24 



FUMIGATION INVESTIGATIONS IN CALIFORNIA, 



vary considerably in their estimates, many trees in the above-men- 

 tioned orchards must have received a much greater dosage than was 

 necessary for scale eradication, thus resulting in a waste of cyanid 

 and acid. 



In Table I have been arranged the dosage estimates which were 

 scheduled in different orchards by three different fumigators. After 

 the trees had been covered with tents the exact contents were com- 

 puted by the writer from actual measurements. The dosages given 

 in these tables are not for scattered individual trees selected because 

 of their irregularity in size, but each table embraces a continuous 

 number in a single row taken at random, regardless of the size or 

 regularity of the trees. As great a lack of uniformity as that shown 

 in each table might be looked for throughout the orchard. These 

 schedules of dosage were used against the red and purple scales, 

 species considered by most fumigators to be about equally resistant 

 to the gas. The reader will note the wide difference in the dosage in 

 the estimates of the different fumigators. 



Table I. 



Variation in the dosages estimated for several consecutive trees hij three different 

 fumigators. 



THE INITIAL PROBLEM CONFRONTING THIS INVESTIGATION. 



After becoming acquainted with the existing methods of fumiga- 

 tion, it was realized that one of the first problems to be solved was 

 to devise some accurate system of determining dosage which would 

 obviate the errors due to guesswork. It at once became apparent 

 that the only way in which this result could be attained was by 

 determining accurately the cubic contents of the space inclosed by 

 the tent and giving the tree a dose proportionate to the contents. 

 It was also apparent that before such a system could be put into 

 operation, after having been worked out in practice, it would be 



