Trial 1. Evaluation of foliar fungicides for control of potato white mold and foliar early blight in Wisconsin, 2025.
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 prior to planting on 29 Apr. 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. At-hilling applications were applied directly over freshly hilled plots on 16 May using 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. Fertility, insect, and weed management were accomplished using standard commercial practices for the region. Fungicide treatments were initiated at 50% row closure, starting on 24 Jun, and were sprayed a total of 7 applications. (9 Jul, 16 Jul, 23 Jul, 30 Jul, 6 Aug, 13 Aug). Foliar fungicides were applied with the previously described applicator. Plots were not inoculated for white mold or early blight pathogens. We relied on natural inoculum from the research field and region. White mold ‘strike’ (symptom) counts and early blight severity across 20 ft of the two center rows were rated on 19 Jun, 26 Jun, 10 Jul, 25 Jul, 7 Aug, 14 Aug, 22 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 2 Sep with an application of Diquat E 1.5 pt/acre with a subsequent application on 8 Sep. Tubers from the center 2 rows of each 4-row plot were harvested and graded on 16 Sep. Supplemental irrigation was applied 42 times with a total of 16.7 inches of water. Natural precipitation during the growing season totaled 16.26 inches. 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 typical, and progressed normally. White mold strikes were limited with no visible infections found during the growing season. There was no visible phytotoxicity associated with any of the treatments. There were no significant differences among treatments in yield, tuber sizing, and emergence. Numerically, the non-treated control had the greatest severity of early blight but there were no significant differences among treatments for early blight control.
Trial 2. Evaluation of at-plant fungicides for control of black dot of potato in Wisconsin, 2025
Potatoes were planted on 30 April at the University of Wisconsin Hancock Agricultural Research Station in central WI to evaluate in-furrow-applied fungicides for the control of black dot disease of potato. Two potato cultivars were selected for the trial: ‘Russet Burbank’ and ‘Colomba.’ Both cultivars were treated identically in conducting the trial. In preparation for planting, US#1 seed tubers were cut into approximately 2 oz pieces on 24 Apr. Seed pieces were allowed to heal at 55°F with 98% relative humidity and good airflow for suberization. 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. 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/1,000 row feet at 30 psi. Fertility, insect, and weed management was accomplished using standard commercial practices for the region. Plots relied upon natural inocula from seed and field sources for disease establishment. Seed emergence data were collected on 12 Jun from 20 linear feet of each of the center two rows of each plot (% seed emergence = number of emerged vines /maximum possible emerged vines) *100). Vines were killed with a desiccant treatment of Diquat + non-ionic surfactant applied on 8 Sep. Plots were harvested and graded on 30 Sep. At harvest, tubers from the center two, 20-ft long rows of each 4-row plot were graded for size and yield. Twenty tubers were randomly selected from each plot, after washing, and after 2 months under storage conditions, were visually evaluated for symptoms of black dot (% incidence = number of symptomatic tubers/20*100). All data were analyzed using ANOVA (P =0.05) and Fisher’s LSD at P =0.05 (SAS version 9.2). Precipitation in Hancock during the potato production season was 17.09 in. Supplemental irrigation was applied 45 times during the potato production season for an additional 17.8 in.
There were no significant differences among treatments for emergence, yield, tuber sizing (data not shown) and cull weight (data not shown). Black dot disease incidence on ‘Colomba’ tubers was significantly reduced with application of the lower rate of Azterknot and Elatus when compared to the non-treated control.
Trial 3. Evaluation of at-plant fungicides for control of Rhizoctonia diseases of potato in Wisconsin, 2025
Potatoes were planted on 30 April at the University of Wisconsin Hancock Agricultural Research Station in central WI to evaluate seed- and in-furrow- applied fungicides for the control of Rhizoctonia diseases of potato, including seedling damping-off and tuber black scurf. In preparation for planting, US#1 seed tubers were cut into approximately 2 oz pieces on 24 Apr. Seed pieces were allowed to heal at 55°F with 98% relative humidity and good airflow for suberization. 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. Inoculum was prepared by growing active cultures of a Wisconsin isolate of Rhizoctonia solani on sterile rye berries for 21 days. All plots, except for the non-treated control, were inoculated. The center rows of each plot were inoculated by placing 250 grams per row of infected rye berries directly over and between treated seed pieces prior to row closure. Seed treatments were applied to tubers after seed cutting using a 1.06 qt Solo Hand Pump Sprayer at a rate equivalent to 3.70 L water/ton seed. 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/1,000 row feet at 30 psi. Applications applied to mimic chemigation (treatments 16, 17, 18) were applied at 50% row closure (19 June) and row closure (2 July) 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). Mock chemigation applications were immediately followed with irrigation (0.4 in rate). Fertility, insect, and weed management was accomplished using standard commercial practices for the region. Seed emergence data were collected on 12 Jun from 20 linear feet of each of the center two rows of each plot (% seed emergence = number of emerged vines /maximum possible emerged vines) *100). The number of vines exhibiting rhizoctonia stem lesions above the soil line were counted from the 2 center rows of each plot on 2 Aug. Vines were killed with a desiccant treatment of Diquat + non-ionic surfactant applied on 8 Sep. Plots were harvested and graded on 30 Sep. At harvest, tubers from the center two, 20-ft long rows of each 4-row plot were graded for size and yield. Twenty tubers were randomly selected from each plot, after washing, and were visually evaluated for symptoms of black scurf (% incidence = number of symptomatic tubers/20*100). All data were analyzed using ANOVA (P =0.05) and Fisher’s LSD at P =0.05 (SAS version 9.2). Precipitation in Hancock during the potato production season was 17.09 in. Supplemental irrigation was applied 45 times during the potato production season for an additional 17.8 in.
There were no significant differences among treatments for B size yield, C size yield, and cull weight (data not shown). There were significant differences in emergence with the seed treatments Annoint (13) and Cruiser Maxx Vibrance Potato (15) significantly reducing emergence when compared to the non-treated, non-inoculated control. While there were significant differences among treatments for marketable yield, no treatment had significantly more marketable yield than the non-treated, inoculated control. No treatment had a significantly greater marketable yield when compared to the non-treated control (non-inoculated). Four treatments (3, 5, 7, and 8) had a significant increase in the mean tuber weight when compared to both non-treated controls (inoculated and non-inoculated). All treatments had a significant reduction in Rhizoctonia stem canker incidence when compared to the non-treated, inoculated control. Elatus in furrow (12) was the only treatment that significantly reduced both black scurf incidence and severity on tubers when compared to the inoculated control. There was no phytotoxicity during the growing season associated with any treatment.
Trial 4. Evaluation of commercial sweet corn cultivars for response to tar spot in Hancock, Wisconsin, 2025
A trial was established on 30 Jun at the University of Wisconsin Hancock Agricultural Research Station in Hancock, WI, to evaluate commercial cultivar resistance to tar spot. Eighteen commercial sweet corn cultivars 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, and from the general agricultural region of Hancock. 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 5 dates, 14 Aug, 28 Aug, 11 Sept, 18 Sept, and 2 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. Ten feet of the center 2 rows was hand-harvested for each plot on 2 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 later planting, yields were lower than expected for commercial sweet corn. There were significant differences in the yield, average ear weight, ear number per acre, and disease severity (RAUDPC) across the cultivars tested. The top six yielding cultivars included Forerunner, GH9335, GSS3951, Coachman, Triple Threat, and CSHYP16-1027. The top 5 cultivars with the least amount of disease were CSHYP16-1027, GSS2259P, GH9335, GSS3951, GSS2259P.
Trial 5. Evaluation of fungicides for control of white mold and foliar early blight on potato in Antigo, Wisconsin, 2025
A trial was established on 27 May at the University of Wisconsin Madison Division of Extension Langlade County Research Area in Antigo, Wisconsin to evaluate treatments for the management of white mold and foliar early blight. Two-ounce-sized seed pieces were mechanically cut from US#1 ‘Atlantic’ 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 24-ft-long rows spaced 36 in. apart with 12 in. spacing in the row. Plots were not inoculated for white mold or early bight, but relied on natural dispersal of inocula from field and regional history of susceptible crops. Seed treatments were applied to tubers using a 1.06 qt Solo Hand Pump Sprayer at a rate equivalent to 3.70 L water/ton seed. The soil type was Antigo silt loam. Standard grower practices were used for field maintenance, fertility, insect, and weed management as per the production region. Crop emergence was evaluated on 16 June and 14 July by counting vines from 24 linear feet of each of the center two rows of each plot (% seed emergence = number of emerged plants /maximum possible # of plants (48*100). Foliar fungicides were started at row closure, starting on 7 Jul, and were sprayed every week for early blight and white mold control (7 Jul, 14 Jul, 21 Jul, 28 Jul, 4 Aug, 11 Aug, 19 Aug, 25 Aug, 1 Sep, and 8 Sep). Foliar fungicides were applied with a plot sprayer consisting of a tractor-mounted boom, pressurized with an air compressor, using flat fan nozzles with a carrier volume of 20 gal per acre. White mold symptoms or ‘strike counts’ and early blight severity across 24 ft of all four rows were rated on 14 Jul, 31 Jul, 12 Aug, 4 Sep, and 18 Sep, using the Horsfall-Barratt rating scale (0-11 rating with 0=no disease, 11=100% disease severity). For early blight evaluation, 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. Tubers from the center 2 rows of each 4-row plot were harvested and graded (C size (<1.5 in), B size (1.5 to 2.25 in), A size (≥2.25 in)) on 10 Oct. All data were analyzed using ANOVA (α=0.05) and Fisher’s LSD at α=0.05 (SAS Version 9.2).
There were no significant differences in yield or tuber sizing between treatments. Treatment 4 which included Cruiser Maxx Vibrance seed treatment had significantly lower emergence when compared to the nontreated control or Treatment 3 (which included Emesto Silver seed treatment). All 3 fungicide programs significantly reduced white mold strikes when compared to the nontreated control (final white mold rating on 9/18). All 3 fungicide programs significantly reduced foliar early blight when compared to the nontreated control (RAUDPC). Numerically, Treatment 4 (which included Miravis Prime) had the best early blight control. The second best early blight control program was the grower standard (Treatment 2). The third best program for early blight control was Treatment 3 (which included Luna Pro). There was no visible phytotoxicity. There were no differences in plant vigor among treatments.
Trial 6. Evaluation of foliar fungicides for control of potato early blight in Wisconsin, 2025
A field trial was conducted at the University of Wisconsin Agricultural Research Station in Hancock, WI to evaluate 24 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 prior to planting on 29 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. At-hilling applications were applied directly over freshly hilled plots on 16 May using 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. Treatments 23 and 24 received a special foliar application 2 weeks prior to row closure on 25 Jun. Standard foliar fungicide treatments were initiated on 9 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:16 Jul, 23 Jul, 30 Jul, 6 Aug, 13 Aug, 20 Aug, 27 Aug, 3 Sep, for a total of nine fungicide applications. Foliar fungicides were applied with the previously described applicator. 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 19 Jun, 26 Jun, 10 Jul, 25 Jul, 7 Aug, 14 Aug, 22 Aug, and 28 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. Vine kill was initiated 8 Sep with an application of Diquat E 1.5 pt/acre. Tubers from the center two rows of each 4-row plot were harvested and graded on 29 Sep. Total precipitation in Hancock during the potato production season was 17.39 in with supplemental irrigation applied 46 times for an additional 18.2 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. There were no significant differences across programs for total plot yield, tuber sizing (data not shown) and cull weight (data not shown). There were no significant differences in marketable yield (A size tubers, greater than 2.25 in in diameter). There were 4 programs that had significantly lower RAUDPC than the non-treated control program (2, 3, 4, and 23). No phytotoxicity was observed with any of the fungicide programs throughout the duration of the trial.