Post-harvesting glyphosate and imazapyr application on Eucalyptus stumps to control coppice

Abstract

ABSTRACT The objective of this research was to assess the efficiency of applying glyphosate and imazapyr to Eucalyptus cut-stump surfaces after harvesting to control sprouting. Two experiments were conducted in Eucalyptus grandis × Eucalyptus urophylla plantations arranged in a randomised block design with five treatments and five replicates. In experiment 1, 0, 0.84, 1.67, 2.50 and 3.34 kg of acid equivalent (a.e.) ha−1 of glyphosate was applied. Experiment 2 involved the application of 0, 0.028, 0.083, 0.140 and 0.195 kg a.e. ha−1 of imazapyr. The application was carried out between 42 and 48 hours after harvesting in replicates of 36 stumps. Increased glyphosate doses increased coppice control to more than 90%. Coppice was present on approximately 30% of the stumps treated with the highest glyphosate dose. However, these shoots showed low vigour 225 days after application, with mean values of about 0.30 m in height and 0.5 shoots per stump. In the control treatment, coppice reached 3.0 m in height and 8.0 kg green mass weight, and coppice was present on 97% of the stumps. The highest imazapyr doses increased shoot control to 80%. Post-harvesting application to cut stumps reduced coppice development. However, only the glyphosate doses of 2.50 and 3.34 kg a.e. ha−1 presented satisfactory coppice control levels without follow-up operations.