SHEPODY: MANAGEMENT PROFILE
Because eyes are unevenly distributed and tend to be prevalent at the apical (bud) end, blind seed-pieces can occur from the basal (stem) end of large tubers. Planting of "single drops" (whole 2-inch tubers) is preferred for better stands and heavier sets of moderately-sized tubers. If cut seed is used, it is suggested to precut 7-10 days for quicker and more even emergence and better stand.
Planting to Emergence
For French fry production, seed-pieces should be spaced 8 to 11 inches within the row (34-36 inch row-spacing) depending on tuber set. Since Shepody oversizes easily and may green, pieces should be planted about 4 inches deep in a hill as large as possible. A wider hill is preferred over a taller one. Avoid scabby ground. Avoid using metribuzin (Lexone or Sencor); if used, apply pre-emergence safely before ground cracking.
Shepody needs about 80% of the nitrogen required for Russet Burbank. In Idaho and Maine, process quality was reduced even though yields were not. Do not exceed 200 lb N/acre. In alkaline soils, application of ammonium sulfate is recommended. Mild nitrogen deprivation before vine desiccation will allow an increase in tuber specific gravity (dry matter content) and make for easier vine desiccation.
Under sprinkler irrigation, supplemental nitrogen may be added until full bloom to maintain nitrate levels in petioles. Shepody has a narrow and high range for petiole nitrate content. In Idaho (Figure 1), the "sufficiency nutrient range" (SNR) for Shepody is from 20,000 to 24,000 ppm at 55 days after planting and drops to 8,000 to 11,000 ppm at tuber maturation. [Note: SNR is the minimum to maximum nitrate concentration that should be present in petioles at different stages of the crop's growth. Petiole nitrate levels outside this range indicate a potential loss of tuber quality such as shape defects and sugar ends.]
Phosphorus at 50 to 75 lb/acre is added to prevent nitrogen-caused reduction in specific gravity. Potassium may reduce specific gravity.
Up to flower drop, available soil moisture needs to be above 70%; afterwards, it can drop to 60%. Shepody requires less water applied more often than longer season varieties such as Russet Burbank. At the end of the growing season, irrigate less to avoid water rot, tuber oversizing and difficult vine desiccation.
Shepody is susceptible to early and late blight. Treatment should begin early depending on weather and may require 3 or more applications of a protectant, 7-14 days apart.
Tuber Quality Note
Because of tuber oversizing and shallow set, Shepody tubers are prone to greening. Shepody is more resistant to sugar ends than Russet Burbank but under very hot and dry conditions, especially if overfertilized, sugar ends can be a problem. With hot, dry surface soil, field sprouting can occur. These conditions may also result in a low specific gravity.
Actively growing Shepody is hard to desiccate. Sample tubers to determine optimal size and specific gravity for vine desiccation. Due to Shepody's tendency to oversize, chemical desiccation is recommended. Sometimes a pre-desiccation, mild vine beating has been performed prior to chemical application. Sulfuric acid may be used if the tubers will not be stored else sugar ends may occur. Shepody should be ready to harvest 120 days after planting (95-100 days after emergence). In late blight areas, vines must be completely desiccated if tubers are to be stored. Rapid desiccation of green vines should be avoided if tubers will be harvested later and stored. Metalaxyl (Ridomil) applied mid-season is suggested for tubers going into storage to inhibit leak, pink rot and late blight development.
Shepody is not recommended for storage when tubers are to be processed. Tubers tend to accumulate sugars and reduce process quality. If stored, maintain temperature at 50-55 F and apply a sprout inhibitor (CIPC, Sprout Nip) after 2 months of storage.
- Young, D.A., T.R. Tarn and H.T. Davies. 1983. Shepody: a long, smooth, white-skinned potato of medium maturity with excellent French fry quality. Am. Potato Jour. 60:109-113.
- Rex, B.I., W.A. Russell and H.R. Wolfe. 1987. The effect of spacing of seedpieces on yield, quality and economic value for processing of Shepody potatoes in Manitoba. Am. Potato Jour. 64:177-189.
- Porter, G.A. and J.A. Sisson. 1991. Response of Russet Burbank and Shepody potatoes to nitrogen fertilization in two cropping systems. Am. Potato Jour. 68:425-443.
- Porter, G.A. and J.A. Sisson. 1991. Petiole nitrate content of Maine-grown Russet Burbank and Shepody potatoes in response to varying nitrogen rate. Am. Potato Jour. 68:493-505.
- Pritchard, M.K. and L.R. Adam. 1994. Relationship between fry color and sugar concentration in stored Russet Burbank and Shepody potatoes. Am. Potato Jour. 71:59-68.
Key Management Points for Shepody
120 days after planting
early blight, late blight, viruses, Verticillium wilt
sensitive to metribuzin
short dormancy, shallow set, tend to oversize and green
few eyes at stem end, precut
8-11 inch spacing, 4 inches deep
<200 lb/acre by full bloom
20-24,000 ppm, 55 days post-plant, 8-11,000 ppm, tuber maturation
>70% available soil moisture to flower drop
difficult with green vines
avoid - sugars buildup, sprouting