Field Trial Reports

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Potato

Trial 2. Evaluation of foliar fungicides for control of white mold and early blight of potato in Wisconsin, 2023

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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 on 24 Apr. Seed pieces were allowed to heal prior to planting on 5 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. Seed treatments were applied to tubers within 24 hours of planting 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/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. (21 Jun, 5 Jul, 19 Jul, 2 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 from soil and residue. White mold strike counts and early blight severity across 20 ft of the two center rows was rated on 23 Jun, 30 Jun, 13 Jul, 25 Jul, 8 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 30 Aug with an application of Diquat E at 1.5 pt/A followed by a second application on 5 Sep. Tubers from the center 2 rows of each 4-row plot were harvested and graded on 12 Sep. Total precipitation in Hancock during the potato production season was 7.76 in. Supplemental irrigation was applied 42 times during the potato production season for an additional 18.4 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 typical, but June and July were hotter and drier than normal, leading to slower disease development as the season progressed. There were no significant differences in early blight RAUDPC among programs No measurable white mold strikes were found during the duration of the trial. There were no significant differences in emergence or marketable yields among fungicide programs. Program 3 had significantly lower B size yield when compared to the non-treated control. Programs 16, 19, 22, and 24 had significantly greater B size yield than the non-treated control. Programs 9, 22, and 24 had significantly greater C size yield when compared to the non-treated control. No phytotoxicity was observed with any of the fungicide programs throughout the duration of the trial.

 

Trial 3. Evaluation of foliar fungicides for control of potato early blight in Wisconsin, 2023

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A field trial was conducted at the University of Wisconsin Agricultural Research Station in Hancock, WI to evaluate 53 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 on 24 Apr. Seed pieces were allowed to heal prior to planting on 28 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 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. Foliar fungicide treatments were initiated on 5 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: 12 Jul, 19 Jul, 26 Jul, 2 Aug, 9 Aug, 16 Aug, 23 Aug, 30 Aug, and 6 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 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 23 Jun, 30 Jun, 13 Jul, 25 Jul, 8 Aug, 28 Aug, 1 Sep, and 8 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 18 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 10.31 in. Supplemental irrigation was applied 52 times during the potato production season for an additional 22.4 in. 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 June and July were hotter and drier than normal, leading to slower disease development as the season progressed. 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 9 programs that had significantly lower RAUDPC than the non-treated control program (11, 16, 7, 10, 15, 12, 8, 46, 29).  No phytotoxicity was observed with any of the fungicide programs throughout the duration of the trial.

 

Trial 4. Evaluation of at-plant fungicides for control of Rhizoctonia diseases of potato in Wisconsin, 2023

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Potatoes were planted on 3 May 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 (12.8°C) 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 (6.1 m) rows spaced 36 in. (0.91 m) apart with 12 in. (0.30 m) spacing in the row. Seed treatments were applied to tubers after seed cutting using a 1.06 qt (1003 ml) Solo Hand Pump Sprayer at a rate equivalent to 3.70 L water/ton (or 907.2 kg) 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. 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 10 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). Precipitation in Hancock during the potato production season was 7.75 in. Supplemental irrigation was applied 50 times during the potato production season for an additional 21.4 in. Vines were killed with a desiccant treatment of Diquat + non-ionic surfactant applied on 13 Sep with a subsequent application on 19 Sep. Plots were harvested and graded on 5 Oct. 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).

There were no significant differences among treatments for emergence, C size yield (data not shown) and cull weight (data not shown). Six treatments (4, 5, 6, 8, 19, and 25) had a significant reduction in marketable yield when compared to the non-treated control. No treatment had a significantly greater marketable yield when compared to the non-treated control. Five treatments (4, 5, 6, 10, and 11) had a significant increase in the yield of B size tubers when compared to the non-treated control. Treatment 14, had a significantly reduced yield of B size tubers when compared to the non-treated control. All treatments, except 21 and 25, had a significant reduction in both black scurf incidence and severity when compared to the non-treated control. There was no phytotoxicity during the growing season associated with any treatment.

 

Trial 5. Evaluation of treatments for control of silver scurf and black dot of potato in Wisconsin, 2023

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Potatoes were planted on 3 May at the University of Wisconsin Hancock Agricultural Research Station in central WI to evaluate seed-applied treatments and in-furrow-applied fungicides for the control of silver scurf and black dot of potato. Seed pieces, approximately 2 oz in size, were cut mechanically from US#1 ‘Dark Red Norland’ tubers and allowed to heal prior to planting under conditions of 55°F and 98% relative humidity. A randomized complete block design with four replications was used for the trial. 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 rows used for foliar and yield evaluations, drive rows for pesticide application equipment were placed adjacent to plots. Seed treatments were applied to tubers after 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 9.5 L water/1,000 row feet at 30 psi. Plots were not artificially inoculated; they relied on natural inocula from seed, soil, and plant residue for disease establishment. Fertility, insect, weed, and foliar disease management were accomplished using standard commercial practices for the region. Seed emergence data were collected on 7 Jun from 20 linear feet of each of the center rows of each plot (% seed emergence = (number of emerged vines /maximum possible emerged vines) *100). Precipitation in Hancock during the potato production season was 7.75 in. Supplemental irrigation was applied 50 times during the potato production season for an additional 21.4 in. Vines were killed with a desiccant treatment of Diquat applied on 28 Aug with a second application on 5 Sept. Plots were harvested and graded for size distribution on 11 Sep. At harvest, 20 tubers were randomly selected from each plot and visually evaluated for silver scurf and/or black dot incidence and severity (percentage of symptomatic tuber surface). Because the two tuber blemish diseases can be indiscernible based on visual symptoms alone, we report our disease results collectively.

There were no significant differences in emergence and marketable yield, B size yield (data not shown), C size yield (data not shown) and cull weight (data not shown) between treatments. Nine treatments significantly reduced both the incidence and severity of silver scurf on the tubers (2, 3, 7, 8, 11, 13, 14, 17 and 19). No phytotoxicity was observed with any of the fungicide programs throughout the duration of the trial.

 

Kidney Bean

Trial 6. Evaluation of fungicides to control white mold in dark red kidney bean, Hancock, WI, 2023

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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 (20 Jul) and 14 days after 10% bloom (3 Aug). 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, 15 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 5.26 in. Supplemental irrigation was applied 28 times during the production season for an additional 12.6 in.

Weather conditions during bloom were only moderately conducive to infection of flowers and subsequent disease spread, but most infections did occur through flowers and not via the ground. All but one program (Howler EVO 2X) 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.

 

Snap Bean

Trial 7. Evaluation of fungicides to control Fusarium crown and root rot in snap beans, Hancock, WI, 2023

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A trial to evaluate the effectiveness of in-furrow applied fungicides, with and without a seed treatment, to control Fusarium crown 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, ‘Hystyle’ 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 single seed treatment was used in the trial and consisted of streptomycin sulfate (AS-50), thiram (480 DP), captan 4L ST, metalaxyl (Belmont 2.7 FS), fludioxonil (Maxim), ipconazole (Rancona 3.8 FS), and thiamethoxam (Cruiser 5FS). The seed treatment was commercially applied. A regionally-sourced isolate of Fusarium solani f.sp. pisi 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 lb of autoclave disinfested rye berries per container. Rye berries were incubated on the benchtop for 21 days prior to field inoculation. At the time of planting, 100 g of inoculated rye was placed in-furrow over the seed in the 2 center rows of each plot. 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 closed by hand after fungicide treatment and inoculation. Emergence data were recorded on 26 Jun by counting the number of emerged plants in the two center rows. On 15 Aug, ten feet from the two center rows were machine harvested and weighed. Ten roots samples were collected prior to harvest and evaluated 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 13.3 in. of irrigation (30 applications) to supplement 11.01 in. of natural precipitation.

Weather conditions during this trial were warmer and drier than typical for the region. No phytotoxicity was observed with any of the fungicide programs throughout the duration of the trial. There were no significant differences among treatments for yield. Only one treatment, Velum Prime in furrow without the seed treatment, had a significant reduction in emergence when compared to the controls. No treatments had a significantly greater emergence than the inoculated control. Four treatments (all with no seed treatment), Ridomil Gold + Quadris, Quadris, Propulse 6 fl oz, and Propulse 10 fl oz, had a significant reduction in root rot disease rating when compared to the inoculated control. The presence of the seed treatment did not positively affect root rot management.

 


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