Environment

Asthma Weed

Botanical name: Parietaria judaica
Environmental Weed Special note: Asthma Weed pollen may cause asthma, conjunctivitis, rhinitis and hay fever. Contact with plants may cause skin rashes and other allergic reactions. It is recommended that long clothing, a dust mask or half face respirator, eye protection (goggles or glasses) and protective gloves be worn when handling this weed.

Photos: Adam Burrowes Drawing: Marita Macrae

Description

Originating from Europe, Asthma Weed is also known as Pellitory or Sticky Weed. Asthma Weed is a many-branched perennial herb that grows up to 1 metre high. Leaves are green, soft, an oval shape with pointed ends, and are 2 cm to 8 cm long. Leaves are arranged alternately along pink or red stems.

Roots are pink or red, and woody on older plants. Flowers are very small, light green in colour, and clustered along the stems. Leaves, flowers and stems are covered with sticky hairs that will stick to skin, clothing and animal fur.

Dispersal

Seeds are dispersed by wind, water and by attachment to clothing and animals by sticky hairs. Seeds are also spread in soil and mud attached to shoes, tyres and machinery.

Impact on bushland

Asthma Weed is common on wasteground, in moist gullies, in and around sandstone outcrops, and as a groundcover in disturbed areas. Is also commonly found in gardens, often growing out of rock crevices, walls and cracks in cement.

Plants grow and produce seed very rapidly (within 2-3 weeks under favourable conditions). Regrowth is persistent, and plants can flower and set seed most of the year.

Control

Manual:

• Hand pull Asthma Weed plants taking care to remove the entire root system, or else it will reshoot.
• Place in a plastic bag and dispose in the garbage.
• Check clothing, tools and gloves for pieces of the plant, to prevent further spread.
• Mulch bare soils to reduce regrowth.
• Follow up treatment will need to occur within three weeks of initial treatment, and may need to repeated several times to eradicate this weed.
• It is crucial to control Asthma Weed prior to seeding.
• All herbicide use should be undertaken with a registered herbicide as specified on the herbicide product label or relevant off-label permit published by the Australian Pesticides & Veterinary Medicines Authority.
• If roots are firmly caught in cracks in stone walls or concrete, herbicide may need to be used. Apply the herbicide to the plants while actively growing, and prior to flowering if possible. Spray the plants thoroughly for effective treatment.

See Manual Weed Control Techniques.

Chemical: Before commencing any chemical control program contact your local council's weeds officer on 9970 1369 for advice tailored to your situation.

References

Dept of Primary Industries - Agnote. Pellitory.

Source: Pittwater Council