Prepared by Susie Thompson, Ph.D. and Robert D. Davidson, Ph.D., Department of Horticulture & Landscape Architecture, San Luis Valley Research Center, Colorado State University
This profile was developed for production in the San Luis Valley. While some guidelines may be appropriate regardless of growing area, fine-tuning for specific production locales is recommended.
Alpha is a late maturing cultivar released in 1925 by Professor Ir. J.C. Dorst of Leeuwarden, Holland. Primary use is for the fresh market, and it is particularly suited for boiling.
Plant/roots: Plants emerge uniformly and quickly, with a large, upright vine and light red-purple flowers. If dormant (seed tubers not warmed, eyes not peeping) tubers are used, emergence may be quite erratic. Alpha has a determinate growth habit, with a medium sized root system.
Tubers: Tubers have yellow flesh, are round to slightly oval, with a buff to pale yellow, slightly flaky skin. Eyes are shallow and well distributed. Specific gravity levels are medium (1.080).
Yield potential: Yield potential is medium (350 cwt./acre).
Pre-planting considerations: Tuber dormancy is strong. Whole or cut seed is acceptable, however, precut seed may be preferred, as the increased stem number aids in limiting oversized tubers late in the season. Chitting (green sprouting) may be advantageous if whole seed is utilized. A 6 to 8-inch within-row spacing maximizes production of small tubers desired by the tablestock industry. Plant 4 inches deep in a broad, well-shaped hill to minimize late season greening.
Fertility: Apply total fertilizer in the range: N(120#), P(80-190#), K(0-100#) for Alpha. Pre-plant N should be in a range of 60-80#. Sprinkler applied N should be in the range of 40-60#. There may be a benefit from applications at a rate of 7-10# per application, but not exceeding 20# per application. All nitrogen should be applied prior to July 31 in the San Luis Valley. Vines may become quite large if excessive nitrogen is used early in the season. Tuberization may also be delayed.
Irrigation: The interval at the maximum ET is approximately 3 days. Drought tolerance is moderate. Due to the large vine size, monitor moisture closely during extended periods of hot weather.
Weeds: Alpha competes well with weeds. It is not sensitive to common potato herbicides.
Insects: Standard insect control measures are suitable.
Fungicides: Apply first application in conjunction with the early blight degree-day model. Utilize a typical spray program for the San Luis Valley.
Tuberization/bulking: Tuber set is medium to high and in the middle of the hill. Greening may be a problem without proper hill conformation. Tuber bulking occurs rapidly mid to late season. Growth cracks, misshapen tubers and deeper eyes may result if plants are stressed during tuber bulking.
Vine Kill: The average number of days from planting to vine kill is about 110. Adequate skin set occurs in 14 days. Tubers may become excessively large late in the season; close monitoring is warranted by early August.
Alpha generally has few storage problems. Alpha is somewhat susceptible to blackspot bruise.
Overall, disease problems are minimal. Bacterial ring rot symptom expression is adequate. Symptoms appear later in the season, 90+ days after planting. Reaction to PVY infection is normal, and infected plants are easily detected.
Foliar early blight Moderate
Verticillium wilt Unknown
Seedpiece decay Susceptible
Leafroll virus Moderate
Leafroll net necrosis Unknown
Tobacco Rattle Virus Susceptible
Common scab Moderately resistant
Powdery scab Moderately susceptible
Bacterial ring rot Susceptible
Late blight Moderately resistant
Tuber early blight Moderately resistant
Bacterial soft rot Unknown
Fusarium dry rot Unknown
Pythium leak Moderate
Pink rot (P. erythroseptica) Moderate
Silver scurf Susceptible
Rhizoctonia scurf Susceptible
Disease reaction ratings = susceptible, moderately susceptible, moderate, moderately resistant and resistant.