Effect of sulphur and potassium chloride on the control of rust and black spot on modern cultivars: A thesis presented in partial fulfilment for the National Diploma in Horticulture

Abstract

There were a total of 96 Rose Cultivars in the trials from October 1995 - April 1996. Sulphur and Potassium Chloride were applied at monthly intervals. Each chemical was applied at two rates, 100gms per m2 and 200gms per m2, some cultivars being treated with the l00gms rate and others with the 200gms rate. A 50/50 mixture of the fertiliser was applied to some cultivars while 24 cultivars received neither Sulphur or Potassium Chloride. Assessments of each cultivar were recorded monthly between Oct 95 - Apr 96 to monitor disease levels and growth performance. Rust, caused by Phragmidium mucronatum and Black spot, caused by Diplocarpon rosae were not significantly controlled by monthly applications of these fertilisers. Differences in response to Rust and Black spot among the cultivars ranged from complete resistance to high susceptibility. Rust caused the more serious damage.