The response of different varieties of potatoes to different amounts of copper in a modified spray program

Summary: Working with the Irish Cobbler, Rural Russet and Green Mountain varieties of potatoes at Pittsford, N. Y., it was found that all these varieties respond to copper treatments in the form of bordeaux mixture to approximately the same extent in final increases in yields. Using a Bordeaux mixture composed of the equivalent of half as much quick lime as copper sulfate, and applying most of the copper early in the season, there appeared to be no advantage in using more than a total of 60 pounds of copper sulfate per acre during the season. All copper-sprayed plants retained more tubers per plant than unsprayed plants of the same variety.All varieties showed evidence of a retardation in tuber development due to spraying. The retardation was less pronounced with the Cobblers and most pronounced with the Green Mountains. In the Green Mountains, the unsprayed plants yielded more than the sprayed until after September 21.