16 MASS. EXPERIMENT STATION BULLETIN No. 285 



Thp critical period in the control of the plum rurculio in apples in Massa- 

 chusetts occurs during the first warm weather after the blossom petals have 

 fallen when the maximum temperature remains above 75° F. for two or more 

 days. 



High temperatures about the time when apple trees are in bloom cause the 

 plum curculio beetles to enter the trees in large numbers. 



In 1930, the critical period for control occurred from June 1 to 5, 12 to 14 

 daj's after the caly.x spray was applied, and records from 29 orchards in Worcester 

 County showed 11 per cent better control on Mcintosh and 14 per cent better 

 control on Baldwin where sprays were applied just before or during the early 

 part of the critical period. 



In 1931, the critical period occurred from May 26 to June 1, 4 to 6 days after 

 the caly.x application. In Worcester County, timely sprays during the early 

 part of the critical period gave 20 per cent better control on Baldwins and 14 

 per cent on Mcintosh than later applications. Similar results were secured in 

 30 orchards in Middlesex County. 



In 1931, a timely application of 85-15 sulfur-lead arsenate dust controlled 

 the plum curculio in Gravenstein apples almost as well as a spray of lead arsenate 

 and fish oil, the difference in favor of the spray being 0.89 per cent. 



LITERATURE CITED 



1. Crumb, S. E. Tobacco cutworms. I^. S. Dept. Agr. Tech. Bui. 88, 180 p., 



illus. 1929. 



2. Carman, Philip, and Zappe, M. P. Control studies on the plum curculio 



in Connecticut apple orchards. Conn. (State) Agr. Expt. Sta. Bui. 

 301:371-437, illus. 1929. 



3. Glenn, P. A. Codling moth investigations of the State Entomologist's 



Office. Bui. 111. Nat. Hist. Surv. 14:218-288. 1915-1917. 



4. Lathrop, F. H., and Sazama, R. F. A laboratory field method for the study 



of the efficiency of codling moth sprays. Jour. Econ. Ent. 25:83-96. 

 Feb., 1932. 



5. Miller, Ralph L. Manganese arsenate as a control for the codling moth. 



Jour. Econ. Ent. 22:340-345. Apr., 1929. 



6. Peterson, Alvah, and Haeussler, G. J. Life history of the Oriental peach 



moth at Riverton, N. J., in relation to temperature. U. S. Dept. 

 Agr. Tech. Bui. 183, 38 p. 1930. 



7. Shelford, Victor E. An experimental investigation of the relation of the 



codling moth to weather and climate. Bui. 111. Nat. Hist. Surv. 16 

 (Art. V and VI) : 307-440. March, 1927. ? 



8. Stellwaag, F. Giftigkeit und Giftwert der Insecticide, vii. Teil: Grundlagen 



und besondere Methodik der Bestimmung des "Giftwertes" im "Serien- 

 versuch." Ztschr. Angew. Ent. 18:698-725, 5 figs., 36 refs. 1931. (Ab- 

 stract in Rev. Appl. Ent.) 



9. Whitcomb, W. D. The plum curculio in apples in Massachusetts. Mass. 



Agr. Expt. Sta. Bui. 249:26-52, illus. 1929. 



Publication of this Document Approved by Commission on Administration and Finance 

 6M-7-'32. No. 5816. 



