Expansion and impact of cassava brown streak and cassava mosaic diseases in Africa: A review

Abstract

Africa produces over half of global cassava; however, the continent's average yield is below the potential yields achieved under experimental conditions. Many factors contributing to low yield include lack of quality varieties, poor soils, limited access to capital, competition for labor, as well as pests and diseases. Plant diseases are the major biotic constraints to cassava production and have caused considerable food insecurity in Africa. Although there has been some level of disease management which has contributed to the increase in cassava production, the two viral diseases: cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) still claim between 30–40% and upto 70%, respectively of Africa's cassava harvest. Given the importance of the two diseases in Africa, we review the expansion of CBSD and CMD; impacts of the two diseases on food security and how they can be managed. We provide insights in the spread of the two diseases, management efforts, and future directions.

Occurrence, Distribution and Farmers' Perceptions of Cassava Diseases in Gabon, Central Africa

“…Several authors have previously reported the existence of this virus disease in Gabon [7,12,13]. Moreover, this disease has already been reported in several Central African countries as the primary threat to cassava cultivation [11,31,32]. This viral disease is caused by a geminivirus transmitted by a vector, whitefly, belonging to the species Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) [31,33].…”

Strengthening Plant Health Systems in South Sudan: Addressing Challenges and Enhancing System Efficiency and Sustainability

“…For example, the papaya mealybug, a new crop pest in South Sudan, causes up to 91% yield losses of papaya, severely affecting the livelihoods of smallholder farmers in the country (CABI, 2021). The spread of cassava brown streak disease (CBSD) (Alicai et al, 2016) and the increasing prevalence of cassava mosaic disease (CMD) in South Sudan (Chikoti & Tembo, 2022) could be having a sizeable economic impact. Available data from East and Central Africa that encompasses South Sudan indicate that CBSD and CMD cause up to 70% and between 77% and 97% yield losses estimated at US$100 million and US$1.9-2.7 billion dollars per year (Chikoti & Tembo, 2022), respectively.…”

“…The spread of cassava brown streak disease (CBSD) (Alicai et al, 2016) and the increasing prevalence of cassava mosaic disease (CMD) in South Sudan (Chikoti & Tembo, 2022) could be having a sizeable economic impact. Available data from East and Central Africa that encompasses South Sudan indicate that CBSD and CMD cause up to 70% and between 77% and 97% yield losses estimated at US$100 million and US$1.9-2.7 billion dollars per year (Chikoti & Tembo, 2022), respectively. These example data point to the devasting effects of pests on crop production in South Sudan, which largely remain uncounted.…”

“…Besides the fragile state of the nation and climate change devastations, plant health in South Sudan is further complicated by the limited availability of quality and clean planting materials. For instance, CBSD, which was initially prevalent in coastal East Africa and the shores of Lake Malawi, has spread across borders, with outbreaks reported in South Sudan, a country that was previously disease-free (Alicia et al, 2016;Chikoti & Tembo, 2022). This suggests that the plant health system in South Sudan confronts multifaceted challenges, including high dependency on imported seeds, seed sector challenges with seed companies engaging in sales rather than production or extension services, direct and indirect effects of political and social instability, environmental and climate challenges, and weak institutional and regulatory capacity (UNEP, 2018; Access to Seeds Foundation, 2019).…”

A random forest-based analysis of cassava mosaic disease-related factors affecting the on-farm livelihoods of cassava farmers

“…The symptoms of CMD are characterized by leaf curling and distortion, mosaic patterns, yellowing, and stunting, which ultimately lead to reduced plant growth, lowered yields, or even complete loss of the crop. The disease is primarily spread through contaminated cuttings, although whitefly-borne infection can also occur in some regions (Cassava Mosaic Disease, n.d.;Fondong, 2017;Chikoti & Tembo, 2022;Uke et al, 2022;Hareesh et al, 2023;Sheat & Winter, 2023). The severity of CMD varies across different regions and years.…”