30 



FUMIGATION OF APPLES FOR SAN JOSE SCALE. 



Table XIII. — Corroborative results of effect of fumigation with hydrocyanic-acid gas on 

 scales and fruit in different kinds of packages. (Package series 1907-8.) 



Experi- 

 ment 

 No.- 



Variety of apple. 



Kind of package. 



Rate at 



which J Length 

 potassium of ex- 

 cyanid was ' posure. 

 used. 



Num- 

 ber of 

 scales 

 exam- 

 ined. 



Effect on 



scales. 



Effect on 

 fruit. 



ss 



Baldwin 



do 



do 



do 



Barrel, top open 



Gr.percvft. Hours. 



0.30 [ 1 



.30 3 



.30 1 



.30 3 

 .30 1 



.30 3 



3,400 

 3,231 

 2,748 



3,290 

 2,768 

 2,567 



All dead. 



...do 



...do.... 



...do.... 



...do 



...do.... 



No injury. 

 Do 



89 



do 



90 



91 



Barrel, with 20 |-inch 

 auger holes in each end. 

 ...do 



Do. 

 Do 



92 



93 



Roxburv Russet. 

 do.". 



Box, fruit wrapped 



do 



Do, 

 Do 









One barrel of scale-infested Rhode Island Greening apples, from 

 Niagara County, N. Y., but from another orchard than the first used 

 in 1906-7, was fumigated February 5 to determine if injury would 

 result as in the earlier tests. An iron header replaced the usual barrel 

 head, the open end turned down over the generator. Three examina- 

 tions of this fruit were made, the counts including 2,860 scales, all 

 of which were found to be dead. The fruit, however, was more or 

 less injured and scalded as described for 1906-7. 



SUMMARY OF RESULTS. 



Strengih-of-gas series (Table III). — In the fumigation of fruit loose 

 in baskets all scales were killed with strengths of potassium cyanid 

 at rate of from 0.10 to 0.50 gram per cubic foot, and exposed forty- 

 five minutes. Five hundredths of a gram of cyanid per cubic foot 

 was not entirely effective. No injury resulted to the fruit treated, 

 namely, the Baldwin. 



Length-of-exposure series (Table IV). — Baldwin apples loose in 

 baskets were not injured by the use of potassium cyanid at the rate 

 of 0.20 gram per cubic foot with periods of exposure ranging from 

 twenty minutes to three hours. In every instance the scale insects 

 were all killed. 



Package series, 1906-7 (Table V). — Fumigation of fruit in barrels 

 opened in various ways to permit access of gas gave apparently 

 variable results as to effect on the scales. All insects were not with 

 certainty killed, except in the case of fruit in boxes, wrapped and un- 

 wrapped, and in barrels in which each head had been perforated with 

 numerous auger holes. Scales on apples in unopened barrels were 

 not killed to any extent, as the packages were too tight to allow 

 entrance of the gas. 



Package series, 1907-8 (Table XII). — In the package series of tests 

 in 1907-8, with boxes, fruit wrapped and unwrapped, and with barrels 

 opened in various ways, using potassium cyanid at the rate of 0.3G 



