, roots were washed and percentage infection was visually assessed.  Among the yellow varieties, Legend, Trident and Caldwell appeared among the most susceptible to pink root whilst Sedona and Calliber were the least susceptible. Purple haze was least susceptible of the red onion varieties.    New York: A variety trial conducted in Elba, NY investigated the relative susceptibility of 16 onion varieties to onion thrips, bacterial bulb rot, pink root and Stemphylium leaf blight. The trial was arranged as a split-plot design with variety as the main factor and insecticide treatment as the sub-plot factor. Treatments were replicated 4 times. Data were also collected on leaf color, upright plant architecture, vigor, neck diameter, maturity and yield. Grading was completed in early January 2023 and data analysis is pending.  The trial will be repeated in 2023.   New Mexico: NMSU breeding lines exhibited a lower Fusarium basal rot (FBR) incidence and severity than a FBR-susceptible and a FBR-resistant cultivar, indicating breeding efforts to be successful. When exposed to high onion thrips pressure conditions conducive for Iris yellow spot (IYS) disease development, other NMSU breeding lines exhibited fewer thrips per plant and a lower disease severity early in the growing season, and greater bulb size at harvest than a commercial cultivar grown under the same conditions.   Washington: Bulbs from the 2021 Washington State University Onion Cultivar Trial were evaluated in Feb. 2022 after 5 months in storage, for quality and bulb rots. Results were summarized and shared with onion stakeholders on the WSU Onion Alerts (>600 subscribers), demonstrating how >50 cultivars fared under Columbia Basin conditions. The 2022 Washington State University Onion Cultivar Trial was planted in April 2022 near Quincy, WA, with three replicate plots of each of 54 cultivars submitted by seed companies. Plots were evaluated for diseases and pests. Bulbs were harvested in September to assess yield, and 50 bulbs/plot placed in storage to evaluate storage quality and bulb rots in Feb. 2023. The WSU Onion Field Day was held on Aug. 25, the first in-person field day since 2019 (>100 attendees).   Objective 2. Investigate the biology, ecology and management of onion insect pests.   California: Several treatments provided effective control of seedcorn maggot in field trials evaluating insecticide seed treatment efficacy for spring seed onions.    Oregon: Threshold-based sampling plans reduced insecticide applications for thrips and IYSV and input costs without reducing yields. Further trials demonstrated that tank-mixing of most insecticides does not improve thrips management and is not cost effective.   Idaho: 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 experimental insecticides from Gowan (GWN‐12030 and GXP-60513) applied via the drip irrigation system. All insecticide programs reduced thrips populations and IYSV incidence compared to the untreated, and some drip programs were equal in efficacy to the standard foliar program. The total yield and the proportion of ≥3‐inch diameter onions were also increased by insecticide programs.   New York: Syngenta’s new insecticide, isocycloseram (PLINAZOLIN® technology), was evaluated for managing onion thrips as a foliar spray. Several foliar applications of a high rate of isocycloseram provided a commercially acceptable and equivalent level of control as high rate of cyantraniliprole (Exirel), and both provided better control than a high rate of spinetoram (Radiant SC).  Isocycloseram alone and in combination with thiamethoxam (Cruiser 5FS) were evaluated as an onion seed treatment for onion maggot control. Results in 2022 showed that a high rate of isocycloseram provided a similar and excellent level of maggot control as the two standards, FarMore FI500 with Regard SC and FarMore FI500 with Trigard. Field studies in 2022 identified cyclaniliprole (Harvanta 50SL) and flupydifurone (Sivanto Prime) as effective in reducing onion thrips infestations in green onion. Future registrations for these products are being explored on onion for thrips control. Field research in 2022 documented a new formulation of spinosad (Lumiverd) that can be used as an onion seed treatment for maggot control. Results were used to assist Corteva, in getting Lumiverd registered as a seed treatment on onion for the 2023 field season.   Washington: Insecticide efficacy trials in 2022 evaluated control options for onion thrips (Thrips tabaci). One trial featured new unregistered insecticides, one of which was nearly as efficacious as Radiant (spinetoram), currently the most effective insecticide available to onion producers in WA. Another trial evaluated insecticides currently registered for use on onions but that are not used to manage onion thrips, but none proved effective compared to currently used products.   In trials assessing control of Seedcorn maggot, all insecticide treatments improved stands numerically compared to non-treated, but not all treatments improved stands statistically. Diazinon applied pre-planting, Diazinon applied post-planting, and Capture LFR were the most effective. They did not differ significantly from one another but caused significantly better stands than the non-treated check plots. Seedcorn maggot pressure was high in the trial, with only 58% stand in the non-treated. The best treatment resulted in 80% stands. Plots treated with Regard only had 68% plant stands, which is not acceptable commercially. FarMore FI500 and Capture LFR treatments resulted in acceptable stands of 72 and 74% respectively.  Under the significant pest pressure, there was evidence that Diazinon, Farmore FI500, and Capture LFR can be used to reduce seedcorn maggot pressure and achieve adequate plant stands.   Objective 3. Investigate the biology, epidemiology and management of onion plant pathogens.   Pennsylvania:  As part of the Stop the Rot SCRI project, during 2022 a third year of field sampling was conducted to identify bacteria associated with symptomatic onion foliage and bulbs. Ten whole onion plant samples were collected from each of five fields in PA and in NY at two times during the season. From each plant, isolations were made onto nutrient agar and up to three unique bacterial colonies were selected. Approximately 153 bacterial isolates were collected from PA and 77 from NY under an APHIS 526 permit and stored (-80C). The post-harvest samples are currently being processed. The majority of isolates were non-pathogenic based on the red scale necrosis assay and all are in the process of being identified to genus.   A bactericide efficacy trial was repeated in 2022 but disease pressure was variable despite multiple inoculations. There were no significant differences in total marketable bulb weight although numerically, the non-inoculated, untreated control was the highest and the inoculated untreated control was near the lowest (P=0.136). The percent of bulbs with bacterial rot symptoms at harvest (interior and exterior) was numerically highest in the copper treated plots and lowest in the plots treated with LifeGard or the non-inoculated, untreated control plots (P=0.670).   A nitrogen rate and timing trial with four nitrogen rates (0, 50, 105, and 160 lb/A) at two timings (half and full season) was repeated to evaluate the effect on center rot disease incidence and marketable yield. Although there was a significant rep effect, the percent of plants with foliar symptoms of center rot was significantly higher in the treatments with higher rates of nitrogen (P=0.003) and also numerically higher for symptomatic bulbs at harvest. Total marketable bulb weight was significantly higher in plots that received nitrogen (P=0.001) compared to the no nitrogen control. Nitrogen application timing and inoculation status (inoculated vs non-inoculated) did not significantly affect disease incidence or marketable weight.   Georgia: The efficacy of fungicides to manage Botrytis leaf blight (BLB) on onion was evaluated in Georgia. Four rows of ‘Vidora’ onion were transplanted into 6-ft beds (panels) on 10 Dec (2020) at the Vidalia Onion and Vegetable Research Center, Lyons, GA.  Natural inoculum was relied upon. Disease severity was assessed on 22 Mar, 4 Apr, and 20 Apr as percent leaf area with symptoms per plot. Area under disease progress curve (AUDPC) was calculated using disease severity ratings from the four assessment periods.   BLB symptoms first appeared on 22 Mar with significantly higher disease severity for the non-treated check (63.8%) and Scala (55.0%) than for the other fungicide-treated plots, with no significant differences among other treatments. Disease progressed over a four-week period and reached 88.8% (disease severity) on 20 Apr, in non-treated plots and Scala-fungicide treated (81.3%) plots, which were significantly higher than the other fungicide-treated plots. Non-treated check and Scala-fungicide treated plots had significantly higher AUDPC compared with the fungicide treatments. Phytotoxicity was not observed with any treatment.   An evaluation of the effect of N-fertility on bacterial internal rot in onion was conduted. There was no observable difference in percent bulb incidence in field or in storage for any of the N-fertility and timing of the final N application. Different copper products and biological control products were evaluated under field conditions. Multiple bactericide programs were evaluated with LifeGard. Foliar symptoms were not observed; however, bulb incidence of internal rot after 30-days of storage differed significantly. Bactericides (Nu Cop, Mankocide, Nordox, Champ) along with LifeGard significantly reduced internal bulb rot compared to non-treated check. Cultural practices to reduce bacterial internal rot in onion were evaluated.  Based on the multiple assessments, onion clipping length (2 cm or longer) resulted in significantly reduced internal bulb rot compared to the shorter neck length.   Utah: Laboratory studies were conducted to determine if temperature could influence outbreaks of Fusarium bulb rot. Fusarium proliferatum grew best between 25-30C. A field trial was conducted to determine the effect of cultural and chemical practices used in Utah onion production. Fungicides showed very little to no effect on the disease. There was a 10% reduction in bulb rot when onions were topped with a 3-in neck vs 1.5-in neck.   California:  Pathogen screening for bacterial diseases affecting CA fresh market and dehydration onions was undertaken in seven counties. Pathogens isolated included: Pantoea agglomerans, Burkholderia cepacia, Burkholderia gladioli, and Pectobacterium carotovorum.  Bactericides for management of bacterial diseases was studied in Kern and San Joaquin counties.  Preliminary conclusion based on just a single successful trial is that the bactericides are not effective for bacterial disease control in CA.  An irrigation study at the Intermountain REC in Tulelake evaluated the influence of sprinkler irrigation and drip irrigation on bacterial diseases.  A significant decrease in bacterial disease incidence and severity was observed when onions were grown under drip compared to sprinkler irrigation in 2021 and 2022. Two studies in Southern California evaluated weather-based models for management of onion downy mildew. Fewer treatments were made in the model treatments compared to the standard calendar and no disease was observed in the study areas, indicating the potential to forgo applications when disease pressure is low.   Oregon: Over irrigation and excess N-fertilization increase the incidence of fungal neck rot. Optimizing irrigation and fertility through soil moisture monitoring, and plant and soil nutrient testing can reduce risks for bulb rots.   The application of dry formulations of encapsulated DADS and garlic oil resulted in a 74% and 75% reduction in white rot sclerotia populations, respectively, compared to the non-treated control in naturally infested soils. Encapsulated DADS and garlic oil is easier to handle and apply than traditional liquid formulations, which could promote the adoption of sclerotial germination stimulants in a white rot IPM program.    Idaho: 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.  None of the fungicide programs significantly reduced disease incidence and severity in July and August compared to the untreated.  Additional trials with biological based programs (Symborg) and fall solarization treatments also failed to show any reduction in pink root compared to the untreated.  The second half of the 2022 growing season was exceptionally hot and 100% of the roots showed disease symptoms by early August.   Studies were completed in which onion bulbs were inoculated with Rahnella spp. and incubated  at 25°C (77°F), 30°C (86°F) or 35°C (95°F) and evaluated for bulb rot at 3, 5, or 8 weeks.  Bulb rot increased over time, resulting in up to 60% of the bulb being impacted by 8 weeks post inoculation. Incubation at 30°C (86°F) after inoculation with Rahnella spp. resulted in only 36% bulb rot.  A second assay incubated the onion bulbs for 2 days or 2 weeks after inoculation with Rahnella spp. followed by storage at 5C (41F) and evaluated bulbs for rot at 4 and 6 months.  Bulbs incubated at 30C for 2 days or 2 weeks resulted in 35% bulb rot compared to 60-70% when incubated at 25°C (77°F) or 35°C (95°F).  This demonstrates that temperature can significantly impact disease development.    The level Stemphylium vesicarium spores were monitored over the spring/summer from 2019 to 2022 in an effort to inform fungicide timing and understand the relationship of the pathogen with environmental conditions. A Burkard Multivial Cyclone spore trap was situated on Field block D at Parma and operated continuously over 24-hour periods. DNA was extracted from the spore trap samples and DNA of S. vesicarium was quantified using real-time PCR. DNA was recovered in all four years. In 2019 there was relatively low-level detection before mid-July which coincided with the observation of symptoms in late summer. In 2020, which was arguably when the most severe outbreaks of Stemphylium were observed in the Treasure Valley, relatively high levels of Stemphylium spores were detected throughout June and again from mid-August. Fewer spores were detected from mid-August in 2021 which coincided with arguably less disease observed that year.   Colorado: Bactericidal products were evaluated for the management of onion bacterial rots in inoculated field trials.  In addition, we evaluated three post-harvest fogging treatments to assess their effectiveness in managing internal rot of stored onion bulbs.  Bulbs will be cut and bulb rots quantified in February of 2023.   New York: In New York, three field trials were conducted in commercial onion fields to evaluate efficacy of fungicides for control of Botrytis leaf blight and Stemphylium leaf blight (SLB), in Elba (2 trials) and Oswego, NY (Hoepting). Each trial was arranged as a randomized complete block design with 24 treatments and 4 replications. Fungicide sprays began in mid-June and continued weekly for 8-9 weeks until mid- to late-August. Trials investigated the efficacy and development of fungicide resistance to FRAC 3 active ingredients when applied alone, in tank mixes with other FRAC group fungicides and in rotation with other FRAC group fungicides. A few novel products were trialed to identify another FRAC group with activity on SLB including Oso (FRAC 19), as well as several tank mixes and premixes. Data analysis is pending.   Control of Stemphylium leaf blight (SLB) in NY is difficult because S. vesicarium has developed resistance to fungicides within the FRAC 2, 7, 9 and 11 groups. Currently the most effective fungicides are in FRAC 3. However, there is also concern of resistance development in this group. Isolates of S. vesicarium collected from diseased onion fields in four regions of NY in 2020 (n=114) and 2021 (n=81) were tested for fungicide sensitivity to three FRAC 3 active ingredients (a.i.). Results suggest insensitivity is developing to all three a.i’s but is developing more slowly to difenoconazole than to tebuconazole, with propiconazole intermediate between these. Some regional differences were also apparent. Results will be used to inform changes in fungicide programs to maintain disease control and slow the development of resistance. Other studies determined that transplants from interstate were a source of SLB, but that seed was not. The disease forecaster BSPcast was tested in a field trial but was found to be a poor predictor of disease.   Field studies showed that supplemental foliar applications of insecticides sprayed early in the season targeting adult onion thrips in an attempt to reduce transmission of IYSV were not effective. Levels of IYSV at the end of the season were similar between onion fields that received the supplemental sprays (5% incidence) and those that did not (9% incidence). However, final levels of IYSV were low.   This study will be repeated in 2023.   Another field study showed that IYSV levels were similar between transplanted and direct-seeded fields early in the season, indicating that transplanted fields should not be considered the only major source of early-season IYSV epidemics. Rather, adult onion thrips that are viruliferous may be overwintering in New York and colonize onion fields early in the season. There is some evidence that thrips may prefer to initially colonize onion fields that have the largest plants in the vicinity, often those with an early planting date.   Texas:. A total of 218 bacterial strain samples from Texas (n=208) and New Mexico (n=10) were isolated from onion and identified using 16S rRNA in 2022, encompassing 34 bacterial genera. On the red scale assay, 97.2% of bacteria were non-pathogenic. Out of the 218 samples, the predominant genus was Pantoea (56), Pseudomonas (27), Enterobacter (22), and Bacillus (20). The survey identified a novel bacterial species - Curtobacterium allii.   Washington: As part of the ‘Stop the Rot’ USDA NIFA SCRI Project No. 2019-51181-30013, we continued the 3-season, 11-state survey across the USA to determine the diversity and prevalence of bacteria associated with onion diseases. Five onion bulb crops were surveyed across the Columbia Basin in Jul – Sep. 2022. Isolations from 75 plant samples with symptoms of bacterial infection resulted in 84 bacterial isolates.  Isolates are being identified to genus and species with 16S rDNA sequencing, and all isolates are being tested for pathogenicity . This will complete 3 seasons of survey in WA. We are also completing sequencing and foliar and bulb pathogenicity tests for 33 isolates obtained from symptomatic onion bulb crops in CA that were surveyed by Brenna Aegerter at UC-ANR. Strains of bacteria from Seasons 1 and 2 were submitted to the National Onion Bacterial Strain Collection at the Univ. of Georgia. In addition, soil, plant, and water samples were collected in some fields surveyed in WA in 2022, and sent to James Woodhall, Univ. of Idaho, for testing with real-time PCR assays being developed to detect pathogenic strains of Pantoea.   Six field trials were carried out in 2022 on management of onion bacterial diseases evaluating: 1) cultivar susceptibility, 2) chemigation vs. spray boom application of 3 bactericides, 3) timing of rolling tops, 4) timing of topping bulbs, 5) timing of undercutting bulbs, and 6) postharvest application of disinfectants. These trials were repeats of the 2021-22 trials. Bulbs were harvested in Aug.-Sep., placed in storage, and will be cut and rated in Feb. 2023. Results of the Season 2 (2021-22) trials for these same objectives demonstrated: 1) there was more bacterial leaf blight in inoculated plots of earlier maturing cultivars, with ~50% bulb rot for cultivars in maturity groups 1 and 2, 34.5% for those in maturity group 4, and 18.5% for those in maturity group 3; 2) Five weekly, preventative applications of Badge SC, ManKocide, or Lifegard WG did not control bacterial leaf blight or bulb rot, and there was no effect of the herbicide Outlook on leaf blight or bulb rot; 3) rolling tops increased leaf blight but not bulb yield or bulb rot; 4) early topping increased bacterial bulb rot compared to normal or late topping; 5) timing of undercutting did not affect bacterial leaf blight, yield, or bulb rot; and 6) none of four disinfectant treatments reduced bacterial bulb rot, as observed the year prior. We are continuing to develop a risk assessment model for onion bacterial diseases in the Pacific Northwest, using results from the 3 seasons of field trials, and we will invite growers to test the risk model in 2023.   Objective 4. Investigate the biology, epidemiology and management of weedy plant species that impact onion production.   Utah: Claudia Nischwitz presented information on Fusarium bulb rot and Dan Drost gave a presentation on Seed priming and plant population responses at the Utah Onion Association meeting February 8, 2022 attended by 28 people.. On August 9, 2022, Dan Drost held a field day demonstrating his onion variety trial and introduced the new irrigation specialist, attended by 36 people.   New York: In New York, a pre-emergent herbicide trial was conducted in a commercial onion field in Elba, arranged as a randomized complete block design with 18 treatments and 4 replications. The objective of this trial was to optimize weed control and crop safety.  It compared a one-step to a two-step barley-kill herbicide program, heavy vs. light rates of pre-emergent herbicides up until barley-kill, different timings of multiple applications of Outlook and Prowl, and incorporation of bicyclopyrone into the onion herbicide program. Data were collected on onion stand, visual crop injury, stunting and vigor, as well as on weed control by species. Data analysis is pending. New Mexico: A post planting, delayed preemergence application of pendimethalin resulted in similar or better control of annual weeds than current weed control methods using Bensulide and DCPA herbicides or pendimethalin applied at the 2-leaf stage for autumn-sown and winter-sown onions in New Mexico. This same application of pendimethalin did not impact onion stand and bulb yield and did not leave detectable residues on onion bulbs after harvest.

Publications

Belo, T., LaHue, G., and du Toit, L.J. 2023. Reducing the risk of onion bacterial diseases through irrigation, fertility, and other cultural management strategies. Agronomy Journal: accepted. doi: 10.1002/agj2.21301.   du Toit, L.J., Derie, M.L., Gundersen, B., Waters, T.D., and Darner, J. 2022. Effects of bactericide and herbicide applications on bacterial leaf blight and bulb rot of onion, Pasco, WA, 2021-22. Plant Disease Management Reports 16:V150.   du Toit, L.J., Derie, M.L., Gundersen, B., Waters, T.D., and Darner, J. 2022. Effects of late-season cultural practices on bacterial leaf blight and bulb rot in an onion crop, Pasco, WA, 2021-22. Plant Disease Management Reports 16:V149.   du Toit, L.J., Derie, M.L., Gundersen, B., Waters, T.D., and Darner, J. 2022. Efficacy of disinfectants applied to onion bulbs in storage for control of bacterial bulb rots, Pasco, WA, 2021-22. Plant Disease Management Reports 16:V148.   du Toit, L.J., Derie, M.L., Gundersen, B., Waters, T.D., and Darner, J. 2022. Susceptibility of 12 onion cultivars to bacterial leaf blight and bulb rot in Pasco, WA, 2021-22. Plant Disease Management Reports 16:V151.   Dung, J.K.S. and Hua, K.. 2022. Comparison of fungicides for control of white rot on garlic in Oregon, 2020-2021. Plant Disease Management Reports 16:CF029. doi: 10.1094/PDMR16   Dutta, B., Foster, M.J., and Donahoo, W.M. 2022. Evaluation of fungicides to manage Botrytis leaf blight on onion in Georgia, 2021. PDMR 16:V043.   Dutta, B., Foster, M.J., and Donahoo, W.M. 2022. Evaluation of bactericides and plant defense inducers to manage internal bacterial rot of onion in Georgia, 2021. PDMR 16:V044.   Dutta, B., and Tyson, C. 2022. Evaluation of neck-clipping length on post-harvest incidence of external and internal bacterial bulb rot in onion, Georgia, 2021. PDMR 16:V107.   Dutta, B., and Tyson, C. 2022. Evaluation of harvesting methods on post-harvest incidence of external and internal bacterial bulb rot in onion, Georgia, 2021. PDMR 16:V108.   Dutta, B., and Tyson, C. 2022. Evaluation of digging methods on post-harvest incidence of external and internal bacterial bulb in onion, Georgia, 2021. PDMR 16:V109.   Feibert, E., C. Shock, S. Reitz, A. Rivera-Ramires, and K. Wieland. 2022. Performance of Onion Cultivars in the Treasure Valley of Eastern Oregon and Southwestern Idaho in 2010—20. Hortechnology, 32:435-446   <h1>Hay, F.S. D.W. Heck, A. Klein and S. Sharma, C.A. Hoepting and S.J. Pethybridge.  2022.  Spaciotemporal dynamics of Stemphylium leaf blight and potential inoculum sources in New York onion fields.  Plant Disease, 106(5): 1381-1391.</h1>   Hay, F.S., D.W. Heck, S. Sharma, A. Klein, C.A. Hoepting and S.J. Pethybridge.  2022.  Stemphylium leaf blight of onion.  The Plant Health Instructor, 22: online: doi: 10.1094/PH-P-2022-01-0001.   Hay, F., A. Klein, S. Murphy, S., and B. Nault. 2022. Efficacy of OMRI-listed products for Stemphylium leaf blight control in onion in New York, 2018. Plant Disease Management Reports 16: V121.   Hay, F., A. Klein, S. Murphy, and B. Nault. 2022. Effect of OMRI-listed products for Stemphylium leaf blight control in onion in New York, 2019. Plant Disease Management Reports 16: V152.   Hoepting, C.A. 2022. Rolling onions to “Stop the Rot” (cover).  Veg Edge, 18(12): 1, 3.   Hoepting, C.A. 2022. Bactericides not effective for control of onion bulb rot in on-farm field trials in New York (cover).  Veg Edge, 18(17): 1, 3-4.   Hoepting, C.A. 2022. Primary vs. secondary Stemphylium leaf blight in onion.  Veg Edge, 18(16): 5-6.   Hoepting, C.A. 2022. Scouting tips for onion thrips in onion.  Veg Edge, 18(13): 9.   Hoepting, C.A. and F.S. Hay. 2022. 2021 fungicide research highlights for Stemphylium leaf blight in onion – The fall of the FRAC 3s and keeping onions green despite poor SLB control.  Veg Edge, 18(13): 3-5.   Hoepting, C.A. 2022. Slim pickings for fungicides to control Stemphylium leaf blight of onion in 2022.  Veg Edge, 18(12): 4-5.   Hoepting, C.A. 2022. Best fungicide options for control of Botrytis leaf blight in onion: It depends on what kind of spot you got.  Veg Edge, 18(11): 4-6.   Hoepting, C.A. 2022. Effective post-emergent weed control in onion: Knocking back and knocking out (cover).  Veg Edge, 18(8): 6-9.   Hoepting, C.A. 2022. The weed race – Trial notes on spraying small onions with post-emergent herbicides.  Veg Edge, 18(7): 6-7.   Hoepting, C.A. 2022. Onion updates and killing of barley nurse crop.  Veg Edge, 18(6): 6.   Hoepting, C.A., S.K. Caldwell and E.R. van der Heide.  2022.  Evaluation of cultural practices to reduce bacterial bulb rot in onions that are failing to lodge, 2021.  Plant Disease Management Reports 16: V167.   Hoepting, C.A., S.K. Caldwell and E.R. van der Heide.  2022.  Efficacy of fungicide products for control of Botrytis leaf blight and Stemphylium leaf blight in onion in Oswego, 2021.  Plant Disease Management Reports 16: V140.   Hoepting, C.A., S.K. Caldwell and E.R. van der Heide.  2022.  Efficacy of FRAC 3 and 7 tank mixes for control of Botrytis leaf blight and Stemphylium leaf blight in onion, 2021.  Plant Disease Management Reports 16: V139.   Hoepting, C.A., S.K. Caldwell and E.R. van der Heide.  2022.  Efficacy of fungicide tank mixes for control of Botrytis leaf blight and Stemphylium leaf blight in onion, Elba, 2021.  Plant Disease Management Reports 16: V138.   Hoepting, C.A., S.K. Caldwell and E.R. van der Heide.  2022.  Evaluation of in-furrow drenches for control of pink root and Fusarium basal rot in direct seeded onion, 2020-2021.  Plant Disease Management Reports 16: V132.   Hoepting, C.A., S.K. Caldwell and E.R. van der Heide.  2022.  Evaluation of in-furrow and soil line drenches for control of pink root and Fusarium basal rot in direct seeded onions, 2021-2022.  Plant Disease Management Reports 16: V174.   Hoepting, C.A., S.K. Caldwell and E.R. van der Heide.  2022.  Evaluation of selected pesticides for control of bacterial bulb rot in onion, 2021.  Plant Disease Management Reports 16: V168.   Hoepting, C., and B. Nault. 2022. Lorsban is banned: How to control cabbage maggot in brassicas now? Cornell Cooperative Extension, Cornell Vegetable Program. VegEdge 18(4): 4-6. <a href="https://rvpadmin.cce.cornell.edu/pdf/veg_edge/pdf235_pdf.pdf">https://rvpadmin.cce.cornell.edu/pdf/veg_edge/pdf235_pdf.pdf</a>.   Iftikhar, R., A. Ghosh, and H.R. Pappu. 2022. Mitochondrial genetic diversity of Thrips tabaci (Thysanoptera: Thripidae) in onion growing regions of the USA. J. Econ. Entomol. In Press.   Khanal M., B.P. Bhatta, and S. Malla. 2022. Isolation and characterization of bacteria associated with onion and first report of onion diseases caused by five bacterial pathogens in Texas, U.S.A. Plant Dis. <a href="https://doi.org/10.1094/PDIS-09-22-2206-SR">https://doi.org/10.1094/PDIS-09-22-2206-SR</a>   Khanal, M., B.P. Bhatta, S. Timilsina, S. Ghimire, K. Cochran, and S. Malla. 2023. Curtobacterium allii sp. nov., the actinobacteria species causing onion bulb disease. Antonie van Leeuwenhoek 116:83–96. DOI: <a href="https://doi.org/10.1007/s10482-022-01775-z">https://doi.org/10.1007/s10482-022-01775-z</a>   Khanal, M., S. Timilsina, B.P. Bhatta, K. Bophela, T. Coutinho, K. Cochran, and S. Malla. 2022. Pseudomonas uvaldensis sp. nov., a bacterial pathogen causing onion bulb rot, isolated from Texas, USA. Int. J. Syst. Evol. Microbiol. 72:005311. https://doi.org/10.1099/ijsem.0.005311   Lai, P.-C., and B. Nault. 2022. Are onion thrips allies of bulb-rot causing bacteria in organic onion production? Cornell Cooperative Extension, Cornell Vegetable Program. VegEdge 18(16):  9-10. <a href="https://rvpadmin.cce.cornell.edu/pdf/veg_edge/pdf247_pdf.pdf">https://rvpadmin.cce.cornell.edu/pdf/veg_edge/pdf247_pdf.pdf</a>.   Lai, P.-C. and B. Nault. 2022. Do thrips facilitate bulb rot disease? Onion World 38(8): <a href="https://issuu.com/columbiamediagroup/docs/onion_world_december_2022?fr=sMzU1YzQ5MDQ1MjQ">https://issuu.com/columbiamediagroup/docs/onion_world_december_2022?fr=sMzU1YzQ5MDQ1MjQ</a>.   Lai, P.-C., L. Iglesias, R.L. Groves, M.J. Havey, and B.A. Nault. 2022. Performance of a semi-glossy onion hybrid in certified organic onion fields infested with Thrips tabaci and bulb-rot causing bacteria. Crop Protect. 160 (1-9). <a href="https://doi.org/10.1016/j.cropro.2022.106037">https://doi.org/10.1016/j.cropro.2022.106037</a>   Machado-Burke, A., M. Uchanski, and J. Davey. 2022. Evaluation of bactericides to manage slippery skin in onion in Colorado, 2021. Plant Disease Management Reports (PDMR), the American Phytopathological Society (APS), V128.   MacKay, H., du Toit, L., Havey, M., and Rogers, P. 2022. Joint Allium research meeting held in Denver showcases latest research on onion production, pests and diseases. Onion World May/June 2022:14-16. <a href="https://issuu.com/columbiamediagroup/docs/onion_world_may-june_2022/14">https://issuu.com/columbiamediagroup/docs/onion_world_may-june_2022/14</a>   MacKay, H., du Toit, L., and Hoepting, C. 2022. Stop the Rot Half-Time Report: News from the Stop the Rot project on onion bacterial diseases. Onion World March/April 2022:16-17.   Machado-Burke, A., M. Uchanski, and J. Davey. 2022. Evaluation of bactericides to manage slippery skin in onion in Colorado, 2021. Plant Disease Management Reports (PDMR), the American Phytopathological Society (APS), V128.   Murdock, M.R., Pizolotto, C.A., and Woodhall, J.W. 2022. Evaluating Pristine and Luna Tranquility against Botrytis leaf spot, Stemphylium leaf blight and other foliar diseases on drip-irrigated onions in Idaho, 2020. Plant Disease Management Reports 16, V105.   Murray, K., I. Sandlin, P. Ellsworth, P. Jepson, A. Fournier, H. Luh and S. Reitz. 2022. The Economic Impact of Onion Pests in the Treasure Valley - A Look at Pests and Associated Management Practices, 2018–2019. Oregon State University Extension Service, EM 9347, 34 pp. <a href="https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9347.pdf">https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9347.pdf</a>   Myers, B. Shin, G.Y., Stice, S., Agarwal, G., Gitaitis, R., Kvitko, B., and Dutta, B.  2022. Genome-wide association and dissociation studies in P. ananatis reveal potential virulence factors affecting Allium porrum and A. fistulosum x A. cepa hybrid. Frontiers in Microbiology (in press)   Nault, B.A. 2022. Onion thrips control in onion, 2021. Arthropod Management Tests 47(1): tsac052, <a href="https://doi.org/10.1093/amt/tsac052">https://doi.org/10.1093/amt/tsac052</a>.   Nault, B.A. 2022. Onion maggot control using seed treatments in onion, 2021. Arthropod Management Tests, 47(1): tsac055, <a href="https://doi.org/10.1093/amt/tsac055">https://doi.org/10.1093/amt/tsac055</a>.   Nault, B., and C. Hoepting. 2022. Guidelines for maggot and disease control in onion with an emphasis on seed treatments. Cornell Cooperative Extension, Cornell Vegetable Program. VegEdge 18(22):  7-10. <a href="https://rvpadmin.cce.cornell.edu/pdf/veg_edge/pdf253_pdf.pdf">https://rvpadmin.cce.cornell.edu/pdf/veg_edge/pdf253_pdf.pdf</a>.   Nault, B., and C. Hoepting. 2022. Guidelines for maggot and disease control in onion with an emphasis on seed treatments. Cornell Cooperative Extension, Cornell Vegetable Program. VegEdge 18(22):  7-10. <a href="https://rvpadmin.cce.cornell.edu/pdf/veg_edge/pdf253_pdf.pdf">https://rvpadmin.cce.cornell.edu/pdf/veg_edge/pdf253_pdf.pdf</a>.   Nault, B.A. and C. Hoepting. 2022. Seed treatments: What to know to protect your 2023 onion crop. Onion World 38(7): 28-31. <a href="https://issuu.com/columbiamediagroup/docs/onion_world_november_2022?fr=sYmE1NDQ5MDQ1MjQ">https://issuu.com/columbiamediagroup/docs/onion_world_november_2022?fr=sYmE1NDQ5MDQ1MjQ</a>.   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. 115(2): 618–623. <a href="https://doi.org/10.1093/jee/toac016">https://doi.org/10.1093/jee/toac016</a>   Qian, Y., Hua, G.K.H., Scott, J.C., Dung, J.K.S., and Qian, M. 2022. Evaluation of sulfur-based biostimulants for the germination of Sclerotium cepivorum sclerotia and their interaction with soil. Journal of Agricultural and Food Chemistry Manuscript (in print). <a href="https://doi.org/10.1021/acs.jafc.2c05862">https://doi.org/10.1021/acs.jafc.2c05862</a>   Regan, K.H. and B.A. Nault. 2022. Impact of reducing synthetic chemical inputs on pest and disease management in commercial onion production systems. Agronomy 12(6), 1292; <a href="https://doi.org/10.3390/agronomy12061292">https://doi.org/10.3390/agronomy12061292</a>   Shahabeddin Nourbakhsh, S. and C.S. Cramer. 2022. Onion germplasm possess lower early season thrips numbers. Horticulturae 8:123. https://doi.og/10.3390/horticulturae8080123.   Shahabeddin Nourbakhsh, S. and C.S. Cramer. 2022. Onion size measurements as predictors for onion bulb size. Horticulturae 8:682. https://doi.og/10.3390/horticulturae8080682.   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).   Sidhu, J., Dubose, J., Fernberg, J. and Aegerter, B.J. 2022. Evaluation of bactericides for management of bacterial leaf blight and bacterial bulb rot in onions, 2021. Plant Disease Management Reports 16:V026. <a href="https://doi.org/10.1094/PDMR16">https://doi.org/10.1094/PDMR16</a>   Wilson, R., K. Nicholson, and B. Aegerter. 2022. The influence of irrigation method on bacterial diseases of onion in Northeast California, 2021 Plant Disease Management Reports 16: V154. <a href="https://doi.org/10.1094/PDMR16">https://doi.org/10.1094/PDMR16</a>   Woodhall, J., M. Murdock, K. Beck and M. Thornton. 2021. Pink root disease of onion – biology and control. Extension Bulletin 1000, University of Idaho. Colorado   Zhao, M., Tyson, C., Chen, H.C., Paudel, S., Gitaitis, R., Kvitko, B., and Dutta. B. 2022. 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.   Zhao, M., Shin, G.Y., Stice, S., Coutinho, T., Gitaitis, R., Kvitko, B., and Dutta, B.  2022.  A novel biosynthetic gene cluster across the Pantoea species complex is important for pathogenicity in onion.  Mol. Plant Microbe Interact. (in press)   Zhao, M., Tyson, C., Gitaitis, R.,  Kvitko, B., and  Dutta, B. 2022. Rouxiella badensis, a new bacterial pathogen of onion causing bulb rot. Frontiers in Microbiology 13:1054813.

Impact Statements

A post planting, delayed preemergence application of pendimethalin could provide comparable or better control of annual weeds as currently used herbicides in autumn-sown and winter-sown onions in New Mexico while reducing herbicide costs by 92-95% ($99-$156/acre) and reducing the legacy costs on the environment by 74-88%. This simple switch could save the NM onion industry $1 million per year.