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Effects of Herbicide Application Timing on Johnsongrass (Sorghum halepense) and Pitted Morningglory (Ipomoea lacunosa) Control

David R. Shaw, Sunil Ratnayake and Clyde A. Smith
Weed Technology
Vol. 4, No. 4 (Oct. - Dec., 1990), pp. 900-903
Stable URL: http://www.jstor.org/stable/3986769
Page Count: 4
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Effects of Herbicide Application Timing on Johnsongrass (Sorghum halepense) and Pitted Morningglory (Ipomoea lacunosa) Control
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Abstract

Field experiments were conducted to evaluate the influence of application timing of imazethapyr and fluazifop-P on rhizome johnsongrass and pitted morningglory control in soybean. Herbicides were applied at three timings keyed to johnsongrass heights of 15, 30, and 60 cm and 3-, 6-, and 9-leaf pitted morningglory. Evaluations 6 wk after the final treatment indicated imazethapyr controlled both species best when applied at the 15-cm johnsongrass growth stage. Increasing imazethapyr rate did not increase control of pitted morningglory, but did increase johnsongrass control at the 15-cm application timing. However, at the 30-cm johnsongrass application timing, increasing the rate from 0.07 to 0.10 kg ha-1 improved control of both species. Johnsongrass control with imazethapyr was no more than 64% when applications were delayed to 30-cm or larger johnsongrass. Fluazifop-P controlled johnsongrass well at all timings.

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