Madison, WI Page 1

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1 POTATO (Solanum tuberosum) Russet Burbank Blight; Alternaria solani Late Blight; Phytophthora infestans W. R. Stevenson and R. V. James Department of Plant Pathology University of Wisconsin-Madison Madison, WI Evaluation of fungicides to control early blight and late blight of potato - Hancock, 2002 A field trial was established 29 Apr at the Hancock Agricultural Research Station in central WI to evaluate selected fungicides for early blight and late blight control. US#1 Russet Burbank tubers were mechanically cut into approximately 2 oz seedpieces 24 Apr and allowed to heal before planting. A randomized complete block design with four replications was used for the experiment, with each plot consisting of four 24-ft-long rows spaced 36 in. apart with tubers 15 in. apart in the row. To avoid soil compaction in treatment rows, drive rows for pesticide application equipment were placed adjacent to plots. The soil type was Plainfield loamy sand, ph 6.7. Fertilizer applied was: , 300 lb/a, broadcast 10 Apr, before planting, , 522 lb/a, banded in the row at planting, sidedress applications on 28 May (21-0-0, 350 lb/a) and 10 Jun (34-0-0, 375 lb/a), Cal-Sul, 500 lb/a, 31 May, and 28% UAN, applied through irrigation water 27 Jun (50 lb/a) and 30 Jul (30 lb/a). Insects were controlled with Admire 2F incorporated in the fertilizer at planting (16 fl oz/500 lb) and foliar application of Baythroid 2E (2.8 fl oz/a, 12 Jul), Actara (1.5 oz, 19 Jul) and Spintor 2SC (4.0 fl oz/a, 9 Aug). Lorox DF was applied for weed control (1.0 lb/a, 6 May). Fungicide treatments were applied to all four rows of each plot at weekly intervals from 26 Jun to 21 Aug, according to treatment protocol, for a total of nine weeks. Some treatments required an application a week ahead of our standard program and this was done 19 Jun. All treatments were applied with a plot sprayer consisting of a tractor-mounted boom pressurized with an air compressor. The majority of treatments were applied using Tee Jet Hollow Disc Cone D3-23 nozzles at a rate equivalent to 35 gal water/a at 40 psi (15 nozzles at 8-in. spacing). Five additional types of nozzles were also tested: Extended Range Flat Fan XR110 03VS, Lurmark Venturi ULD , TwinJet TJ VS, Air Induction AI11003VS, and Agrotop. s with these nozzles were applied at a rate equivalent to 31 gal water/a at 40 psi (8 nozzles at 16-in. spacing). Plots were not inoculated but relied on natural dispersal of both Phytophthora infestans and Alternaria solani for disease establishment (the P. infestans isolate was identified as US-8 in Dr. J. P. Helgeson's lab at the UW). Disease severity was rated 18 and 24 Jun, 1, 9, 16, and 22 Jul, and 2, 6, 12, 19, and 26 Aug using the Horsfall-Barratt rating scale. Reglone (1.0 pt/a) plus Peptoil (1.0 qt/a) was applied on 28 Aug and 11 Sep to kill vines prior to harvest. The two center rows of each plot (a total of 48 ft of row) were machine harvested and graded Sep. Tubers were graded into US#1, undersize, and cull categories, and all potatoes in the US#1 category from each treatment plot were sorted using an optical size grader into six categories: < 4 oz, 4-6 oz, 6-10 oz, oz, oz and >16 oz. Specific gravity was determined for a tuber sample from each plot and pound samples from selected treatments were placed in storage. These will be evaluated for tuber decay, silver scurf, and black scurf after several months in storage. Rainfall recorded during the growing season (in.) was May, 2.89; Jun, 16.54; Jul, 3.16; Aug, 3.99; and 1-22 Sep, 2.53). An additional 16 in. of water was applied as overhead sprinkler irrigation in 24 applications (18 Jun 13 Sep). The 2002 growing season provided environmental extremes of excessive moisture early in the season and moisture stress at other times combined with high temperatures during the tuber bulking period. Even though the trial site was fumigated with metam sodium the previous fall, symptoms of early dying were prevalent by early August throughout the trial area. blight was first detected in this trial on 18 Jun and the first lesion of late blight was observed on 19 Jul. However, a prolonged period of unusually hot and dry weather continuing from early Jul to mid-aug, restricted both early blight and late blight movement for the middle part of the growing season. By late Aug, significant defoliation due to late blight was observed only in untreated plots. At the 12 Aug evaluation, approximately 25% of the foliage in untreated control plots exhibited symptoms of early blight. Control of early blight in all plots was considered good to excellent at this time with early blight severity less than 10% in many plots and less than 5% in a few plots. By 19 Aug, plants in the untreated control plots exhibited symptoms of early blight and late blight on over 40% of the foliage, respectively, while early blight severity was less than 25% in plots treated with Quadris 2.08F (3 sprays) alternated with TD (6 sprays), Quadris 2.08F, 0.36 pt, plus (2 sprays) alternated with alone (8 sprays), and Quadris 2.08F (3 sprays) alternated with Bravo Zn 4.17F (6 sprays). The lowest level of early blight was observed on this rating date in plots treated with Quadris 2.08F (3 sprays) alternated with Bravo Zn 4.17F (6 sprays) and applied with either the Tee Jet Hollow Disc Cone D3-23, the Lurmark Venturi ULD , Agrotop , or the TwinJet TJ VS nozzles. Given the widespread distribution of early dying symptoms in the trial, it is noteworthy that none of the treatments applied weekly to the plant foliage appeared to reduce the severity of early dying symptoms. At harvest, symptoms of advanced pinkeye, appearing as severe decay at the bud ends of tubers, were noted in most plots. The fungicide treatments applied in this trial did not affect the incidence of this disease. Total yields were lowest in the untreated control plots. Some of the highest total yields were recorded in plots treated with Quadris 2.08F (3 sprays) Page 1

2 alternated with Bravo Zn 4.17F (6 sprays) using the nozzle types listed above. In general tuber size was smaller than normal across all treatments. The proportion of tubers in the 6-10 oz size category was somewhat higher in plots where early blight progress was slowed by fungicide sprays. Significant differences in undersize and cull (misshapen and green) potatoes were not observed between treatments. Likewise, fungicide treatment did not appear to affect specific gravity. There was no evidence of treatment phytotoxicity in this trial. Efficacy, yield, and yield quality are important ways to evaluate fungicide performance. For the past several years we ve also used the market cost of fungicide sprays, a typical 2002 processing contract to compute crop value, and a typical 2002 return on fresh market sales to compute the economic return a grower might expect after treating the crop throughout the growing season. The value of treating the crop with fungicide varied widely in the 2002 trial depending on product efficacy and material cost that ranged from $55 to $190 for the season. While there were significant (P = 0.10) differences in values between treatments, the LSD was large. Using the fresh market value of harvested tubers for the value calculation, we find treatment values that range from +$957 (Quadris plus Bravo [3 sprays] and [6 sprays]) to negative values for several treatment protocols. When the processing contract values were used, the highest treatment value was +378 (same Quadris/ program) and there were many treatment values in the negative category. Table 1. treatment on foliar disease severity (percent foliage infection, early blight and late blight combined). Foliar Disease Severity (%) Rate/Acre Blight and Late Blight 2 Total Application Product AI Schedule 1 Jun Jun Jul Jul Jul Jul Aug Aug Aug Aug Aug 3 1 Untreated Bravo Ultrex 82.5 WDG Reason + Bond Previcur N 0.7 lb 0.52 pt 0.25 pt 1.2 pt 0.58 lb Appl lb Appl lb 0.90 lb Appl Bravo Ultrex 82.5WDG 0.91 lb 0.75 lb Bravo Ultrex 82.5 WDG Reason + Previcur N Bravo Ultrex 82.5 WDG 4 Bravo Ultrex 82.5 WDG Reason + Scala 5 BAS 510F 70WG + Ranman 400SC + Silwet L-77 Bravo Zn 4.17F 6 BAS 510F 70WG + Bravo Zn 4.17F Bravo Zn 4.17F 7 Headline (BAS500)2.08EC BAS 510F 70WG + Ranman 400SC + Silwet L-77 Acrobat 50WP + Polyram 80DF Bravo Zn 4.17F Page lb 0.35 pt 0.7 pt 1.4 lb 0.7 lb 0.35 pt 0.64 pt 0.14 lb 0.17 pt pt 0.14 lb 1.44 pt 0.39pt 0.14 lb 0.17 pt pt 0.4 lb 1.6 lb 0.58 lb 0.18 lb 0.53 lb 1.16 lb 0.58 lb 0.18 lb 0.27 lb 0.07 lb Appl 1-3 Appl 4-7 Appl Appl 1-3 Appl 4-9 Appl lb Appl Appl 1,3, lb 1.11 lb Appl 2,4, Appl 1,4 Appl 2, lb 0.2 lb 1.3 lb 1.11 lb Appl 3,6 Appl BAS 536F 18.7WG 1.66 lb 0.31 lb Weekly BAS 536F 18.7WG 1.66 lb 0.31 lb Weekly + Silwet L pt BAS 536F 18.7WG 1.66 lb 0.31 lb Appl 1,3,5,7,9 BAS 510F 70WG + Ranman 400SC 0.14 lb 0.17 pt 0.07 lb Appl 2,4,6,8 + Silwet L pt BAS 536F 18.7WG Bravo Zn 4.17F 12 Quadris Bravo Zn 4.17F 13 Gem 25 WG + Echo Zn Echo Zn 1.66 lb 0.39pt 0.78 pt 8 oz 1.6 pt 2.13 pt 0.31 lb Appl 1,3, lb Appl 2,4, Appl lb Appl 3, lb Appl 2,4, oz 0.84 lb 1.11 lb Appl 1,3,5,7,9 Appl 2,4,6,

3 Foliar Disease Severity (%) Rate/Acre Blight and Late Blight 2 Application Schedule 1 Jun Jun Jul Jul Jul Jul Aug Aug Aug 19 Aug Total 26 Aug 3 Product AI 14 Quadris 2.08 F 0.39pt Appl 1,3,5 Penncozeb 75WP Appl 2,4, Quadris 2.08 F 0.39pt Appl 1,3,5 TD pt Appl 2,4, Quadris 2.08 F 0.39pt Appl 1,3,5 TD pt Appl 2,4, Quadris 2.08 F 0.39pt Appl 1,3,5 Dithane 75DF Appl 2 Gavel 75DF Appl 4, Quadris 2.08 F Gavel 75DF 19 Quadris 2.08 F Dithane 75DF + Curzate 60 DF Gavel 75DF 20 KQ WG 21 KQ WG 22 KQ WG 23 KQ WG Manzate 200DF 75WG 24 KP WG + Manzate 200DF 75WG 25 Manzate 200DF 75WG Curzate 60 DF + Quadris 2.08 F 26 Manzate 200DF 75WG Manzate 200DF 75WG + Super Tin + Curzate 60 DF 27 Manzate 200DF 75WG Quadris 2.08 F. + Curzate 60 DF 0.39pt 0.39pt 1 lb 0.5 lb 1.0 lb 0.38 pt 0.188lb 0.38 pt 5.0 oz 5.0 oz 1.1 lb 0.69 lb 1.03 lb 1.38 lb 1.03 lb 0.25 lb 0.75 lb 0.15 lb 0.19 lb 1.12 lb 0.19 lb Appl 1,3,5 Appl 2, 4, Appl 1,3 Appl 2 Appl 4 Appl Appl 1,3,5,7,9 Appl 3, 5, 7, 9 Appl 2, 4, 6, 8 Appl 2, 4, Appl 1,3,5,7,9 Appl 3, 5, 7, 9 Appl 2, 4, 6, 8 Appl 2, 4, Appl 1,3,5,7,9 Appl 3, 5, 7, 9 Appl 2, 4, 6, 8 Appl 2, 4, Appl 1, 3, 5 Appl 3, 5 Appl 2, 4, 6-9 Appl 2, 4, Appl 1, 3, 5 Appl 2, 4, 6-9 Appl 2, 4, Appl 1 3 Appl 4, 6, 8, 9 Appl 5, Appl 1 4 Appl 5 9 Appl 1, 2 Appl 3,5 Appl 3 Appl 5 Appl 4, Curzate 60 DF KQ WG 1.03 lb Weekly + Curzate 60 DF Appl 2-5, Messenger (20 ppm=2.5g/gal) Appl 0, 3, 8 Quadris 2.08 F 0.38 pt Appl 1, 3, lb Appl 2,4, Equus lb Appl 1,4,7 Quadris 2.08 F 0.38 pt Appl 2, 5, 8 + Manzate 200DF 75WG Equus lb Appl 3, 6, 9 + Super Tin 2.5 oz 0.13 lb Equus 500 Zn 2.1 pt 0.57 lb Weekly Equus lb Appl 1, 4, 7 Headline (BAS500)2.08EC 0.39 pt Appl 2, 5, 8 + Manzate 200DF 75WG Equus lb Appl 3, 6, 9 + Super Tin 2.5 oz 0.13 lb Page 3

4 Page 4 Foliar Disease Severity (%) Rate/Acre Blight and Late Blight 2 Application Schedule 1 Jun Jun Jul Jul Jul Jul Aug Aug Aug 19 Aug Total 26 Aug 3 Product AI 33 Ranman 400 SC 0.17 pt 0.07 lb Appl 1,3,5,7,9 BAS 536F 18.7WG 1.6 lb 0.3 lb Appl 2, 4, 6, Ranman 400 SC 0.17 pt 0.07 lb Appl 1,3,5,7,9 BAS F (Headline) 0.77 pt 0.2 lb Appl 2, 4, 6, Ranman 400 SC 0.17 pt 0.07 lb Appl 1, 4, 7 BAS F (Headline) 0.77 pt 0.2 lb Appl 2, 5, 8 Acrobat 50WP 0.4 lb 0.2 lb Appl 3, 6, 9 + Polyram 80 DF 1.6 lb Ranman 400 SC BAS 536F 18.7WG 37 Champ DF + Bravo Zn 0.13 pt 1.6 lb 2 lb 1 pt 1.56 pt 2.13 pt 0.05 lb 0.3 lb 0.52 lb 0.81 lb 1.11 lb Appl 1,3,5,7,9 Appl 2, 4, 6, Weekly Appl 1-3 Appl 4-6 Appl Fluoronil Bravo Zn 2 lb 1 pt 1.56 pt Appl 3,5, lb Appl lb Appl 4, pt 1.11 lb Appl 8, Echo Zn 1.11 lb Weekly Echo Zn + Quadris 2.08 F Echo Zn Polyram 80 WP + Super Tin 80 WP Echo Zn + Polyram 80 WP 41 Gem 25 WG + Echo Zn Echo Zn 42 YF YF YF Quadris 2.08 F + 46 Quadris 2.08 F pt 2.13 pt 0.23 lb 1.25 pt 0.375lb 1.6 pt 2.13 pt 1.19 pt 2.25 pt 0.36 pt 1.25 pt 0.54 pt 1.88 pt 0.78 lb 1.11 lb 1.6 lb 0.18 lb 0.65 lb 1.2 lb 1.5 oz 0.84 lb 1.11 lb Appl 1, 3 Appl 2, 4, 5 Appl 6, 8 Appl 7,9 Appl 1,3,5,7, Appl 2, 4, 6, lb Appl 1, 3, 5 Appl 2, 4, lb Appl 1, 3, 5 Appl 2, 4, lb Appl 1, 3, 5 Appl 2, 4, lb Appl 1, 3, lb Appl 2, 4, lb 1.41 lb Appl 1, 3, 5 Appl 2, 4, Quadris 2.08 F 0.39 pt Appl 1, 3, 5 Appl 2, 4, Weekly Headline (BAS500)2.08EC 0.38 pt Appl 1, 3 Bravo Ultrex 82.5 WDG 1.0 lb 0.83 lb Appl 2 Polyram 80DF + Super Tin 0.156lb 1.6 lb 0.13 lb Appl 4-8 Bravo Ultrex 82.5 WDG 1.0 lb 0.83 lb Appl Headline (BAS500)2.08EC Bravo Ultrex 82.5 WDG Polyram + Acrobat 50 WP Headline (BAS500)2.08EC + Bravo Ultrex Bravo Ultrex 82.5 WDG 51 Bravo Zn 4.17 F + Curzate 60 DF 52 Quadris 2.08 F + Curzate 60 DF Bravo Zn 4.17 F + Curzate 60 DF 53 Quadris 2.08 F Bravo Zn 4.17 F 0.38 pt 1.0 lb 0.4 lb 0.38 pt 0.5 lb 1.0 lb 0.39 pt 0.39 pt 0.83 lb 1.6 lb 0.2 lb 0.41 lb 0.83 lb Appl 1, 3 Appl 2 Appl 4, 6-8 Appl 5 Appl lb Weekly Appl 1-4, Appl 1,3,5 Appl 1, lb Appl 2,4 6-9 Appl 2, lb Appl 1 Appl 0,

5 Foliar Disease Severity (%) Rate/Acre Blight and Late Blight 2 Total Application Product AI Schedule 1 Jun Jun Jul Jul Jul Jul Aug Aug Aug Aug Aug 3 54 Quadris 2.08 F 0.39 pt Appl 1,3 Bravo Zn 4.17 F 1.11 lb Appl 0,2, Quadris 2.08 F 0.39 pt Appl 1,3,5,7 Bravo Zn 4.17 F 1.11 lb Appl 0,2,4,6,8, Quadris 2.08 F 0.39 pt Appl 0,2,4,6,7 Bravo Zn 4.17 F 1.11 lb Appl 1,3,5,8, Quadris 2.08 F 0.39 pt Appl 0,2,4-7 Bravo Zn 4.17 F 1.11 lb Appl 1,3,8, Bravo Zn 4.17 F 1.11 lb Weekly Quadris 2.08 F 0.39 pt Appl 1, 3, 5 Bravo Zn 4.17 F 1.11 lb Appl 0,2,4, s all received the same fungicide treatment but with different nozzle types. All were applied at 40 psi, using 8 nozzles with 16" spacing, at 31 GPA Quadris 0.39pt 0.78 pt 0.2 lb 1.11 lb Appl 1 Appl 3,5 Appl 2,4,6-9 Bravo Zn 4.17F Agrotop (Venturi body w/ Ext. Range Flat Fan nozzle XR110 03VS) XR110 03VS Ext. Range Flat Fan nozzle ULD Lurmark Venturi nozzle TJ VS TwinJet nozzle A111003VS Air induction nozzle Pr > F <0.01 < LSD 4 NS NS NS NS NS NS Application dates for our standard spray program: 1 = 26 Jun, 2 = 3 Jul, 3 = 10 Jul, 4 = 17 Jul, 5 = 24 Jul, 6 = 31 Jul, 7 = 7 Aug, 8 = 14 Aug, 9 = 21 Aug. Some treatments required an application a week ahead of our standard program. This was done 19 Jun and is designated application 0. 2 Severity rated on a Horsfall-Barratt scale of 0 (no infection) to 11 (all foliage and stems dead). Ratings were converted to percentages. disease severity (early blight and late blight, attempting to exclude damage from early dying) was assessed first. Then amount of early and late blight were estimated separately (the separate estimates do not necessarily add up to the combined defoliation figure as they were done independently). 3 For the final rating the Total severity evaluation includes defoliation due to early blight, late blight and early dying. Severity of early blight and late blight was then estimated separately for each plot. 4 Analysis of variance was performed on data, and Fisher s protected least significant difference (LSD) was calculated. NS = not significant at P = 0.10 (* indicates differences between pairs of treatments were significant at P = 0.10, but not at P = 0.05). Table 2. treatment on early blight and late blight severity (percent foliage infection). ( numbers correspond to those listed in Table 1). # 18 Jun 24 Jun 1 Jul 9 Jul Foliar Disease Severity (%) 1 Blight Alone Jul Jul Aug Aug Aug Aug Aug Page 5 9 Jul 16 Jul Late Blight Alone Aug Aug Aug 19 Aug 26 Aug

6 Foliar Disease Severity (%) 1 Blight Alone Late Blight Alone # Jun Jun Jul Jul Jul Jul Aug Aug Aug Aug Aug Jul Jul Aug Aug Aug Aug Aug Pr >F <0.01 < <0.01 <0.01 < LSD 3 NS NS NS NS NS NS NS NS NS NS 1 Severity rated on a Horsfall-Barratt scale of 0 (no infection) to 11 (all foliage and stems dead). Ratings were converted to percentages. foliage infection was assessed first. Then amount of early and late blight were estimated separately (the separate estimates do not necessarily add up to the combined defoliation figure as they were done independently). 2 Disease had progressed sufficiently that early and late blight could not be evaluated separately on 26 Aug for the untreated control plots thus analysis for early and late blight for 26 Aug is for differences AMONG treatments, excluding the untreated control. 3 Analysis of variance was performed on data, and Fisher s protected least significant difference (LSD) was calculated. NS = not significant at P = 0.10 (* indicates differences between pairs of treatments were significant at P = 0.10, but not at P = 0.05). Page 6

7 Table 3. fungicide treatment on relative area under the disease progress curve, yield, proportion of US#1, undersize and cull potatoes, specific gravity, and size grades of US#1 potatoes ( numbers correspond to those listed in Table 1). Relative AUDPC 1 Yield No. of Size Grades of US # 1 Potatoes - % Late TOTAL US#1 Undersize 2 Culls Specific Rotted Blight Blight cwt/a cwt/a % cwt/a % cwt/a % Gravity tubers 3 < 4 oz 4-6 oz 6-10 oz oz 6-13 oz oz > 16 oz Page 7

8 Page 8 Relative AUDPC 1 Yield No. of Size Grades of US # 1 Potatoes - % Late cwt/a cwt/a % cwt/a % cwt/a % Gravity tubers 3 < 4 oz 4-6 oz 6-10 oz oz 6-13 oz oz > 16 TOTAL US#1 Undersize 2 Culls Specific Rotted Blight Blight oz Pr>F < 0.01 < LSD * 62.6* NS NS NS NS NS NS NS NS NS 8.9* NS NS NS Relative area under the disease progress curve. Data for each observation date were plotted on a graph and the area under the line was calculated for each treatment providing a measure of the relative severity of disease throughout the season. A disease rating of 100% severity for the entire season would produce a value of 1.0. All relative AUDPC values are expressed as a proportion of this value. Either decreased disease severity or later disease development will contribute to lower relative AUDPC. and late blight AUDPC values were calculated from 18 Jun - 19 Aug. Disease had progressed sufficiently that early and late blight could not be evaluated separately on 26 Aug for the untreated control plots. The combined AUDPC was calculated from combined blight rating data (total defoliation of the plot, combining both early and late blight) from 19 Jun - 26 Aug (if only early blight was seen in a plot, total disease was equal to early blight). 2. Undersize indicates potatoes < 1 7/8 in diameter. 3. The average number of tubers per treatment with any kind of rot observed during grading. 4. Analysis of variance was performed on data, and Fisher s protected least significant difference (LSD) was calculated. NS = not significant at P = 0.10 (* indicates differences between pairs of treatments were significant at P = 0.10, but not at P = 0.05).

9 Table 4. No. experimental treatment on value per acre of Russet Burbank tubers. ( numbers correspond to those listed in Table 1) Cost of Chemicals/Acre ($) 1 Fresh Market 2 Processing 3 Fresh Market 2 Processing 3 Fresh Market 2 Processing of Yield ($/A) Net of Yield ($/A) 4 on ($/A) Page 9

10 No. Cost of Chemicals/Acre ($) 1 Fresh Market 2 Processing 3 Fresh Market 2 Processing 3 Fresh Market 2 Processing of Yield ($/A) Net of Yield ($/A) 4 on ($/A) Pr > F LSD NS NS 719* 339* 719* 339* Season-long cost of chemicals/acre (rate, number of applications and retail cost are included in calculation). Application costs are not included. Typical retail prices used: Acrobat 50WP - $ 19.25/lb Curzate 60DF - $ 29.00/lb Gavel 75DF - $4.50/lb Previcur Flex - $ 62/gal Bond - $28.95/gal Dithane DF Rainshield - $ 2.50/lb Gem 25 WG- $ 3.10/oz Quadris 2.08 F - $ 250/gal 6F - $ 42.50/gal Echo Zn - $ 32.00/gal Manzate - $ 2.00/lb Silwet L77 - $159/gal Bravo Zn 4.17F - $ 32.00/gal Equus 500 Zn - $ 32.00/gal Messenger - $4.50/oz Super Tin 80WP- $ 30/lb Bravo Ultrex - $ 6.50/lb Equus /gal Penncozeb - $ 2.00/lb Champ DF - $3.08/lb Fluoronil - $13.85/lb Polyram 80DF - $ 2.10/lb If ANY component of the treatment was an experimental product with no retail price, the cost of chemicals was not calculated. 2 Typical 2002 fresh market pricing: 4-6 oz $11.00/cwt, 6-10 oz $13.50/cwt, oz $14.50, >13 oz $15, < 4 oz and culls $4.00/cwt. 3 Typical 2002 processing contract pricing: Base price is $4.92/cwt for 69% US#1 (4 oz minimum) with specific gravity of A premium is paid for > 18% 10 oz or greater. For each 1% above 18% (to a maximum of 32%) > 10 oz the price increases $0.01/cwt. The price decreases $0.01/cwt for each 1% below 19%. There is an increase or decrease in price per hundred weight depending on specific gravity: > $.17; $.14; $.11; $.08; $.06; $.04; $.02; $.00; for each decrease in specific gravity below 1.078, there is a $0.02 penalty ( $.02, $.04, $.06, etc). There is a payment of $2.00/cwt for processing culls (up to a maximum of 15% of the total by weight). 4 value minus cost of chemicals applied. 5 Net value for the treatment minus net value of the untreated control. 6 Analysis of variance was performed on data, and Fisher s protected least significant difference (LSD) was calculated. NS = not significant at P = 0.10 (* indicates differences between pairs of treatments were significant at P = 0.10, but not at P = 0.05). Table 5. Data ranked according to several disease and yield measurements ( numbers correspond to those listed in Table 1. Footnotes for all sections of this table appear on page 14). Sorted by Relative AUDPC ( Blight) (increasing) Relative AUDPC 1 Yield Processing 3 Late Page 10 Relative AUDPC 1 Yield Processing 3 Late

11 Relative AUDPC 1 Yield Processing 3 Late Relative AUDPC 1 Yield Processing 3 Late Pr>F < 0.01 < LSD * 62.6* NS 339* Sorted by Relative AUDPC (Late Blight) (increasing) Relative AUDPC 1 Yield Processing Relative AUDPC 1 Yield Processing Pr>F < 0.01 < LSD * 62.6* NS 339* Sorted by Relative AUDPC ( EB & LB) (increasing) Relative AUDPC 1 Yield Processing Page 11 Relative AUDPC 1 Yield Processing

12 Relative AUDPC 1 Yield Processing Relative AUDPC 1 Yield Processing Pr>F < 0.01 < LSD * 62.6* NS 339* Sorted by total yield (decreasing) Relative AUDPC 1 Yield Processing Relative AUDPC 1 Yield Processing Pr>F < 0.01 < LSD * 62.6* NS 339* Sorted by yield of US#1 potatoes (decreasing) Relative AUDPC 1 Yield Processing Page 12 Relative AUDPC 1 Yield Processing