12 



BULLETIN 113, U. S. DEPAETVLENT OF AGRICULTURE. 



Table T. — Spraying experiments against the lesser hud-moth on apple. Benton 



Harbor, Mich., 1913. 



Plat 

 No. 



Treatment. 



Number 

 of buds 

 infested. 



Number Total 

 of buds number 

 sound, i of buds. 



Total 

 percent- 

 age of 

 sound 

 buds. 



II 



ni 



11V 

 IV 



VI 



One application of commercial lime-sulphur solu- 

 tion (1 gal. to 8 gals, of water) on Apr. 8. Trees 

 dormant 



One application of soda-sulphur solution (1 lb. to 

 5 gals, of water) on Apr. 3. Trees dormant 



One application of mi filtered lime-sulphur solu- 

 tion (1 gal. to 8 gals, of water) on Apr. 8. Trees 

 dormant 



Two applications of arsenate of lead (2 lbs. to 50 

 gals, of water) on Apr. 16, when buds began to 

 swell, and on May 1, when cluster buds opened. . 



Three applications'of arsenate of lead (2 lbs. to 50 

 gals, of water) on Apr. 16, when buds began to 

 swell, on Apr. 24. when cluster buds were half 

 open, and on May 1. when cluster buds were open. 



Check (unsprayed) 



924 



956 



523 

 4,949 



7,534 

 4,228 



5,918 



7,019 



s. ooc 



4,129 



9, 172 

 4,908 



8,529 

 9,078 



82.14 

 S6.14 



86.49 



88.01 



93.86 

 45.48 



i Lime-sulphur solution, 1J gallons to 50 gallons of spray, was added in the last application in plats IV 

 and V, mainly for the control of apple scab. 



As will be noted, the best results were obtained on Plat Y. where 

 three applications of arsenate of lead were used. In this case the 

 buds were kept covered with poison, so that the larvae had little 

 chance to gain entrance into them. The next best results were 

 obtained where two applications of arsenate of lead were used. How- 

 ever, the application of the lime-sulphur and the soda-sulphur solu- 

 tions when the trees were dormant, both used at the strength recom- 

 mended for the San Jose scale, were almost as effective as the arsen- 

 ate of lead. The action of the sulphur compounds on the larva? is 

 not known, but they probably act largely as repellents. 1 The larvae 

 were examined in their hibernacula at various intervals from the 

 time the application was made until they came out to enter the buds, 

 and in all cases they were found unhurt and untouched by the spray. 

 However, this was expected, since their hibernacula were protected 

 from .the spray by the loose bark under which they were hidden. 

 Then. too. the hibernacular cases are of such construction that they 

 can not be easily penetrated by spray. "When the larvae emerged, 

 they disappeared, either having been repelled from the tree or killed 

 by the action of the sulphur sprays subsequent to their emergence. 



Almost the entire crop of fruit on the check trees was lost on 

 account of the work of the larvae, there being less than half a dozen 

 apples on each tree, while the crop was unhurt on the sprayed trees. 



Experivcext II. — An apple orchard of the Rhode Island Greening 

 variety, consisting of 120 trees about -10 years old, belonging to Mr. 

 W. H. "Woodruff. Benton Harbor. Mich., was also used for ex- 



1 Lime-sulphur solution was found to act as a strong repellent against certain other 

 lepidopterous larva? in other experiments conducted during the season. 



