FUMIGATION OF NTJESEKY STOCK. 79 
In limestone regions, or where the water is very hard, some of the 
soap will combine with the lime or magnesia in the water, and more or 
less of the oil will be freed, especially when the emulsion is diluted. 
Before use such water should be broken with lye, or rain water 
should be employed. 
For winter sprays dilute the emulsion with either 3, 4, or 5 parts of 
water, giving a percentage of oil of approximately 17, 13, and 11 per 
cent. The strength in oil of this application on trees as compared with 
the oil-water sprays is the equivalent of 25, 20, and 15 per cent oil, 
because relatively more of the heavier oil-soap emulsion is held by the 
bark. The two stronger mixtures may be used on the apple and pear 
and the weaker one on peach and plum. 
For summer applications dilute with 7, 10, or 15 parts of water, giv- 
ing approximately 8, 6, and 1 per cent of oil. The weaker strengths 
may be used on trees with tender foliage, such as that of peach, and the 
greater strength for strong foliage plants, like the apple and pear. 
FUMIGATION OF NURSERY STOCK. 
All nursery stock which is under the least suspicion of contamination 
with the San Jose scale should be fumigated; and it is perhaps worth 
while to fumigate in any case to give the utmost assurance of safety 
to the purchaser. The hydrocyanic-acid-gas fumigation is the one to 
use. This gas is generated by combining potassium cyanide, sulfuric 
acid, and water. The proportions of the chemicals are as follows: 
Refined potassium C3^anide (98 per cent), 1 ounce; commercial sulfuric 
acid, 1 ounce; water, 3 fluid ounces — to every 100 cubic feet of space 
in the fumigating room or house. The latter should be as nearly air- 
tight as possible and provided with means of ventilation above and at 
the side, operated from without, so that at the end of the treatment 
the poisonous gases can be allowed to escape without the necessity of 
airyone entering the chamber. The generator of the gas may be any 
glazed earthenware vessel of 1 or 2 gallons capacity, and should be 
placed on the floor of the fumigating room and the water and acid 
necessary to generate the gas added to it. The cyanide should be 
added last, preferably in lumps the size of a walnut. Promptly after 
adding the cyanide the room should be vacated and the door made 
fast. The treatment should continue forty minutes. It must be borne 
in mind that the gas is extremely poisonous and must under no circum- 
stances be inhaled. The gas treatment is effective against the scale on 
growing trees in the orchard also; but the difficult}' and expense of 
the treatment, except for nursery stock, make it prohibitive in the case 
of deciduous fruits. 
8449— No. 62—06 6 
