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Organic Potatoes - Growing Information

PLANTING INFO:
Planting depth: 3-6"; Plant spacing: 12"; Row spacing: 30-36".

CULTURAL INFO:
Potatoes are a hardy cool season crop. They are classified by early, mid, and late season varieties, which refers to the days to maturity. Potatoes can be planted 1-2 weeks before the last frost date in spring. Small potatoes (1-1.5� diameter) can be planted whole or larger potatoes can be cut into pieces. Each piece of the tuber should have at least one eye (dormant bud). Cut the tubers a day early in order for the skin to dry before planting. Sprouts appear in 2 weeks. Hill plants shortly after emergence and again 3 weeks later, making sure to cover all exposed tubers to avoid greening, increase number of tubers, and promote larger growth. New potatoes (young potatoes) can be harvested when plants begin to flower, around 7-8 weeks after planting. Storage potatoes should be harvested no earlier than 2 weeks after plants have died back. Potatoes should be left out in a dry dark place to cure. Store potatoes in burlap, boxes, or crates in a dark, moist area at 38- 40�F. Potatoes generally have a 4-8 week dormancy after harvest before they will sprout.

DISEASE & PESTS:
The two most difficult potato diseases are scab and late blight. Scab, caused primarily by the bacteria Streptomyces scabies, adversely affects grade and cooking quality, though not yield and storage. Scab is most severe in dry weather, when bacteria antagonistic to Streptomyces in the potato lenticel dry up, allowing scab to more easily infect the plant. For prevention, select scab-resistant varieties and maintain good soil moisture. Unlike scab, late blight is severely destructive, with the potential of total crop loss. Caused by the fungus Phytophthora infestans, late blight is most prevalent in moister climates such as the eastern regions of the U.S. Symptoms of late blight include water-soaked areas at the leaf tips that spread inwards and become dark brown and brittle after one or two days. Symptoms can superficially resemble early blight, but are distinguished by the fact that late blight obliterates the pattern of leaf veins where as early blight does not. Action muct be taken quickly if symptoms appear. Use fungicidal sprays such as oxidate (such as Storox�, see Supplies) and/or copper hydroxide (such as Champion WP�). Check with your organic certifier before applying suggested compounds. The Colorado potato beetle (CPB) can be a significant pest. While Bacillus thuringiensis var. tenenbrionis. is effective against CPB and was formerly the easiest insecticide to use, the current formulations have been removed from OMRI-A status due to difficulties with assessing inert ingredients. Luckily there is a new addition to the arsenal in the form of spinosad (such as Entrust�). Spinosad works rapidly and effectively against CPB, as well as against corn earworm, imported cabbage worm, codling moth, and several other difficult lepidopterous pests. Ideally we will regain access to Bt so that these two formulas can be used in rotation with one another to prevent selection of resistant insects. Crop rotation, control of solanaceous weeds, barrier trenches between old and new plantings, trap cropping, use of straw mulch or row cover can delay or reduce CPB pressure.

RESISTANCE KEY:
SCAB - Scab

SEED SPECS:
Fingerling- 20 pieces/lb avg; Full Size- 8-10 pieces/lb avg.

SEEDING RATES:
Fingerling- 50 lb/1000�, 900 lbs/acre, using 12� plant spacing, 30� row spacing. Full Size- 80-100lb/1000�, 1,100-1,450 lb/acre, using 12� plant spacing, 36� row spacing.