Wednesday December 13, 2017

The Marlothii Conservancy

The Marlothii Conservancy is registered with the Mpumalanga Parks Board as an Urban Conservancy and was the first in Mpumalanga to do so. It aims to generate interest and active participation by registered land owners, accredited residents and the business community in the conservation of indigenous and endemic fauna and flora and the protection of the environment in the area based on scientific principles of nature conservation and sustainable utilization of the area's natural resources. The Conservancy exists in partnership with the Marloth Park Honorary Rangers and the Marloth Park Property Owners Association. You can see our registration certificate by clicking here and read a brief historical note by clicking here.

It is advisable to take the time to read this article (compiled March 2013) as the future value of your stand or house in Marloth Park could be severely negatively affected should Parthenium spread uncontrolled in this area. And for those of you who don’t know, it is already in Marloth Park and Lionspruit and spreading rapidly.

 

Parthenium is a “Category 1” weed of national significance. It is regarded as one of the worst weeds because of its invasiveness, potential for spread, economic and environmental impacts.

Scientific name

Parthenium hysterophorus  (Parthenious = virgin; hyster = womb; phorous = to bear)

Common name

Parthenium, Demoina weed.

Family

Asteraceae/Compositae (Daisy family)

Origin

Native to Mexico, Central America, the Caribbean and South America.

During the last hundred years, it has spread worldwide. It is thought to have originated as a result of natural hybridization between Parthenium confertum and P. bipinnatifidum .

Distribution

In South Africa this species is establishing itself in the coastal and sub-coastal districts of KZN and Mpumalanga and is spreading to other areas.

Also spreading in other parts of the world, including majority Sub-Sahara Africa, Madagascar, the Australian continent, the Indian and Asian sub-continent, Seychelles, Mauritius and the American central continent.

Habitat

weed of semi-arid, sub-tropicaltropical and warmer temperate regions. It is found along roadsides, railways and waterways and in pastures, floodplains, grasslands, open woodlands, waste areas, disturbed sites, lawns, gardens and crops. It is particularly aggressive in degraded or disturbed pastures.

The plant is thermo- and photo-insensitive; hence, it grows round the year (dependant on moisture) except in severe winters; in other words, it survives the environmental extremes. It is a rapid coloniser and out competes other vegetation in its vicinity within two growing seasons.

Key points

Parthenium matures quickly and produces large quantities of seed (in excess of 25,000 seeds per plant).

Parthenium can germinate, grow, mature and set seed in four weeks.

Seed bank density up to 95 000 m2.

Parthenium can flower year round.

Parthenium is toxic to game and contact with Parthenium, particularly its pollen can cause allergic reactions such as dermatitis, hay fever and asthma in people. It is best to avoid direct contact with the plant.

Pay close attention to property hygiene. Seeds are spread very easily by people, vehicles, and game fodder (Lucerne).

Do not allow over grazing to take place.

Distinguishing features

An annual (or, under certain conditions, a short-lived perennial) herbaceous plant forming a basal rosette of leaves in the early stages of growth.

Produces upright stems, 0.5-1.5 m tall that are ribbed lengthwise, hairy, and much-branched at maturity.

Leaves are deeply divided (bi-pinnatisect) and smaller towards the top of the plant.

Large numbers of small white flower-heads (4-5 mm across) are borne at the tips of its branches.

Each flower-heads produce five small winged 'seeds' (about 2 mm long).

 

 

 

 

Flowers

Flowering can occur at any time of the year, but are most common during spring and summer, and least common during winter.

Five small 'seeds' are usually produced in each flower-head. These seeds (1.5-2.5 mm long) consist of a black seed, topped with two or three small scales about 0.5-1 mm long, two straw-coloured papery structures (actually dead tubular florets), and a flat bract.

 

Reproduction and dispersal

Enormous numbers of pollen grains (over 600 million per plant) are produced by wind pollination. It is an extremely prolific seed producer with up to 25,000 seeds per plant. These seeds are dispersed by wind, water, animals, vehicles, machinery and in clothing.

Parthenium normally germinates in spring and early summer, produces flowers and seed throughout its short life and dies in late autumn. However, with the right conditions (rain, available moisture, soil and air temperatures), Parthenium can grow and produce flowers at any time of the year and the plant may live longer than a year. In a good season, four or five generations may emerge. In summer, if plants are stressed (eg due to lack of water), Parthenium can complete its life cycle in as little as four weeks. Buried seeds have been found to last much longer than seeds on the soil surface, and a significant proportion can still germinate after eight to ten years.

Once established, Parthenium very quickly builds huge seed banks in the soil that makes eradication difficult.

 

Impact on humans

Parthenium contains powerful allergens that cause a range of human health problems, including respiratory problems, asthma and severe contact dermatitis in sensitised individuals.

Landowners are advised to never touch the plant with bare hands and always use a dust mask if working near the weed for extended periods.

Allergic reactions are not always experienced with the first contact with the plant but can develop after a number of exposures. Once a reaction to Parthenium develops, some individuals may show similar reactions to related plants in the Asteraceae family, of which there are many. This reaction can be so severe that allergic people can be forced to move away from Parthenium infested areas.

In India, a period of 1 to 10 years exposure, resulted in 10 to 20 % of the people being directly affected.

 

Impact on flora and fauna

The impact of Parthenium on game production is diverse (both direct and indirect) affecting grazing land, animal health, milk and meat quality. In grasslands in India with severe Parthenium infestations, stock-carrying capacity has been reduced by up to 90%. 

The impact of Parthenium on natural vegetation production may be direct and indirect. Allelopathogenicity (direct toxicity) due to release of phytotoxic substances such as caffeic, vannilic, chlorogenic,parthenin,                 p -hydroxybenzoic acids, ambrosin and coronopilin inhibit several plants and grasses.

While buffalo sparingly feed on Parthenium, goats readily graze it. In artificial feeding tests in India, buffalo bull calves accepted the weed in mixtures with green fodder with severe consequences. The majority (11 out of 16) developed severe dermatitis and toxic symptoms and died within 8-30 days.

The invasive capacity and alleolopathic properties have rendered P. hysterophorus with the potential to disrupt the natural ecosystems. It has been reported to be causing a total habitat change in native Australian grasslands, open woodlands, river banks and flood plains.  Similar invasions of national wild life parks have been observed recently in Southern India. 

 

Biological control

Biotic factors suppress the plant within its native range compared to its increased fitness or vigour in their absence, as in Australia, India, SE Asia and USA and therefore biological control may offer the best (and only) long-term solution for the management of this weed.

Biological control of Parthenium has been investigated in Australia for more than 30 years.

 

In the 1980s, after preliminary screening in Mexico and final evaluation in quarantine in Australia, six oligophagous or monophagous species were released from quarantine in Queensland, Australia.

These agents (11 in total) have established since their first releases in the 1980s but have not eradicated the weed but have of late been able to contain and control the weed.

  1. A defoliating beetle, Zygogramma bicolorata (removes foliage)
  2. A seed-feeding weevil, Smicronyx lutulentus (lays eggs in flowers, larvae feed on seed heads)
  3. A stem galling moth, Epiblema strenuana
  4. A leaf mining moth Bucculatrix parthenica (larvaefeed on the leaves)
  5. A sap-feeding planthopper , Stobaera concinna

6.      A stem boring curculionid weevil,Listronotus setosipennis (limited success)

The leaf beetle Zygogramma bicolorata and the stem moth Epiblema strenuana cause the most damage. The beetle emerges in late spring and is active until autumn. The moth is established in all Parthenium areas. Its larvae feed inside the stem, stunting the plant’s growth and reducing its competitiveness and seed production.

Z. bicolorata failed testing in Sri Lanka.

Z. bicolorata has been undergoing tests in South Africa since 2003. (Was released mid 2013)

Biological control is one tool that forms part of an integrated management program for large-scale scattered and dense infestations. However, biological control on its own may not eradicate Parthenium infestations.

 

Herbicides

Well known herbicides fail to control Parthenium. Timing of chemical control is critical. They should be treated when plants are small and have not produced seed and when grasses are actively growing to re-colonise the infested area. I.e. Spring.

Maintaining competition is important for the control of Parthenium; therefore, spraying with a selective herbicide that will not kill other species is recommended.

Parthenium is a dicot and grass is a monocot.

Keep a close watch on treated areas for at least seven years and spot spray isolated outbreaks.

When using herbicides always read the label and follow instructions carefully. Particular care should be taken when using herbicides near waterways because rainfall running off the land into waterways can carry herbicides with it.

 

How it spreads

The weed reproduces only by seed and the seed is adapted to dispersal over short distances and localised areas. Dispersal by natural forces is by strong winds, flowing streams and animal movement. Long distance dispersal of seed is solely by unintentional human agency, contaminated machinery, vehicles and produce.

Outward spread from the margins of the core area of infestation, tends to be due to natural forces but spread into clean areas is mainly caused by the movement of seed on vehicles.

More than 340 million Parthenium seeds per hectare can be present in the surface soil, compared to 120,000 native grass seeds.

 

Where it grows

It grows best on alkaline, clay-loam to heavy black clay soils but tolerates a wide variety of soil types. It aggressively colonises areas with poor groundcover and exposed soil such as roadsides and overgrazed areas. It does not usually become established in undisturbed vegetation. (Clean swept properties in Marloth??, watch this space) Parthenium is termed a “disturbance specialist”.

Drought, and subsequent reduced grass cover, create the ideal opportunity for Parthenium to establish. Parthenium is best suited to areas with an annual summer rainfall greater than 500 mm.

 

 

What to do about it

Preventing the spread of Parthenium is the most cost-effective management strategy.

Property hygiene is also important. Double-check machinery (including the interior of the vehicle) moving onto your property. Always wash down vehicles and machinery in the same area to allow easy follow-up control of any seeds that may germinate. Ensure that service provider vehicles eg municipal, electricity, (Vodacom - Peter Craig-Cooper can attest to this) are free of Parthenium seeds. Grading of roads, Two trees/ Park benches at river etc are all currently source areas of Parthenium.

Conservative game stocking to keep a good pasture cover is one of the ways of controlling large-scale Parthenium infestations and preventing new infestations in clean areas. Areas where game congregate, such as watering points, often have low groundcover and are highly susceptible to Parthenium infestation.

 

Control of new outbreaks

Once Parthenium has been positively identified, it is essential to treat isolated patches (before flowering) immediately with herbicides. Watch the area closely for at least seven years as repeated spraying will be necessary to kill new germinations. Don’t pull up plants by hand, particularly if they have already set seed. There is a danger that mature seeds will drop off the plant and increase the area of infestation.

 

Mechanical removal

Hand removal or cutting is not recommended on mature Parthenium plants as seeds are further dispersed. It should only be done if the plant has not reached the flowering stage. So cutting it, only provides a false sense of security for a few weeks.

 

Burning

Burning is not a useful control strategy for Parthenium. However, research suggests that burning for other purposes (eg woody weed control) will not result in an increased infestation of Parthenium so long as the ground is allowed to recover before game are introduced. Burntareas, once they start to recover are known to attract higher game numbers than normal which results in overgrazing, trampling etc This decreases the natural vegetation competition for Parthenium, ultimately creating a more serious infestation.

 

Summary

Prevention is better than cure, so at least monitor your own stand and this should include adjacent stands. Herbicide at present is probably the best form of attack.

Be warned, once Parthenium has established in an area it will be extremely difficult if not impossible to eliminate it.It will require absolute dedication to that area for a period of possibly up to 10 years before success is achieved. There are already large established infestations along the Seekooi Road and at a number of other “viewing spots” in Marloth Park and Lionspruit.

It “steals” grazing ground from our game which will result in increased culling being required. In times of stress, animals may resort to eating Parthenium with dire results, probably resulting in death.

Bio control may be the one thing that can halt or reduce the spread of this plant, this could be years away or may never happen at all in South Africa.  (Update: Zygogramma bicolorata and Smicronyx lutulentus were both released in SA during 2013) See other article.

Parthenium is at present probably the single most serious threat to Marloth Park and must not be under estimated.

 

 

Most of the above information was provided by Dr’s Andrew McConnachie and Lorraine Strathie from the South African Agricultural Research Centre. (ARC) and also from the Australian Department of Agriculture. Should you not be convinced about how serious a problem Parthenium is then Google “Parthenium” and see for yourself.

 

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