Studies on spray deposition on cashew trees in Tanzania with reference to the use of fungicides to control Oidium anacardii
1997
Smith, D.N. | King, W.J. | Topper, C.P. | Mhando, H. | Cooper, J.F.
Water-based organic fungicides are being introduced into Tanzania as an alternative to sulphur dust for the control of powdery mildew on cashew trees, caused by the fungus Oidium anacardii. Spray application trials using motorised knapsack mistblowers were carried out to determine the minimum volume of spray required to achieve acceptable canopy coverage. Further trials assessed the feasibility of using lever operated knapsack sprayers with both commercially available and customised lance assemblies. In both cases, spray distribution on the cashew tree canopy was determined using a dye tracer with colorimetric analysis of foliage and image analysis of card spray targets. Application using the motorised mistblower gave uneven canopy coverage with a typical estimated application efficiency of 45%. Although it was possible to achieve relatively good spray distribution over the cashew canopy and an application efficiency of better than 50% using the knapsack sprayer and lance, the method resulted in unacceptably high levels of operator contamination.
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