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

Published online by Cambridge University Press:  12 June 2017

David R. Shaw
Affiliation:
Dep. Plant Pathol. Weed Sci., Miss. State Univ., Mississippi State, MS 39762
Sunil Ratnayake
Affiliation:
Dep. Plant Pathol. Weed Sci., Miss. State Univ., Mississippi State, MS 39762
Clyde A. Smith
Affiliation:
Dep. Plant Pathol. Weed Sci., Miss. State Univ., Mississippi State, MS 39762

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.

Type
Research
Copyright
Copyright © 1990 Weed Science Society of America 

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