Glyphosate and imazapyr to eucalyptus sprout control: application to the main stem before the harvesting of the tree

Abstract

Herbicide spraying on eucalyptus regrowth prior to planting reform is a common practice in the forest sector. However, several operations are needed in the same area for an effective sprout control. The objective of this work was to evaluate the efficiency of the herbicides glyphosate and imazapyr, applied to the main stem before the harvesting of the tree to eucalyptus sprouts control. There were set up 7 treatments, with application of doses of 3.0; 4.0; and 5.0 mL/stem of glyphosate (Gli-Up^® 360g i.a L^-1) and doses of 0.3; 0.5; and 0.7 mL/stem of imazapyr (Chopper Florestal^® 250g i.a. L^-1), in addition to a control treatment. The herbicide spraying consisted of the directed spraying of the herbicides on incisions carried out on the stem of the trees. The harvest of the trees was carried out 30 days after the herbicide spraying. Assessments about the number of sprouts per stump were carried out, the number of stump with presence of coppice, height and control efficiency of the coppice 150 days after harvesting. The glyphosate spraying promoted reduction of the sprout development and vigor. However, even with this reduction, it was observed presence of sprouts in at least 80% of the assessed stumps. The spraying of the dose of 3 mL of glyphosate promoted values next to 80% of control efficiency. Nevertheless, it was observed that new control operations would be necessary. The spraying of imazapyr was inefficient with control efficiency values less than 25%. In conclusion, the application of glyphosate to the main stem before the harvesting of the tree presents reduction in the eucalyptus sprout development. Additionally, the application of imazapyr, in the doses and form application tested, is not recommended to eucalyptus sprout control.

Keywords:
Eucalyptus grandis x Eucalyptus urophylla; Sprouts eradication; Unwanted sprouts; Chemistry control