April. "09] JOURNAL OF ECONOMIC ENTOMOLOGY 169 



SUMMARY OF FUMIGATION AND DIPPING EXPERI- 

 MENTS 

 By Thomas B. Symoxs, College Park. Mil. 



The desire to verify the results of the rather limited amount of work 

 eonducted ]\v other investigators on the effect of various strengths of 

 hydrocyanic acid gas with different exposures upon tender peach buds 

 and at the same time to demonstrate to the nurserymen of the state the 

 great importance of fumigating all propagating stock to prevent the 

 introduction and dissemination of the San Jose scale prompted us to 

 conduct a series of experiments with this gas during the past three 

 years. The experiments in fumigating buds were conducted at two 

 nurseries in the state under as normal conditions as possible. In ad- 

 dition a series of tests with salable nursery stock badly infested with 

 San Jose scale was conducted to observe the effect of the gas upon the 

 scale and trees. The trees were fumigated at the nursery and planted 

 out on the Experiment Station Farm. I cheerfully acknowledge the 

 assistance of Messrs. A. B. Gahan, Geo. P. Weldon and L. M. Peairs in 

 conducting these experiments. 



1. On September 7, 1906, 505 peach buds w-ere fumigated with 0.40 

 and 0.50 grams cyanide per cubic foot and exposed to the gas for 30 

 minutes and 805 peach buds were fumigated with the same strengths 

 of gas and exposed to the gas for one hour. There was a check of 750 

 buds. The buds were cut from the Early Crawford, Late Crawford, 

 Reeves Favorite, Elberta and Beers Smock varieties of trees in the 

 nursery. The check buds w^ere taken from the same varieties of trees. 



An examination of the buds in the experiment October 3, 1906. 

 more than a month after fumigation, showed an average of 98.5 per 

 cent of the buds to be alive, while an examination and count of the 

 buds August 30, 1907, show-ed 62.6 per cent of those exposed to the 

 gas one half hour and 53.2 per cent of those exposed one hour to be 

 alive. Only 20.9 per cent of the buds in the check were alive at the 

 final examination. The normal per cent to grow in this state is from 

 60 to 65 per cent. 



2. A second experiment conducted at another nursery September 

 1, 1906, consisted of 2,647 peach buds, Elberta and Champion varieties 

 about equally divided into different tests. They were fumigated with 

 0.15, 0.18, 0.20 and 0.25 grams of cyanide per cubic foot, with 30 and 

 60-minute exposures. 



An examination of these buds October 9, 1906, showed only 41.2 per 

 cent as an average of buds alive fumigated with the various strengths 

 gas and exposed for 30 minutes, while 49.1 per cent ^vas the average of 



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