Interaction of Glyphosate and 2,4-DB for the Control of Selected Morningglory (Ipomoeaspp.) Species

Abstract

Interaction of glyphosate and 2,4-DB was evaluated in greenhouse and laboratory studies with respect to control of four species of annual morningglory. The greenhouse study included smallflower, pitted, palmleaf, and ivyleaf morningglory at three growth stages: seedling, juvenile, and vining. A series of glyphosate rates (0.28 to 1.26 kg ae/ha) and 2,4-DB (0.022 and 0.045 kg ae/ha) were applied alone, and in all possible two-way tank mixtures. Morningglory response to both glyphosate and 2,4-DB applied alone was species- and growth stage-dependent. All combinations were either additive or synergistic for control of pitted, palmleaf, and ivyleaf morningglory. Response of smallflower morningglory ranged from antagonistic to synergistic. Absorption and translocation of14C-2,4-DB was independent of the addition of glyphosate in all four species. By contrast, absorption of foliar-applied14C-glyphosate and translocation of14C from treated leaves to other plant parts were enhanced by the addition of 2,4-DB in all species except palmleaf morningglory. In palmleaf morningglory,14C-glyphosate absorption and translocation were independent of the addition of 2,4-DB. Absorption and translocation data were in agreement with greenhouse studies.