No. 7. DEPARTMENT OF AGRICULTURE. 533 



of the room, using the above formula for each one hundred cubic 

 feet, and have them weighed and measured, and the cyanide placed 

 in a small paper bag ready to drop in at once and permit the imme- 

 diate escape of the operator from the fumes, which are most deadly. 



It has been found by actual experimentation that prolonged ex- 

 posure of a low grade of material, or to fumes from a less quantity 

 of material, is more likely to injure the plants, without being so 

 sure of killing the scale, as is exposure to the fumes of a sufficient 

 amount for a shorter time. That is to say, short exposure (about 

 forty minutes) with the above formula is proven to be more in- 

 jurious to the insects and less injurious to the plants, than longer 

 exposure with less material, or with weaker material. 



It is necessary (1) that the cubic contents of the room be accu- 

 rately determined; (2) that the room be air-tight or gas-tight; (3) 

 that the cyanide of potassium be 98 per cent, pure; (4) that the sul- 

 phuric acid be as strong as 1.83 per cent.; (5) that a sufficient amount 

 be used to preserve this formula according to each one hundred 

 cubic feet of space; (6) that the fumigating house be not over 

 packed with tightly crowded plants; (7) that the plants be not wet 

 during the time of fumigation; (8) that the fumigation continue for 

 at least forty minutes; (9) that the gas be administered from below 

 rather than from above; (10) that the fumigating house be air-tight 

 and kept tightly closed during the entire period of fumigation, and 

 (11) that the plants be practically dormant. .It also is important 

 that the room be so constructed that it can be quickly ventilated 

 after fumigation is finished, and that this ventilation be done 

 rapidly, according to directions. If the trees be covered with mud 

 or be encased in any covering that the gas does not readily pene- 

 trate, those scales that are covered will not be killed. If the roots 

 of the trees be packed in damp moss or other material at the time 

 of fumigation, there is especial danger of injury to them. 



With these facts in mind, let us first say why all nursery stock in 

 this State of kinds not liable to attack by the San Jos^ Scale should 

 be fumigated before being sold, shipped or transplanted. It should 

 be said that by the expression of "kinds not liable to infestation by 

 the San Jos6 Scale" we mean conifers, strawberry plants, bulbs and 

 tubers, herbaceous perennials and bedding plants. 



1. It is acknowledged by all practical entomologists who have 

 made a careful study and proper tests in this subject that fumiga- 

 tion is effective in killing the scale when properly done. Much of 

 importance depends upon the expression "when properly done." 



2. Fumigation does not injure any kind of nursery stock that is 

 attacked by the San Jos6 Scale, when properly fumigated. In the 

 early fall and late spring while the trees are not dormant there may 

 be slight injury, but this is proven to be insignificant. A fruit grower 

 and nurserymen in this State recently told the writer that he had 

 fumigated apple trees in the spring after they had started to grow 

 and when the new shoots were from three to six inches long. He 

 used the above formula and transplanted the trees in his own or- 

 chard. The growth was not checked, the trees were not injured, 

 and the scales were killed. 



3. Another argument for fumigation is that it prevents the dis- 

 semination of scale insects and many other pests from any and all 

 nurseries, whether the inspector has found it in them or not. No 



