ABSTRACT

REIL, W.O. 1979. Pressure-injecting chemicals into trees. California Agriculture 33(6): 16-19.

Equipment to inject pesticides or nutrients into trees under high pressures has been developed and used in the last five years. Because of such recent development, limited knowledge is available on techniques, procedures, and uses of injection. Observations and the experiences of researchers and farmers are summarized here to improve injection techniques. Drill holes on the thickest areas of the trunk (ridges). These areas are in active growth and will take up liquid rapidly. Liquids move more rapidly in the recently formed xylem directly underneath the bark and transfusion rate decreases with depth. The screw, therefore, needs to be set as shallowly as possible. Materials inject most readily when the tree is vegetatively active; therefore, late spring, summer, and early fall are the best times for maximum uptake. The ideal injection pressure is that amount that will provide the maximum movement of solution into the tree without physically damaging it; pressures may vary from 100 to 200 psi, depending on tree species. Water-soluble materials can generally be injected easily, although many of the larger-molecule organic materials go in at progressively slower rates.