Role of nitrogen and herbicides in integrated management of mugwort (Artemisia vulgaris) in cool-season forage grasses

Abstract

Mugwort (Artemisia vulgaris L.) is becoming increasingly problematic in cool-season pastures and grasslands. A 3-yr field experiment evaluated different rates of nitrogen and herbicides for A. vulgaris management in a permanent grassland. The main plot had three nitrogen rates, 0, 62, and 124 kg N ha–1; the sub plot had three herbicides, aminopyralid, clopyralid, and glyphosate; and the sub-subplot had three herbicide rates, aminopyralid (61, 122, and 244 g ae ha–1); clopyralid (140, 280, and 560 g ae ha–1); and glyphosate (552, 1,104, and 2,208 g ae ha–1). Results revealed that nitrogen had no effect on A. vulgaris control, rhizome biomass, and stem density. However, cool-season grass biomass was the highest (7,126 kg ha–1) in the plots that received 124 kg N ha–1 and 244 g ae ha–1 of aminopyralid. Only glyphosate caused grass injury which varied from 65% to 100% depending upon application rate. By 9 MAIT, A. vulgaris was controlled 60% to 98% with aminopyralid at ≥61 g ae ha–1 or glyphosate at ≥552 g ae ha–1. By 21 MAIT, aminopyralid at ≥122 g ae ha–1 or glyphosate at ≥1,104 g ae ha–1 resulted in >95% reduction in A. vulgaris stem density and rhizome biomass, and provided ≥98% visual control. By 33 MAIT, complete control of A. vulgaris was confirmed in plots treated with aminopyralid at ≥122 g ae ha–1 or glyphosate at ≥1,104 g ae ha–1. Clopyralid was not effective; A. vulgaris control was <40% even after three annual applications at 560 g ae ha–1. Results indicate that integration of nitrogen fertilization with aminopyralid did not improve A. vulgaris control, but was advantageous in enhancing cool-season grass productivity.

Intraspecific trait plasticity to N and P of the wetland invader, Alternanthera philoxeroides under flooded conditions

“…For example, successful biological control of weeds with insects can be highly dependent on plant nutrition, with significant effects of nitrogen on the timing of agent establishment (Room & Thomas, 1985 ), population buildup (Harms & Cronin, 2019 ; Harms, Cronin, et al, 2020 ), and dispersal (Wilson et al, 2007 ). The relationship between eutrophication and herbicide efficacy is less clear, but there are numerous examples of increased herbicide efficacy when plants are grown with supplemental fertilization before application (Aulakh, 2020 ; Cathcart et al, 2004 ).…”