Residual herbicide treatments reduce
            Andropogon gayanus
            (Gamba Grass) recruitment for mine site restoration in northern Australia

AbstractCover crops have increased in popularity in midwestern U.S. corn and soybean systems in recent years. However, little research has been conducted to evaluate how cover crops and residual herbicides are effectively integrated together for weed control in a soybean production system. Field studies were conducted in 2016 and 2017 to evaluate summer annual weed control and to determine the effect of cover crop biomass on residual herbicide reaching the soil. The herbicide treatments consisted of preplant (PP) applications of glyphosate plus 2,4-D with or without sulfentrazone plus chlorimuron at two different timings, 21 and 7 d prior to soybean planting (DPP). Cover crops evaluated included winter vetch, cereal rye, Italian ryegrass, oat, Austrian winter pea, winter wheat, and a winter vetch plus cereal rye mixture. Herbicide treatments were applied to tilled and nontilled soil without cover crop for comparison. The tillage treatment resulted in low weed biomass at all collection intervals after both application timings, which corresponded to tilled soil having the highest sulfentrazone concentration (171 ng g−1) compared with all cover crop treatments. When applied PP, herbicide treatments applied 21 DPP with sulfentrazone had greater weed (93%) and waterhemp (89%) control than when applied 7 DPP (60% and 69%, respectively). When applied POST, herbicide treatments with a residual herbicide resulted in greater weed and waterhemp control at 7 DPP (83% and 77%, respectively) than at 21 DPP (74% and 61%, respectively). Herbicide programs that included a residual herbicide had the highest soybean yields (≥3,403 kg ha−1). Results from this study indicate that residual herbicides can be effectively integrated either PP or POST in conjunction with cover crop termination applications, but termination timing and biomass accumulation will affect the amount of sulfentrazone reaching the soil.

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The extent of Mission grasses and Gamba Grass in the Darwin region of Australia's Northern Territory

Pacific Conservation Biology ◽

10.1071/pc030281 ◽

2002 ◽

Vol 8 (4) ◽

pp. 281 ◽

Cited By ~ 8

Author(s):

Louise Kean ◽

Owen Price

Keyword(s):

Land Tenure ◽

Hot Spots ◽

Northern Australia ◽

Weed Species ◽

Small Areas ◽

Major Threat ◽

Potential Habitat ◽

Potential Source ◽

Andropogon Gayanus ◽

Prompt Action

Mission grasses Pennisetum polystachion (L.) Schult. and P. pedicellatum (Trin) and Gamba Grass Andropogon gayanus (Kunth) are three weed species that are thought to be spreading rapidly in the vicinity of Darwin and may pose a major threat to ecosystems in northern Australia. The distribution of the species was assessed from a vehicle along 913 km of roads near Darwin. The study provided data on the potential source of further spread and an analysis of the potential habitat of the weeds. For analysis, roadsides were divided up into 200 m cells and the distributions of the grasses were compared against land tenure and broad land unit maps, Mission grasses were present in approximately 52% of cells, and were particularly common around the rural residential/horticultural area of Humpty Doo. They occurred equally commonly in all broad land units, but differed among tenures, being particularly common on freehold land. Gamba Grass occurred in 15% of cells, with hot spots in a number of areas. It was most common on freehold land, and was rare on conservation reserves. It also showed an association with broad land units reflecting wetter areas. Mission grasses are so widespread in the Darwin region that control can only be contemplated in very small areas requiring frequent treatment of re-invading plants. It may be possible to control Gamba Grass in conservation reserves and Crown land if prompt action is taken. For all three species, preventing their spread to new areas should be a high priority.

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Evaluation of POST-Harvest Herbicide Applications for Seed Prevention of Glyphosate-Resistant Palmer amaranth (Amaranthus palmeri)

Weed Technology ◽

10.1614/wt-d-14-00146.1 ◽

2015 ◽

Vol 29 (3) ◽

pp. 405-411 ◽

Cited By ~ 7

Author(s):

Whitney D. Crow ◽

Lawrence E. Steckel ◽

Robert M. Hayes ◽

Thomas C. Mueller

Keyword(s):

Weed Management ◽

Control Strategies ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Wheat Grain ◽

Herbicide Application ◽

Post Harvest ◽

Herbicide Treatments ◽

Soil Seedbank ◽

Residual Herbicide

Recent increases in the prevalence of glyphosate-resistant (GR) Palmer amaranth mandate that new control strategies be developed to optimize weed control and crop performance. A field study was conducted in 2012 and 2013 in Jackson, TN, and in 2013 in Knoxville, TN, to evaluate POST weed management programs applied after harvest (POST-harvest) for prevention of seed production from GR Palmer amaranth and to evaluate herbicide carryover to winter wheat. Treatments were applied POST-harvest to corn stubble, with three applications followed by a PRE herbicide applied at wheat planting. Paraquat alone or mixed withS-metolachlor controlled 91% of existing Palmer amaranth 14 d after treatment but did not control regrowth. Paraquat tank-mixed with a residual herbicide of metribuzin, pyroxasulfone, saflufenacil, flumioxazin, pyroxasulfone plus flumioxazin, or pyroxasulfone plus fluthiacet improved control of regrowth or new emergence compared with paraquat alone. All residual herbicide treatments provided similar GR Palmer amaranth control. Through implementation of POST-harvest herbicide applications, the addition of 1,200 seed m−2or approximately 12 million seed ha−1to the soil seedbank was prevented. Overall, the addition of a residual herbicide provided only 4 to 7% more GR Palmer amaranth control than paraquat alone. Wheat injury was evident (< 10%) in 2012 from the PRE applications, but not in 2013. Wheat grain yield was not adversely affected by any herbicide application.

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