TREATMENT. 25 



water supply is an important factor. The cranberry plant is natu- 

 rally water loving and grows in its wild condition in the sphagnum 

 bogs of deep swamps. "When it is cultivated in open meadows and 

 without a constant and suflicient water supply it quite naturally 

 becomes weakened and susceptible to disease. In order to keep the 

 plants in a thrifty condition the water supply should not only be 

 sufficient but well controlled, so that the moisture may be kept near 

 the surface during the growing season. In many cases there are local 

 soil conditions which interfere with the healthy growth of the plants. 

 The practice of applying a thin layer of sand to the surface of the 

 bog every few years is quite general in Massachusetts and is believed 

 to tend to keep the plants in a thrifty and vigorous condition. In 

 New Jersey this practice is not so common and the beneficial results 

 where it has been tried do not seem to have been so apparent as in 

 Massachusetts. The practice of sanding, since the sand would cover 

 all the fallen diseased leaves and many of the old dead vines, would 

 tend to prevent the development and spread of the spores and might 

 prove beneficial in this way, if in no other. It is also desirable as a 

 sanitary measure to rake out and destroy all dead and dying plants. 

 The fungus Guignardia paccinii produces its spores in great abund- 

 ance upon such plants, and these, therefore, serve as a source of dis- 

 tribution for the parasite. All such dead and diseased matter should 

 be destroyed by burning, preferably in the fall of the year. 



Selection of resistant rarieties. — It has been frequently observed 

 that even in the most diseased areas of cranberry plants there is an 

 occasional vine bearing fruit which appears to be free from disease. 

 It seems probable, therefore, that by the selection and propagation 

 of such plants a variety might be produced Avhich would show a 

 very considerable degree of resistance to this disease. As the cran- 

 berry is generally reproduced by cuttings, the propagation of a re- 

 sistant variety would be simpler and more likely to succeed than 

 in the case of plants propagated by seed. 



Application of fungicides. — As already stated, Doctor Halsted " 

 recommended spraying with ammoniacal copper carbonate. He also 

 reports* trying several fungicides, including Bordeaux mixture and 

 potassium sulphid, making two applications of each. No benefit 

 from these applications was observed. 



After determining the parasitic nature of the cranberry scald, 

 the relationship of the parasite, and the probable manner of infec- 

 tion, it seemed reasonable that the disease should be prevented by 

 the proper use of fungicides. In our first experiments the ammonia- 

 cal copper carbonate solution, potassium sulphid solution, and Bor- 

 deaux mixture were used. As very little benefit was apparently 

 derived from the use of the two fungicides first mentioned, later 

 3525— No. 110—07 m 4 



