DEWN: a novel surveillance system

Innocent Ndyetabula*, indyetabura@yahoo.com and James Legg, j.legg@cgiar.org
*Maruku Agricultural Research Institute, PO Box 127, Bukoba, Tanzania

Researchers inspect cassava plants for disease incidence. Photo by IITA.
Researchers inspect cassava plants for disease incidence. Photo by IITA.

Pandemics of cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) are the most important biotic constraints to cassava production in East and Central Africa.

For several years, researchers have tracked these two diseases and monitored patterns of pandemic expansion. However, costs have been high, and the visits made once a year have barely kept pace with the rate of disease spread.

Hence, researchers working to control these problems resolved to explore other monitoring options. During early discussions, two themes were frequently highlighted: community participation and new technology. Could both of these be incorporated into an alternative approach to monitoring disease spread in such a way that the system would provide an early warning of new outbreaks?

The result was the Digital Early Warning Network or DEWN. After extensive consultation, a plan was developed for its pilot-level implementation. This system works with six farmers’ groups in each of 10 disease-threatened districts of northwestern Tanzania, and provides them with a system based on the use of the mobile phone for reporting incidences of CMD and CBSD in their farms. By communicating monthly with farmers’ groups, it was expected that new outbreaks would be identified quickly, allowing the timely implementation of control measures.

Partnerships
The pilot phase of DEWN has been primarily implemented by the Lake Zone Agricultural Research Institute (LZARDI), under the IITA-coordinated Disease Objective of the Great Lakes Cassava Initiative (GLCI). GLCI is funded by the Bill and Melinda Gates Foundation (BMGF) and is led by the Catholic Relief Services (CRS). The partners of GLCI in the DEWN target districts included several local NGOs (TAHEA, MRHP, KUMKUMAKA, RUDDO, and TCRS) as well as the local government agricultural advisory system.

Training
At the outset, it was essential to train all participating farmers’ groups to recognize the symptoms of the two virus diseases, and introduce the SMS-based communication system. A total of 1281 farmers were trained in the 60 groups, and district partners were provided with a GPS unit and digital camera to record field locations and any unusual disease symptoms.

Each of the farmers’ groups was provided with a basic GSM phone and SIM card and introduced to the simple texting system for sending monthly disease reports. A straightforward text format was used for the farmers’ groups to provide information on how many farmers had observed each of the two diseases in their fields that month, and for how many farmers each disease had become more severe, less severe, or stayed the same. Once reports had been compiled at the farmers’ group level, they were sent as a single text to the LZARDI modem.

Outcomes
Validation visit. A follow-up visit was made after 6 months to validate farmers’ reports. A refresher course was provided, but the farmers generally indicated a good knowledge of the main symptoms of both diseases. Partly as a consequence of their new understanding of the significance of CMD and CBSD, there was a strong demand from participating farmers for improved varieties.

Voice of the Farmer reports. Participating farmers were linked to the Voice of the Farmer project (VOF). This is a project that is executed by Synovate and financed by BMGF. It aims to use a network of call centers to provide monitoring and evaluation support to existing BMGF programs.

Map based on farmers and researchers' report of CMD occurrence in Lake Zone districts of Tanzania.
Map based on farmers and researchers' report of CMD occurrence in Lake Zone districts of Tanzania.

DEWN provided a means for VOF to communicate directly with many of the participating farmers. This enabled VOF to conduct two surveys to assess the effectiveness of DEWN’s training program on the identification and management of cassava pests and diseases. Participating farmers were called directly by VOF call center staff and were asked a series of short questions in Swahili. Although farmers’ responses indicated a good general knowledge of CMD and CBSD, some confusion about symptoms was evident, highlighting the need for further training support. The VOF–DEWN reports are available online at www.vof.synovate.co.ke.

Mapping new disease outbreaks. Information obtained from the DEWN reports received from farmers’ groups was used to generate maps. One of the most significant findings was that CBSD, reported by farmers via SMS, was then confirmed by researchers’ visits in two districts (Bukombe and Urambo) in which CBSD had not previously been reported. This has allowed project teams to focus extra disease mitigation efforts on these areas.

Extending DEWN. Recognizing the potential value of DEWN for providing communities with a means of doing their own monitoring of crop disease, the GLCI cassava team in Rwanda decided to start a similar scheme. Farmers’ representatives from Rwanda visited DEWN partners in Tanzania in October 2010 and were introduced to the approach and given training in recognizing CBSD and CMD. The Rwanda team will initiate its own DEWN program in 2011.

Map based on farmers and researchers' report of CBSD occurrence in Lake Zone districts of Tanzania.
Map based on farmers and researchers' report of CBSD occurrence in Lake Zone districts of Tanzania.

DEWN has provided an innovative, informative, and relatively cheap means for involving communities in monitoring the health of their own crops. Farmers’ participation has been enthusiastic, and some important practical outcomes have been achieved. Two of the greatest challenges which remain, however, are the accurate diagnosis of CBSD, which has cryptic or unrecognized symptoms and the regular provision of feedback to participating communities.

Plans are already being developed to address these problems. As these difficulties are overcome and as connectivity in rural areas continues to expand, it seems certain that there is great potential for the more widespread use of digital networks such as DEWN for the community-based monitoring of crop diseases.

Developing clean seed systems for cassava

James Legg, j.legg@cgiar.org

Cassava stems for future crop. Photo by L. Kumar, IITA.
Cassava stems for future crop. Photo by L. Kumar, IITA.

Cassava is one of those crops that uses part of the plant for propagation. It is very convenient to use vegetative material from a previous crop to plant a new one. This is one of the beauties of vegetatively propagated crops. However, this convenience comes at a price. The use of planting material from a previous generation to establish the next provides an easy way for disease-causing pathogens, particularly viruses, to pass directly from one plant generation to another. So, while they offer convenience, vegetatively-propagated crops are often more widely affected by pathogens than those planted in the form of true seeds.

In Africa, cassava is the most widely cultivated of the vegetatively-propagated crops, being grown on more than 12 million ha across the continent. The exotic pest introductions, cassava mealybug and cassava green mite, caused great damage to Africa’s cassava crop in the 1980s and 1990s, but both have been effectively managed through the implementation of a classical biological control program.

The fungal diseases, cassava bacterial blight (Xanthomonas axonopodis pv. manihotis) and cassava anthracnose (Colletotrichum gloeosporioides f. sp. manihotis) are locally important. The greatest current constraints to cassava production, however, are the virus diseases, cassava mosaic disease (CMD) caused by cassava mosaic geminiviruses (CMGs) and cassava brown streak disease (CBSD) caused by cassava brown streak viruses (CBSVs), which together cause crop losses worth more than US$1 billion annually.

One of the most important approaches to controlling these virus diseases, as well as other pathogens of cassava, is through the avoidance of infection. This can be achieved by starting out with pathogen-tested plants, and then bulking the planting material through a series of quality controlled multiplication steps. Although it sounds very simple, this can be difficult to achieve in practice.

Pathogen testing requires well-equipped laboratories run by adequately trained staff. Quality management in the field requires extensive grassroots knowledge of disease symptoms and the involvement of an appropriately trained and resourced national plant protection organization. In many parts of sub-Saharan Africa, capacity for these functions remains insufficient to meet the demands.

IITA and its partners have made significant progress in developing and implementing new systems to maintain the health of cassava through seed systems. For instance, through the Great Lakes Cassava Initiative (GLCI), a multi-partnered project implemented from 2007 to the present in Burundi, Democratic Republic of Congo, Kenya, Rwanda, Tanzania, and Uganda, a rigorous system has been put in place to assure the health of cassava planting material. This has been particularly important in view of the rapid recent spread of a devastating pandemic of CBSD in East Africa.

Healthy cassava plant. Photo by IITA.
Healthy cassava plant. Photo by IITA.

The key components of the quality and health management system are as follows: Primary (centralized seed production sites) managed by researchers or qualified seed producers, secondary, and tertiary multiplication sites (usually in farmers’ fields) are all assessed, at least once in a year, using the Quality Management Protocol (QMP). This sets out quality levels, primarily in terms of disease and pest incidence and material quality that must be met if the field is to “pass”.

The QMP standards for CMD and CBSD incidences ascertained by diagnostic tests are <10% for primary and secondary sites and <20% for tertiary sites in endemic areas. Planting materials from fields that fail to meet QMP standards are not distributed or used for further multiplication, although the tuberous roots can be used by the growers for consumption. Fields that meet the QMP standard and test negative for CBSVs are approved for more widespread dissemination.

This is the first time that this level of rigor has been applied to maintaining the health of cassava through multiplication programs in sub-Saharan Africa. It has been invaluable in assuring the health of the planting material provided to more than half a million beneficiaries in six countries, and provides an important model for other current and future cassava development programs.

Much remains to be done before such an approach can be used in a more sustainable way. Most importantly, basic capacity needs to be strengthened in most countries. Key elements of this include the laboratory and human capacity for virus indexing, as well as the knowledge of QMP and the capacity of the national plant quarantine organization to monitor cassava seed systems.

In addition, the management of cassava diseases could be greatly enhanced by the establishment of isolated nuclear multiplication sites planted with virus-tested cassava plantlets derived from tissue culture, as well as by raising awareness among growers about the importance of establishing the next crop with healthy planting material.

A long-term goal, as the commercial value of cassava increases, will be to provide a mechanism through which planting material certified through the QMP attracts a price premium. Creating added value is certain to be the key to the future development of clean seed systems for cassava in Africa. IITA and its partners are strongly committed to reaching this goal.