EXPERIMENT STATION BULLETINS. 



469 



The percentage of control refers to the effect of the para-dichlorobenzene 

 upon borers occurring below the surface of the mound placed around the tree 

 when treated. In this orchard the infestation was largely on the trunk above 

 the level of the mounds so that a large proportion of the borers were not 

 subject to the effects of the material. The trunks of these trees were rough 

 and had many wounds and dead places in the bark and it was around such 

 places that many of the borers were found. The lesser peach-tree borer usually 

 prefers to work on older trees with rough bark and around wounds but the 

 species working on these trees was not determined. 



EXPERIMENT AT PENNVILLE. 



Another experiment was begun in 1921 at Fennville on the Wadsworth 

 Brothers' farm. This work was on trees in two separate blocks, one of six- 

 year-old Elberta and the other of older trees of several varieties but mostly 

 New Prolific. The trees of the younger block were in good condition and 

 generally had smooth, sound trunks. The soil there was quite sandy. In the 

 older block the soil was much heavier and the trees had much rough bark 

 with many old wounds on the trunks. 



Application. The para-dichlorobenzene was applied in this orchard on 

 September 2 in the usual way and at the rate of ^ to 1 ounce per tree. About 

 125 trees were treated and alternate rows left as checks in the Elberta block, 

 and an equal number were treated in the block of older trees with checks left 

 in the same way. 



Results. A portion of the trees in each block were examined on October 

 4 and 5. The borers were dug only from that part of each treated tree which 

 was below the top of the mound placed around them and from comparable 

 parts of the untreated trees. The record of results obtained in each block 

 is shown in tables 18 and 19. 



TABLE 18. PEACH BORER CONTROL ON ELBERTA AT FENNVILLE_, 1921. 



Percentage of control — 98.1 per cent. 



TABLE 19. PEACH BORER CONTROL ON OLDER TREES AT PENNVILLE_, 1921. 



Percentage of control — 100 per cent. 



In the older trees the control of borers which were in a position to be affected 

 by the para-dichlorobenzene was perfect, but this does not mean that a large 



