The Action of Copper Fungicides in the Control of Dothistroma Blight of Pines-A Pilot Study

Abstract

Experiments to determine the retention of copper fungicides on the foliage of young Pinus radiata show that there was little difference amongst the rates of weathering of five materials based on copper oxychloride and cuprous oxide after application at the same initial dosage of copper. The rate of weathering of a cuprous oxide formulation was also studied after application at a range of dosages. This showed that high dosages combined with a small number of spray operations might prove more economical than a larger number of operations at a lower dose rate, when copper fungicides were used to control Dothistroma blight of pines in the field. Control of blight by copper fungicides was shown to be related to the fact that the pathogen was highly sensitive to copper in solution. Copper was shown to be trans-located in surface water on the host in quantities toxic to germinating conidia of Dothistroma pini providing protection to foliage and eradicating inoculum established in diseased portions of the tree.