1913.] PUBLIC DOCUMENT — No. 31. 211 



with water at about sunrise, and so drawing the frost out 

 of them gradually before the heat of the sun strikes them. 

 Frost injury appears to be caused not by the freezing but by 

 too rapid withdrawal of the frost. If this is true, it may be 

 possible to sprinkle a cranberry bog with the Skinner system, 

 or some other similar system, a section at a time, and so provide 

 protection for the whole bog with an engine and pump only 

 large enough to })ump water for one section. Experiments have 

 been planned to tost the practicability of this method. 



Another drawback to the Skinner s^-stem is the clogging of the 

 nozzles. This gave much trouble in the small system installed 

 at the station bog, and market gardeners who have had long 

 experience with this system meet the same difficulty. Because 

 of this it is now planned to test another system, which has been 

 devised for the same purpose, with rotating nozzles set far 

 apart and large enough to allow small particles in the water to 

 pass through them instead of clogging. 



Two extensive tests with 65 3-gallon Hamilton orchard 

 heaters were carried out in the late fall and early winter. These 

 tests showed that it is possible to raise the temperature suffi- 

 ciently to protect from frost by means of these heaters, but the 

 expense connected with their use seems to be so great that this 

 method of protection cannot be considered practicable with fuel 

 oil at the present price. The heaters were loaned to the sub- 

 station by the Hamilton Orchard Heater Company, through 

 the courtesy of its local agent, Mr. Chester D. Holmes of Pljmi- 

 outh, Mass. 



3. Fungous Diseases. 



As in previous years, this work was carried on in co-operation 

 with the Bureau of Plant Industry of the TTnited States De- 

 partment of Agriculture. Dr. C. L. Shear of that Bureau has 

 done much laboratory work and has had general supervision 

 of the spraying experiments, having kept in touch with the 

 work on the bogs by several trips to the Cape. Co-operative 

 spraying tests were carried on by several growers. The five 

 plots, each four rods square, which were sprayed in the season 

 of 1911, as reported in the last annual report of the station, 

 were sprayed again in 1912 on dates and with fungicides as 

 follows : — 



