Different pests and diseases threaten crop production in the tropics. Vegetative propagated crops, such as cassava, are particularly sensitive to damage from pest infestation and pathogen infections, as they tend to build up in successive cycles of propagation. Continuously monitoring the spatial spread and incidence of pest and pathogen is necessary to act swiftly to new outbreaks and reduce the chances of spreading and re-introductions. A first step is to define and identify characteristic disease symptoms for each disease, including leaf mosaics, apical necrosis, root deformation etc. For decades CIAT has been working extensively on the understanding and the development of diagnostic tools and solutions for pathogens associated with such diseases. PestDisPlace is a collaborative initiative to integrate and collectively monitor the occurrence of such symptoms and associated pests and pathogens (including confirmation by molecular diagnostics). It is a modern LAMP (Linux, Apache, MySQL and PHP) web application that runs on the latest version of MariaDB and Laravel PHP framework. A team of CGIAR researchers curates the data before it is included into the PestDisPlace database and maps.
Cassava Mosaic Disease (CMD)
CMD is caused by different species of viruses (geminiviruses), transmitted by whiteflies (Bemisa tabaci) and disseminated through infected cuttings. The most recent outbreak of severe CMD in Africa began in Uganda in the late 1980s and by now the disease has invaded more than 12 countries in East, Central and West Africa, and continues to spread. CMD, caused by distinct species of geminiviruses, has also been reported in south India and Sri Lanka, Indian cassava mosaic virus (ICMV) was recorded from South Asia in 1985, followed by Sri Lankan cassava mosaic virus (SLCMV) in 2002. One characteristic of CMD epidemics in Africa (and South India), is its association with mixed geminivirus infections that favor the rise of new more severe recombinant variants of the virus. In sub-Saharan Africa, CMD epidemics have caused average storage root yield losses of 20%, and up to 70% in susceptible cultivars. To this date, only one species of geminivirus (SLCMV) has been recorded associated with CMD in South East Asia (SEA). Cassava mosaic disease (CMD) was also recorded in eastern and central Cambodia in 2016 and is now probably present in other regions of SEA.
Cassava Common Mosaic Disease (CCMD)
CCMD accounts for significant yield losses in South America, with recent reports indicating up to on 30% yield losses in Brazil. The disease has been reported in cassava and other crops in Brazil (since 1938), Colombia and Paraguay (1991), Venezuela (1995; 2015) and Mexico (1986; 1987). The disease is caused by a mechanically transmitted potexvirus known as Cassava common mosaic virus (CsCMV). The occurrence of distinct biological and serological strains of CsCMV has been described in previous reports and is being confirmed by sequencing strains recently isolated from CCMD-symptomatic plants collected in Argentina (2015, 2016), Venezuela (2015) and Peru (2017).
Cassava Frogskin Disease (CFSD)
First reported by CIAT scientists in Colombia in 1971 in Colombia, is considered to be one of the most economically important disease in the Americas. Due to the uncertainty about the precise aetiology, work had focused on unravelling the cause, the aerial transmitter and possibilities for diagnosing this disease. The accumulated information suggests that CFSD is associated with mixed-pathogen infections, is not transmitted by neither contaminated soils nor botanical seed and has only been reported in the Americas.
Cassava Witches' Broom Disease (CWBD)
CWBD threatens up to 40 million smallholder farmers in southeast Asia that depend on the crop for their livelihood. Named after the broom-like leaf proliferation it causes at the top of cassava plants, the disease has already swept through Vietnam, Thailand, Cambodia, Lao, China and the Philippines, resulting in dramatic reductions in cassava root starch content and massive yield losses. While CWB is present in Asia’s cassava crops and occurs at pandemic levels in Cambodia and central Vietnam, little or nothing is known about the ecology and epidemiology of this debilitating disease. Also, there’s a critical lack of information on the abundance, diversity and temporal dynamics of the insect groups that spread the disease in local cassava crops, and their ability to transmit CWB disease. Outbreaks of CWB have been reported in Asia in recent years, resulting in yield losses in Thailand, Cambodia, Laos, Vietnam Philippines and China. As described above, CIAT, together with local partners, conducted surveillance on more than 700 cassava fields in multiple Southeast Asian countries monitoring for pests and diseases12. CWB was found to affect 64% cassava fields in several prime cassava-growing areas, and was especially problematic in Cambodia where 78% of the cassava fields were impacted by CWB.
Concept by: Wilmer J. Cuellar, Leroy Mwanzia, Joe Tohme
Developers: Leroy Mwanzia, Derlyn Lourido, Carolina Garcia, Paola Cruz, Lizbeth Pino, Andrés Felipe Martínez, and Wilmer J. Cuellar.
Thanks to all our colleagues in CIAT and collaborating institutions for data sharing. Visuals and data from PestDisPlace may be used as long as a link to 'https://pestdisplace.org' is provided together with the following citation:
PestDisPlace: Monitoring the distribution of pests and diseases
W Cuellar, L Mwanzia, D Lourido, C Garcia, A Martínez, P Cruz, L Pino, J Tohme
International Center for Tropical Agriculture (CIAT), 2018