Growing Food: A Guide to Food Production

Altitude: from sea level to 2500 m, on the equator.
Pests: Sweet Potato Weevil is the most serious pest of sweet potatoes. The larvae
feed mainly on the tubers but also on the leaves and vines, especially with late
planted or dry season crops. Controlled with crop rotations and destroying or
feeding all infected plant material; plant only clean cuttings or slips.
Oth

Diseases: not usually a big problem in the tropics. There are two main types:
a)field diseases of leaves, vines and tubers; Black Rot, Soft and Dry Rots, Leaf
Spot, Scurf (Rust), Stem Rot (Wilt) and Soil Rot (Pox) are the most common.
Mainly easily kept under control, if necessary, with fungicides.
b)storage diseases, especially of damaged tubers. Soft Rot is the most common,

(Some diseases appear at both stages).

YIELD
The tubers are ready for harvest when the leaves turn yellow and begin to drop.
Although the potential yield of sweet potatoes is well over 50 MT/ha they
commonly yield no more than 15 MT/ha or less, mainly because they are very often
grown on poor land and are not carefully cultivated.

UTILISATION

•

tropics and subtropics, mainly for subsistence purposes. They are normally

either boiled or baked. Tubers are also often fed to animals. For storage they can

be sliced and dried in the sun. Products manufactured from the tubers include

LIMITATIONS

er, normally less damaging, insects include the Sweet Potato Leaf Beetle,
wireworms, grasshoppers, fleabeetles and termites. Leaf-eating caterpillars can be
controlled with insecticides.

control is by using resistant varieties, crop rotations and planting clean cuttings/
slips. Dry Rot, Java Black Rot and Charcoal Rot can give problems. As mentioned,
the tubers are best left stored in the ground.

T he global average estimated by FAO in 2004 was 14.8 MT/ha, from the highest
average in Israel of 35 MT/ha to a low in Mauritania of 1.0 MT/ha.

214 TONY WINCH

Sweet potato tubers are an important part of the diet in many countries in the

starch flour, syrup, glucose and alcohol.

The haulm (vines and leaves) can be either fed directly to animals or ensilaged.

The young leaves and tender parts of the stem are sometimes eaten as a

vegetable.

Sweet potatoes have a high labour requirement for land preparation and

harvesting.

They are also sensitive to waterlogging, salinity and alkalinity.

weeks.

The plants are “heavy feeders” and need plenty of calcium, boron and

magnesium as well as the major elements to produce good crops.

The tubers do not store well, unless dried, and lose much moisture within a few