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 i 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 hquid 

 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 

 i^ feet apart and i foot deep over the area occupied by the roots, but 

 no hole should be within a foot of the trunk. Use ^ 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 f 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 Jose 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 Jose 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. 



