Studies on the application of a copper fungicide for the control of coffee leaf rust :

A proprietary cuprous oxide fungicide was applied to unshaded single-stem coffee as both a high- and a low-volume spray. Initial deposition of fungicide was not affected by the volume of application. An improved sampling method, used in the second year of the trial, showed that despite efforts to direct the spray on to the under leaf surface, more fungicide was applied to the upper. The deposits arising from high-volume applications were more susceptible to weathering and this weathering was most marked from the upper leaf surfaces. It was noted that irrigation within 48hr. of spraying caused a considerable reduction in fungicide deposit. A visual scoring technique indicated that a large proportion of the leaves received no fungicide at all and it was concluded that subsequent redistribution may occur. The biological assessments indicated that high- and low-volume application of copper fungicide gave equally good leaf rust control and leaf retention. Reducing the fungicide applicationfrom 5 to 1 lb./acre resulted in reduced fungicidal efficiency. A "disease control index" was developed to show the relationship between the level of fungicide deposit and the degree of leaf rust control. A mean total deposit of approximately 60 mg./m2 leaf area was required for satisfactory protection