14 CIRCULAR 112, BUREAU OF PLANT INDUSTRY. 



Plat III with 2 pounds, and Plat IV with 5 pounds of arsenate of lead to each 50 

 gallons of the diluted lime-sulphur solution. Three applications were made in 

 accordance with the usual directions for the control of the codling moth, i. e., (1) as 

 soon as the petals fell, (2) three weeks later, and (3) ten weeks after the petals fell. 

 The trees were thoroughly sprayed each time, so that the fruit remained coated with 

 the arsenate of lead well on toward picking time. Plat V was left unsprayed as a 

 check. 



The crop was picked on September 12 and found to be practically 

 free from insects and diseases. No spotting was discernible at this 

 time. Two boxes of fruit from each plat were immediately sliipped 

 to Washington, reaching the laboratory on September 15, three days 

 after picking. On this date a careful examination revealed no 

 indication of the disease on any of the fruit, sprayed or unsprayed. 

 One box from each of the five plats was then placed in cold storage, 

 while the remaining five boxes were stored in a moderately cool 

 basement. 



The basement-stored apples were examined on September 30 with 

 the following results: The fruit from Plat I showed 41 per cent 

 affected with the Jonathan fruit-spot, Plat II 52 per cent, Plat III 

 36 per cent, Plat IV 36 per cent, and Plat V (check) 46 per cent. A 

 reexamination of the same apples on October 23 showed Plat I to 

 have 56 per cent of the fruit affected, Plat II 70 per cent, Plat III 52 

 per cent, Plat IV 42 per cent, and Plat V (check) 64 per cent. Many 

 of these apples were seriously injured, being literally covered with 

 spots measuring from 5 mm. to 1 cm. in diameter. These results 

 show that unsprayed fruit may become quite as badly affected with 

 the Jonathan fruit-spot as fruit sprayed with arsenate of lead. An 

 unusually heavy dose of the poison, as shown in the results from 

 Plat IV, which was sprayed with 5 pounds of arsenate of lead to 50 

 grallons of water, did not increase the amount of affected fruit. 



The fruit which was placed in cold storage was examined on 

 November 10 and all of it found to be free from the disease. Finally, 

 on December 18 these apples were removed from cold storage and 

 examined with the following results: Plat I had 5 per cent of its 

 fruit spotted, Plat II 10 per cent, Plat III 20 per cent, Plat IV 14 

 per cent, and Plat V (check) 33 per cent. In most cases the spots 

 were small, inconspicuous, and few to an apple, being in these respects 

 in great contrast to those appearing on the basement-stored fruit. 

 The cold storage prevented the spotting for at least two months, 

 and at the end of nearly three months tins fruit was not nearly so 

 much affected as the cellar-stored fruit was at the end of six weeks. 



On September 25, 1911, one bushel of unsprayed and one bushel of 

 sprayed Jonathan apples were received from Watervliet, Mich. These 

 were sent in by Mr. E. W. Scott, of the Bureau of Entomology; they 

 were taken from an orchard in which that bureau was conducting spray- 



[Cir. 112] 



