Weed Alert: Muskweed

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Muskweed (Myagrum perfoliatum)

The Problem | Identification | Control

A new threat to NSW cropping

World Status

Muskweed (Myagrum perfoliatum) is a native of Europe, north Africa and western Asia. It is regarded as a weed of cropping in Italy, Lebanon, Turkey, parts of the United States and Australia. Muskweed is considered a serious weed of broadleaf crops such as chickpeas, canola, lupins, faba beans, field peas and lentils on heavy soils in South Australia and western Victoria.

Specimens were collected from the Darling Downs in Queensland from the 1950s to early 1960s, however, none have been collected since. A major infestation was also discovered in 1999 in northern NSW in canola, wheat and lucerne. This was the first outbreak positively identified in NSW.

The Problem

Muskweed fits the same niche on alkaline clay soils as does wild radish (Raphanus raphanistrum) on lighter-textured soils. As such, muskweed poses a serious threat to our most productive agricultural lands. Muskweed can compete strongly with crops thereby reducing yields by up to 50%. It is also a contaminant of seed and hay and creates blockages during harvest.

It is tolerant to a range of commonly-used herbicides and, currently, there are limited herbicide registrations for cereals and fallow. There are no herbicides registered for selective control in broadleaved crops.

Muskweed has a staggered germination from April – October and so will re-establish following pre or post-emergent herbicide treatment. Soil seedbank is thought to last for up to 10 years with seed being found up to 40 cm depths on self-mulching soils.

Heavily-infested paddocks can have up to 3000 seeds per square metre.

Identification

Muskweed is an annual broadleaf plant growing up to 1 m tall. Seed leaves (cotyledons) are broad clubs, making them unlike any other brassica weed in Australia.

• Leaves are a waxy blue-green and hairless. Rosettes can grow up to 45 cm in diameter.
• Stems are erect, blue-green and waxy, becoming very branched. The leaves do not have leaf stems (petioles).
• Flowers are small (2–4 mm diameter), with four, pale yellow petals. Pods are hard, wedgeshaped 5–7 mm long and 4–5 mm wide.

Plants that are commonly confused with muskweed include:

• Turnip weed (Rapistrum rugosum) Family: Brassicaceae — when they are podded.
• Common sowthistle (Sonchus oleraceus) Family: Asteraceae — when they are seedlings.
• Prickly lettuce (Lactuca serriola) Family: Asteraceae — when they are seedlings and elongating.
• Willow lettuce (Lactuca saligna) Family: Asteraceae — when they are seedlings and elongating.

Control

Any suspected infestations should be reported to your local agronomist.

Acknowledgements

Andrew Storrie & Tony Cook NSW Agriculture