28 



FUMIGATION OF APPLES FOR SAN JOSE SCALE. 



as to give rise to doubt as to their condition, and these were there- 

 fore uniformly regarded as alive. The preceding season's work 

 indicated that great range in strengths of gas was possible without 

 injury to the fruit, excepting in the case of one variety, and in the 

 case of loose fruit at least was entirely reliable in killing the scales. 

 The variability in results of treatment of fruit in barrels required 

 further tests, as if put to practical test it would be highly desirable 

 that fumigation could be done without disturbing the fruit as 

 originally packed. The tests in 1907-8 were therefore directed 

 toward establishing a treatment for fruit in original packages, 

 varying the strength of gas and the period of exposure. As in the 

 preceding season, 0.30 gram of chemically pure potassium cyanid 

 was adopted as a normal, and, while perhaps stronger than actually 

 required, it was desirable to have an excess of strength, especially 

 since considerable latitude was allowable without danger of injury 

 to the fruit. This dosage is furthermore approximately that already 

 employed in treatment of dormant, deciduous-fruit nursery stock — 

 that is, 1 ounce to each 100 cubic feet of space in the fumigatorium. 

 The Baldwin variety was used, obtained, as previously, from Niagara 

 County, N. Y., but from another orchard than the fruit used in 1906-7. 

 The fruit was fumigated from November 29 to December 2, and at 

 once placed in the outbuilding on the Agricultural Department 

 grounds previously mentioned, in which the temperature ranged 

 mostly from 30° to 40° F. 



Extended examinations of scales on apples before fumigation 

 showed that 81.1 per cent of these were alive, ranging in age from 

 quite young to mature gravid females, occurring mostly in the stem 

 and calyx cavities. The condition of the scales on fruit at this time 

 and at different dates subsequently is shown in Table XI, serving for 

 comparison as to condition of scales in fumigated fruit. 



Table XI. — Condition of San Jose scale on unfumigated Baldwin apples during the 

 winter of 1907-8 for comparison with condition of scale on fumigated fruit. 



Date examined. 



November 29, 1907 

 December 16, 1907. 

 December 27, 1907. 

 January 3, 1908.... 

 February 3, 1908.. 

 March 3, 1908 



Number 



of scales 



alive. 



Number 



of scales 



dead. 



Total 

 number 

 scales ex- 

 amined. 



524 



122 



646 



796 



217 



1,013 



344 



109 



453 



930 



499 



1,429 



302 



454 



756 



101 



954 



1,055 



Per cent 

 alive. 



81.10 

 78.50 

 78.00 

 65. 08 

 39.94 

 9.57 



PACKAGE SERIES, 1907-8. 



The fruit had been held in cold storage for a few weeks and at the 

 time of fumigation the apples from the middle of the barrels were 

 somewhat moist, not having yet dried from the condensation of 



