Vegetable Information Note 103
Charles W Averre, Extension Plant Pathologist
scurf appears in North Carolina sweetpotatoes. In some cases much of the
crop is affected at harvest; in other cases, only a few scurfy roots are
present. Scurf reduces the market value and serious cases may be rejected
by buyers. All growers should learn to control scurf by a total program:
Set healthy plants, use land free of scurf, and harvest and store sweetpotatoes
in clean baskets and houses. This program will also control black rot.
Facts About Scurf
Scurf is caused by the fungus Monilochaetes infuscans. The fungus
grows only in the skin of the sweetpotato and produces spores (reproductive
bodies) on the surface. The diseased areas are grayish-brown to black
and are only skin-deep. Scurf
Scurfy roots will produce sprouts but some will be infected and many become
contaminated with spores in the soil around the bedded roots.
Healthy roots may become contaminated with fungus spores from diseased
roots, and contaminated crates, baskets, and storage houses. During grading
operations, spores from diseased roots are dislodged with soil and distributed
by air currents and contaminate containers and other sweetpotatoes.
Contaminated seed roots may become infected during presprouting at high
The scurf fungus only attacks underground portions of sweetpotatoes. It
does not attack other crops.
The fungus will survive in field or plant bed soils.
Scurf is usually worse during rainy seasons.
A. Set healthy plants.
Certified seed is the best source of disease-free plants.
B. Use land
free of scurf.
Carefully select seed for bedding. Whether certified seed is used or not,
every root should be inspected when selected. Wetting the roots makes
scurf spots easier to see.
Treat the seed before bedding. Unseen contaminating spores can be killed
by dipping the roots in a fungicide. See fungicides below.
Use vine cuttings or cut sprouts. Sprouts cut above the soil level, or
vine cuttings, will be scurf-free. The cut sprouts or vines should be
dipped to a depth of about 5 inches in a fungicide. See fungicides below.
Do not contaminate plants by placing them in contaminated containers,
holding them in contaminated houses, or hauling on contaminated truck
bodies. Disinfest contaminated equipment before using. See fungicides
Locate beds in a site known to have been free from sweetpotatoes for three
in scurf-free soils. Rotate sweetpotatoes with other crops to eliminate
scurf. In light soils, such as Norfolk sandy loam, a 2- to 3-year rotation
is adequate. In heavier soils or those rich in organic matter use a 3- to
Harvest and store sweetpotatoes in clean containers and houses.
Before harvest clean and disinfest storage houses, containers, and equipment.
Use chloropicrin at a rate of 0.5 lb/1000 cu. ft. or 5 fl. oz/100 cu.
ft. High humidity in the storage house prior to (24 to 48 hours) and during
fumigation is essential for satisfactory results. Maintain temperatures
of 70 degrees F or above during fumigation. Disinfest containers by first
cleaning them and then by leaving them in the house during fumigation.
The floor and walls of houses that cannot be made "airtight" should be
sprayed thoroughly with a fungicide, and cleaned containers dipped in
a fungicide. See fungicides below.
The above procedure can be used to produce seed roots. Plant vine cuttings
in land free of the scurf fungus. Harvest and store in clean containers
in separate houses or clean houses in which diseased potatoes are not
stored at the same time.
with a specific problem, contact your local North
Carolina Cooperative Extension Service
Fungicides approved and suggested for treating sweetpotato roots, baskets
or crates, and storage facilities are listed annually in the N. C. Agricultural
Chemicals manual. Currently labeled fungicides for control of scurf are
Botran (1.0 lb/100 gal water) for postharvest application and Mertect
340F (107 fl oz./100 gal water) and Botran (3-3.75 lb/14 gal water/1000
sq. ft.) for application in the plantbed. Follow label directions carefully.
Disease Information Notes Home Page
Carolina Insect Notes
Carolina Agricultural Chemicals Manual
of specific chemicals are based upon information on the manufacturer's
label and performance in a limited number of trials. Because environmental
conditions and methods of application by growers may vary widely, performance
of the chemical will not always conform to the safety and pest control
standards indicated by experimental data. All recommendations for pesticide
use were legal at the time of publication, but the status of registration
and use patterns are subject to change by actions of state and federal
North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June
Employment and program opportunities are offered to all people regardless
race, color, national origin, sex, age, or disability. North Carolina
University at Raleigh, North Carolina A&T State University, U.S. Department
Agriculture, and local governments cooperating.
Dec. 2000 by G. J. Holmes