41 



necessary, and when these were finished the third point was taken up 

 and continued from October 16 to November 27, 1897. 



The orchard chosen for these operations belongs to Mr. Emory, and con- 

 tains about 2,500 nine-year old dwarf Bartlett pear trees, which had 

 become infested with the scale from an adjoining young Lawson pear 

 orchard. All the trees were full of foliage. The scales were breeding 

 and active, and, taking it all in all, the conditions could not have been 

 more favorable for my experiments. The preliminary tests were begun 

 September 27, 1897, and continued at all hours of the day and at night, 

 and were finished October 1. 



These tests show conclusively — 



(1) That the gas is not injurious to foliage during sunshiny days, late 

 in the fall, between 9 a. m. and 4 p. m. In every instance where trees 

 were treated between these hours, the foliage was singed. In several 

 instances it was perfectly brown, looking much like the effects resulting 

 from a heavy frost. One important point was noted, however, that the 

 leaf petioles were blackened about two-thirds their length, the base 

 being perfectly green, and, therefore, the leaves fell readily a few weeks 

 later. Another point that should be noted in this place, is the fact 

 that the function of the foliage had been performed; consequently, we 

 used the gas much stronger than we would have done at any other 

 season when the trees were in full foliage. 



(2) That the dormant leaf and fruit buds on the trees treated with 

 gas sufficient to turn the leaves brown in the fall are not injured. 



(3) That leaves which have been injured by the gas fall readily and 

 do not remain clinging to the tree. 



(4) That trees treated in the morning before 9 and in the afternoon 

 after 4 have the foliage very little affected by the gas. 



(5) That trees treated at night with very strong doses of gas do not 

 have the foliage, dormant leaf, and fruit buds affected at all, even where 

 double the amount of gas ordinarily used is generated. 



(6) That the San Jose scale is entirely destroyed by the gas when 

 applied during a calm, sunny, or cloudy day. 



(7) That the cost of treatment, aside from the equipment, is less than 

 for whale-oil soap. 



(8) That the gas can not be used when the foliage is wet with dew, 

 fog, or immediately after a rain. 



(9) That the gas can not be used with tents upon trees under 5 feet 

 in height with satisfactory results. 



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 

 those fumigated when the foliage was wet with dew or fog, or imme- 

 diately after a rain, and even on these trees the young larva3 are very 



