12 



AGRICULTURE HANDBOOK 134, U.S. DEFT. OF AGRICULTURE 



taphole rather than by air drying of the wood 

 tissue (13, 102, 103). When the microbial growth 

 has reached a count of 1 million per cubic 

 centimeter, sap will no longer flow from the 

 hole, and it is said to be dried up (J7). 



In the past, a dried-up taphole was reamed to 

 make it flow again; it was assumed that this 

 procedure would remove the air-dried wood tis- 

 sue. However, reaming was never successful. 

 Research has shown that the reaming bit did 

 not sterilize the hole. Reaming removed only a 

 layer of the microbial deposit; the remaining 

 bacteria kept on growing. Soon, sufficient num- 

 bers were again produced to stop the flow of 

 sap. The newly developed germicidal pellets 

 have prevented premature drying of the tap- 

 hole. 



PN-4714 



Figure 18. — In a healthy, vigorously growing tree, the 

 taphole will be completely covered with new wood and 

 bark in 1 year. 



Figure 17: 



PN^ni:) 

 -Tapholes arranged in a spiral about the tree. 



Figure 19. — A split section of a tapped maple log showing 

 the longitudinal stain area above and below the tap- 

 hole and the new growth of bark that has covered the 

 outside end of the hole (left). 



Sanitizing Tapholes 



Germicidal Pellets 



A germicidal taphole pellet (fig. 21) has been 

 developed at Michigan State University (17). If 

 put into the taphole as soon as it is bored, the 



