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Alexander D. Pavlista

Chemical vine desiccation of potato (Solanum tuberosum L.) is widely used in the USA. Diquat is the major vine desiccant but has some drawbacks such as incomplete stem desiccation allowing regrowth. A new herbicide, UCC-C4243, was evaluated as a replacement for diquat. The potato cultivar `Atlantic' was treated with UCC-C4243 (a.i.) at 0.25 to 2.5 oz/acre (17.5 to 175 g·ha-1), and leaf and stem desiccation efficiency was compared to diquat (a.i.) at 4 oz/acre (280 g·ha-1). Split applications of UCC-C4243 were compared to double applications of diquat. Subjective evaluations were made on regrowth and tuber skinning, and objective measurements on specific gravity and yield. Trials were conducted from 1991 to 1995 at Scottsbluff, NE. UCC-C4243 at 1.5 oz/acre (105 g·ha-1) and higher significantly increased leaf and stem desiccation compared to diquat. There was no difference between single and split applications of UCC-C4243. UCC-C4243 suppressed regrowth at 1 oz/acre (70 g·ha-1) and prevented it at 2.5 oz/acre at 3 weeks after treatment while diquat did not. Skin set of tubers was promoted equally by all desiccants. Specific gravity was not lowered by UCC-C4243 but was by diquat. Yields were not affected by either UCC-C4243 at 1.5 oz/acre or diquat at 4 oz/acre. UCC-C4243 was more effective than diquat as a vine desiccant without the regrowth and tuber specific gravity effects associated with diquat.

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Elzette van Rooyen* and Randolph Beaudry

The objective of this study was to evaluate preharvest fertilizer application and postharvest storage temperature and duration as they affect the intensity and stability of color in red and purple potato cultivars during storage. `Michigan Purple', `Dakota Rose', and `Chieftain' were stored at 4 °C and hue angle (h°) was measured weekly. The initial `Michigan Purple' h° of 1.1° changed to 23.2° after 18 weeks of storage (a shift in h° from 350° to 30° changes from purple to red) while the initial hue angle of 18.5° and 34.1° for red-skinned cultivars, `Dakota Rose' and `Chieftain', changed to 27.2° and 43.2°, respectively. Hence, the degree of color shift was greater in `Michigan Purple' although all the cultivars in this experiment underwent significant color change during storage. Hue angle of `Michigan Purple' tubers stored at 4°, 10°, and 20 °C for 8 weeks changed 19.4°, 12°, and 14.2° toward the redder h°, respectively. Thus, the color of `Michigan Purple' tubers changed the least at 10°C. Hue angle of `Michigan Purple' tubers fertilized with 180 lbs/acre slow-releasing nitrogen, 180 lbs/acre nitrogen, 270 lbs/acre nitrogen, and 2.5 lbs/acre poultry manure was measured after 5 weeks at 4 °C. Hue angles were 0.92°, 11.65°, 3.99°, and 1.34°, respectively. The hue of the first three treatments differed significantly from one another, but the hue of the potatoes treated with 180 lbs/acre slow-releasing nitrogen and 2.5 lbs/acre poultry manure did not differ. Preharvest factors like plant nutrition can influence tuber color in storage and `Michigan Purple' tuber color is particularly sensitive to storage temperature.

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Martha Maletta, Melvin Henninger, and Kristian Holmstrom

Potato leafhopper (PLH) control and plastic mulch culture for certified organic potato production were evaluated in 2003 and 2004. The trials were conducted on the Rutgers Snyder Research and Extension Farm's certified organic fields. Production practices conformed to the National Organic Program. The potato cultivar grown was `Superior'. In 2003, PLH controls were: untreated control (UTC); Surround WP, 25 lb/acre; PyGanic EC 1.4, 1 pt/acre; Surround plus PyGanic; and silver plastic mulch. PyGanic and Surround/PyGanic treatment reduced PLH nymph counts and damage (hopperburn–HB), when compared to the UTC. Counts were higher and HB more severe in silver mulch plots than in the UTC, but marketable yield was more than double the UTC. PyGanic and Surround/PyGanic treatment yields were 50% higher than the UTC. In 2004, PLH controls were: PyGanic EC 1.4, 1–2 pt/acre; Diatect V, 2–4 lb/acre; and Surround WP, 25 lb/acre. The crop was grown on bare ground or silver plastic mulch. Nymph counts and HB were lowest on PyGanic- and Diatect-treated plots. Nymph counts and HB for UTC and Surround treatment were higher on plastic mulch than bare ground plots. Marketable yield was highest from PyGanic-treated plots. PyGanic or Diatect treatment yields were higher from plastic mulched than from bare ground plots. The PLH control and plastic mulch culture significantly increased organic potato yields. Marketable yield from the UTC was lower than the New Jersey average for conventional potato (275 hundred wt/acre) by 71% on bare ground and by 39% with plastic mulch in 2003; 59% on bare ground; and 52% with plastic mulch in 2004. PLH control with PyGanic combined with plastic mulch culture resulted in yields just 7% less than the state average; yield on bare ground was 26% less.

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Kathleen G. Haynes, Lincoln Zotarelli, Christian T. Christensen, and Stephanie Walker

Potatoes are the most widely consumed vegetable in the United States ( USDA, ERS, 2013 ). Most U.S. potato cultivars are white fleshed, although several yellow-flesh cultivars have also met with considerable consumer acceptance, and more recently

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William B. Evans and Darryl D. Warncke

Six potato cultivars (Atlantic, Sebago, Onaway, Russet Burbank, Lemhi Russet,and Norland) were evaluated for phosphorus uptake efficiency in solution culture. Individual rooted cuttings of each cultivar were transferred from a standard 1/5 Hoagland's solution into solutions containing one of six P concentrations (0.05,0.1,0.22,0.5,1.1 and 2.3mg/l). After a 24h adjustment period P uptake was followed over a 6h period by collecting solution aliquots every two hours. All cultivars depleted the two lowest initial P concentrations to similar stable P concentration. The P uptake rate per unit length of root showed a sigmoidal relationship to the initial P solution concentration. The general nature of the P uptake relation to solution P concentration was similar among the cultivars, although the actual values varied. In general, P uptake rate increased from 5.0 × 10-4 at the lowest concentration to 7.0 × 10-2μg·cm-1·h-1 at the highest P solution concentration.

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Kathleen G. Haynes, William E. Potts, Jesse L. Chittams, and Diane L. Fleck

For the yellow-flesh fresh market, potato (Solanum tuberosum L.) varieties with intense yellow flesh are desired. Twenty-five yellow-flesh clones, including 24 U.S. Dept. of Agriculture (USDA) selections and the check variety `Yukon Gold', were evaluated for tuber yellow-flesh color, as measured by a reflectance colorimeter, and for individual tuber weight in replicated field trials in Presque Isle, Maine, in 1991 and 1992. There were significant differences among clones for yellow-flesh intensity. Yellow-flesh intensity in two USDA selections was significantly less than in `Yukon Gold'. In four USDA selections, yellow-flesh intensity was significantly greater than in `Yukon Gold'. In general, there was an inverse relationship between tuber weight and yellow-flesh intensity. Subsamples of tubers whose weight fell between the 10 to 90, 25 to 75, 35 to 65, and 40 to 60 percentile were compared to the full sample. There was good agreement between the 10 to 90 and 25 to 75 percentile subsample and the full sample regarding the average yellow-flesh intensity and in the consistency of pairwise comparisons between individual selections and `Yukon Gold'. For determining yellow-flesh intensity, the 25 to 75 percentile subsample was as informative as the full sample.

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Zana C. Somda and Stanley J. Kays

Changes in leaf distribution of the sweet potato [Ipomoea batatas (L.) Lam.] cultivar Jewel were assessed bi-weekly for 18 weeks at three plant densities (15, 30, and 45 cm × 96-cm spacing). The distribution of leaves on the branches and the timing at which leaf number stabilized were affected by the plant density. Plant density resulted in significant differences in the number of leaves and percentage of missing leaves during the growing season. Leaf number and total leaf area varied substantially in response to plant density, but individual lamina and petiole lengths and leaf area did not vary. Average petiole and leaf lengths and leaf size increased during the season, with the maximum length and area dependent on the type of branch on which the leaf was formed. Average petiole length per branch and the susceptibility to leaf loss increased with descending branch hierarchy (secondary branch < primary branch < main stem). Leaf losses after the 4th week tended to parallel a progressive increase in petiole length of new leaves, suggesting shading as a primary cause of leaf shedding and the loss of the oldest leaves first.

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Matthew D. Kleinhenz, Jiwan P. Palta, Christopher C. Gunter, and Keith A. Kelling

by a grant from the Wis. State Potato Industry Board to Jiwan P. Palta. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely

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Joseph F. Guenthner

Vegetable producers and marketers make business decisions based on supply estimates. The U.S. Dept. of Agriculture provides estimates of planting intentions for field crops but not for most vegetable crops. This study developed models that can be used to forecast vegetable crop plantings. Multiple linear regression analysis was used to determine the factors that influence plantings of potatoes and onions. Field crop planting intentions, industry structure, lagged values of plantings, prices received, price volatility, and the price of sugar beets were found to be significant factors. The models and/or methods used in this study should be useful to those interested in forecasting vegetable plantings.

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Mack Wilson, Victor Khan, and Clauzell Stevens

A randomized design was conducted in 1994 to determine the effect of flower removal on yield of two potato and three sweetpotato cultivars. The results showed a three-way interaction with mean height of `Atlantic' and `Snowden' potatoes evaluated in this study. Total root numbers of the two potato cultivars were significantly greater when rowcovers were used. The yield of grade A sweetpotato cultivars was greater when flowers were removed. The yield and marketable yield of U.S. no. 1 sweet potatoes was significant when flowers were removed.