First Report of Dactylispa lenta Weise (Coleoptera: Chrysomelidae) as a Vector of Rice Yellow Mottle Virus

Rice yellow mottle virus (RYMV) is a severe disease of rice in Africa. It is naturally transmitted by several species of beetles. Chaetocnema pulla is widely believed to be an important vector of RYMV in Tanzania. However, the high incidence of RYMV in some rice fields where C. pulla was not seen in large numbers indicated that more vectors of the virus might exist. Transmission studies conducted showed Dactylispa lenta to be a vector of RYMV in Tanzania. This has not been previously known

Social networks, governance and transaction costs effects on organic tomato and sweet pepper tourist hotels market in Arusha and Unguja

PhD ThesisThe objectives of this study were to (i) determine the social networks of the main actors in the organic food value chain in the tourism sector (ii) determine governance in the value chain of organic tomatoes and sweet peppers for the tourism sector in Arusha and Unguja and (iii) to evaluate production and transaction costs of actors in the organic tomatoes and sweet peppers value chain in Arusha and Unguja. The study was conducted in Arusha and Unguja. A preliminary survey was conducted in 2014. Then a stratified sampling procedure was used to select a sample of producers, tourist hoteliers and traders/suppliers. Key informants interviews and snowballing sampling procedures were also used. The results indicated that producers were close to other actors by closeness centrality of 2.12 in Arusha and 3.12 in Unguja. Suppliers/traders were central in the marketing of tomatoes and sweet peppers by betweenness centrality of 91 in Arusha while in Unguja producers‟ organization was central by betweenness of 533. Producers‟ organizations had many actors connected to them by a degree of 17 in Arusha and 28 in Unguja. The density of networks was low 0.01 due to fewer supporting institutions and lack of organic input suppliers. About four forms of governance structures were prominent in organic tomato and pepper value chain: market, modular, rational and captive. The probit results from the Heckman‟s two-stage process show that ownership of assets such as storage facilities, transportation assets and being under contract farming increased the probability of market participation, while experience in marketing increased the quantities of tomatoes and sweet peppers marketed. High marketing costs such as market levy, brokers and mobile phones costs decreased the quantities of tomatoes and sweet peppers marketed. Institutional arrangements (contract farming) were the possible solutions to reduce transaction costs effect, improve access to the tourist hotels market, increasing shelf life by having collective storage facilities and transport. Producers‟ cooperatives andcompanies enabled the promotion and production of organic tomatoes and peppers. The choice of captive and modular governance structure by lead actors ensured access to organic input and market

Identification of vectors of rice yellow mottle virus in Tanzania

Archives of Phytopathology and Plant Protection, 2001; 33 (5): 395-403countries in East Africa and almost all the countries in West Africa. At present, it is undoubtedly the most important disease of rice in Tanzania. It was first reported in the 1980's. It has spread fast and is now found in almost all the rice growing areas. In view of the increasing incidence and importance of RYMV on rice production in Tanzania, studies on the epidemiology of the disease were initiated in order to find ways of controlling the disease. Transmission studies were carried out on seventy-seven species of beetles and grasshoppers collected from different rice growing locations to determine vector identity. Four vectors have been identified (three chrysomelids; Dactylispa sp., Chaetocnema sp. and Chaetocnema pulla) and one tetrigid grasshopper. The wide distribution of Chaetocnema spp. in the RYMV endemic areas suggests that the species are the most important vectors responsible for infections in these areas

Newly recorded species of Chaetocnema, vector of rice yellow mottle virus in Tanzania

New Zealand Journal of Crop and Horticultural Science, 2001; 29:61-65Rice yellow mottle virus (RYMV) belongs to the Sobemovirus group and causes the only known virus disease of rice (Oryza sativa L.) peculiar to the African continent to date. It was first recorded in Kenya in 1966 and was not reported in Tanzania until in the 1980s. It has spread fast and is found in almost all the rice growing areas. Clearly, it is the most important disease of rice in Tanzania. RYMV is transmitted mechanically and by chrysomelid beetles. Chaetocnema pulla Chapuis is thought to be an important vector of the disease in Tanzania. Transmission studies conducted revealed a new species, Chaetocnema sp. nov. prope varicornis Jacoby, found in Tanzania as also a vector of RYMV. This species has not been previously reported to occur and to vector RYMV in any of the countries where the disease is prevalent. Further studies on the roles of these vectors and the dynamics of virus spread are necessary to provide more information on the epidemiology of this disease in Tanzania

Newly recorded species of Chaetocnema, vector of rice yellow mottle virus in Tanzania

New Zealand Journal of Crop and Horticultural Science, 2001; 29:61-65Rice yellow mottle virus (RYMV) belongs to the Sobemovirus group and causes the only known virus disease of rice (Oryza sativa L.) peculiar to the African continent to date. It was first recorded in Kenya in 1966 and was not reported in Tanzania until in the 1980s. It has spread fast and is found in almost all the rice growing areas. Clearly, it is the most important disease of rice in Tanzania. RYMV is transmitted mechanically and by chrysomelid beetles. Chaetocnema pulla Chapuis is thought to be an important vector of the disease in Tanzania. Transmission studies conducted revealed a new species, Chaetocnema sp. nov. prope varicornis Jacoby, found in Tanzania as also a vector of RYMV. This species has not been previously reported to occur and to vector RYMV in any of the countries where the disease is prevalent. Further studies on the roles of these vectors and the dynamics of virus spread are necessary to provide more information on the epidemiology of this disease in Tanzania

ournal of Sustainable Agriculture

Journal of Sustainable Agriculture, Vol. 20(4) 2002 by The Haworth Press, Inc.Regular samplings of two important vectors in farmers’ fields were made at crop stages susceptible to rice yellow mottle virus on a traditional rice variety (Supa) under rainfed lowland conditions to pro- vide information on the dynamic nature of the disease and the bionomics and importance of vectors in the disease transmission. The population of an unknown Chaetocnema sp. was significantly higher in hotspot than non-hotspot areas. However, there was no significant difference in C. pulla Chapuis population between both areas. In general the unkown Chaetocnema sp. population was higher than C. pulla, and both vectors reached the peak of their population at 63 days after planting. Also, early planting in the hotspot areas is suggested as a disease management strategy

ournal of Sustainable Agriculture

Journal of Sustainable Agriculture, Vol. 20(4) 2002 by The Haworth Press, Inc.Regular samplings of two important vectors in farmers’ fields were made at crop stages susceptible to rice yellow mottle virus on a traditional rice variety (Supa) under rainfed lowland conditions to pro- vide information on the dynamic nature of the disease and the bionomics and importance of vectors in the disease transmission. The population of an unknown Chaetocnema sp. was significantly higher in hotspot than non-hotspot areas. However, there was no significant difference in C. pulla Chapuis population between both areas. In general the unkown Chaetocnema sp. population was higher than C. pulla, and both vectors reached the peak of their population at 63 days after planting. Also, early planting in the hotspot areas is suggested as a disease management strategy