The effect of basal injections of 2,4,5-T on mature trees of Eucalyptus populnea

Abstract

Experiments at Talwood, south-western Queensland, showed that mechanical penetration of the bark at the base of the trunk and simultaneous injection with 2,4,5-T effectively killed mature single stemmed trees of Eucalyptus populnea (Bimble or Poplar Box). The method gave similar results in autumn, spring, and summer. The butyl and butoxy ethanol esters were seemingly equal in effect, and emulsions in water gave results comparable with solutions in diesel distillate. All injections were made into cuts two inches wide and one inch apart, with an average of 7.5 C.C. being injected into each cut. All concentrations of 2,4,5-T (1, 2.5, and 4 per cent active ingredient) gave good results, but the higher rates produced high percentage kills more consistently than the 1 per cent level. The addition of 0-phthalic acid to the water and of its dimethyl ester to the oil based treatments appeared to increase the rapidity of action but did not increase the percentage of trees killed at the lower concentrations. Picloram (Tordon 22K), applied in January 1964, killed all trees treated with both 0.5 and 1 per cent concentrations. This compound is being tested at lower concentrations and fewer injections per unit circumference.