Palmer amaranth control by glufosinate depends on application time of day

Document Type

Article

Publication Date

1-1-2021

Abstract

Glufosinate is used widely to control glypho-sate-resistant Palmer amaranth (Amaranthus palmeri S. Wats.) in cotton (Gossypium hirsutum L.). Previous research has shown weed control with several herbicides, including glufosinate, can be affected by application time of day. The response sometimes has been attributed to diurnal leaf movement (leaf orientation) in the weeds. The objectives of our research were to determine the influence of time of day of glufosinate application on Palmer amaranth control and to determine if the response was related to diurnal leaf orientation. Field experiments in five states evaluated Palmer amaranth control with glufosinate applied at nine intervals ranging from 1 h before sunrise to 6 h after sunrise and nine intervals ranging from 6 h before sunset to 1 h after sunset. Greatest Palmer amaranth control was achieved with glufosinate applied 2 h after sunrise to 1 h before sunset. Am-monium sulfate, added only to glufosinate 1 h before sunrise or 1 h after sunset treatments, did not improve control. Leaf angles of Palmer amaranth and velvetleaf (Abutilon theophrasti L.) were deter-mined in a greenhouse at 1 h before light, 2 h after light, mid-day, 2 h before dark, and 1 h after dark. Leaves of velvetleaf oriented downward during the dark periods but time of day had no effect on leaf orientation of Palmer amaranth. These results demonstrate the need for sunlight for optimum glufosinate efficacy on Palmer amaranth.

Publication Source (Journal or Book title)

Journal of Cotton Science

First Page

58

Last Page

66

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