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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 15 



We believe that table 5 shows quite accurately the relation between 

 temperature and the time of appearance of the first eggs, larvae, pupae 

 and adults of the three generations of the codling-moth in central 

 and southern Illinois. These relations will probably hold true in other 

 fruit-growing States, but difference in latitude, altitude, and condi- 

 tions as to moisture may modify them. Should this be the case, it 

 will be easy to ascertain the relations which apply to localities in which 

 these modifying conditions prevail. 



The advantages to be derived from the use of a table showing the 

 relations of effective day-degree accumulations to the seasonal 

 history of the insects are apparent. Temperature records are much more 

 easily kept than records of the progress of the seasonal history of the 

 codling moth based upon field observations and the former are more 

 accurate than the latter. A spray program based upon the above 

 table can be made out and the dates when the sprays should be applied 

 anticipated a week or more in advance. By the use of temperature 

 records the normal daily accumulations and the total accumulations 

 for every day of the season may be ascertained for any locality and from 

 these data the dates when the first individuals of each brood may be expec- 

 ted to appear under normal conditions may be known for that locality. 



Spray programs based on fixed dates or on the time of the fall of the 

 petals do not take into account seasonal variations and variations 

 due to local peculiarities, to altitude, to latitude, or to other circum- 

 stances which may affect temperature. 



The following program is suggested based upon the relation of ac- 

 cumulated effective day-degrees and the time of the appearance of the 

 first larvae of each generation. The program provides for seven sprays, 

 three for the first brood, two for the second, and two for the third. This 

 program is suggested with the hope that it will be thoroughly tested 

 and freely criticised. 



'The application of the first spray for the codling moth should begin when the petals are about 

 two-thirds off. The t'me of full bloom is not dependent upon effective day-degrees as defined in 

 the preceding pages and hence the time of the application of the first spray cannot be determined by 

 the accumulation of effective day-degrees. 



