Abstract
Apple scab caused by Venturia inaequalis (Cooke) wint, and apple powdery mildew, caused by Podosphaera leucotricha (Ell. and Ev.), are the most important diseases of apples in Uganda. Control of apple scab and powdery mildew require the application of fungicides in absence of resistant apple cultivars. This study was conducted to identify effective control fungicides and to document the status of these diseases in south western Uganda. The survey results of 2012 indicated that scab incidence was highest in districts of Kanungu (71.90%), followed by Kisoro (48.14%), Kabale (41.03%), Buhweju (29.23%), Mbarara (28.75%) and Rukungiri (17.80%). The severity of apple scab measured as percentage leaf area affected ranged from 20.12 to 76.19%. Powdery mildew incidence ranged from 30.00 to 70.00% with severity score ranging from 14.63 to 76.19%. Fungicides containing propineb (70% a.i), metalazyl (4% a.i) + macozeb (64% a.i), and bupirimate (25% a.i) were found to be effective at controlling apple scab with potential to reduce the disease severity by 61.11, 61.11 and 58.33%, respectively, while fungicides containing bupirimate (25% a.i), tebuconazole (43% a.i) and propineb (58% a.i) + cymoxanil (4.8% a.i) were more effective in the control of powdery mildew with potential to reduce the infection by 55.95, 39.12 and 20.84%, respectively. Key words: Apple scab, powdery mildew and fungicides.
Highlights
Apple production is new agro enterprise that was established in Uganda since 2000 in South-western highlands mainly in Kabale district (ICRAF, 2003). 13 apple cultivars were introduced by NARO and ICRAF following farmers' demand for fruit trees
The disease severity was scored as percentage plant leaf area affected (PLAA) with scab according to a scale of 0 to 7 developed by Parisi et al (1993), Croxall et al (1952) 0 to 7 where 1 = 0% < percentage of scabbed leaf surface< 1%; 2 = 1%
The results of the current work showed a high incidence of apple scab and powdery mildew in the majority of districts surveyed
Summary
Apple production is new agro enterprise that was established in Uganda since 2000 in South-western highlands mainly in Kabale district (ICRAF, 2003). 13 apple cultivars were introduced by NARO and ICRAF following farmers' demand for fruit trees. Apple production is new agro enterprise that was established in Uganda since 2000 in South-western highlands mainly in Kabale district (ICRAF, 2003). Apple scab and powdery mildew were identified as the most important diseases of apples in the country, with a potential to cause significant effects on the developing temperate fruit agro enterprise (Chemining et al, 2005). In the absence of proven diseases management technologies in Uganda, attempts to control these two diseases have been initiated through the use of fungicides and screening for tolerance among the introduced apple cultivars. This study was established to document the status of these diseases in the country and to evaluate the effectiveness of the available fungicides in the control of the diseases at Bungongi substation, in Kabale located at 1830 m a.s.l so that information on effective fungicides could be released and recommended for farmers to use
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