Experience with trunk injections of zinc has been disappointing in all cases despite rumors of success.
It would seem logical that placement of any form of zinc in the secondary xylem of an actively
transpiring tree would utilize the xylem vessels to rapidly transport the zinc to the actively growing
meristems. However, many researchers including Millikan and Hanger (35,36)
have proven that
zinc transport is more complex than injecting zinc in any form into tree trunks. Millikan and Hanger (36)
reported that 65
Zn moved from the injection point only when zinc was injected into the bark of
2-year-old apple trees. Supplying ethylenediaminetetraacetic acid (EDTA) enhanced 65
in an acropetal (upward) direction only. The 65
Zn was distributed to spurs and laterals on the
distal side of the injection point. Millikan and Hanger (36)
also reported that 65
Zn accumulated at
the nodes on lateral branches and in the petioles, midrib, and major veins of the leaves.