APPENDICES. 139 



all this care, some of the Icerya escaped and soon covered the trees 

 again, spreading in a north-easterly direction through the grove. We 

 then cut the trees back, letting the branches drop upon a large canvas 

 and afterwards burning them ; we washed the stubs and trunks of the 

 trees with the whale-oil soap solution, but even this severe treatment 

 was not effective, so we concluded that spraying would not check this 

 prolific creeping curse. 



" Knowing the fatal effects of a high temperature upon the young of 

 the Black Scale, Mr. Wolfskill suggested experimenting with heat ; 

 accordingly he had a tent constructed, and also a sheet-iron stove that 

 would send the heat into the tent. We put the tent over an orange 

 tree, and raised the temperature to 128° Fahrenheit for over an hour ; 

 this killed the Black Scales, but the Icerya seemed to enjoy the heat. 

 The tree was injured, so we gave up dry heat. We next tried steam 

 from a small steam-boiler ; this cooked the top of the tree, but upon the 

 lower half the Icerya was as lively as ever. Our next experiment was 

 with tobacco smoke ; this test lasted six hours, but had no eifect upon 

 the tree or scales. Sulphur fumes were also tried ; this bleached the 

 foliage, but did not harm the Icerya; a heavier charge killed both the tree 

 and the scales. Among other experiments made under the tent were : 

 Concussion from gunpowder ; muriaticacid gas ; carbonic acid gas; liquid 

 chloroform, and also the gaseous chloroform manufactured imder the tent 

 from chloride of lime and methyl alcohol ; arsenic, and other fumes and gases. 

 W^e had very encouraging results from the liquid bisulphide of carbon ; 

 when confined for ten, twenty, or thirty minutes, or even for one hour, 

 no satisfactory results were obtained, but when it was confined three 

 hours it killed all of the scales, which soon assumed a pale buff colour. 

 The gas, being a very powerful solvent, also acted upon the eggs, and 

 they were destroyed, while the trees were not injured ; in fact, a few 

 weeks afterward they started into a vigorous growth. Our efforts were 

 then directed towards evaporating the bisulphide quickly ; heat, steam- 

 baths, agitation, circulating the air in the tent, exposing the bisulphide 

 in shallow pans, and saturating sponges with it were tried, but without 

 hurrying matters much. 



" Prof. D. W. Coquillett was so well impressed with oi;r method of 

 treating trees that he decided to investigate the subject ; accordingly, 

 in the month of September, 1886, he began experimenting in the 

 Wolfskill orange grove, and soon discovered that hydrocyanic acid gas 

 would kill the scales and their eggs, but it also injured the foliage of 

 the tree. We then united our efforts to remedy this evil, but it was 

 something that required very close observation. We found that by 

 withholding the water and allowing the sulphuric acid to come in contact 

 with the dry cyanide of potassium in a fine stream we could treat trees 

 without injuring even a blossom, while the gas proved fatal to the Black 

 Scale {^Lecanium oleo'), Red Scale {Aspidiotus aurantii), and the San 

 Jose Scale (Aspidiotus perniciost/s) confined in it ten minutes, but the 

 Cottony Cushion-scale (Icerya purchasi) and eggs required a confinement 

 of nearly thirty minutes. 



