All parts of the crop (stems, leaves and tuberous
roots) can be harvested for specific markets.
There is usually a high demand for planting materials of improved varieties at the beginning of the planting season. You can harvest, package and sell stems to increase your profit margin from the farm.
Stem harvesting can be total or partial. In total harvesting all the stems are pruned leaving only the stumps to regrow while in partial harvesting a few stems are pruned from plants having multiple stems. In a well-established production field 400 or more bundles of stem can be harvested per hectare depending on the variety, plant population and environment.
As vegetable, harvest only the young succulent leaves and process. As silage for animal feed, all the green leaves including the young parts of the stem are harvested, chopped and ensiled.
Plants can be harvested at 9 – 18 months after planting to give root yields ranging from 15 – 50 tons or more per hectare depending on the variety, environment (soil fertility status, acidity level, moisture level and sunshine hours) and agronomic practices adopted.
Harvest roots only when you have a ready market. Avoid bruising the roots excessively during harvesting otherwise they will deteriorate very rapidly. For quality products, process the roots as soon as they are harvested and not later than 48 hours. The major quality trait for market acceptability of roots is dry matter content. It is usually high soon after the rains and during the harmattan period but low in plants recovering from stress particularly during the reflushing of new leaves.
Harvesting of Cassava
Management of pests and diseases
A good pest and disease information and management is necessary for high productivity in cassava.
- Cassava Mosaic Disease (CMD):
The disease is caused by a complex of viruses and transmitted by a whitefly (Bemisia tabaci). Leaves become smaller, wrinkled and chlorotic. In severe cases root yield losses are very high (near 100%). The best control measure is to plant resistant varieties. Rogue off infected plants during the early stage to reduce secondary spread. Intercrop with tall growing plants like maize to reduce vector movement and transmission of the disease.
- Cassava Bacterial Blight (CBB):
The disease is caused by bacteria (Xanthomonas sp.) Symptoms are first characterized by wet angular spots on the lower leaf surface, which finally lead to blighting and exudates on petioles and stems. Infected leaves drop early and in severe cases the stem is leafless and appears burnt (candlestick). As control, plant resistant or at least tolerant varieties. Plants infected at an early stage should be pruned to allow for new regrowth or uprooted entirely and burnt.
Anthracnose, cercospora leaf spot and root rot are less worrisome diseases since most of the newly improved varieties have desired levels of multiple pest and disease resistance in them.
- Cassava Mealybug (CM):
Causes reductions in internode length resulting in ‘bunchy tops’. This pest has been managed in several African countries through biological control. It is no longer seen as a serious threat to production in Nigeria.
- Cassava Green Spidermite:
Damage is characterised by tiny chlorotic spots on the upper surface of the leaf, reduced leaf size, premature leaf drop and candlestick of the stem. As control, simply plant resistant varieties. This will be complemented by the activities of biological agents, which have been released to keep the pest population low.
Highly voracious white ants. They bore through stakes and eat them up as soon as they are planted or later in the season thus destroying whole plants. The damage is most severe when there is moisture stress particularly in the savanna belt. Plant when the rains have stabilised and the soil is moist. Pre-sprout stakes in plastic bags for 3-5 days before planting for rapid take off. Plant vertically to reduce lodging which can predispose plants to termite damage. Keep fields free of dead woods and crop residues. Destroy anthills and treat with D-Aldrex 20 as recommended by the manufacturer.
- Variegated Grasshopper:
Nymphs and adult grasshoppers eat up cassava leaves and the young part of the stem. Damage is most serious during the dry season starting from the end of the rains in September. If the incidence of the pest is mild it could be overlooked but need to treat the plants with Gamalin 20. Spraying should be done early in the morning or in the evening when the pests are not very active. Advice farmers in neighboring fields to do the same in order to ensure effective control of the pest.
- Vertebrate Pests:
Grasscutters and bush fowls frequently expose and eat up roots in the soil. The damage to the roots can provide an entry for the microorganisms that cause roots to rot. Use traps to catch them, poisoned grains to kill them or wire mesh fencing to prevent the grass cutters from entering your field. Keep the farm and its surroundings weed free. Plant on the flat to make root exposure difficult for them.