Water stress and triclopyr on clopyralid efficacy in honey mesquite
2002
Roche, A.R. | Bovey, R.W. | Senseman, S.A.
Water stress may affect herbicide efficacy in herbaceous and woody plants. Chamber studies were conducted to evaluate the influence of water stress (-1.3 to -2.8 MPa) and triclopyr on the absorption and translocation of clopyralid in greenhouse-grown honey mesquite (Prosopus glandulosa Torr.). Xylem water potential was determined in honey mesquite at time of herbicide application. Absorption and translocation of clopyralid was determined at low (-1.3 MPa), medium (-2.2 MPa), and high (-2.8 MPa) water stress at 4 h after application for 1.5-mo-old plants, while only translocation was determined at either a low (-1.4 or -1.6 MPa) or a high (-2.4 MPa) water stress treatment at 24 hours after herbicide application for 3-mo-old plants. Water stress did not affect (P < 0.05) absorption or translocation of clopyralid alone in either study. With 1.5-mo-old plants, the addition of triclopyr to clopyralid increased (P < 0.05) clopyralid absorption in leaves at low (63 microgram) and medium (54 microgram) water stress compared to high water stress (33 microgram) but did not affect (P > 0.05) translocation at 4 hours after application. On 3-mo-old plants, triclopyr decreased (P < 0.01) clopyralid translocation 24 hours after treatment at high water stress. The reasons for reduced uptake and 24 hours post-treatment translocation of clopyralid when applied with triclopyr at high water stress are unclear, but have implications for field applications.
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