Results of spraying and dusting potatoes in Michigan in 1946

Abstract

In the experiments at the Lake City Experiment Station, potatoes sprayed with Dithane-zinc sulfate-lime DDT and F48-Bordow-Dethyl gave yields significanly better than those of any other materials employed. It seems possible that lack of injury to the plants from these materials or this factor and the added effect of DDT may be responsible for the increased yields. Bordeaux mixture 8-12-100, Zerlate and Yellow Cuprocide Tribasic-DDT ground together and DDT alone resulted in yields higher than those of the other materials employed, although these differences in yield were not statistically significant in every case. The results of the dusting experiments, using fixed coppers in comparison with monohydrated copper sulfate-lime showed no significant differences in yield between these materials plus DDT or DDT alone. Considerable variation in yield was found between plots sprayed with the same materials in different counties in the Upper Peninsula. Using the plots of identical materials in each of three counties as added replicates of materials, there was no significant difference in yield between the various sprays. Late blight was absent in the Lake City Experiment Station tests and early blight was present in only slight amounts. In the Upper Peninsula plots late blight was present in Menominee, Schoolcraft, Marquette and Houghton counties but its development was stopped by early killing frosts before any appreciable damage resulted.