« APPLE BLIGHT IN REVIEW. 2O9 



In 1863 J. H. and C. B. Salisbury ascribe the disease to fungi. 



In the proceedings of the American Pomological Society in 1867, 

 T. Meehan also says, "Here, I believe, we have to deal with a para- 

 sitic fungus. It grows in the bark, causing fermentation." 



In 1870 a pear tree was successfully inoculated by lifting the bark 

 and inserting a piece of bark from a blighted apple tree. 



As late as 1891, G. F. B. Leighton, of Virginia, tells the American 

 Pomological Society that blight is due to a change of thirty degrees 

 or more in temperature within twenty-four hours, and will show in 

 just nine days after such change. 



In 1879 Prof. Burrill, of Illinois State University, now an old 

 man; discovered that apple blight is a bacterial disease, due to a 

 parasite which lives, feeds and multiplies beneath the bark. He 

 named it micrococus amylovorus. It is now commonly called bacillus 

 amylovorus. 



Prof. J. C. Arthur, then of N. Y. Agricultural Experiment 

 Station corps, now of Purdue University, next set about proving this 

 parasite to be the cause of the disease. He infected trees with the 

 virus from other trees. He made what are called pure cultures of 

 the bacteria from infected trees. Then to determine whether the 

 medium in which they had lived and worked would produce the dis- 

 ease without the bacteria, he strained the liquid through unglazed 

 earthenware to remove the parasite and tried inoculation, but the 

 strained liquid would in no case produce the blight. To find whether 

 any other bacteria would produce the blight he inoculated healthy 

 trees with all of the other kinds of bacteria in his laboratory, but 

 without success. 



To learn whether the wind may distribute the disease he forced 

 a current of air over blighted parts on to a potted pear, but got no 

 blight. To see whether rain might be effective, he dropped water 

 from a blighted branch on to a potted pear at the rate of four drops 

 per minute, and got a slight infection. He tried to communicate 

 the disease through the root by watering the plant but failed. To 

 learn whether the bacteria would live through the winter in dead 

 matter, he tested and found them the next April in a branch which 

 had been cut in midsummer and thrown into a tank of water, the 

 water being drained off in the fall, leaving the sediment moist, how- 

 ever. By inoculation with one virus he produced blight in apple, 

 pear, quince, wild crab, hawthorn and mountain ash. 



H. M. Waite, of the Agricultural Department at Washington, 

 is the next man who does extensive work in the experimental line. 

 Although Kennicott, in 1850, calls attention to blight in flowers and 

 fruit spurs, and Geo. Peffer of Wisconsin does the same again in 



