46 



fore, to believe that in some cases at least the primary injury is due to 

 the depredations of grubs, myriapods or otber small animals/ or it may 

 be brought about by the irritating or corroding action of some substance 

 in the soil. In any event the final result is practically the same as 

 where the original damage is caused by an enlargement of the lenticels. 



All who have thoroughly investigated the disease agree in tne opin- 

 ion that extreme humidity favors its development, Out what influence 

 beyond this the character of the soil has upon the malady is not posi- 

 tively known. There have been many theories advanced having a bear- 

 ing upon this question, but they are so conflicting that nothing of value 

 can be derived from them. During the year 1887 a number of trials 

 were made at the New York Agricultural Experiment Station with a 

 view of testing (1) influence of the soil, (2) effects of excessive moisture, 

 (3) use of scabby seed, (4) effects of color of skin, (5) effects of fungicides, 

 and (6) effects of chemical fertilizers and stable manure upon the devel- 

 opment of scab. It was shown by these experiments that an excess of 

 moisture and the use of fresh stable manure materially increased the 

 number of scabby potatoes. The data obtained are summed up as fol- 

 lows : 



"(1) The scab is not primarily caused by a fungus. 



"(2) It is not due to the work of insects. 



" (3) In nearly every instance an increased yield was accompanied by 

 an increased percentage of scabby potatoes. 



" (4) Any marked change in the rapidity of growth, either an increase 

 or a decrease, tends to an increased production of scab. 



"(5) A continuous growth from the time of first vegetation until the 

 tubers are fully matured appears to be the condition least favorable to 

 the production of scabby potatoes." 



BIBLIOGRAPHY. 



Arthur : Sixth Eeport of the New York Agricultural Experiment Station, 1887, p. 

 344. 



Beckivith : Sixth Report of the New York Agricultural Experiment Station, 1887, 

 p. 307. 



Frank: Krankheiten der Pflauzen, 1880, p. 140. 



Ploivright : Gardener's Chronicle, vol. 23, 1885, p. 60. 



Report of the Counecticut Agricultural Experiment Station, 1877, p. 67; 1886, p. 79. 



Sorauer : Handhuch der Pflauzen Krankheiten, 1st ed., 1884, p. 84; 2d ed., 1686, p. 

 227. 



1 Mr. Alfred Rose, writing to the Rural New Yorker under date of March 7, 1885, says 

 that he has experimented largely for forty years on potato culture, and he thinks 

 the wire worm (lulus) causes scab; that these " worms" are more prevalent and the 

 scab much worse on rather moist soils than on those light and sandy; that where 

 scab prevails, the sooner the potatoes are dug the better, and that anything that for- 

 wards the crop aids in escaping the scab. He has found that the use of lime slaked 

 with water which has been saturated with salt and into which 2 pounds of sulphur 

 have been stirred for each bushel of lime has effectually driven out these " worms " 

 and prevented scab. He thinks that land infested with these worms should be 

 plowed in the fall and have 250 pounds of kaiuit and 5 bushels of lime, prepared 

 as above described, sown broadcast per acre and well cultivated iu. 



