338 Journal of Agricultural Research voi. iv, N0.4 



trolling the fungus on clematis. Up to August 8 the results were satis- 

 factory, and no injury was observed. Soon after the pruning of August 

 8 there were several hot, dry days followed by a period of rainy weather, 

 during which water accumulated at the end of bed i . Up to the end of 

 the season only one plant in plot 8 had sent forth a new shoot. The 

 other vines were dead, and the stems at the surface of the ground for 

 about an inch were discolored. A particle of soil placed on the tongue 

 had an acid taste. According to a test made by Mr. R. F. Keeler, i gm. of 

 this soil is equivalent to 0.5 c. c. of o.i A'^ acid, while soil from the adjoin- 

 ing check plot 7 was neutral. In check plot 7 a few vines died, owing to 

 the lack of drainage, but it seems apparent that in the other cases the 

 injury was caused by sulphur that had washed from the foliage and had 

 accumulated in the upper layer of soil. As the season advanced, sulphur 

 injury was observed in the other treated plots, but in these cases the 

 injury was localized in areas not larger than 2 feet in diameter. The 

 injury began to show on the plots sprayed with the soap-and-sulphur 

 mixture after nine applications had been made, while in the plots dusted 

 with sulphur it appeared after six applications had been made. 



SOAP AND SULPHUR AS A SPRAY MIXTURE 



A mixture of about i pound of laundry soap and 6 pounds of sulphur in 

 15 gallons of water was in common use as a greenhouse spray at the nursery 

 where the spraying experiments were conducted. It was used with suc- 

 cess in the control of leaf-blotch, Diplocarpon rosae Wolf, on susceptible 

 varieties of roses grown in the forcing houses. Halsted and Kelsey (6) 

 used Ivory soap at the rate of i ounce to 4 gallons of water for spraying 

 Phlox drummondii and the common verbena attacked by powdery mil- 

 dew and were able to check it. Another (15) has shown that soap at 

 the rate of i ounce to i gallon of water controlled the mildew and 

 aphids of roses. R, K. Smith (12) recommended that, in the absence of 

 dew, whale-oil soap be sprayed on asparagus tops to hold the sulphur 

 that is to be dusted over them for the control of the rust. Spiecker- 

 mann (14) has shown that weak solutions of soap have a nutritive value 

 and can be assimilated by the higher fungi. 



In order to test the toxic effect of soap, mycelium of A. dematidina was 

 transferred to Petri dishes containing soap agar of different strengths — 

 viz, 2 per cent agar containing alkali-free Ivory soap in the proportion 

 of I pound to 5, 10, 15, 20, and 40 gallons of the medium. Fifteen c. c. 

 of such media were placed in each Petri dish. When the fungus became 

 established, the diameter of the culture was measured daily, and the 

 rate of growth was considered as a measurement for toxicity. Cultures 

 on 2 per cent agar and nutrient-glucose agar served as checks. Table 11 

 gives the averages of growth of four or five cultures on each medium 

 grown under the same conditions at room temperature. 



