14 FUMIGATION METHODS 



Orchard experiments. In the fall of 1897 I began, 

 perhaps, the largest serie^ of experiments ever under- 

 taken in the East for the destruction of San Jose scale. 

 The orchard chosen was a nine-year-old Bartlett dwarf- 

 pear in full foliage. Canvas tents were used. The 

 trees were fumigated at all hours of the day and under 

 varying conditions of weather. We had sunshine, 

 cloudy and foggy days, rain, sleet and snow, windy 

 and calm weather. In one series, September 29th, with 

 a temperature of 70 F. , we used 0.40 gramme cya- 

 nide per cubic foot instead of 0.20, as in most of our 

 experiments. The leaves on all the trees were very 

 brown, in fact, almost black. Within five minutes 

 after the tents were removed the petioles were black 

 almost to the base ; the leaves fell a few days later. 

 The following spring the leaves came out as normally 

 as on any other trees in the orchard where no fumiga- 

 tion occurred. There was about one-quarter as much 

 fruit on these trees, however, as upon those that had 

 been fumigated with the normal strength, that is, 0.20 

 gramme. Other trees were treated at night with the 

 same double dose, at a temperature of 58 F. The 

 foliage, the first week, showed no injurious effect 

 whatever, and remained just as green as on trees not 

 fumigated. The eighth day, however, the leaves be- 

 gan dropping, and a few days later were all off. The 

 leaf buds came out the following spring, but the fruit 

 was only about half as abundant as on surrounding 

 trees. The double dose, it would therefore seem, is 

 injurious at least to the fruit buds of Bartlett pear 

 under such conditions. 



The final outcome of the whole series of experi- 



