Local Weeds of the Wilson Inlet Catchment
Blackberries (Rubus anglocandicans, R. fruticosus, R. laudatus, R. rugosus, and R. ulmifolius)
Blackberry is a perennial and semi-deciduous prickly weed that most of us are familiar with, often forming dense thickets on or near waterways.
Begin control measures only if you have plans to return for at least three years in a row. It is recommended to spray during summer growth, or manually remove anytime during the growing season. Manual control can be achieved on small infestations, especially in natural bushland, and larger infestations along waterways where spraying is not permitted.
Metsulfuron plus Pulse is one of several spraying options. On larger infestations it can be used before the more expensive Grazon that has little effect on grasses. If you are using chemicals, use no more than recommended by the manufacturer (it won’t make it any more effective). Surfactants (like Pulse) are harmful to our frogs. Good rule of thumb is "if you hear croaking don't use surfactants".
Goats have proved effective at control so long as in well secured enclosures.
Rusts have turned up and been experimented with in our region but their usefulness is seemingly dependent on specific seasonal weather conditions being met.
Contact WICC if you would like us to recommend a good chemical contractor.
Feral Olive (Olea europea)
WICC has started mapping escapee olives throughout the catchment.
The humble olive tree (Olea europea) is a potential sleeper weed in our region.
A sleeper weed exists in the landscape as a seemingly benign species that can quickly expand in range and density when conditions change. Two key factors contribute to this: patterns of reducing rainfall and widespread commercial plantings. Longer dry seasons in our catchment are creating similar opportunities for infestations that led to the plant becoming a declared weed in South Australia.
Summer is an ideal time for taking stock of any outbreaks on your property and developing a long term control plan. In the wetter months, seedlings can be hand pulled and larger plants cut back and grubbed out. In periods of active growth, chemical control methods can be used.
Information is sourced from Feral Olive Fact Sheet (SA) and other weed references including ‘Western Weeds’ and ‘Southern Weeds’.
Arum Lily, (Zantedeschia aethiopica)
The Arum Lily was introduced to WA from South Africa more than 100 years ago as a garden plant. It is now a widespread and well-established weed, and the sale or propagation of this declared pest has been prohibited since 2006. It thrives in the moist conditions of the Southwest, where it chokes out native vegetation and invades pastures. Contact with Arum Lily can cause eczema in humans, and ingestion is toxic to animals, with stock losses documented. It spreads by growth of underground tubers, and by seed dispersal via birds.
TIP: In WA, landowners are required to control Arum Lily on their property.
Mechanical removal (multiple rotary hoeing over several years) may be effective, but only if all the root fragments are removed. Control is usually achieved through herbicide application. Metsulfuron (0.2g in a 10L backpack sprayer, or 20g/hectare) is applied, with a wetting agent (Pulse, others) added at 1:400 dilution. Glyphosate is not effective against Arum Lily.
TIP: Add a red dye to the mix; the pink blossoms will mark your progress.
Optimal time to spray is June-October, when the flowers are in bloom. Metsulfuron is effective in very dilute concentrations, and degrades rapidly in the environment. The wetting agent can be harmful to amphibians however, so steer clear of frog habitats while spraying.
TIP: The bad news is that the spraying needs to be repeated several years in a row to be effective.
On a recent Sunday, 3 Nullaki Conservation Initiative volunteers assisted Nullaki landowner Tom Wang in spraying 155L of herbicide on 3 large infestations in the bush, along a road verge, and in a paddock. We hope to treat even more areas as our window of opportunity fades.
TIP: If you can’t get to that last patch, cut off and destroy the flowers to prevent seed dispersal.
For more information go to https://www.agric.wa.gov.au/declared-plants/arum-lily-declared-pest
Snowflake Lilly (Leucojum aestivum)
Commonly known as Snowflake Lilly, this strappy-like plant from the Mediterranean belongs to the Daffodil family of flowering plants. Forming clumps of leaves and stalks, it is highly invasive and contains toxic alkaloid compounds. One of these compounds, Galantamine is extracted for medical research in the treatment and study of Alzheimer's disease.
There are some 13 species of the daffodil family in Western Australia and this bulbous perennial weed can be found on the shady edges of the Wilson Inlet, flowering in winter and spring. It prefers wet and damp conditions, turning dormant during the summer.
The drooping white flowers are distinguished by small little green spots on the tip end of each petal. Flowers contain six white petals and produce little black seeds of about 5mm long.
These seeds and root bulbs are carried by water in the landscape, therefore creating an invasive seedbank lasting many seasons. Hand weeding this strappy plant is best, as the bulbous-like roots need to be removed from the soil. Crushing the bulbs will prevent them from germinating the next year. A glyphosate-based herbicide may destroy the bulbs but must be applied while the plant is in flower, though care should be taken when treating near waterways.
Birdsfoot Trefoils (Lotus angustissimus)
Birdsfoot Trefoils are sprawling herbs native to Europe that have become weeds along roadsides, in damp pastures, gardens and along creek lines. They flower in spring and summer with small yellow flowers 4-7mm long with their leaves divided into 5, often hairy, leaflets. Apart from hairiness, they are best distinguished by the length of their pods which are up to 1.4cm.
Mowing to 5cm every 3 weeks provides reasonable control and may reduce seed production and spread. Don’t burn infested area as it will promote seed germination and will promote seedling establishment. Glyphosate is also not effective. Grazing provides little control and cultivation tends to make infestations worse but planting native trees and shrubs to increase the shade can help.
Herbicides provide the most effective control.
Grass dominant situations/small infestations: Use Picloram based products like Tordon.
Hand spraying: Use Logran or Lontrel in winter to early summer.
Around native vegetation: Use Logran or Lontrel. Metsulfuron also provides good control but but may damage young native species.
Pennyroyal (Mentha pulegium)
Pennyroyal (Mentha pulegium) is a perennial noxious invasive herb that is found in poorly drained soils throughout the South West. Native to Europe and western Asia, the herb is one of 21 varieties from the mint family.
It flowers in late spring and summer with mauve flowers that are produced in dense clusters. This flower emits a pungent mint aroma and prefers water courses. Pennyroyal seeds can germinate under water and survive prolonged periods of inundation and remains viable and dormant in the soil for many years. This toxic weed can invade pastures, though is unattractive to grazing stock. The herb may cause respiratory problems in cattle.
Cultivation during the flowering stage is the best long term removal method, as to reduce the seed bank. Kikuyu grass may be able to supress Pennyroyal as they both prefer moist environments. Chemical control is costly with short-term impacts because of regrowth from the rhizome roots. Herbicides must be applied before the flowering stage.
Sydney Golden Wattle (Acacia longifolia)
Acacia longifolia, or Sydney Golden Wattle, continues to be a pest throughout the region. This time of the year it starts making a showy yellow statement in the landscape. A perfect time for locating and removing these woody weeds.
A Sydney Golden Wattle blitz is underway this month in Denmark with the Shire of Denmark leading a weed control program targeting the invasive wattle. Shire officers have been at work mapping known and reported sightings of Sydney Golden Wattle within the bounds of the Shire with a long-term aim to eradicate the weed locally.
Because Sydney Golden Wattle fixes nitrogen in the soil, it is a pathway to weedy grasses moving into farmed and bushland areas. The ideal control time is before seed sets. Fell as close to ground level as possible to prevent resprouting and remove material from site to prevent vegetative regrowth. Small plants can be hand pulled, loosening the soil if need. An annual follow up seedling check is required.
Chemical controls can be applied depending on the situation of the infestation. Eg a thick area of seedlings could be sprayed with a 10% glyphosate solution.
For community members eager to get involved in invasive weed management volunteer programs in Denmark, the Shire encourages people to get in touch with local environmental groups and organisations such as South Coast Bushcare Services, Greenskills and Denmark Environment Centre.
Bridal creeper (Asparagus asparagoides)
Bridal creeper (Asparagus asparagoides) is a declared pest in WA and is on the list of Weeds of National Significance. It is a highly invasive climbing herb or vine arising from a rhizome attached to tuberous roots. It has white flowers with six petals. In spring it produces a berry which contains three to four seeds. Being an early season food source, birds, rabbits and foxes disperse it widely over immense areas. Biological rusts have been used to limited success.
Manual control can be used for small plants and infestations. The rhizomes (main growing points at the top of the soil where the stem emerge) should be removed when hand pulling. If the plant breaks leaving any or all the rhizome, plants will immediately regrow if conditions allow.
The best time to chemically control bridal creeper is coming up (June - late August). Metsulforun can be used with a wetting agent (surfactant) such as pulse. If using in bushland be cautious when applying chemicals as the creeper will inevitably be climbing native vegetation. Use a mister or hand held spray equipment. Be cautious of your proximity to waterways and frogs when using surfactants.
Dolichos Pea (Dipogon lignosus (L.) Verdc.)
Dolichos Pea (Dipogon ligneous) is a twining perennial spreading by seed and rhizomes. It is identifiable by clusters of large pea flowers that are white or pink to purple. The flat seed pod is 2-4.5 cm long and 7-9 mm wide.
Seeds germinate in autumn and germination is prolific after fire or denudation. The seedling forms a woody base within six months. The top growth dies off each summer. The next autumn the rootstock sends up stronger shoots that climb over other vegetation. The seed is ejected explosively from the pods in summer and may be thrown several metres. Stems may form roots and new daughter plants where they contact the soil. The parent may live for more than 10 years.
Dolichos Pea forms dense mats that smothers low growing vegetation and climbs trees and shrubs often breaking branches with its weight.
It increases the soil nitrogen levels which affects the persistence of some species.
Suggested method of management and control. Hand pull seedlings and small plants ensuring removal of all root material; sever the vines of larger plants and leave to dry in the canopy, then dig out woody roots; scrape and paint using 100% glyphosate or foliar spray in highly degraded sites with 1.5% glyphosate; in more sensitive sites, cut the stems off at chest height, lay lower sections on the ground and apply 1.5% glyphosate over them. Soil disturbance can generate mass seed germination. Read the manufacturers' labels and material safety data sheets.
Watsonia spp (W.borbonica hybrid Gladiolus caryophyllaceus)
Many Watsonia species are cultivated in gardens across Australia, the weedy forms are all believed to be garden escapees. Watsonias are erect, perennial herbs forming large clumps similar to gladiolus up to 2 m high with pink, orange or red flowers. The stems arise from underground corms (swollen underground plant stem) and clusters of small corms, these corms are carried along natural watercourses and in roadside drains. Leaves and flowering heads are produced annually, with the plants dying off over winter.
The production of very large numbers of stem cormils has enabled it to become a very successful weed, forming dense stands which exclude other vegetation. Corms and cormils can remain dormant in the soil for a considerable period.
Selective grazing by stock results in desirable pasture species being replaced by Bulbil Watsonia with a consequent decrease in stocking capacity. Wild Watsonia impoverishes soil and crowds out desirable pasture plants. It can cause serious loss of production.
Eradication methods: Remove seed heads. In heavy soil, cut roots with a knife and pull out. Spray or wipe during July/August with Glyphosate or Metsulfuron Methyl