The Crop Cassava (Manihot esculenta Crantz) from the family Euphorbiaceae, a native and origin from South America, is believed to have been introduced into Sub-Saharan Africa by the Portuguese during the 16th century (17th). Despite the breeding efforts and strategies for high yielding varieties available, the average yields in the country are low (< 10 tons/ha), which is attributed due to many factors including virus diseases, poor agronomic measures, poor or inadequate soil fertility and moisture supply due to prolonged drought conditions. Although other virus diseases of cassava have been reported, in Tanzania, the most chronic cassava viruses of cassava are Cassava Mosaic Virus (CMV) and Cassava brown streak virus (CBSV). Moreover, currently, there is scant information or has never been a review on their distribution, spread, persistence, severity. But, again the efforts and methods of disease prevention or cultural disease control and management strategy of the diseases in the regions, particularly where they are still regarded as hot spot/high pressure areas for the disease persistence and severity country wide is very little or low. Therefore, this review considers, aim and focuses on; (1) Estimating the total contributing factors to the decline of the cassava yield and productivity hence, Food and Nutrition Insecurity in Mara Region. (2) Occurrence of different viruses of cassava in Mara Region-Tanzania, and (3) Agricultural or cultural practice, strategy and methods for prevention, control and managing these devastating virus diseases. However, the adoption of Improved cassava varieties and Improved Agricultural practices, cropping system, cultural practice or methods of management and control. Using varietal mixtures, such as crop rotation, fallow, intercrops, mono-copping, planting dates or other cropping systems have also been neglected. There is also a need for much additional research before they can be deployed effectively. Nevertheless, the severe losses accounted for a yield loss of up to 70% (Patil 2015; Ndyetabula 2016; Shirima et al., 2020; Chikoti et al., 2019). In a more realistic assumptions estimated losses in Africa ranged from 15-24%, equivalent to 12-23 million tons compared with actual production estimates of 73-97 million tons at the time (Thresh et al., 1994b, 1997; Legg and Okao-Okuja 1999; Legg et al., 2003, 2006; FAO. 2003 and IITA 2014) translating to USD assuming a conservative financial value of USD 100 per ton, this amount to US$ 1.2 to 2.3 billion. However, the disease incidence, persistence and severity now being caused by CMD and CBSD in many parts of sub-Saharan Africa, Tanzania, Mara and Coast province in particular could be greatly decreased through the application of the existing Improved cassava varieties and Agricultural knowledge and practices.

Keywords: Agro-ecology, (CMV), (CBSV), Anthills, long-rainfall, Cultural and Agricultural-practices.