1. I. Application of General Certification Standards

   1. A. Sweet potato stock eligible for certification must be produced:

      1. 1. On land which did not produce sweet potatoes during the past three years.
      2. 2. On land that did not receive manure or sweet potato residue during the past three years.
      3. 3. On land not subject to drainage water from fields that are now growing or have grown sweet potatoes during the last three years.
   2. B. Sweet potato land shall be treated by approved methods for the control of wireworms and other soil insects where they are known to be a problem.

   3. C. Plant Bed Requirements.

      1. 1. The plant bed must be located on well drained soil that has not produced sweet potatoes within the last three years unless disinfected by approved methods. The land must not be subject to drainage from barnyards or poultry yards or fields that are now or have grown sweet potatoes during the past three years.
      2. 2. Manure must not be used in the plant bed.

      3. 3. Seed sweet potatoes must be treated with an approved pesticide prior to planting.

         III. Field Inspection

   4. A. Plant Bed

      One inspection shall be made when plants are nearly large enough to transplant.

   5. B. Field

      At least two field inspections shall be made, one shortly after transplanting of sprouts cut from the bed or vine cuttings. The final field inspection shall be performed at least 21 days after the first inspection and when diseases and varietal mixtures can be most easily detected.

      IV. Field Standards

   6. A. 1. Unit of certification.

      1. 2. Isolation

         All fields producing a class of certified seed potatoes shall be isolated from other sweet potato fields in such a manner as to prevent mechanical mixture.

      2. 3. Planting stock requirements

         1. a. Certified sweet potatoes must be produced from either vine cuttings or from sprouts cut from the bed.
         2. b. Sprouts must be cut approximately 1 inch above the soil surface, using a knife which has been disinfected.

      A field or a portion of a field.

   7. B. Specific Requirements.

      		Maximum Permitted in Each Class
      	Factor	Foundation	Registered	Certified
      	Plant Bed
      		Blackrot	None	None	None
      		Wilt	None	None	None
      		Other Varieties	None	None	None
      		Scurf	None	None	None
      	Field
      		Wilt	None	None	5 plants/acre
      		Viruses	None	None	10 plants/acre
      		*Other Varieties	None	None	None
      	*Five plants current mutations allowed.

   The General Certification Standards, Clemson University Regulation 27-190, are basic and applicable.

   II. Land Requirements

2. V. Seed and Storage Standards

   1. A. Seed

      1. 1. At least one storage inspection shall be made.
      2. 2. Seed stock must conform to the minimum standards for U.S. No. 1 grade except that minimum size shall not be less than 3 inches in length and 1 ¹⁄₄ inches in diameter, and shall not exceed 10 inches in length and 3-³⁄₄ inches in diameter.^*

      3. 3. Root standards

         		Maximum Permitted
         	Factor	Foundation	Registered	Certified
         	Common Storage Rots	None	None	None
         	Blackrot	None	None	None
         	Scurf	None	None	0.1%
         	Wilt	None	None	0.1%
         	Internal Cork	5.0%	5.0%	5.0%
         	*Nematode	None	None	0.5%
         	*Wireworm	1.0%	2.0%	5.0%
         	Sweet Potato Weevil	None	None	None
         	Other Varieties	None	None	0.1%
         	*Tolerance applied to severely infected roots.

   2. B. Storage

      1. 1. Storage potatoes grown for certification shall be stored in new containers, or used containers that have been disinfected with an approved pesticide.
      2. 2. Sweet potatoes must be stored in a facility that has been cleaned and disinfected.

      3. 3. Each unit of sweet potatoes that passes field inspection shall be stored according to production unit and treated separately and distinctly at the time of storage inspection. Each crate shall be marked or labeled to correspond with the field unit that passed inspection.

         ^*Specific sizes of sweet potatoes in accordance with Federal Regulations shall be optional to grower and purchaser.

HISTORY: Amended by State Register Volume 8, Issue No. 12, eff December 28, 1984; State Register Volume 25, Issue No. 5, Part 1, eff May 25, 2001.