Grown across the continent, cassava is one of Africa’s staple crops, both in terms of production volume and calorific value (faostat.org). Compared to other staples, cassava offers several advantages: it is sturdy, adaptable to different environments, tolerant of poor soil quality and resilient to adverse climatic conditions. Moreover, the ability of cassava roots to be “stored” below ground enables farmers to time their harvests to achieve higher prices.
Cassava is propagated vegetatively; it has a multiplication rate of around 1:8. This is very low in comparison to, for example, maize with 1:300. This makes it difficult to produce sufficient planting material to successfully disseminate improved varieties. Moreover, in smallholder farming systems, cassava has very low intrinsic seed value. Farmers often pay little or nothing for seed stakes. There are no formal seed markets for cassava planting material or any quality criteria assuring certain genetic and phytosanitary attributes. As a consequence, viruses and other seed-borne plant diseases (bacteria, root rots, phytoplasms) contaminate large amounts of planting material, causing yield losses of up to 80%.
These problems can be addressed by using certified, disease-free planting material. This has already been achieved with potatoes, which are also propagated vegetatively. In addition to disease control, such a formal seed system could constitute an important vehicle for the distribution of new varieties and improved germplasm, and is thus regarded as a driver of seed technology adoption.
Highly effective, low-cost seed treatments are generally considered to be efficient crop management interventions for resource-poor crop producers. Seed treatment is the application to seed of products designed to maintain or enhance its genetic yield potential. This can either be achieved by adding components which protect the seed of any emerging plant against pests and diseases or which stimulate early plant vigour, such as growth stimulants and nutrients. If done centrally (or by trained operators), seed treatment is often a safer option than foliar sprayed pesticides as it requires little knowledge or training for the farmers planting the seeds. Treatments with compounds contributing to plant vigour and growth can increase the intrinsic seed value (e.g. through improved germination rates, stress tolerance or storage). This can help establish a formal seed system, especially in a vegetatively propagated crop like cassava, where planting material is often bigger, less uniform and more perishable than a conventional seed.
The Syngenta Foundation and the Brazilian Agricultural Research Corporation (Embrapa) have developed a seed stake processing and treatment system that enables farmers to use significantly shorter planting pieces. Each piece is coated with a variety of protectants and stimulants. This treatment improves shelf-life, plant vigourand yield potential compared with traditional, larger planting pieces. The smaller and more uniform seed stakes also allow for mechanized planting, which enables progression towards optimal planting densities as well as decreasing labour costs. This technology is based on a Syngenta system designed for Brazilian sugarcane. The version adapted for cassava is called “MandiPlus” – from the Portuguese name for the crop, mandioca.
The Project – Developing a superior cassava seed piece
Following very successful first trials in Brazil, the approach has been replicated under African conditions, in collaboration with the National Crops Resources Research Institute (NaCRRI) in Uganda. The funds for this project were provided by the Bill and Melinda Gates Foundation. In addition to assessing agronomic aspects (e.g. the impact of different treatments on crop germination and yields), the project team aimed to test the economic viability and stakeholder acceptance and develop a scale-up strategy.
The project started towards the end of 2016 and runs until the end of 2018. There have been three trialling seasons in this period. The first harvest results showed that shorter, treated seed pieces perform as well as untreated, longer seed stakes. In addition, none of the treated plots were damaged by termites. We also expect to see this effect against other insects, such as major vectors for viral diseases. The combination of shorter seed pieces and optimum field plot management to maximize propagule production tripled the multiplication rate. The technology has therefore successfully been adapted to and validated under Ugandan conditions.
These good results open the way to accelerating seed production. Proper selection of isolated multiplication plots and intense disease management, including indexing (checking the plants for diseases) and rogueing (removing infected plants), should moreover result in clean and high-quality seed material.
Stakeholder Workshop in Kampala, September 2018
Releasing MandiPlus as a “product” will mean that smallholders, cassava seed multipliers and entrepreneurs will be able to access either the treatment itself or treated seed pieces. This September, a workshop for stakeholders along the value chain took place in Kampala. Its aim was to demonstrate the technology’s benefits, guide the stakeholders through the project’s progress and receive feedback.
As workshop speakers explained, MandiPlus greatly simplifies planting logistics, as far lower volumes of material are required. It also allows for denser planting as the seed pieces can now be placed vertically rather than horizontally. During early growth, MandiPlus protects the plants against fungi and insect pests such as termites (and potentially whiteflies). The latter not only feed on the plants but also spread Cassava Mosaic Virus and Brown Streak Virus.
Agronomic aspects are, however, only one part of the story. It is also very important that the technology is economically viable. The chemicals used, and the act of treatment itself both cost money. One key question during the economic assessment was whether lower costs related to the reduction in length could compensate for those of the treatment. This analysis was conducted in collaboration with NaCRRI and the Mennonite Economic Development Associates (MEDA). MEDA is also involved with a project aiming for Building an Economically-Sustainable Cassava Seed Systems (BEST) in Tanzania.
The first results of the cost-benefit analysis look promising. The major cost factor when growing cassava is the field costs, regardless of whether or not seed pieces are treated. Treatment accounts for less than 16% of the total cost. Economies of scale will also help: the more farmers request and apply the technology, the more affordable it will get. Therefore, it is very important to raise the awareness and to create a framework which ensures the technology’s availability for farmers.
Further measures are now required for the successful delivery of the technology. These include full registration. The first step consists of a label extension for the products in the formulation so that these are allowed to be used on cassava. On-farm participatory trials with selected seed multipliers, cassava seed entrepreneurs and farmers will aim to further assess and demonstrate MandiPlus’ benefits. It will also be crucial to building a map of private sector demand for cassava roots and seed pieces to better understand seasonal and regional fluctuations. Commercial delivery models will need to be further refined, including plans for a commercially more viable seed production. Lastly, a policy paper to promote the technology’s inclusion into the existing seed certification schemes will be compiled as well, to allow Cassava Seed Entrepreneurs to utilize the MandiPlus technology in multiplying their seed stakes.