Noncrop Herbicide Weed Control

K. Umeda and G. Gal

Abstract

Paraquat and diquat were effective against weeds immediately at 3 DAT. Glyphosate, sulfosate, and glufosinate exhibited activity against the weeds at 7 to 10 DAT. Paraquat provided the most complete weed control of most weeds at 10 to 16 DAT. Most of the diquat treated weed recovered and exhibited regrowth after 22 DAT. Glufosinate did not provide adequate control of most weeds at 22 DAT similar to diquat. Glyphosate and sulfosate were nearly equivalent at 0.50 and 2.0 lb AI/A against most weeds at most of the rating dates.

Introduction

Several nonselective postemergence herbicides are available for noncrop weed control. The rate of control provided by each of the herbicides vary from a rapid burndown of the vegetation to a slower complete weed control with translocation of the herbicide throughout the plant roots and shoots. Five herbicides were evaluated and compared for relative efficacy of weed control of typical summer annual weeds and nutsedge.

Materials and Methods

A small plot field test was established at the University of Arizona Maricopa Agricultural Center, Maricopa, Arizona. In a noncrop area that was basin flood irrigated, treatment plots measured 6.7 ft by 25 ft and replicated three times in a randomized complete block design. The postemergence herbicide treatments were applied on 14 July 1997. All treatments were applied using a hand-held boom equipped with four flat fan 8002 nozzle tips. The sprays were pressurized with a backpack CO2 system at 40 psi that delivered 22 gpa water. All treatments included a nonionic surfactant, Latron CS-7, at 0.25% v/v. The dominant weeds present were common purslane (Portulaca oleracea, POROL), horse purslane (Trianthema portulacastrum, TRTPO), prostrate pigweed (Amaranthus blitoides, AMABL), tumble pigweed (A. albus, AMAAL), purple nutsedge (Cyperus rotundus, CYPRO), and summer annual grasses, sprangletop (Leptochloa sp.) and watergrass (Echinochloa sp.). The purslanes ranged in size 6 to 10 inches long stems, prostrate pigweed was 4 to 6 inches long stems, tumble pigweed was 8 to 10 inches height, and nutsedge and grasses were 6 to 8 inches height. At the time of application, the weather was clear, negligible wind, and 100F. Weed control ratings were evaluated at 3, 7, 10, 16, and 22 days after treatment (DAT).

Results and Conclusions

For the six weed species that were evaluated, at 3 DAT, paraquat at 2.0 lb AI/A demonstrated very rapid and effective weed control of better than 90% except for nutsedge. Near complete control of the broadleaved weeds was achieved and maintained until 22 DAT. Grass weeds (sprangletop and junglerice) and nutsedge in treated plots had new plants emerging and recovery of larger treated weeds. Diquat at 2.0 lb AI/A exhibited rapid control of common purslane and prostrate pigweed similar to paraquat. Diquat at 2.0 lb AI/A was comparable to paraquat at 0.50 lb AI/A to suppress grasses, nutsedge, and horse purslane at the early rating dates. Most of the diquat treated weed recovered and exhibited regrowth after 22 DAT.

Glyphosate and sulfosate were very similar at most rating dates for control of all of the weeds. For both herbicides, the highest rate tested was required to provide sufficient activity against most weeds. Rates of 0.50 lb AI/A or less were not effective against the treated weed spectrum. Both at 2.0 lb AI/A required 7 days to demonstrate better than acceptable control (>85%) of common purslane and prostrate pigweed. Glyphosate marginally controlled grasses at 85% and sulfosate was less effective against grasses providing 75% control at 22 DAT. Glyphosate and sulfosate did not adequately control tumble pigweed and nutsedge. Sulfosate was slightly more effective against horse purslane than glyphosate at most of the rating dates. Glufosinate at 2.0 lb AI/A was comparable to glyphosate and sulfosate against common and horse purslane. Glufosinate marginally controlled grasses and nutsedge at 16 DAT then following a rainfall, both recovered and regrew.

Paraquat and diquat were effective against weeds immediately at 3 DAT. Glyphosate, sulfosate, and glufosinate exhibited activity against the weeds at 7 to 10 DAT. Glufosinate did not provide adequate control of most weeds at 22 DAT similar to diquat. Glyphosate and sulfosate were nearly equivalent at 0.50 and 2.0 lb AI/A against most weeds at most of the rating dates. Paraquat provided the most complete weed control of most weeds at 10 to 16 DAT. Grasses and nutsedge emerged and injured larger weeds regrew following rainfall.

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This is a part of publication az1101: "1998 Vegetable Report," College of Agriculture, The University of Arizona, Tucson, Arizona, 85721.
This document located at http://ag.arizona.edu/pubs/crops/az1101/az1101_10.html
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