418 Report of the Mycologist op the 



On Long Island downy mildew appeared earlier and was more 

 destructive in 1896 than in 1897, although the rainfall for July 

 and August was much heavier in the latter season. The high 

 temperature of August l-lo, 1896, was probably responsible for 

 the virulence of the disease in that year. 



In an experiment at Woodbury an acre of late cucumbers which 

 were sprayed eight times with Bordeaux mixture yielded 101,960 

 " pickles." The average yield of unsprayed cucumbers in this 

 section was probably less than 20,000 per acre. 



Plasmopara cubensis has been found on Cucmnis moscliata 

 (winter crook-neck squash), which is a new host for this fungus. 



I. PLOWING UNDER GREEN RYE TO PREVENT POTATO 



SCAB. 



There appears to be a quite widespread notion among farmers 

 that potatoes will be free from scab {Oospora scabies) if grown on 

 soil in which green rye has been plowed under just before plant- 

 ing. Some even assert that this method will insure a smooth 

 crop of tubers on land w^hich has produced a scabby crop the 

 previous season. 



It is highly important to know if this opinion has any founda- 

 tion in fact, because at the present time there is no thoroughly 

 practical method known for circumventing the evil influence of 

 scab-infested soil. Halsted* has advocated the use of flowers of 

 sulphur, applied to the " seed " and in the drills at the rate of 

 about 300 pounds per acre, but for some reason farmers are un- 

 able, in practice, to confirm the results of his experiment. 



Why green rye should have any power to prevent potato scab 

 is not clear. Flagg,t assuming the rye theory to be true, has 

 suggested, as a possible explanation, that the rye brings about an 

 acid condition of the soil which is well known to be unfavorable 

 to the growth of the scab fungus. 



Although there appeared to be no good reason why green rye 

 should possess the merits claimed for it, it was deemed worth 

 while to test the matter by experiment; for experience has shown 



•Halsted, B. D. Field Experiments with PoUtoes. N. J. Agl. Expt. Stas. Bui. 112; 

 and N. J. Agl. Expt. Stas. Kept. 1896, pp. 309-318. 



tFlagg, C. O. Green Manuring and Potato Scab. Cult, and Country Gent., Vol. LXI, 

 p. 779. 



