Cassava or tapioca (Manihot esculenta Crantz) belonging to the family Euphorbiaceae (Dicotyledonae) is a diploid (2n = 36). It is a native of south America widely cultivated in the topics especially in South America, Mexico, Central America, the Caribbean Islands, Africa (East, West, South& Central) and Asia (India, Malaysia, Indonesia, China, Myanmar, the Philippines, Sri Lanka, Thailand and Vitenam). It is an erect growing shrub branched or unbranched with palmately partite leaves. It is monoecious and protogynous.
The adventitious roots store food and form the tubers. In India, it occupies 0.24 m ha with a production of 5.1 million tonnes. It is cultivated predominantly in the southern states of which Kerala and Tamil Nadu are responsible for 61% and 29% of area and 55% and 41% of production respectively. It is also grown in Andhra Pradesh, Assam, Karnataka, Madhya Pradesh, Pondicherry, Nagaland, Tripura, Mizoram and the Andaman & Nicobar group of Islands. Cassava tubers being rich in starch, is an important subsidiary food. It forms a raw material for industry (starch& sago) and is a component of animal, fish and poultry feeds. Cassava starch has more purity than potato or maize starch, the tubers being practically free from non-starchy constituents such as protein and lipids and the extraction is easier and direct. Thailand and India are major exporters of cassava starch to international market where it is used as filler material in paints, medicine and health drinks. Recently it has found place in the manufacture of biodegradable plastic. It is processed into food products like chips, sago, vermicelli, pappads etc. Technology has been developed for economic production of alcohol from cassava tubers. The crop provides 300 K calories of energy per day to more than 400-500 million people in the world especially in the under developed countries.
Cassava crop is raised by planting stem cuttings. Mature healthy stems of 8-12 month growth having thickness of 2-3 cm free from diseases and pests should be selected for planting. A stake length of 15-20 cm and planting depth of 5 cm are generally practiced. Stakes are planted vertically on mounds, ridges or well tilled plot at a spacing of 90 x 90 cm. In non-traditional areas with 4-5 months limited rainfall (eg., Andhra Pradesh ) stakes can be closely planted in nursery beds under irrigation and later transplanted (20-25 days) to field as and when the rains set in. Spacing of 75 x 75 cm is recommended for semi and non-branching varieties , 90 x 90 cm, 90 x 75 cm(eg., Madhya Pradesh) and 75 X 90 cm(eg., Tamil Nadu) recommended for non-branching varieties.
Farm yard manure or compost may be applied @ 10-15 t ha-1 during land preparation. N, P2O5 and K2O recommended for high yielding varieties is 100, 50 & 100 kg ha-1 respectively. For short duration varieties like Sree Prakash application of NPK @ 75:25:75 kg ha-1 is recommended under a close spacing of 75 x 75 cm for Tamil Nadu. Cassava is mostly grown as rain fed crop. It can be grown between 300 N and 300 S latitude and an altitude upto 2000 metre but performs better at lower altitudes. It is cultivated in humid (more than 200 mm annual rainfall) to semi-arid (500-750 mm annual rain fall) condition. It is a drought tolerant crop. However it cannot withstand frost as its growth ceases at temperatures below 100 C. Cassava comes up well in all types of soils. Saline , alkaline, heavy and ill drained soils are unsuitable. It can be grown on hill slopes and on waste lands with low fertility.
The cassava mosaic disease caused by a virus is a serious problem affecting growth and yield under severe conditions. The leaves exhibit mosaic pattern with dark and light green patches and reduction and crumbling of lamina. Most of the cultivars/varieties are susceptible. Spread of the disease is through infected planting material. Diseases-free plants should be selected for use as planting stakes. Screening and rogueing out the diseased plants in field as well as use of screened nursery raised settlings have been found effective in control of the disease. Spider mite which occurs during dry season is another important pest. Spraying water at run-off level on the foliage at 10 days interval is an effective control measure. Scale insects have been found to affect stems when stored for subsequent planting. Spraying dimethoate or methyl demeton (0.05%) thrice at monthly intervals during January-February is found effective in controlling these pests.