52 MASS. EXPERIMENT STATION BULLETIN 427 



ing, the toxic action being due to the naphthalene component of the dust mixture. 

 Without moisture on the spore-bearing surface, no effect from copper or calcium 

 arsenate in the confined atmosphere of a Petri dish was shown. In the presence 

 of moisture, naphthalene, copper sulfate, or calcium arsenate exerted a lethal 

 effect upon the spores. The results corroborate the evidence of other investi- 

 gators claiming the strong fungicidal action of calcium arsenate. The concen- 

 tration of naphthalene vapor in the small and confined atmosphere of a Petri 

 dish was derived from mixtures containing 30 percent naphthalene. Weaker 

 concentrations might have been adequate. A spray containing 1.6 pints of 40 

 percent nicotine sulfate (.2 percent) and 40 pounds of salt in 100 gallons of 

 water (5 percent) was not significantly toxic. 



Table 17. Toxicity of Fungicides to Spores of Alternaria Dianthi. 



Dry Spores Teated Water 



Dry Spores with Fungicide Suspension 



Fungicide Applied to of Spores 



Dry Residue Incubated Incubated Applied to 

 Dry Wet Dry Residue 



(1) (2) (3) (4) 



Dusts^ 



Sulfur + + + -I- 



Copper^ 20, Lime 80 -|- + - - 



Naphthalene 30, Lime 70 — — — — 



Naphthalene 30, Sulfur 20, Copper-Lime 50. _ _ _ _ 

 Naphthalene 30, Calcium Arsenate 20, 



Copper-Lime — — — — 



Naphthalene 30, Calcium Arsenate 20, 



Sulfur 50 - - - - 



Sprays^ 



Hammond's Copper Solution (1-50) 4- + * — — 



Potassium Sulfide (1-200) +* - - + 



Lime-Sulfur (1-40) -|- - - + 



Bordeaux (4-4-50) + -|-* - - 



Lead Arsenate (2 lb. -50 gal.) -1- -f + + 



Calcium Arsenate (2 lb. -50 gal.) + + * - - 



Calcium Arsenate 2 lb.. Lime 2 Ib.-SO gal.. . . -h -|- * - — 



No Treatment (Water) + + + -|- 



-f Germination. — No Germination. * Germination considerably inhibited. 



^Figures indicate weight in pounds 



^Copper in dust mixture derived from monohydrated copper sulfate. 



^Figures indicate gallons unless otherwise specified. 



Laboratory Experiments 



Two potted carnation plants of the Jewel variety were used for each treatment. 

 The fungicides were applied on January 9 and the plants were sprayed with a 

 water suspension of spores on January 10. The results were recorded on February 

 12, 1929 (Table 18). The results were clearly in favor of calcium arsenate and 

 Bordeaux mixture, and each of these materials was more effective in combination 

 with fish oil than alone. Sulfur materials gave poor control. In another experi- 

 ment with the same variety, Jewel, infections were evident January 27 and the 

 results were recorded on February 1 1 (Table 19). Bordeaux mixture and calcium 

 arsenate again showed superior fungicidal efficiency. No benefit was shown 

 from the addition of saponin as a spreader. 



