FREMONT RUSSET

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.

Fremont Russet is a medium yielding, medium-late maturing, fresh market russet cultivar. Tubers are oblong to long, with medium specific gravity. Due to excellent late-season storage capabilities, Fremont is suitable to fill the Centennial Russet niche as a late storage potato. It performs well in rocky soils. Release is pending by the Colorado Agricultural Experiment Station. Fremont Russet was tested as CO85026-4 and is the result of a cross between Century Russet x WNC630-2. Plant variety protection will be pursued.

Plants/roots: Emergence is uniform, with a medium-sized vine, similar to Century Russet in color and vine architecture. Flowers are white. It has a determinate growth habit and a moderate to shallow root system.

Tubers: Tubers are oblong to long, with a dark, medium-heavy russet skin. Eyes are shallow and most prevalent on the apical end. Tuber flesh is white. Specific gravity is medium (1.084 avg.).

Yield potential: Yield potential is medium (+350 cwt./acre).

GROWING SEASON MANAGEMENT

Pre-planting considerations: Tubers have medium dormancy. Whole or cut seed is acceptable. A seed spacing of 12-inches may optimize total yield and desired tuber size for the commercial market. Wider plant spacing often increases tuber yield, however due to rough and misshapen tubers, more culls are produced.

Fertility: Apply total fertilizer in the following range N(140-150#), P(80-190#), K (0-100#). Fertility needs are very minimal compared to many other major russet cultivars. Pre-plant N applications should be in the range of 50-70#. Timing of tuberization is affected by N applications. Tuberization does not seem to be delayed, however tubers tend to grow extremely rapidly and misshapen in the process. Spoon-feed remaining N at the rate of 7-10# per application (do not exceed 20# per application).

Irrigation: Interval at the maximum ET is 3 days. Drought tolerance is moderate. Enlarged lenticels have been noted when water applications were excessive, particularly late in the season.

Pest Control

Weeds: Fremont Russet is resistant to metribuzin (Sencor, Lexone) applications.

Insects: Standard insect control measures generally are effective but timing and rotation of appropriate control is important.

Fungicides: Fremont is susceptible to late blight, thus if the pathogen is present, utilize an appropriately timed preventative program.

Tuberization/bulking: Fremont sets about 7 tubers per plant, on about 2.5 stems per plant. Tubers are set mid to low in the hill. Tuber initiation and bulking rate are medium. Tubers are moderately susceptible to blackspot bruise and shatter bruise. In trials and grower evaluation, Fremont has exhibited a low incidence of internal and external defects. Deep eyes, growth cracks, enlarged lenticels and alligator hide have occasionally been noted.

Vine Kill: Average days from planting to vine kill are 115 to 120. Vine killing is required most years. Adequate skin set occurs within 14 days.

STORAGE MANAGEMENT

Fremont Russet is an excellent long-term storage cultivar.

DISEASE REACTION

Overall, disease problems are minimal. Bacterial ring rot foliar expression is adequate with typical symptoms and occurs at or slightly past 90 days after planting.

Field

Foliar early blight Susceptible

Verticillium wilt Unknown

Blackleg Susceptible

Seedpiece decay Susceptible

Leafroll virus Susceptible

Leafroll net necrosis Unknown

PVY Susceptible

PVX Susceptible

Common scab Unknown

Powdery scab Unknown

Bacterial ring rot Susceptible

Storage

Tuber early blight Moderately Resistant to Resistant

Bacterial soft rot Susceptible

Fusarium dry rot Susceptible

Pythium leak Unknown

Pink rot (Phytophthora) Unknown

Silver scurf Moderately Resistant

Rhizoctonia scurf Unknown

Disease reaction ratings = susceptible, moderately susceptible, moderate, moderately resistant and resistant.

February 2001