Notes on the San Jose Scaee. ' 165 



tember. In our own experience we have obtained satisfactory 

 results by using kerosene in the spring or early summer as soon 

 as the young insects began to appear. 



In using whale-oil soap, the nature of the case demands that it 

 be applied only when the plants to be treated are dormant. Since 

 it must be used at the rate of two pounds to a gallon of water in 

 order to destroy the scale, and at this strength it is destructive 

 to the foliage, a summer treatment with whale-oil soap is out of 

 the question unless it be applied only to the trunks and larger 

 limbs of infested trees and shrubs. 



Fumigating. 



As a method of treating infested nursery stock, fumigating with 

 hydrocyanic acid gas is doubtless the most satisf actor}- and effective 

 treatment which has been extensively used. The value of this 

 treatment was recognized in California some years ago, but for vari- 

 ous reasons it has not been generally used in the East. However, 

 there seems to be no adequate reason why it should not prove as 

 effective here as in the West. Probably the most extensive use of 

 the gas treatment in the eastern States has been in the experiments 

 of Johnson, of Maryland. In his recent report* there is detailed a 

 long list of experiments in which is seemingl}^ proved the adapta- 

 bility of this method of treatment for eastern as well as for w-estern 

 conditions. The most of Johnson's work, however, was in bearing 

 orchards where tents were used for covering the trees during 

 treatment. 



The chemicals used by him in giving the gas treatment are 

 approximately as follows : 



Fused cyanide of potassium, 98 per cent pure. . . i oz. by weight 



Sulfuric acid i ^ oz. by measure 



Water 2 oz. by measure 



The above quantities of material are sufficient for 100 cubic 

 feet of space. 



In fumigating nursery stock in small quantities, a large box 

 which can be made perfectly air-tight is convenient. The stock 

 is first placed in the box, then an earthen or glass vessel placed 

 near the center of the box, the cubical contents of which has 

 been previously estimated. The chemicals are then weighed out 



*Bul]etin 57, Maryland Experiment Station. 



