L'ro Homestead AREC Research Report SB81-1 November 23, 1981
1 Tropical Root and Tuber Crops and Their Potential in Florida
Part 1. Cassava
S. K. O'HairME L BlI
Assistant Professor 98
University of Florida, IFAS [0 98-
Agricultural Research and Education Center
Homestead, Florida 33031 -.UnivV. of F0
Cassava (Manihot esculenta Crantz) is one of the more important of the starchy
staples in the tropics. Cassava importance internationally has recently been re-
cognized in the development of crop programs at two international research centers,
the International Center for Tropical Agriculture (CIAT) and the International
Institute for Tropical Agriculture (IITA). It is in the Euphorbiaceae family and is
known as yuca (Spanish), mandioca (Portuguese), tapioca and manioc (French).
The center of origin of cassava is considered to be in the Brazil-Paraguay area
with the largest number of species located in east-central Brazil. Wild species of
Manihot can be found as far north as southern Mexico and Arizona (21).
There are no definite records that indicate when cassava was first grown in the
United States. It was used during the Civil War for starch production and as an
energy food at the turn of the century. It was planted in various places along the
Gulf Coast as far west as Louisiana, and briefly as far north as Atlanta and Memphis
(26). In Florida it once was the basis of a small starch producing industry (17).
W World production of cassava is currently over 119 x 10 MT/annum with Brazil, Thai-
land, Zaire and Indonesia, in order of production, being the greatest producers (6).
In Florida current production is limited to less than 200 ha south of Lake Okeechobee.
M. esculenta Crantz has also been listed in synonymy under M. utilissima Pohl.
The plant is generally described as a short-lived perennial tropical shrub, one to
four m tall. Adventitious roots arising from stem cuttings can become enlarged vary-
ing from long and slender to globose. The stems are woody and are variously branched.
Simple leaves are generally dark green with palmate lobes. Leaf veins and petioles
vary from red to green. In Florida it produces monoecious flowers beginning in mid-
summer. The larger pistillate basal flowers open before the apical staminate flowers.
The fruit is a schizocarp and is usually winged. The brown seeds are carunculate and
elongated to rounded.
About four to eight enlarged roots are borne by each plant. The size and number
of enlarged roots increases with favorable growth conditions and plant age. The root
diameter ranges 1-15 cm. The shape most resembles a long straight sweetpotato. Root
surface is slightly rough with a thin bark that is usually brown, but can be cream in
The white starch-filled flesh of the root is crisp and uniformly fine grained.
The raw flesh may be toxic due to the presence of free and bound cyanogenic glucosides
(cyanide). The total cyanide content, reported as hydrocyanic acid (HCN), varies
with cultivar, environment and plant age (1, 5, 15, 16, 13). HCN is found in all
parts of the plant and is highest in the phelloderm (skin) of the root (1). HCN is
produced in the leaves and is translocated to the roots. The amount found in the
roots appears to be related to taste and varies from small amounts restricted to the
phelloderm to considerable quantities distributed throughout the root. These are
termed "sweet" and "bitter" cultivars, respectively (1, 24). HCN levels in fresh-
phelloderm, peeled root and leaves ranged 5-77, 1-40 and 0.3 29 mg/100 g, respec-
One main cultivar, Senorita, is grown in Florida, Its origin is believed to
have been Cuba; and it is of the low HCN type. It grows 2-3 m tall, branching
* dictomously once late in the growing season. Leaves are green with a light red
petiole. The mature stem is a 3ight grey-brown color, It seldom flowers and sets
fruit in Florida. Roots have a medium brown bark.
Other cultivars are recent introductions that have not been tested adequately
for recommendations to be made. Large germplasm collections are maintained at the
international research centers and several national research centers. However, cur-
rent U.S. federal plant quarantine regulations prohibit the importation of cassava
germplasm into the U.S. or any of its territories. This will limit expanded cultivar
evaluation to clones bred in the United States and clones processed through appropri-
ate U.S. plant quarantine facilities.
Cassava is a very adaptable crop and is considered to be outstanding in food
producing ability and production economy (3, 12, 13). In Florida 25-30 cm stem
cuttings from mature mid-lower plant sections are early spring planted in freshly
tilled soil. Fungicide treatment of the stem cuttings is recommended prior to plant-
ing. Although not labeled for use in the United States, captain + carbendazim, chloro-
thalonil + mancozeb, mancozeb, chloroneb, quintozene and copper oxychloride have been
successfully used in other countries ( 2, 8). The highest yields have been obtained
in well drained sand (20). Cassava will grow quite well in a wide range of soil
types and pH (3.5-7.9). However, it will not survive under extended water-logged or
saline soil conditions.
Stem cuttings should be handled carefully selecting the healthiest ones from
healthy plants. Stem cuttings can be planted flat in the horizontal position or at
a 450 angle to vertical position in the soil with the top one-third exposed. The
Preferred positioning varies with soil conditions and planting time. If the depth
is shallow or if the cuttings are planted in the fall or before the last freeze date,
then horizontal planting with complete soil coverage is recommended. Otherwise the
latter positioning is recommended, since loding potential is reduced. In this in-
stance stem polarity must be observed in the planting process as the plant will not
grow if the cutting is planted upside down. Currently cassava is planted by hand;
however, machines are being developed to perform this task. It is best to plant in
moist soil and on beds in wet regions with a between plant spacing of 0.9-1 m. In
regions where the growing season is short, a closer spacing down to 0.5 m between
plants may increase yields/ha. In hand cultivated plantings other short season
vegetables may be planted between the cassava plants.
Once when the plants begin to grow and again one month later fertilization is
recommended at a N, P and K rate of 45, 90 and 90 kg/ha each time. Excessive nitro-
gen availability will promote top growth at the expense of root production. In
Florida, irrigation during the growth of the crop is not needed and if applied gener-
ally will not result in increased yields.
Weed control is essential for optimal growth. Herbicides may be applied at
planting, however none are registered in the United States for use on cassava.
Several pre-emergence herbicides that have been used in other countries include:
alachlor,diuron, fluometuron and TCA (2). Various amounts of toxicity may occur
following the use of these herbicides; thus, care must be taken in their use.
Diseases that have been observed on cassava in Florida include: cassava bac-
terial blight (CBB) (Xanthomonas manihotis), brown leaf spot (Cerocospora hennigsii),
anthracnose (Colletotrichum manihotis) and various root rots. Yield loss due to
disease presence has not been documented in Florida. Control methods include selec-
tion of cuttings from disease-free plants, use of tolerant cultivars, isolation of
new plantings from fields with infected plants, good field sanitation and crop ro-
Cassava pests in Florida include: mites (Mononychellus tanojoa, Tetranychus
urticae and Oligonychus peruvianus), cassava hornworm (Erinnyis ello), shoot fly,
O (Neosilba perezi) n-nroot-knot nematode (Meloidogyne incognita) (21). None of them
have proven to cause yield loss in Florida. Good field sanitation and crop rotation
are recommended control methods.
Cassava can be harvested 8-18 months after planting in most of Florida. Late
fall and early winter harvesting is most common. If leaves are present, plant tops
can be cut at 25-50 cm from the soil surface at any time up to 2 weeks prior to har-
vest. Root shelf life is increased with a 2 week interval between leaf removal and
actual harvest. In central and northern Florida the plants can be allowed to grow a
second season by cutting the tops at 25-50 cm above the soil surface, followed by
mulching of the remaining plant with soil or straw. New growth will appear in the
spring from the lower stem area. Since harvesting is not currently fully mechanized,
the roots are pulled from the ground by hand or with the aid of a rope wound around
the stem. Several aids are being developed which will reduce harvesting labor re-
quirements (9). The stems will not remain viable if subjected to freezing tempera-
tures or extended low humidity periods. Covering the intact stems with soil or some
other protective material is the best way to store the cuttings until they are needed
Yields of cassava in Florida range up to 30 t fresh roots in 8-10 months with
starch concentrations ranging 15-38% depending on cultivar, plant age and growing
conditions (19, 20). Once harvested, roots are usable for 7-10 days. A dip in a
dilute (0.5-1.0%) sodium hypochlorite solution is sometimes beneficial in extending
shelf life. For longer storage the roots must be frozen or chipped or grated and
dried. The starch can be purified by grating the root into water, followed by
straining of the fiber from the suspension, repeated washing of the starch and quick
drying of the purified starch.
The low HCN cultivars can be prepared for eating similar to the way that pota-
toes are prepared. They can be peeled and then boiled, baked or fried. The high
HCN types are usually grated and washed or pressed and then heated or fermented prior
to consumption. Juice extraction, heat and fermentation are processing treatments
that aid in reducing HCN levels in both leaves and roots (9).
The leaves and dried roots can be utilized in animal rations (1, 23). In Brazil
the roots are used to make alcohol (25). Cassava flour has been used as a partial
wheat flour substitute with varied success (9).
Nutritionally, cassava roots are low in protein, while the leaves are high,
21-40% on a dry weight basis (1, 4, 5, 7, 13, 16, 22, 23, 27). The main food value
of cassava roots is energy from the carbohydrates (Table 1). Cassava leaves are high
in most amino acids including lysine. However, they are deficient in methionine and
to some extent tryptophan (4, 24, 27). The leaves can be used to make a liquid pro-
tein concentrate which can have various applications (13, 15).
1. Barrios, E. A. and R. Bressani. 1967. Composicion quimico de la raiz y de la
hoja de algunas variedades de yuca Manihot. Turrialba 17:314-320.
S2:. Centre for Overseas Pest Research. 1978. Pest control in tropical root crops.
PANS Manual No. 4. Centre for Overseas Pest Research, London.
3. Cummings, R. W., Jr. 1976. Food crops in the low-income countries: the state of
present and expected agricultural research and technology. The Rockefeller
Foundation, N. Y.
4. Eggum, B. 0. 1970. The protein quality of cassava leaves. Brit. J. Nutr.
5. Figuerredo, I. B., P. Vitti, and A. S. Pereira. 1977. Comportamento de
substancias nitrogenadas e carotene em duas variedades de mandioca. Boletin
Inst. Food Tech. 51:115-124.
6. FAO production yearbook. 1978. FAO, Rome.
7. Fox, R. H., H. Talleyrand, and T. W. Scott. 1975. Effect of nitrogen on
yields and nitrogen content of cassava llanera cultivar. J. Agr. Univ. P. R.
8. IDRC. 1975. In B. Nestel and R. MacIntyre (eds.) The international exchange
and testing of cassava germplasm. IDRC, Ottawa.
9. IDRC. 1978. In E. J. Weber, J. H. Cock and A. Choninard (eds.). Cassava
harvesting and processing. IDRC, Ottawa.
10. Leung, W. W. 1968. In Food composition table for use in Africa. U.S. Dept.
H.E.W. and F.A.O.
11. Leung, W. W., R. R. Butrum, N. M. Rao, and W. Polacchi. 1972. In Food
composition table for use in East Asia. U.S. Dept. H.E.W. and F.A.O.
12. Loomis, R. S. and H. Rapoport. 1976. Productivity of root crops. In J. Cock,
R. Maclntyre and M. Graham (eds.) Int. Soc. Trop. Root Crops. Proc. Fourth
Symp. pp. 70-84. IDRC, Ottawa.
13. Luiza, M., V. C. Tupynamba, and E. C. Viera. 1979. Isolation of cassava leaf
protein and determination of its nutritive value. Nutr. Rep. Int. 19:249-259.
14. McCann, D. J. 1976. Cassava utilization in agro-industrial systems. In
J. Cock, R. MacIntyre and M. Graham (eds.) Int. Soc. Trop. Root Crops. Proc.
Fourth Symp. pp. 215-221. IDRC, Ottawa.
15. Maini, S. B. 1978. In N. Hrishi and R. Gopinathan Nair (eds.) Cassava pro-
duction technology.pp. 49-57. Central Tuber Crops Research Institute,
16. Martin, F. W., L. Talek, and R. Ruberta. 1977. Some tropical leaves as
feasible sources of dietary protein. J. Agr. Univ. P. R. 61:32-40.
17. Moscrip, J. 1940. Possibilities of growing cassava in Florida. Fla. Dept.
Agr. Bul. No. 104.
18. Nestel, B. L. 1974. Current trends in cassava research. p. 32. IDRC, Ottawa.
19. O'Hair, S. K. 1981. Rapid enzymatic determination of starches in root crops.
HortScience 16:289 (Abstr.).
20. O'Hair, S. K., J. M. Dangler, P. H. Everett, R. B. Forbes, L. H. Halsey, S. J.
Locascio, H. J. Trafford, and J. M. White. 1981. Location, growing season
and soil type effects on Florida cassava yields. HortScience 16:462 (Abstr.).
21. Pena, J. E. and V. H. Waddill. Pests of cassava in south Florida. Fla. Ent.
22. Ramos, N. E. 1970. Colombian studies for the improvement of Manihot esculenta
culture. In D. C. Plucknett (ed.). Int. Soc. Trop. Root Crops. Proc. Second
Symp. University of Hawaii, Honolulu.
23. Rogers, D. J. 1959. Cassava leaf protein. Econ. Bot. 13:261-263.
24. Rogers, D. J. 1963. Studies of Manihot esculenta Cranz and related species.
Bul. Tor. Bot. Club 90:43-54.
25. Silva, J. G. da, G. E. Serra, J. R. Moreira, J. C. Concalves, and J. Goldenberg.
1978. Energy balance for ethyl alcohol production from crops. Science 201:
26. Tracy, S. M. 1903. Cassava. U.S.D.A. Farmers' Bul. No. 167.
27. Yeoh, H. H. and M. Y. Chew. 1976. Protein content and amino acid composition
of cassava leaf. Phytochemistry 15:1597-1599.
Table 1. Cassava nutritional value (nutrients in
100 g edible portion).
Calories 135 149z 60
Moisture (%) 65.5 62.0 81
Protein (g) 1.0 1.2 6.9
Fat (g) 0.2 0.4 1.3
Carbohydrate (g) 32.4 35.7 9.2
Fiber (g) 1.0 1.1 2.1
Ash (g) 0.6 0.9 1.6
Calcium (mg) 26 68 144
Phosphorus (mg) 32 42 68
Iron (mg) 0.9 1.9 2.8
Sodium (mg) 2 4
Potassium (mg) 394 409
Retinol (mg) -- -
B-Carotene equiv. (mg) 0 30 8280
Thiamine (mg) 0.04 0.16
Riboflavin (mg) 0.04 0.32
Niacin (mg) 0.6 1.8
Ascorbic acid (mg) 19 31 82
ZFrom: Leung, W. W. (10) and Leung, W. W., R. R.
Butrum, N. M. Rao, and W. Polacchi (11).