Corkscrew weed (Erodium botrys) is one of the most troublesome annual broadleaf weeds across Western Australia—and an especially stubborn foe on the sandy ridges and gravel flats around Morangup. Its corkscrew-shaped seeds embed in sheep wool, goat hair and even household pets, causing fleece downgrades, painful abscesses and avoidable vet bills. Dense mats of this weed also starve pastures of light and moisture, forcing livestock to graze lower-quality forage and exposing soils to wind and water erosion.
This guide compiles the latest research, local farmer experience and proven DPIRD recommendations, giving you a one-stop strategy for long-term suppression. We cover biology, monitoring, cultural, mechanical and chemical tactics, plus essential hygiene and record-keeping routines.
Common & Botanical Synonyms
You’ll also hear Erodium botrys called corkscrew filaree, broadleaf filaree, Mediterranean storksbill, broadleaf storksbill or even heron’s-bill or beak in older agronomy notes. Historic botany texts list several formal synonyms, including Geranium botrys Cav. and Erodium contortum (Cav.) Vign.—all referring to the same weed we battle across Western Australia today.
1. How Corkscrew Weed Harms Livestock & Pets
Wool & Mohair Contamination. Sharp awns tangle in fine fibres, forming hard “burrs” that downgrade clip value by 10–35 % at auction.
Abscesses & Seed Migration. Dogs, cats and wildlife pick up seeds between toes or in fur. If awns drill into skin they create painful abscesses, sometimes migrating internally.
Pasture Displacement. In dense stands, corkscrew weed crowds out clovers and ryegrass, reducing energy and protein available to grazing stock and lowering carrying capacity.
When the Corkscrew Keeps Drilling — Internal Damage & Emergency Care
The barbed awn of Erodium botrys is hygroscopic: it twists tighter whenever the humidity changes, ratcheting itself forward like a miniature drill bit. In paws, this motion drives the seed up between the toes, rupturing skin and tracking bacteria deep into soft tissue. Left unchecked it forms a painful interdigital abscess and can even migrate up the leg sheath toward joints and tendons.
In ears, the awn works down the canal toward the eardrum, causing violent head-shaking, yelping and a pungent otitis infection within 24–48 h. A vet must sedate the animal, locate the awn with an otoscope and remove it intact to avoid perforation or nerve damage.
Eyes & muzzle aren’t immune either. Seeds caught under the third eyelid can abrade the cornea, while awns inhaled through the nose may lodge in the sinuses or migrate toward the lungs—a life-threatening scenario that demands immediate veterinary imaging and surgical retrieval.
Red-flag symptoms: sudden lameness, persistent licking of a single paw, head-tilt or frantic ear-scratching, one swollen eye, foul-smelling nasal discharge, or a weeping “track” lesion along a limb. Act fast—each hour lets the awn twist deeper.
First-aid on farm is limited to flushing and keeping the animal calm; DO NOT attempt to dig out the seed with tweezers, as broken fragments make removal harder and infection worse. Prompt professional extraction, antibiotics and, in abscess cases, surgical drainage are the only sure route to recovery.
2. Botanical ID & Remarkable Self-Burying Seeds
The plant starts as a low rosette (2–5 cm wide) of deeply lobed, hairy leaves. As spring approaches, stems elongate to 40–60 cm bearing pale-pink flowers. After pollination, each flower develops a 5-seed cluster topped by a 6–10 cm “beak”. When the fruit dries it twists like a corkscrew, drilling each seed into the soil for long-term persistence.
An Ancient Name with a Modern Problem
The genus Erodium comes from the Greek erodios (“heron”) owing to the beak-like seed, while botrys (“bunch of grapes”) refers to its clustered fruit. Introduced accidentally in the early 1900s, it has naturalised from the South Coast to the Wheatbelt’s fringe.
3. Seasonal Lifecycle & Critical Monitoring Windows
Autumn — Germination. The first 20–30 mm of rain triggers mass germination; seedlings emerge within 7–10 days.
Winter — Rosette Growth. Plants stay low; this is the best knock-down window (2–4-leaf stage).
Early Spring — Bolting. Herbicide efficacy drops once stems elongate and buds form.
Late Spring — Seed Set. Each surviving plant can add 2,000 + seeds to the soil seed-bank.
Monitoring Tip
Schedule a “weed walk” 10–14 days after each significant autumn rain. Flag patches for immediate follow-up.
4. Cultural & Mechanical Tactics
4.1 Pasture Competition
Oversow bare areas with sub-clover cultivars (e.g. Daliak, Leura) at 8–12 kg/ha. Maintain soil P and K to encourage dense cover. Use rotational grazing so residuals stay above 1,200 kg DM/ha to shade seedlings.
4.2 Spray-Grazing
Apply low-rate phenoxy herbicide (500 mL/ha 2,4-D amine or 1 L/ha MCPA amine) when clovers have 3–8 leaves and rosettes are small. Introduce sheep at 2–4 × normal density for 7–14 days; they gobble wilted weeds first, slashing biomass and seed set.
4.3 Targeted Cultivation
On small outbreaks, a shallow rotary-hoe pass in late autumn, followed by a second pass 10 days later, uproots successive flushes. Avoid deep inversion that resurfaces buried seed.
5. Chemical Control—Post-Emergent Options
2,4-D Amine (625 g/L). 500–800 mL/ha on 2–4-leaf rosettes; delay until clover has 8 leaves to prevent scorch.
MCPA Amine (750 g/L). 0.5–1 L/ha once clovers reach 3 leaves; gentler on legumes.
Ecopar® (pyraflufen-ethyl + MCPA). 400–500 mL/ha Ecopar + 330 mL/ha MCPA: rapid brown-out plus systemic control.
5.1 Pre-Emergent & Residual Options
Sulfometuron-methyl (Shatter 750 WG). 33–67 g/ha on fallow or non-cropped zones in March; observe 12-month plant-back.
Trifluralin. 1–2 L/ha incorporated pre-seeding; useful when establishing new pasture.
6. Biological & Physical Approaches
No commercial biocontrol agents exist yet. Promoting healthy soil biology and competitive pastures aids suppression.
Hand-pull on damp days—remove the full taproot and bag plants for off-site disposal. Mowing pre-flowering reduces biomass but must be followed by grazing or herbicide to stop regrowth.
7. Farm Hygiene & Seed-Spread Prevention
Seeds lodge in tyre treads and undercarriages. Install a gravel wash-down bay at paddock exits; pressure-wash gear and sweep debris. Crutch or brush stock before shifting them to clean country, especially during late-spring seed set.
8. Record-Keeping & Seed-Bank Monitoring
Log every spray date, rate and paddock in a notebook or app. Each spring, collect 10 soil cores (10 cm × 5 cm) per paddock, germinate in trays and count seedlings to track seed-bank trends.
9. Best Practice Checklist—Do’s & Don’ts
Do
- Monitor paddocks 10–14 days after every 20–30 mm autumn rain and flag 2–4-leaf rosettes for immediate action.
- Rotate control tools each season—alternate herbicide groups, spray-grazing, pre-emergents and pasture renovation to slow resistance.
- Maintain dense ground-cover by oversowing clovers and ryegrass, and using rotational grazing to keep residues above 1,200 kg DM/ha.
- Clean down machinery, vehicles & livestock before entering clean paddocks; use a gravel wash-down bay and a high-pressure hose.
- Hand-pull small outbreaks when soil is moist, removing the whole tap-root and bagging plants for off-site disposal.
- Keep detailed records—dates, rates, paddocks and weather—and map treated areas; review seed-bank counts each spring.
- Follow herbicide labels for rates, timing, buffer zones and stock withholding periods.
Don’t
- Don’t wait until flowering; control drops sharply once stems bolt and seeds set.
- Don’t over-graze to bare soil—open gaps invite fresh corkscrew-weed germination.
- Don’t reuse the same herbicide group two seasons in a row; this accelerates resistance.
- Don’t leave pulled plants on the ground—seeds or root fragments can restart the patch.
- Don’t neglect fence lines, gateways & track edges; they’re seed hot-spots that reinfect clean paddocks.
- Don’t spray in windy conditions; drift can damage neighbouring crops and native vegetation.
- Don’t skip seed-bank monitoring; without core-tray counts you can’t measure long-term success.
10. Applying the Plan to Morangup Soils & Terrain
Sandy ridges: rely on competitive pasture plus light pre-emergent rates.
Gravel gullies: use spray-grazing combined with shallow cultivation.
Clay-loam valley floors: rotate sheep grazing with late-winter MCPA clean-ups.
11. Toward Weed-Free, High-Value Pastures
Corkscrew weed’s self-drilling seeds and rapid autumn germination make it formidable. Yet by combining timely monitoring, diverse control methods and strict hygiene, WA producers can steadily drain the seed-bank and restore productive, erosion-resistant pastures. Stick with the plan for five seasons and the improvement in wool returns, stocking rates and paddock condition will speak for itself.
References
- DPIRD – Erodium Control of Doubtful Proposition
- DPIRD – Integrated Weed Management Strategies
- APVMA – ADAMA 2,4-D Amine 625 Herbicide Label
- Apparent Ag – MCPA Amine 750 Product Information
- International Survey of Herbicide Resistant Weeds
- GRDC – Spray Application Manual
- DPIRD – Pest and Disease Information Service (PaDIS)