14 MISSOURI AGRICULTURAL EXPERIMENT STATION BULLETIN 177 



a lid. Cleats were nailed on to the lid so as to fit tightly against the inside 

 of the box when closed and these cleats were covered with felt so as to 

 make the box just as nearly air tight as possible. 



The number of plants to be treated dry with the 1-1-3 formula were 

 dug, the dirt removed from the roots and placecl in the box. The sulphuric 

 acid was weighed out and placed in an earthen jar, then the required 

 amount of water was added slowly so as to prevent sputtering. The jar 

 was then placed in the bottom of the fumigating box in such a way as not 

 to come in contact with the nursery stock. The potassium cyanide, 98 per 

 cent pure, which had been broken up into small pieces, was then added to 

 the mixture and the lid quickly closed and clamped down. The stock was 

 allowed to fumigate for 45 minutes, when the box was opened, the gas 

 allowed to escape, which took about 10 to 15 minutes. The plants were 

 then removed and set about two feet apart in rows 3 feet apart. The residue 

 left in the jar is very poisonous so it was removed and buried to prevent 

 anything from getting hold of it. 



Just as soon as the set of trees were removed from the fumigating box, 

 a second set containing the same number of plants was taken. This set of 

 plants was treated in exactly the same way as the above set with the ex- 

 ception that they were thoroly dampened, both roots and tops, before being 

 placed in the box. The object in fumigating this set of wet plants was to 

 find out exactly if possible to what extent the plants would be injured and 

 also if the effect upon the scale would be the same as upon the scale on the 

 dry plants. 



The third set of plants was treated exactly the same as the first except 

 the yz-Vz-^Vz formula was used. 



A fourth set of plants, which were wet, was also treated with the 

 %-%-!% formula. 



Effect of hydrocyanic-acid gas upon San Jose scale. As is shown by 

 the following table, eighty apple trees with scale, were treated with hydro- 

 cyanic-acid gas in 1916. 



TABLE 1. APPLES TREATED IN 1916 



On May 14, 1916, a count was made to determine the effectiveness of 

 the hydrocyanic-acid gas. In making the counts on these trees, several 

 heavily infested twigs were collected from several of the different trees. 

 The twigs were placed under a high power binocular and the numbers of 



