228 



EXPERIMENT STATION RECORD. 



If the strength of solution be disregarded tlie results of the tests are 

 expressed in the following table: 



I'revoition of scab hij ireatiiKj seed with corrosive fiiihliiiKile. 



From this table it will be seen tliat tliose immersed for an hour or 

 less have a comparatively large percentage of scab. The longer immer- 

 sions show that the scab decreases very slowly, and that for practical 

 purposes 1. J hours is sufficient." It will also be noticed that the yield 

 increases to a certain point, after which there is a gradual decrease. 

 Checking the S(;ab seems to cause increased growth, but where the seed 

 is immersed 2 hours or more the plants are so .slow in starting that the 

 increase is overcome. 



A duidicate of these experiments was tried on land that grew a crop 

 of potatoes in 1892, There was much more scab in the dui)licate experi- 

 ments, showing that the germs from the previous crop remained in the 

 soil aud prevented the treatment from being a complete success, 

 althongh the amount of scab was reduced to about half. 



The effect on the solution of treating the seed was tested, showing 

 that the amount of corrosive sublimate diminishes as the potatoes are 

 soaked in the solution, and taking this as a basis it is advised after 

 soaking about 12 bu. of i)otatoes in 15 gal. of solution to add ^^ of an 

 ounce of the corrosive sublimate; otherwise the solution will become 

 too weak. 



The Bordeaux mixture tested was made by taking 4 lbs. of suli^hate 

 of copper, 3 lbs. of lime, aud 32 gal. of water. It made nearly as good 

 a showing as the corrosive sublimate, so far as the per ceut of scabby 

 tubers is concerned, but in the size of the scab spots there was no dif- 

 ference between those on the treated plats and those on the untreated. 

 Trials under more diverse conditions are necessary to establish the 

 value of this treatment. 



Practical suggestions are given for treating the potatoes for scab. 



Leaf blight of potato, L. K. Taft and R. J. Coryell {Michigan 

 Sta. Bui. lOS, p. 47). — A brief account is given of a bacterial disease 

 which has been injurious at the station for several years. It appears 

 during hot dry weather and is especially severe on the early and medium 

 varieties at the time they are half grown. The vines killed by the leaf 

 blight are readily distinguished from those killed by the drought. In 

 the former case the leaf turns black at or near the tip. This blackened 

 area increases until about one half or three fourths of the leaf surface 



