NCPN Sweetpotato
NCPN Sweetpotato
NCPN Sweetpotato
University of California
NCPN Sweetpotato

Benefits of Using Virus Tested Planting Stock

1. Clean stock is the solution

2. The Southeastern experience

3. Yield comparison

Virus diseases are one of the most important production constraints facing sweetpotato producers. In the US four viruses are common; each is very similar to the most common, Sweetpotato feathery mottle virus (SPFMV).

Chlorotic spots on sweetpotato leaves caused by SPFMV infection.
Chlorotic spots on sweetpotato leaves caused by SPFMV infection.
Yield, skin color, shape and quality of storage roots can be greatly reduced when sweetpotatoes become infected with these viruses. Yield reductions can exceed 40 percent, and cracks may develop in the roots making them unmarketable.  Often 100% plants in a field are infected by the end of one growing season. Many sweetpotato viruses are vectored by aphids and whiteflies. These insects can be carried on machinery and the wind, and are responsible for spreading viruses both short and long distances.
Russet crack symptoms on sweetpotato roots caused by SPFMV-RC
Russet crack symptoms on sweetpotato roots caused by SPFMV-RC


Clean stock is the solution

Planting clean, virus-tested plants can help mitigate the issues caused by sweetpotato viruses.  The first clean seed program for sweetpotato was started in the 1960s in California. At that time, it was well known in the industry that new seed stock was required to prevent Russet crack and “variety decline,” or the gradual loss of yield that occurred in many varieties. The use of virus-tested seed is one of the reasons for substantial sweetpotato yield increases. Clean material, coupled with higher yielding, disease-resistant varieties has resulted in marked increases in yield in recent decades.  In 1967, average yields in California were 5 tons/acre; in 2001 average yield had more than doubled to 12 tons/acre.

Sweetpotato clean seed programs are established in California, Louisiana, North Carolina, and Mississippi. Other sweetpotato producing states are interested in developing clean seed programs.

The Southeastern Experience

Today, North Carolina is the leading producer of sweetpotato in the United States.  In the 1990s, prior to implementing a clean seed program, the sweetpotato crop was devastated by a virus disease - Sweetpotato feathery mottle virus – Russet Crack strain.  Yields were reduced more than 50% in affected fields. In Louisiana yield decline was up to 40%. In response, the Micropropagation Unit at North Carolina State University and the LSU AgCenter virus-tested seed program were started in 1999 to "clean up" and provide clean seed and plant material to growers. Simultaneously, both states began programs to certify sweetpotato plant material.  Due to the fact that the use of certified seed varies greatly between states, NCPN education and outreach efforts are focused on educating sweetpotato producers about the value of using certified planting material.

Yield  Comparison of Clean vs. Virus-Infected Sweetpotato

As shown in the table below, using clean seed can almost double your yield. 

Clark, C.A. and Hoy, M.W. 2006. Effects of common viruses on yield and quality of Beauregard sweetpotato in Louisiana. Plant Dis. 90:83-88

Planted using Yield, expressed as units/acre Yield as a % of yield using clean seed
60 lb bu/A 50 lb bu/A 40 lb boxes/A
Clean seed 471 565.2 706.5 100%
Seed infected with SPFMV-Russet Crack strain 422 506.4 633 90%
Farmer's plant A (infected with SPFMV + other viruses 327 392.4 490.5 69%
Farmer's plant B (infected with SPFMV + other viruses 260 312 390 56%
Farmer's plant C (infected with SPFMV + other viruses 281 337.2 421.5 60%


NCPN LogoThe National Clean Plant Network for Sweetpotato is an association of clean plant centers, scientists, educators, state and federal regulators, certified seed growers, and commercial growers from the fresh market and processing industries concerned with the health of planting stock (seed roots and vine cuttings). The NCPN operates under the auspices of three agencies within the United States Department of Agriculture - Animal and Plant Health Inspection Service (APHIS), Agricultural Research Service (ARS) and National Institute of Food and Agriculture (NIFA).



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