Trial 1. Evaluation of varietal resistance to foliar diseases of carrot, 2024.
A carrot field trial was conducted at the Hancock Research Station in Hancock, WI, to evaluate varietal resistance to common foliar diseases of carrot in the Midwestern United States with and without fungicide management. Nine varieties were selected for evaluation (Table 1) and seeds were sown at approximately 250,000 seed/A with a push seeder on 17 June. The experimental design consisted of 4 replicates arranged in a randomized complete block design. Each treatment plot consisted of 4.5-ft-wide beds with three 18-ft-long seeding rows, 19 in. between rows on bed with 17 in. from row edge to bed edge. Twelve-ft fallow breaks were maintained between plots in the same row. Insecticide, herbicide, and fertilizer applications were made according to standard production practices for the region. Naturally occurring inocula of pathogens were present from nearby agricultural production fields and a neighboring carrot variety trial with no fungicides applied. Each variety was either not treated with fungicides or treated 4 times with a standard fungicide program (7 Aug = Bravo WS 720SC 1.5 pt/A + Kocide 3000 1.5 lb/A, 21 Aug = Bravo WS 720SC 1.5 pt/A + Merivon 4.18SC 5.5 fl oz/A, 4 Sep = Bravo WS 720SC 1.5 pt/A + Kocide 3000 1.5 lb/A, and 18 Sep = Bravo WS 720SC 1.5 pt/A + Merivon 4.18SC 5.5 fl oz/A). Disease assessments took place on 1 Aug, 19 Aug, 28 Aug, and 21 Sep using the Horsfall-Barratt scale (1-11) to assess foliar symptoms in each experimental plot. Foliar disease severity was combined for all pathogens present at each rating. The area under the disease progress curve (AUDPC) was determined by trapezoidal integration and then converted into relative AUDPC (RAUDPC), i.e. percentage of the maximum possible AUDPC for the whole period of the experiment. On 5 Oct, a 5-ft section was hand-harvested from each plot, carrot tops were removed, and carrots (roots) were weighed to determine yield. Precipitation in Hancock during the production season was 13.8 in. Supplemental irrigation was applied 26 times during the production season for an additional 10.1 in. All data were analyzed using ANOVA (α=0.05) and Fisher’s LSD at α=0.05 (SAS Version 9.2).
Disease pressure was averaged for the production season. Yields and individual carrot sizes were significant when comparing between varieties, but there was not a significant effect from fungicide treatments on yield and sizing when compared to non-treated (P-value =0.23 and 0.82, respectively). There was a significant decrease overall in disease (RAUDPC) across treatments when comparing fungicide-treated versus non-treated (P-value = 0.0019). Five varieties, Belgrado, Canberra, Caravel, Cupar, and Naval had significantly less disease when no fungicide was applied and may be less susceptible to foliar disease.
Trial 2. Evaluation of fungicides to control white mold in dark red kidney bean, Hancock, WI, 2024.
A trial to evaluate the effectiveness of fungicides to control white mold in dark red kidney bean was established on 6 Jun at the University of Wisconsin Hancock Agricultural Research Station in central Wisconsin. The commercial cultivar Montcalm was selected for the trial. Plots were seeded at approximately 4.5 seeds per ft.
Plots were 25 ft long with 4 rows spaced 30 in. apart. There were four replications per treatment, and plots were arranged in a randomized complete block design. Snap beans and sunflowers had been planted in this field in previous years with historically high levels of disease. Naturally-occurring inocula were the only source for disease development. Fertility, insects, and weeds were managed during the growing season according to standard grower practices for the region. Twelve fungicide programs were evaluated. Fungicide applications for control of white mold were applied twice: once at 10% bloom (17 Jul) and 14 days after 10% bloom (32 Jul).
Fungicides were applied using a CO2-pressurized backpack sprayer with a 4-nozzle spray boom with 19 in. spacing between standard flat fan spray nozzles (Tee Jet 8002VS) at a rate of 35 gal/A at 40 psi. On the day of harvest, 13 Aug, the two center rows of each plot were evaluated for white mold with the total number of symptomatic plants (or “strikes”) for each plot recorded. Bean pods from the two, center rows of each plot were machine harvested and weighed. All data were analyzed using analysis of variance (ANOVA) (α=0.05) and Fisher’s least significant difference (LSD) test at α=0.05 (SAS Version 9.2). Total precipitation in Hancock during the production season was 11.23 inches. Supplemental irrigation was applied 16 times for a total of 6.25 inches.
Weather conditions during bloom were only moderately conducive for infection of flowers and subsequent disease spread with most strikes occurring on the flowers and pods. All foliar fungicide programs significantly reduced white mold strikes compared to the non-treated control. There were no significant differences between programs for yield. No phytotoxicity was observed with any of the fungicide programs throughout the duration of the trial.
Trial 3. Evaluation of fungicide/bactericide treatments for control of foliar and bulb diseases in onion in Wisconsin, 2024.
An onion fungicide efficacy trial was established on 13 April in a commercial field on muck soil in Friendship, Wisconsin using a standard commercial planter. The experimental design consisted of 4 replicates arranged in a randomized complete block design. Each treatment plot consisted of 5-ft-wide beds with four 20-ft-long rows spaced 15 in. apart with 2-ft non-sprayed buffer alleys between plots in the same row. Insect, weed, and fertility management was carried out as per commercial standards for the production region and were applied by the grower cooperator. Naturally occurring inocula was present from nearby agricultural production fields. Fungicide treatments were applied on 2 Jul, 9 Jul, 16 Jul, 23 Jul, 30 Jul, and 7 Aug for a total of 6 applications using a CO2 backpack sprayer equipped with four TeeJet 8002VS nozzles spaced 19-in. apart and calibrated to deliver 35 gal/A at a boom pressure of 40 psi. The severity of total, combined foliar disease of the two center rows was rated on 15 Jul, 2 Aug, 19 Aug, 28 Aug using the Horsfall-Barratt rating scale (0-11 rating with 0=no disease, 11=100% disease severity). The Area Under the Disease Progress Curve (AUDPC) was determined by trapezoidal integration and then converted into Relative AUDPC (RAUDPC), i.e. percentage of the maximum possible AUDPC for the whole period of the experiment. On 29 Aug, onions in the center five feet of the two center rows were pulled, hand-topped, and weighed. Harvested onion bulbs were then placed in storage at 65 °F and 95% RH to cure. After 2 weeks, onion bulbs were sliced in half and evaluated for the presence of bacterial rot. Data were analyzed using ANOVA (α=0.05) and Fisher’s LSD at α=0.05.
There were no significant differences across treatments for bulb size (data not shown) and plot yield. Disease pressure was relatively low throughout the trial period and no pesticide program was significantly better than the non-treated control for foliar disease management (RAUDPC). Bacterial bulb rot was significantly reduced for programs when compared to the non-treated control. The 2 best performing programs for controlling bulb rot were Kocide 3000 alternating with Dithane 75DF and Badge SC at 6 pt/A alternating with Dithane 75DF without Induce. No phytotoxicity was observed during the growing season.
Trial 4. Evaluation of in-furrow and at-hilling applied fungicides for control of potato common scab in Hancock, Wisconsin, 2024
A trial was established on 3 May at the Hancock Agricultural Research Station in Hancock, WI. to evaluate treatments for the management of common scab. Two-ounce-sized seed pieces were mechanically cut from US#1 ‘Yukon Gold’ seed tubers and healed for 7 days prior to planting under conditions of 55°F and ample air flow to support suberization. A randomized complete block design with four replications was used and treatment plots consisted of two 20-ft-long rows spaced 36 in. apart with 12 in. spacing in the row. Common scab inoculum was introduced in this disease nursery in each of the previous production seasons by incorporating common scab-symptomatic tubers into the soil. In-furrow treatments were applied to seed and soil in an open furrow on the day of planting using a CO2 backpack sprayer equipped with a single TeeJet 8002VS flat fan nozzle calibrated to deliver 12 gal/A at a boom pressure of 40 psi. After in-furrow treatments were applied, furrows were mechanically closed using hilling disks. At-hilling applications were applied directly over freshly hilled plots on 22 May using a CO2-pressurized backpack sprayer with a 4-nozzle spray boom with 19 in. spacing between standard flat fan spray nozzles (Tee Jet 8002VS) at a rate of 35 gal/A at 40 psi. The soil type was Plainfield Sand. Standard grower practices were used for field maintenance, fertility, insect management, and prevention of foliar early and late blight as per the production region. Crop emergence was evaluated at 40 days after planting from 20 linear feet of each of the center two rows of each plot (% seed emergence = number of emerged plants /maximum possible # of plants (40)*100). Tubers from plots were harvested, graded, and weighed on 17 Sept. Twenty tubers from each plot were chosen randomly and assessed for common scab incidence and severity measured as the percentage of tuber surface covered with common scab lesions. Natural precipitation during the trial duration was 20.21 in. Supplemental irrigation was applied 30 times for an additional 11.5 inches of water. All data were analyzed using ANOVA (α=0.05) and Fisher’s LSD at α=0.05 (SAS Version 9.2).
Emergence was poor as was yield across treatments. There were no significant differences across treatments for total plot yield, B size (range between 1.5 and 2.25 in diameter), C size (range less than 1.5 in. in diameter), and cull weight (data not shown). There were no significant differences in marketable yield (A size tubers, greater than 2.25 in in diameter), but data is presented. Disease pressure for this trial was uniform with nearly 100% scab incidence across treatments, but scab severity was low. All treatments significantly reduced scab severity compared to the non-treated control.
Trial 5. Evaluation of foliar fungicides for control of potato white mold and foliar early blight in Wisconsin, 2024.
A field trial was conducted at the University of Wisconsin Agricultural Research Station in Hancock, WI to evaluate fungicide programs for control of white mold and foliar early blight on potato. Seed pieces, approximately 2 oz in size, were cut mechanically from US#1 ‘Atlantic’ seed tubers 7 days prior to planting. Seed pieces were allowed to heal before planting on 6 May. A randomized complete block design with four replications was used for the trial, and treatment plots consisted of four 20-ft-long rows spaced 36 in. apart with 12 in. spacing in the row. To minimize soil compaction and damage to plants in the treatment rows, drive rows for pesticide application equipment were placed adjacent to the plots. One program required an incorporation of fungicide to treated plots one day before planting. This was applied over the top of the treated plot using a CO2-pressurized backpack sprayer with a 4-nozzle spray boom with 19 in. spacing between standard flat fan spray nozzles (Tee Jet 8002VS) at a rate of 35 gal/A at 40 psi followed by shallow incorporation by raking. In-furrow treatments were applied over the top of seed pieces in open furrows in a 12-in. band using a plot sprayer consisting of a tractor-mounted boom, pressurized with an air compressor, using TeeJet Twin Jet Flat Spray Tip nozzles TJ-60 11003VS. In-furrow applied fungicides were applied at a rate equivalent to 9.50 L water/1000 row feet at 30 psi. At-hilling applications were applied directly over freshly hilled plots on 22 May using a CO2-pressurized backpack sprayer with a 4-nozzle spray boom with 19 in. spacing between standard flat fan spray nozzles (Tee Jet 8002VS) at a rate of 35 gal/A at 40 psi. Fertility, insect, and weed management were accomplished using standard commercial practices for the region. Fungicide treatments were initiated at 50% row closure, starting on 21 Jun, and were sprayed a total of 4 applications. (18 Jun, 2 Jul, 16 Jul, 30 Jul). 2 Maintenance applications of Bravo Weatherstik (1.5 pt/A) were applied to all plots on 13 Aug and 27 Aug. Foliar fungicides were applied with a plot sprayer consisting of a tractor-mounted boom, pressurized with an air compressor, using TeeJet Hollow Disc Cone D3-23 nozzles (16 nozzles at 8-in. spacing). Fungicides were applied at a rate equivalent to 35-gal water/A at 40 psi. Plots were not inoculated for white mold or early blight, but relied on natural dispersal of inocula. White mold strike counts and early blight severity across 20 ft of the two center rows was rated on 4 Jul, 16 Jul, 2 Aug, 12 Aug, and 28 Aug using the Horsfall-Barratt rating scale (0-11 rating with 0=no disease, 11=100% disease severity). The Area Under the Disease Progress Curve (AUDPC) was determined by trapezoidal integration and then converted into Relative AUDPC (RAUDPC), i.e. percentage of the maximum possible AUDPC for the whole period of the experiment. Vine kill was initiated on 2 Sep with an application of Diquat E at 1.5 pt/A followed by a second application on 9 Sep. Tubers from the center 2 rows of each 4-row plot were harvested and graded on 18 Sep. Total precipitation in Hancock during the potato production season was 20.16 in. Supplemental irrigation was applied 33 times during the potato production season for an additional 12.6 in. All data were analyzed using ANOVA (P = 0.05) and Fisher’s LSD at P = 0.05 (SAS Version 9.2).
Early Blight onset was as expected for the region yet progressed slowly with drier weather in July and August. White mold infection points were found in low amounts on 17 Jul and recorded, but were not significantly different across treatments. Later evaluations did not find new infections and previous infections were either not growing or had dried out. Nine programs had significantly higher marketable yield (9,18,10,16,12,8,22,15,20) than the non-treated control). There were no significant differences across programs for B size yield (range between 1.5 and 2.25 in diameter), C size yield (range less than 1.5 in. in diameter), and cull weight (data not shown). All of the fungicide programs significantly reduce foliar early blight compared to the non-treated control except for 2 treatments (5 and 7).
Trial 6. Evaluation of in-furrow applied fungicides to control Rhizoctonia damping-off and root rot in snap beans, Hancock, WI, 2024.
A trial to evaluate the effectiveness of in-furrow applied fungicides to control Rhizoctonia damping-off and root rot in snap bean was established on 6 Jun at the University of Wisconsin Hancock Agricultural Research Station located in central Wisconsin. The commercially available cultivar, ‘Huntington’ was used. Plots were 20 ft long with four rows spaced 30 in. apart with a seeding rate of 6 seeds per ft. The trial consisted of four replications, and plots were arranged in a randomized complete block design. Fertility, insects, and weeds were managed during the growing season according to standard grower practices for the region. A regionally sourced isolate of Rhizoctonia solani was used to inoculate the trial. Cultures of the pathogen were grown on Clarified V8 agar for 1 week before inoculating sterile containers with 2 lbs of autoclaved rye berries per container. Rye berries were incubated on the benchtop for 14 days prior to field inoculation. At the time of planting, 100 grams of inoculated rye was placed in-furrow over the seed in the 2 center rows of each plot prior. In-furrow fungicide applications were applied in a 6-inch band directly over the open furrow prior to inoculation using a CO2-pressurized backpack sprayer with a single, standard flat fan spray nozzles (Tee Jet 8002VS) at a rate of 35 gal/A at 40 psi. Furrows were hand closed after fungicide treatment and inoculation. Emergence data was recorded on 19 Jun (13 days post-planting DPP), and 3 Jul (27 DPP) by counting the number of emerged plants in the two center rows. The number of plants exhibiting symptoms of damping off were also recorded on 3 Jul. On 15 Aug, ten feet from the two center rows were machine harvested and weighed. Ten roots samples were collected prior to harvest and evaluate for root rot using the following scale: 1 = 1-20% discoloration with individual lesions, 2 = 21-40% discoloration with coalesced lesions but tissues are firm with some reduction in root mass, 3 = 41-60% discoloration and root tissue lesions combined with considerable softening, 4 = 61-80% discoloration and internal pith tissues of roots affected, 5 = 81-100% discoloration, root softening and rotting along with heavy reduction in root mass. All data were analyzed using analysis of variance (ANOVA) at α=0.05 and Fisher’s least significant difference (LSD) at α=0.05 (SAS Version 9.2). The trial received 4.45 in. of irrigation (12 applications) to supplement 11.23 in. of natural precipitation.
Weather conditions during this trial were typical for the region. No phytotoxicity was observed with any of the fungicide programs throughout the duration of the trial. Disease pressure was very high and every plant sampled had some root rot present (100% incidence, data not shown). Emergence, yield, root weight (data not shown), and number of plants lost to damping off were not significant compared to the inoculated control, but most treatments numerically reduced loss to damping off and increased yield. All fungicide treatments significantly reduced root rot when compared to both the non-inoculated and inoculated controls. Velum Prime, Ridomil Gold + Quadris, Propulse + Quadris, Propulse (6 fl oz), Propulse (8 fl oz) and Howler EVO were the treatments that had the greatest reduction in root rot.
Trial 7. Evaluation of Commercial Sweet Corn varieties for response to Tar Spot in Hancock, Wisconsin, 2024.
A trial was established on 18 Jul at the Hancock Research Station in Hancock, WI, to evaluate varietal resistance to tar spot on commercial sweet corn varieties. 20 commercial sweet corn varieties from 4 suppliers (Seminis, Syngenta, Harris Moran, Crookham Company) were evaluated. The experimental design consisted of 4 replicates arranged in a randomized complete block design. Each treatment plot consisted of four, 25-ft-long rows spaced 30 in. apart with 5-ft barren buffer alleys at the end of plots in the same row. Insect, weed, and fertility management was carried out as per commercial standards for the production region. Naturally occurring inocula of tar spot was present from nearby sweet corn plots not sprayed with fungicides. No fungicides were applied to the plots for the duration of the trial. The trial was rated for disease incidence and severity on the leaves closest to ear set on 3 dates, 1 Sept, 21 Sept, and 15 Oct using the Horsfall-Barratt rating scale (0-11 rating with 0=no disease, 11=100% disease severity). The Area Under the Disease Progress Curve (AUDPC) was determined by trapezoidal integration and then converted into Relative AUDPC (RAUDPC), i.e. percentage of the maximum possible AUDPC for the whole period of the experiment. 5 feet of a center row was hand harvested for each plot on 15 Oct. All ears with silk were harvested, counted, and weighed without shucking Data were analyzed using ANOVA (α=0.05) and Fisher’s LSD at α=0.05.
Disease pressure was heavy with 100% disease incidence in all plots. Due to the late planting, yields were lower than expected for commercial sweet corn plots. There were no significant differences in the ear number per acre, but significant differences between varieties in both yield and disease severity (RAUDPC). The top five yielding varieties were Coachman, Messenger, Triple Threat, GSS3951, Forerunner. The top 5 varieties with the least amount of disease were GSS2259P, GH9335, Townsend, GSS3951, Forerunner. Yield did not closely corelate with disease (r = 0.054).
Trial 8. Evaluation of foliar fungicides for control of potato early blight in Wisconsin, 2024.
A field trial was conducted at the University of Wisconsin Agricultural Research Station in Hancock, WI to evaluate 32 season-long fungicide programs for control of early blight on potato. Seed pieces, approximately 2 oz in size, were mechanically cut from US#1 ‘Russet Burbank’ seed tubers 7 days prior to planting. Seed pieces were allowed to heal before planting on 30 Apr by maintaining cut seed at 55°F under 98% relative humidity. A randomized complete block design with four replications was used for the trial, and treatment plots consisted of four 20- ft-long rows spaced 36 in. apart with 12 in. spacing in the row. To minimize soil compaction and damage to plants in the treatment rows, drive rows for pesticide application equipment were placed adjacent to the plots. Fertility, insect, and weed management were accomplished using standard industry practices for the region. In-furrow treatments were applied over the top of seed pieces in open furrows in a 12-in. band using a plot sprayer consisting of a tractor-mounted boom, pressurized with an air compressor, using TeeJet Twin Jet Flat Spray Tip nozzles TJ-60 11003VS. In-furrow applied fungicides were applied at a rate equivalent to 9.5 L water/1,000 row feet at 30 psi. At-hilling applications were applied directly over freshly hilled plots on 15 May using a CO2-pressurized backpack sprayer with a 4-nozzle spray boom with 19 in. spacing between standard flat fan spray nozzles (Tee Jet 8002VS) at a rate of 35 gal/A at 40 psi. Foliar fungicide treatments were initiated on 3 Jul after the P-day value (generated from a crop physiological model used for early blight prediction and fungicide initiation) reached 300. Subsequent applications were applied on a weekly basis to all four rows of each plot on the following dates: 10 Jul, 17 Jul, 24 Jul, 31 Jul,7 Aug, 14 Aug, 21 Aug, 28 Aug, 4 Sep, for a total of ten fungicide applications. Treatments were applied with a plot sprayer consisting of a tractor-mounted boom pressurized with an air compressor using TeeJet Hollow Disc Cone D3-23 nozzles (16 nozzles at 8-in. spacing). Fungicides were applied at a rate equivalent to 35-gal water/A at 40 psi. Plots were not artificially inoculated but relied on natural inocula from soil and plant residues from the surrounding concentrated potato production region for disease establishment. Early blight severity across 20 ft of the two center rows was visually determined on 4 Jul, 16 Jul, 2 Aug, 12 Aug, 28 Aug, and 6 Sep using the Horsfall-Barratt rating scale (0 to 11 rating with 0=no disease, 11=100% disease severity). The Area Under the Disease Progress Curve (AUDPC) was determined by trapezoidal integration and then converted into Relative AUDPC (RAUDPC), i.e. percentage of the maximum possible AUDPC for the whole period of the experiment. Vines were killed on 16 Sep with an application of the desiccant Diquat E 1.5 pt/acre. Tubers from the center two rows of each 4-row plot were harvested and graded on 4 Oct. Total precipitation in Hancock during the potato production season was 21.93 in. Supplemental irrigation was applied 29 times for an additional 11.35 inches of water. All data were analyzed using ANOVA (α=0.05) and Fisher’s LSD at α=0.05 (SAS Version 9.2).
Disease onset was typical, but progressed slower than normal due to drier weather in July and August. There were no significant differences across programs for total plot yield, B size (range between 1.5 and 2.25 in diameter), C size (range less than 1.5 in. in diameter), and cull weight (data not shown). There were no significant differences in marketable yield (A size tubers, greater than 2.25 in in diameter), but data is presented. There were 20 programs that had significantly lower RAUDPC than the non-treated control program (3, 8, 23, 11, 26, 31, 4, 7, 9, 25, 28, 30, 32, 21, 6, 27, 10, 12, 2, and 17). No phytotoxicity was observed with any of the fungicide programs throughout the duration of the trial.