THE NATIONAL NURSERYMAN 
47 
A FEW POINTS ON FUMIGATION. 
The laws of many states and territories demand fumigation 
of nursery stock before it is delivered to the consignee; all 
of them would like to see all stock fumigated. In fact in 
many instances it would save nurserymen a great deal of 
trouble and delay if a uniform system of treating stock 
existed. 
Now what is the actual value of fumigation with hydro¬ 
cyanic acid gas as a precautionary measure against the intro¬ 
duction of San Jose Scale and other nursery pests into the 
orchards? 
Mr. W. Newell, the State Entomologist of Georgia, states 
his view on the question as follows: 
“It should not be understood, that fumigation will in all 
cases eradicate San Jose scale, but when the work is properly 
done it appears to afford the best protection against this pest 
that has yet been devised. Impure chemicals, inaccurate 
scales, undetected leaks in the fumigating house or too close 
packing of the stock may defeat the object of fumigation 
and since one can rarely be sure that his fumigating arrange¬ 
ments are working perfectly, it cannot be said that fumiga¬ 
tion affords absolute protection. However, results of ex¬ 
periments conducted by this office show that infested trees 
can, in many cases, be entirely freed from scale by this process. 
The object of fumigating all nursery stock, after it has passed 
inspection, is to eradicate (if possible) any slight case of in¬ 
festation which might be over-looked by an inspector. In 
this way two safeguards are provided the orchardist, who 
buys the stock, against the introduction of scale into his or¬ 
chard, whereas in the case of inspection alone, or of fumiga¬ 
tion alone, but one safeguard is provided him.” 
In the case of any section where San Jose scale exists, 
inspection alone, or fumigation alone is not a sufficient guaran¬ 
tee. Mr. Newell well points out the causes responsible for 
poor results. The chief requirement is a perfectly tight 
house, shed or box and for its construction all such precau¬ 
tions as matched lumber, painting of cracks and joints and 
additional paper lining should be faithfully observed. If 
the stock is fumigated immediately when it comes from the 
field the danger of tight-bundling thus affording protection 
from the fumes by shutting off circulation, may be largely 
avoided. We know as yet far too little about the physio¬ 
logical influences of the hydrocyanic acid gas upon plant life 
to give the reasons for various phenomena, but by way of 
practice we have found that certain doses are best adapted 
for certain lines of stock. The standard formula is easily 
remembered as follows—-1—2— 4— 
1. 1 ounce of cyanide of potassium (dry weight.) 
2 ounces of Sulphurie acid (fluid weight.) 
4 ounces of water (fluid weight.) 
for every 100 cubic feet of inside measure. 
The following formula is used for dormant trees, apple, 
pear, plum, hardy forest trees and one year old peaches. 
2. | ounce of cyanide of potassium. 
14 ounces of sulphuric acid. 
3 ounces of water. 
for every 100 cubic feet of inside space, constitutes the charge 
for dormant roses, buds, scions, and June budded stock. 
3. | ounce of cyanide of potassium. 
14 ounces of Sulphuric acid. 
24 ounces of water, 
is the formula for strawberry plants. 
The exposure should be in case of 
2 * I' 40 minutes. 3. 20 minutes. 
In case of tender material it is well to shorten the exposure 
from 40 to 30 minutes. 
The mixing of the chemicals should be done in a wide mouth 
earthen jar. A glass graduated measure should be employed 
for the measuring of the Sulphuric acid and of the water. It 
is absolutely necessary that the best Sulphuric acid be ob¬ 
tained, (spec. grav. 1.83.) Always pour the acid into the 
water, not water into acid. If a man has only one fumigating 
house it is well to calculate the space and then to put up the 
Cyanide in doses as required for his peculiar line of stock. 
This saves much time at the moment of operation, avoids 
errors in hurried weighing and subsequent loss by injured 
trees. When buying the cyanide one should demand pure 
material (98-99%) as the figures have been computed for 
this. The impure stuff is unreliable and should be avoided. 
While other methods are used it is best to drop the cyanide 
(wrapped in paper or cloth to retard the first moment of 
gas generation) into the diluted acid, instead of applying the 
acid last. 
Your experiment station will gladly figure out for you the 
cubic contents of any fumigating house, when inner measure¬ 
ments are given, if you care to apply. 
It is not wise to fumigate any stock when it is wet as it has 
been clearly demonstrated that trees will be injured in that 
condition. 
Man learns more by mistakes than in any other way. There 
fore I think it not amiss to repeat a few of the “Don’ts” 
which Professor Johnson gives in his book on “Fumigation 
Methods.” 
1. “Never fumigate a tree on which there is known to be 
San Jose scale. Burn it. 
2. Never fumigate trees, especially peach, a second time. 
3. Never fumigate trees after they are bundled or boxed. 
4. Never fumigate trees when they are wet. 
5. Do not fumigate conifers. 
6. Never leave the cyanide where children can reach it. 
7. Never leave the cyanide exposed to air. It will absorb 
moisture and be ruined. 
8. Never allow anybody to enter a fumigating room under 
ten to fifteen minutes after the door and ventilators are opened. 
9. Never put a new charge into a jar containing the old 
residue. 
10. Never lose an opportunity to caution persons about 
the danger attending the inhalation of this gas.” 
The most perfect system for rapid ventilation is none too 
good. 
When ready to build a fumigating house you will find it 
advisable to consult with your state entomologist who is 
expected to have the latest information obtainable. 
Cornell University. C. Bues. 
