THE INFLUENCE OF TEMPERATURE AND 

 MOISTURE IN FUMIGATION.* 



W. J. SCHOENE. 



SUMMARY. 



This bulletin discusses a series of fumigation tests with cater- 

 pillars of the brown-tail moth (Euproctis chrysorrhcea Linn.), which 

 were influenced by temperature and humidity. 



A greater number of caterpillars survived the fumigations made 

 at low temperatures than at higher temperatures; also fumigations 

 made under humid conditions were uniformly more destructive to 

 the larvae than tests that were conducted in a relatively dry air. 



It is suggested that the differences in the results referred to above 

 and the unusual resistance cf the caterpillars to fumigation are due 

 largely to the conditions incidental to hibernation, viz., the reduced 

 moisture content and comparative inactivity of the insects. 



INTRODUCTION. 



Nests of the brown-tail moth were discovered about January 4, 

 1909, upon imported seedlings in several of the local nurseries, and 

 during succeeding weeks thousands of them were secured upon similar 

 stock in this and other nursery centers of the State. Seedlings carry- 

 ing nests were destroj'ed as soon as detected, but as the examination 

 of the shipments progressed it was observed that many of the nests 

 were broken, thus permitting the hibernating caterpillars to be 

 scattered promiscuously among the trees. The question then arose 

 as to the most effective means of disinfecting the shipments in addi- 

 tion to destruction of trees bearing winter nests. As the nurserymen 

 were equipped with fumigation plants and were familiar with the use 

 of hydrocyanic acid gas, fumigation was suggested. Preliminary 

 tests by this process failed to kill the hibernating caterpillars at 

 ordinal strengths and at the request of Dr. Raymond A. Pearson, 

 then Commissioner of Agriculture, this Station undertook to deter- 

 mine the conditions which rendered fumigation ineffective. In this 

 work it soon became apparent that temperature and humidity were 

 important factors, and it is desired in this bulletin to call attention 

 to the role played by these two factors under the peculiar conditions 

 in which fumigation was attempted. 



* Reprint of Technical Bulletin Xo. 30, July, 1913. 



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