1920.] PUBLIC DOCUMENT — No. 31. 15a 



unfavorable growing conditions of the summer of 1918. Others 

 were able to make more or less top growth, even under the 

 adverse conditions which prevailed. Apparently, root develop- 

 ment in the dry soil did not go on apace with growth above 

 ground, and consequently the balance between roots and top 

 was destroyed, resulting in dying back of twigs and branches 

 the following (1919) season. It is not unlikely that a small 

 amount of this resultant trouble may appear next summer. 



The condition of the potato crop was in marked contrast to 

 that which prevailed in 1918. Mosaic disease, so widespread 

 and severe the previous year, w^as extremely difficult to detect 

 in most fields, although close examination usually showed it to 

 be present. There is marked seasonal influence on th-e ap- 

 pearance of this disease, and, apparently, conditions in 1919 

 did not favor the extreme development evident in 1918. Leaf 

 roll was much more in evidence, and spindling sprout con- 

 siderably reduced production, especially where home-grown 

 "seed" were planted. 



Efforts were made to follow up the accumulated evidence in 

 regard to the parasitism of Phoma on potatoes, but no bona 

 fide cases of the disease caused by this fungus were found, and 

 attempts to produce it by artificial inoculation were only 

 partially successful. This supports the opinion expressed in 

 our last report that the weather is a prime contributing factor 

 in the parasitism of this Phoma, and that under normal 

 seasonal conditions the disease will not prove of consequence. 



The condition of the potato crop up to the latter part of 

 August was generally good. However, the period from the 

 18th of that month until the time of harvesting the crop was 

 one of relatively low temperatures, high humidity and frequent 

 rainfall, — conditions highly favorable to the development of 

 late blight. The disease appeared in many sections of the 

 State soon after the middle of August. From that time on it 

 developed rapidly, and few fields escaped severe injury. A 

 few heavily sprayed fields remained green to the end. But, as 

 a rule, spraying with Bordeaux mixture only partially con- 

 trolled the disease. These failures should not cause growers 

 to condemn spraying w^ith Bordeaux mixture as a practice, for 

 it is definitely known that blight is very largely controlled by 



