228 NEW YORK STATE MUSEUM 
Fumigation.’ Carbon bisulfid and hydrocyanic acid gas are the 
two substances most frequently employed for killing insects within tight 
inclosures, though the fumes of burning sulfur or pyrethrum are also 
used to a slight extent. The proportion of carbon bisulfid recom- 
mended by Dr Howard, is 1 pound to every thousand cubic feet of 
space. The grain or other substance to be fumigated must be in a tight 
vessel or building and the chemical placed in shallow vessels near the top 
of the inclosure, because the heavy, poisonous vapor from this liquid 
descends rapidly. As carbon bisulfid is inflammable and its gas ex- 
plosive, great care must be exercised that no fire is brought near during 
fumigation. The period of exposure to this insecticide should vary some- 
what according to the mass treated. Grain in large bins should be sub- 
jected to its action for a day or two. As carbon bisulfid evaporates 
rapidly, treatment with it does not injure grain for food purposes and 
unless unduly prolonged, will not affect its germination to an appreciable 
extent. 
This substance is also very effective against root-inhabiting forms. In 
the case of trees and vines, holes should be made with an iron bar about 
14 feet apart and 1 foot deep over the area occupied by the roots, but 
no hole should be within a foot of the trunk. Use 4 ounce? of car- 
bon bisulfid to each hole and close the top at once with soil. In the 
case of cabbage plants make a small hole % inch from the plant and 
pour in a teaspoonful of the insecticide, closing as before. This chemical 
may be used against ants, it being advisable, as recommended by 
Dr Lintner, to cover the nest with a damp blanket, and at the expiration 
of a few moments the accumulated vapor under the blanket should be 
exploded by a light on the end of a pole. The explosion drives the 
fumes deeper into the nest. 
The treatment of trees infested by scale insects with hydrocyanic acid 
gas has been carried on for some years in California. The introduction 
of the San José scale into many states east of the Rocky mountains, has 
led to fumigation being used to a greater or less extent in this region. 
By some it has been reported entirely effective and others have had 
different results. In most cases it will be found advisable to destroy young 
trees infested with the San José scale, though when large numbers are 
but slightly infested, thorough fumigation with hydrocyanic acid gas may 
be preferred. This treatment is also recommended for nursery stock show- 
ing the presence of other pests, as the more common scale insects, plant lice 
or aphids, pear psylla, apple-leaf Bucculatrix and other forms that are 
a The quantities and distances are those recommended by the Division of entomology, U. S. 
Dep’t agriculture. 
