April, "09] JOURNAL OF ECONOMIC ENTOMOLOGY 171 



living scale was found on some of the trees in each test below 0.20 

 grams per cubic foot with the 60-minute exposure. 



Conclusions 



The experiments in fumigating buds demonstrate that a much higher 

 strength of gas and longer exposure than is ordinarily recommended, 

 viz., 0.16 to 0.20 grams per cubic foot, can be employed without endan- 

 gering the vitality of the buds, and that the exposure to the gas, even at 

 the normal recommended strength, should be at least 45 minutes. In 

 fumigating nursery trees at the normal recommended strength, viz., 

 1 ounce of cyanide to 100 cubic feet, the duration of exposure should 

 be one hour, and if less time is desired the strength of the gas may be 

 increased with perfect safety to the trees, in order to insure as far as 

 possible the killing of any scale that may be present. 



Dipping Experiments 



Numerous inquiries as to the effectiveness and practicability of 

 dipping nursery trees in lime-sulfur or other spray mixtures as a pre- 

 ventive against the dissemination of San Jose scale, either for the pur- 

 pose of substituting such treatment for fumigation with hydrocyanic 

 acid gas at the nursery or giving such additional treatment by the or- 

 chardists before planting as a further means of killing any scale that 

 may have escaped previous treatment, led us to conduct a series of ex- 

 periments in dipping during the last three years. The tests were not 

 as extended as was desired on account of various circumstances, but the 

 results will add to the rather limited amount of work published on 

 the subject. 



1. During March, 1906. 240 dormant nursery trees were dipped in- 

 stantaneously in the lime-sulfur and salt wash, which was boiled for 

 one hour with steam. 



a. 40 apple and 20 peach were dipped, roots and stems in the 

 mixture at a temperature of about 170 degrees Fahrenheit, and a like 

 number were dipped, stems only, in the same mixture. 



At the final examination, September, 1906, all trees in the first lot 

 were dead. Only two had started to grow, and all the trees in the 

 second showed that their stems had been scalded. 23 apple and 16 

 peach in this test had started at or near the top of the ground and were 

 growing. 



h. 40 apple and 20 peach were dipped, roots and stems, in the 

 mixture, at a temperature of 120 degrees Fahrenheit, and a like num- 

 ber were dipped, stems only, in the mixture at the same temperature. 



