29 



that "the San Jose scale is entirely destroyed by the g-as when 

 used on calm, dry, sunny or cloudy days"; that "the cost of 

 treatment, aside from the equipment, is less than that for whale- 

 oil soap"; that " trees treated at nig-ht with very strong doses of 

 g-as do not have the foliage or dormant leaf and fruit buds affected 

 at all, even where double the amount of gas ordinarily used is 

 g-enerated "; and that " trees treated in the morning before 9 a. m. 

 and in the afternoon after 4 p. m. have the foliage very little 

 affected by the gas." These tests were thought by him so grati- 

 fying that a meeting- of those especially interested was called for a 

 demonstration of the operation, and at a dinner served by the 

 owner of the infested premises all the speakers "were unanimous 

 in the opinion that the experiment was complete in every respect." 

 In a later report on this same experiment, read August 19, 1898, at 

 the Tenth Annual Meeting of the Association of Economic Ento- 

 mologists, Professor Johnson says: * 



"In order that I might report the definite and final results of 

 these experiments, I made a careful examination of every tree in 

 the orchard on Tuesday and Wednesday of this week. Where 

 there were hundreds and thousands of scales breeding on the trees 

 at this time last year not one can be found now, except upon trees 

 under 5 feet in height and on those fumigated when thefoliag-e was 

 wet with dew or fog or immediately after a rain, and even on 

 these trees the young larvte are very few as compared with their 

 number at this time last year. Where the fruit was much pitted 

 and scarred by the scale last year not one has been seen upon a pear 

 thus far this season. 



"In all, the experiment is thoroughly satisfactory, in that it 

 demonstrates by actual trial that this method can be used in our 

 largest bearing orchards, even under the most adverse conditions, 

 with excellent results." 



Fourteen very badly infested plum-trees were also treated 

 March 17 and 18, 1898, with hydrocyanic acid gas liberated under 

 tents, and no living scales had been found on them three months 

 later. "The general outcome of these experiments," says Profes- 

 sor Johnson, t "up to the present time, June 15, is so far satisfac- 

 tory. We cannot hope to find a remedy for the San Jose scale that 

 is more effective than hydrocyanic acid gas." Referring to this 

 experiment again§ August 19, five months after the treatment was 

 given, he says: 



*BuU. No. 17, N. S., U. S. Dopt. Afrr., Div. Ent., pp. 41 and 42. 



t Md. Bull. 57, p. 90. 



S Bull. No. 17, N. S., U. S. Dept. Affr., Div. Ent., p. 42. 



