230 



Bulletin 176. 



1896-1897. 



Apparently the paint was a very effectual preventive, but the fact 

 that many of the trees were seriously injured and some of them 

 died from its use renders the results as to the number of infested 

 trees and the number of borers found of no value. This experi- 

 ment, in connection with our Paris green and glue combinations, 

 is strong evidence that Paris green is a dangerous ingredient in 

 washes, and we do not believe it increases their effectiveness. 



Ihjdraxilic cement wash. — In 1824, Shotwell recorded that he 

 found a litne nfioTtar or hricTdayer^ s mortar to work perfectly as a 

 wash to keep out peach-tree borers. In 1891 Woodward recom- 

 mended a wash made of dirty soap, sweet skim milk and hydraulic 

 cement (common water-lime) as " a sure and safe remedy for borers." 

 Two years later McCarthy recommended a wash of sour or butter- 

 milk and hydraulic cement, stating that " the weak-jawed grub is 

 unable to break it, and hence soon dies of exhaustion," but further 

 stipulating that it must be applied every two or three weeks, as the 

 growth of the tree causes it to crack. In 1898 Smith recorded 

 some experiments with a wash of skim milk and the cement. He 

 demonstrated that the milk made such a wash last much longer 

 than if water were used, and that as a mechanical coating it left 

 nothing to be desired. One application would last and remain in 

 good condition as long as necessary, but it would not " prevent the 

 exit of borers that were already working in the tree, but would 

 keep out any young larvae that attempted to get in." Smith's 

 results from the use of this cement wash, so far as keeping out the 

 borers is concerned, were inconclusive. 



We made a wash of sweet skim milk (from a separator) and Port- 

 land cement, using about 6 pounds of cement in 3 or 4 quarts of 

 water ; this was sufficient to treat 48 young trees from \^ to 4 



