Botany and Plant Pathology Seminar Series
Speaker: Mr. Jared Roskamp - Department of Botany and Plant Pathology - Purdue University
Topic: The influence of carrier water properties on the efficacy and solubility of herbicides
When: Wednesday, August 29, 2012 at 3:30 pm in WSLR 116
Abstract:

Water comprises 99% of most herbicide solutions used for weed control in Midwest agronomic cropping systems.  Properties of water, specifically hardness and pH, can influence performance of herbicides such as glyphosate or saflufenacil.  Water pH, also known as the acidity of water, can influence polarity of weak acid herbicides and subsequently solubility, and can cause hydrolysis of some herbicides.  Water hardness is a measure of cations dissolved in water, and these dissolved cations can bind to herbicide molecules and reduce efficacy through reduced herbicide uptake or translocation in plants.  Saflufenacil, a newer protoporphyrinogen IX inhibiting herbicide, has yet to be studied with respect to how water properties influence its performance.  Field studies were conducted to evaluate the influence of carrier water pH (4, 5.25, 6.5, 7.75, and 9) as well as hardness (0, 310, and 620 ppm) on control of common lambsquarters (Chenopodium album).  Water hardness had no effect on the efficacy of saflufenacil.  Carrier water with pH levels of 4 and 5.25 reduced efficacy on lambsquarters, as compared to the water with a pH of 7.75, which provided the greatest control.  Visual evaluation of spray solutions suggested that carrier water pH influenced herbicide solubility.  High pressure liquid chromatography (HPLC) detection of saflufenacil revealed that as pH decreased from 7.75 to 4, the amount of saflufenacil in solution decreased. Greenhouse efficacy studies were conducted on hybrid corn with the same pH levels evaluated in the field study.  Saflufenacil in water with a pH of 4 provided lower control than the saflufenacil mixed in carrier water with pH of 5.25, 6.5, 7.75, or 9.  Knowledge of how a product such as saflufenacil is influenced by properties of water allows us to assist growers and custom spray applicators in making proper adjustments in their spray solutions to optimize the effectiveness of the herbicide and better control resistant weed populations.

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