Abstract
Cassava adaptive trial was planted in ten sub counties across West Nile Agro-ecological Zone (WNAEZ) with six cassava varieties to test their performance and reactions to major pests and diseases present in the Zone. Th six cassava varieties comprised of improved (TME 14 and 204, NASE 13 and 14 and Akena – TMS I92/00067) and a local (Abiria) were selected based on their availability and preference in the region. The experiment was planted in RCBD design with three replicates. The experiment was planted in ten locations with the plot size was 6x6 metres. Results showed Cassava green mite (CGM), Cassava mosaic disease (CMD) and cassava bacterial blight (CBB) as major pest and diseases across all sites. Cassava Anthracnose (CA) and Cassava mealy bug (CM) were not present in the study sites. Cassava brown streak disease (CBSD) foliar symptoms was observed in three locations of Dranya s/c, Gimara s/c and Nyaravuru s/c on the three varieties of TME 204, TMS-I92/00067 and TME 14, whereas CBSD root necrosis was seen across all sites on TME 204, TMS-I92/00067, NASE 13, TME 14 and the Local except on NASE 14. In terms of yields, results showed that it was highest in TMS-I92/00067 (53.0 t/ha), TME 204 (46.0 t/ha), NASE 14 (39.4 t/ha), TME 14 (34.6 t/ha), NASE 13 (33.4 t/ha) and the local (22.7 t/ha) in that order. Farmers’ ranking of the studied cassava varieties in order of preference was in the order of NASE 14, TME 204, TMS-I92/00067, TME 14, NASE 13 and the Local. In conclusion, absence of both foliar and root symptoms on NASE 14 across all sites indicated that this variety is still tolerant to CBSD and can still be multiplied for production in West Nile Agro-ecological Zone.
Highlights
Cassava (Manihot esculenta Crantz) is cultivated throughout the lowland tropics, typically between 30°N and 30°S of the equator, in areas where the annual mean temperature is greater than 180C (Nasser & Ortiz, 2007)
Cassava green mite was highest in NASE (67%, 2.1) and lowest in the local (38.9%, 2.0), cassava mosaic disease was highest in the Local (82.5%, 3.4) and not present on NASE (0%, 1), Foliar Cassava brown streak disease (CBSD) was highest in TME 204 (22.5%, 2.0) and not present on NASE 14, NASE and Local (0%, 1), cassava bacterial blight was highest in TME (100%, 2.3) and lowest on NASE 14 (73.8%, 2.0), cassava anthracnose and cassava mealybug were not observed across all study sites
In terms of locations (Figure 1), Foliar CBSD with the highest incidence of 23.1 percent was observed at Gimara sub-county in Moyo with a severity score of 2.3 and not present at Abanga, Abuku, Kijomoro, Moyo and Yivu sub-counties, Cassava mosaic disease (CMD) was highest at Gimara and Yivu sub-counties (100 percent) with a severity of 3.1 and lowest at Abanga (37 percent) with a severity score of 2.3, cassava bacterial blight (CBB) was highest at Abuku and Kijomoro sub-counties (100 percent) with severity score of 2.7 and lowest at Abanga (72 percent) though with the highest severity score of 3.6, and Cassava green mite (CGM) was highest at Nyaravuru (92.5 percent) with severity of 2.5 and lowest at Kijomoro (15.5 percent) with a severity score of 1.3
Summary
Cassava (Manihot esculenta Crantz) is cultivated throughout the lowland tropics, typically between 30°N and 30°S of the equator, in areas where the annual mean temperature is greater than 180C (Nasser & Ortiz, 2007). Cassava yields vary with cultivars, season of planting, soil type and fertility (IFAD & FAO, 2000) as well as with the level of infestation and infection with pests and diseases respectively (Bock, 2004). In Uganda, cassava is the second most important food crop after bananas (Semakula et al, 2004) and in Westnile region it ranks as the most priority crop (NARO Report, 2004). Many pathogens and pests reduce cassava yields, especially in Africa (Dixon et al, 2003; Oerke, 2006) including Uganda. Diseases such as cassava mosaic disease (CMD), transmitted by a whitefly (Bemisia tabaci) vector and spread by infected cuttings, cassava brown streak virus disease (CBSD), Cassava bacterial blight
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