24 



BULLETIN" 847, U. S. DEPARTMENT OF AGRICULTURE. 



The Page orchard and the strip surrounding it were kept clean 

 of borers for three consecutive. years. The plats above (fig. 3) show 

 the condition of the orchard as to infestation at each examination. 



It will be seen that the results of the experiment in the Page or- 

 chard were fully as good as those obtained in the Darnall orchard, 

 although the cleaned strip surrounding the trees was only half as 

 wide. This may be accounted for by the fact that the breeding con- 

 ditions for borers surrounding the Page orchard were much less fa- 

 vorable than those surrounding the Darnall orchard and fewer 

 beetles were developing in the locality. 



The results of the experiments described and illustrated above for 

 determining the distance which beetles will fly during the period of 

 oviposition are suggestive although not entirely conclusive. It will 

 be noted that every year in both orchards after the experiments be- 

 gan there is evidence that female beetles crossed the surrounding 

 strip of borer-cleaned territory to oviposit in the orchard. In all 

 cases, however, there was a decided improvement in the borer con- 

 ditions within the orchards after the development of beetles within 

 cases, however, there was a decided improvement in the boror con- 

 ditions of infestation on the number of young borers found in the 

 orchards at the first examinations, we have thereafter percentages of 

 borer reduction which may be tabulated as follows : 



Table VIII. — Improvement in roundheaded apple-tree borer conditions derived 

 from preventing the development of adults within and adjacent to the 

 orchards. 



Name of orchard. 



Year. 



Width of 

 cleaned-up 

 strip sur- 

 rounding. 



Number of 

 borers 

 found. 



Percentage 

 of gain. 





1914 



Feet. 

 600 

 600 

 600 

 600 

 300 

 300 

 300 



106 



56 



1 



44 



254 

 55 

 38 





Do 



1915 



47.1 



Do - 



1916 



99.1 



Do 



1917 



58.5 





1914 





Do 



1915 



78.3 



Do 



1916 



85.0 











73.6 











As is shown in Table VIII, the average improvement in borer con- 

 ditions in both orchards derived from the stopping of the develop- 

 ment of adults in the immediate localities was 73.6 per cent. 



FURTHER TEST OF THE FLIGHT OF li EM ALE BEETLES. 



One of the orchards used in experiments dealing with the round- 

 headed apple-tree borer contained 992 young apple trees planted in 

 31 rows of 32 trees each. Row 1 extended parallel with the outer 

 row of an older orchard that was heavily infested with borers, the 

 experiment orchard being surrounded on other sides by grown-up 



