Dn. Smith et al., STUDIES ON SPRAY DEPOSITION ON CASHEW TREES IN TANZANIA WITH REFERENCE TO THE USE OF FUNGICIDES TO CONTROL OIDIUM-ANACARDII, Crop protection, 16(4), 1997, pp. 313-322
Water-based organic fungicides are being introduced into Tanzania as a
n alternative to sulphur dust for the control of powdery mildew on cas
hew trees, caused by the fungus Oidium anacardii. Spray application tr
ials using motorised knapsack mistblowers were carried out to determin
e the minimum volume of spray required to achieve acceptable canopy co
verage. Further trials assessed the feasibility of using lever operate
d knapsack sprayers with both commercially available and customised la
nce assemblies. In both cases, spray distribution on the cashew tree c
anopy was determined using a dye tracer with colorimetric analysis of
foliage and image analysis of card spray targets. Application using th
e motorised mistblower gave uneven canopy coverage with a typical esti
mated application efficiency of 45%. Although it was possible to achie
ve relatively good spray distribution over the cashew canopy and an ap
plication efficiency of better than 50% using the knapsack sprayer and
lance, the method resulted in unacceptably high levels of operator co
ntamination. (C) 1997 Published by Elsevier Science Ltd.