EXPERIMENT STATION BULLETINS. 



663 



PREVENTIVE MEASURES 



The first evidence of the control of "tipburn" by means of bordeaux 

 mixture was presented by I'rof. Goff^ in 1891. In testing tliis spray for 

 the control of late blight he reported that the check rows turned yellow 

 and later became brown, while the sprayed vines remained green all 

 through the season. He also noted that "none of the potatoes were 

 decayed at digging time and that there were no indications that the 

 blight which so injuriously affected the foliage of potatoes the past 

 season on the checkrows of our experimental plot and throughout 

 southern Wisconsin was connected in any way with the potato-ror 

 fungus, Phytoplithora itifestans. But whatever the affecting disease 

 was, it is evident that the treatment proved the remedy for it." In- 

 vestigations since that time (Stewart^^', Lutman*) have confirmed 

 Goff's findings and it is repeatedly noted in the literature of bordeaux 

 mixture as a potato spray that the percentage of tipburn is always 

 reduced in the sprayed plots. 



In order to ascertain what effect, if any, bordeaux mixture had on 

 the control of hopperburn, spraying experiments were conducted at the 

 Upper Peninsula Experiment Station, Chatham, Michigan, during tlio 

 1919, 1920 and 1921 sessions. A 5-5-50 bordeaux mixture, to Avhich an 

 arsenical poison was added to control the Colorado potato beetle, was 

 used during the first two seasons, the spray being applied with a 50- 

 gallon traction type sprayer, (Fig. 11) which was remodeled so as to 

 apply the spray to the under sides of the leaves. During the 1921 sea- 

 son a 4-4-50 bordeaux mixture was used, and was applied with a power 

 sprayer which was capable of maintaining a pressure of 225 pounds 

 (Frontispiece). 



The results ()l)taiiied from the three-season spra^'ing program are 

 summarized below 



Table V. Effect of Bordeaux Mixture on Hopperburn 

 Spraying Experiments, U. P. Experiment Station, Chatham, Michigan, 1919, 1520, 1921 



*5-5-50 bordeaux mixture used in 1919, 1920; 4-4-50 in 1921. 



Some very interesting facts were gleaned from the three-year spray 

 ing experiments. The 1910 and 1921 seasons were very favorable to the 

 potato leafhopper and liopperburn caused serious losses. The 1920 

 season, on the other hand, was two Aveeks later tlian normal and rain- 

 fall was abundant. Leafhoppers emerged late and multii^lied veiy slowly 



