350 EXPERIMENT STATION RECORD. [Vol. 37 



will control the trouble. It is recommended that the fungicide be applied by the 

 drip method which is used for the prevention of onion smut. No efficient 

 method has been determined for the treatment of onion sets, but experiments 

 along this line are in progress. 



Investigations on potato diseases (seventh report), G. H. Pethtbkidge 

 (Dcpt. Agr. and Tech. Instr. Ireland Jour., 16 (1916), No. 4, pp. 564-596. pis. 

 12). — The special investigations on potato diseases, which were started in 1909 

 at Clifden, Ireland, and since reported on from time to time (E. S. R., 34, p. 

 443), were continued during 1915, and the results are here described in con- 

 siderable detail. 



Phytophihora infestans appeared very late in 1915. supposedly on account of 

 the fine dry weather which prevailed after planting until the end of June, and 

 after that time supposedly on account of the scarcity of infecting spores. From 

 the work already done, it is thought that in favorable seasons, at least, the use 

 of 1 per cent Bordeaux or Burgundy mixture is about as effective as is the 2 

 per cent application. Tests with a fungicidal powder showed this to be inferior 

 to the ordinary sprays. Burgundy mixture gave slightly greater freedom from 

 blight than Bordeaux mixture, but a somewhat lighter yield of tubers. It is 

 considered better to spray several times at comparatively short intervals with 

 a relatively weak mixture than a few times with a strong one. The names and 

 relative ranks of varieties tested for resistance are detailed. Outbreaks appear 

 to originate only from the planting of diseased potato tubers in which the 

 fungus lives over from one season to the next. 



Stalk, or Sclerotium, disease (Sclerotinia sclerotiorum) was less severe than 

 in any of the five or six previous seasons. Infection occurs first on one or 

 more of the older, yellowing leaves and then passes directly to the stalk. 

 Abnormally early planting, in some localities, is thought to favor the disease. 

 Two sprayings with lime-sulphur or with milk of lime decreased the attack and 

 increa.sed the yield. Attention is called to recent findings tliat this fungus has 

 no Botrytis stage, as formerly held. 



Botrytis cincrea was studied under favorable conditions as it developed, un- 

 masked by blight, in July and the early part of August, and its characters, 

 habits, and effects are detailed. It is regarded as not definitely proved that 

 B. cinerea is the conidial stage of S. fuckeliana. The usual sprays have little 

 or no effect upon this disease, but it is resisted by the same varieties which are 

 resi-stant to blight. 



TerticilHvm alboatrum has thus far been observed at three places in Ireland. 

 It spreads from the infected mother tubers into the young stalks, and practi- 

 cally any part of the plant, if left, will contaminate the soil. Heating tubers 

 for five hours from 41 to 45.5° C. does not kill the fungus nor does it injure 

 the tubers. 



Hypochnus {Rhizoctonia) solani was studied, and it is concluded that under 

 the conditions employed this fungus does not cause a rot of potato tubers. 



Work has been done with other diseases, some of which is still incomplete. 

 Notes given in this connection refer to Spongospora subterranea, Spondylocla- 

 dhnn ntroiHrcns, Fvsarium ccrrulcum. and P. erj/lhronrptira. 



Cork, drought spot, and related diseases of the apple, A. J. Mix (New York 

 State Sta. Bui. 426 (1916), pp. 473-522, pis. 12; ahs., pp. S, figs. 9).— A descrip- 

 tion is given of two little known diseases which were observed in the Champlain 

 Valley, New York. Both are nonparasitic in nature and may be different types 

 of the same disease. They are considered closely related to the well-known 

 fruit pit or stippen disease. The names drought spot and cork are proposed for 

 them. Associated with the drought spot are abnormal conditions of the twigs 



