Mugwort (Artemisia vulgaris)

History

The common name of this weed, mugwort, has several derivations that come from its former uses as an insect repellent.I Its old English name "mugwyrt" comes from "midge" and "wort", an archaic term for a herbaceous plant (Barney and DiTommaso 2003). This plant had been used to flavour beer before the advent of hops. There are a number of homeophatic uses for this weed, including the treatment of irregular menstruation and relief of menopausal pains. The essential oil obtained by distillation of the aerial part is used in perfumes and aromatherapy.

Lifecycle

Mugwort is a perennial that reproduces primarily by fragments of rhizomes, and to a lesser extent by seeds.

Identification Characteristics

Rhizomes: Underground horizontal and branched to 1 cm in diameter.

Stems: Erect, angular, strongly branched in the upper half and shaped like panicle, smooth or slightly hairy, up to 0.5 - 2 m long. The stems can be green, green with purplish ridges, or purple, especially in the upper stem portions.

Leaves: Divided into many segments, leaf size ranges from 1 - 10 cm long and 3 - 7.5 cm wide (Figure 1). Middle and upper leaves are smaller and more divided than the lower leaves. Leaf colour is dark green and slightly hairy above, and silvery-white beneath due to a dense covering of white-woolly hair. Mugwort leaves are similar in shape to those of common ragweed and cultivated chrysantemums. However, mugwort differs from these plants by the silvery appearance of lower side of its leaf blades.

Flowers: From July to September. Flowers resemble a spike like cluster, each flower head will a have a covering of whitish woolly hairs (Figure 2). Can produce between 20,000 - 70,000 seeds per plant. Seeds will germinate in late spring.

Odour: A distinguishing characteristic of this genus is its strong sage-like odour.

Control

General (Non-crop Land)

Bradley and Hagood (2002) noted that based on their field research, excellent long-term control of mugwort was achieved with clopyralid (Lontrel 360) applied at a rate of 0.32 L/acre. Dicamba (Banvel II) applied at 7.4 L/acre and glyphosate applied at 10 L/acre will also provide adequate long-term control of mugwort but at extremely high and uneconomical rates. Table A provides an overview of mugwort control in non-crop land areas one year after sequential herbicide applications.

^(a) adapted from Bradley and Hagood, 2002.
^(b) Indicates sequential herbicide applications applied at 7-wk intervals.

Corn

Bradley and Hagood (2002) evaluated different herbicide options for the control of mugwort in no-till corn. Flumetsulam + clopyralid (Fieldstar) applied early to late postemergent gave between 66 to 78% control (Table B). Fieldstar is registered for use on field corn in Ontario. Clopyralid (Lontrel 360) provided the most consistent control when applied early to late post emergent to corn. However, clopyralid is NOT registered for use in Ontario on Field Corn and should not be used.

^(a) adapted from Bradley and Hagood, 2002.

Soybeans

Few options exist for mugwort control in soybeans. Anecdotal observations would suggest that acifluorfen (Blazer) and fomesafen (Reflex) should provide some suppression through foliar desiccation, but won't affect the underground root system. The use of glyphosate at the highest registered rate on glyphosate-tolerant soybeans should provide some suppression of mugwort.

Best Time for Control

No consistent trends of mugwort control with applications timed at the vegetative or flowering stage have been observed.

References: Barney, J. N. and A. DiTomasso. 2003. The biology of Canadian weeds. 118. Artemisia vulgaris L. Can. J. Bot. 83: 205-215.

Figure 1: Mugwort Leaves

Figure 2: Mugwort Flower Head

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