Quick Facts

Quick facts

• Sicklepod (Senna obtusifolia) and Foetid Senna (Senna tora) are vigorously growing woody shrubs growing 1.5-2.5 m tall and 1 m wide
• Both species degrade pastures and are toxic to stock.
• Both species can build up large seed reserves in the soil.
• Management needs to be integrated and strategic in order to achieve control.

What Does It Look Like?

What is it?

Sicklepod (Senna obtusifolia) and Foetid Senna (Senna tora) are vigorously growing, very competitive, woody shrubs growing 1.5-2.5 m tall and 1 m wide. Foetid Senna is usually shorter and senesces 3 to 4 weeks earlier than the main infestation of Sicklepod. They are normally annuals, but can sometimes reshoot after slashing or failed herbicide treatments and last another year.

Leaves are compound and consist of two to four opposite pairs of leaflets each about 1-6.5 cm long by 0.9-4 cm wide, with rounded tips and wedge-shaped bases. There are 1-2 erect glands between the lowest leaflet pairs.

The flowers are yellow, small, about 1-1.5 cm across and have 5 petals.

The seed pod is 10-25 cm long, and 2-6 mm wide and sickle-shaped, and brownish green when mature. When ripe the pods burst open, shedding their shiny flattened dark brown seeds. Both species emit a foul smell when damaged (Land Protection 2006; Navie 2004).

Sicklepod (Senna obtusifolia) is a declared weed in the Northern Territory; however, Foetid Senna (Senna tora) is not.

For further information and assistance with identification of Sicklepod and Foetid Senna contact the herbarium in your state or territory.

Flower colour

Yellow

Growth form (weed type/habit)

Shrub

Where it currently grows? Preferred habitat

Sicklepod and Foetid Senna are generally weeds of disturbed sites, waste areas, roadsides, waterways, crops and pastures in wetter tropical and sub-tropical environments (Navie 2004).

Are there similar species?

Sicklepod and Foetid Senna are closely related to the weeds Coffee Senna (Senna occidentalis) and Candle Bush (Senna alata). Coffee senna has pointed leaflets and upwardly curving seed pods that are square in cross section. Candle Bush has compound leaves up to 60 cm long, with eight to fourteen pairs of leaflets. The seed pods angle upwards from the stems, are 15 to 25 cm long, about 1.8 cm wide, and have prominent wings running along the sides (Van Rangelrooy 2000).

See taxonomic texts such as Flora of Australia Volume 12 (Randall & Barlow 1998) for detailed distinguishing features of Sennas in Australia, as sicklepod and Foetid Senna are similar to many native species of Senna.

Why Is It A Weed?

What are its impacts?

Sicklepod and Foetid Senna were included in the list of 71 species that were nominated by state and territory governments for assessment as Weeds of National Significance (WONS). Following an assessment process, Sicklepod and Foetid Senna were not included as one of the 20 WONS. However, they remain weeds of potential national signficance.

Agriculture: Sicklepod and Foetid Senna are aggressive invaders of pasture and can completely dominate grass species, eradicating pasture growth and excluding stock. Carrying capacities can be reduced by as much as 85%. It is conceivable that properties could become completely unproductive. Although it is generally unpalatable to stock, if eaten, Sicklepod is toxic to cattle. If left to grow in a sugar cane crop, Sicklepod can have a significant effect on yield. Processing contaminated cane can cause machinery breakdowns at sugar mills because of the woody nature of Sicklepod.

Native ecosystems: Sicklepod is also causing concern as an environmental weed in some native ecosystems in Far North Queensland. Its current distribution suggests that it may be able to invade open native plant communities. Feral cattle, feral pigs and the occurrence of natural events such as cyclone, which open up the forest canopy, are likely to enhance the possibility of invasion into pristine areas and it is currently threatening small remnant areas of native grassland in the Wet Tropics. While there is no evidence that Sicklepod is currently an aggressive environmental weed in Australia, this may be because its impact is not yet evident. The information available suggests that its environmental impacts may increase in the future (Mackey et al. 1997).

How does it spread?

Sicklepod and Foetid Senna shrubs are unpalatable to domestic stock. However, cattle and horses will eat mature seed, which can pass through the animal and germinate in dung. This is the most common manner of seed spread from one property to another. Seeds are explosively released from ripe pods with long distance dispersal occurring mainly by water, in mud, with harvested sugar cane by cane bins on tramways and harvesters, or by vehicles and machinery. Seed production is profuse (8000 seeds per plant) and as the seed is long lived, viable for up to 10 years, an abundant seed bank can become established in the soil. Scarification of the seed is required for germination to occur, and sometimes fires can cause mass emergences of seedlings because of this (Mackey et al. 1997; Land Protection 2006; Weeds Australia undated).

What is its history in Australia?

Sicklepod appears to have been introduced to Australia during the Second World War around Darwin. It was first recorded as a weed from the Northern Territory in 1961 and from Queensland in 1963. Foetid Senna was first recorded in Australia in 1871, but the earliest collection was made at Port Darwin in 1888. It established in Queensland in 1917-18 as an escapee from green manure trial plots (Symon 1966; Parson & Cuthbertson 2001).

How To Manage It?

Best practice management

Sicklepod and Foetid Senna can be controlled by herbicide application to seedlings, mechanically such as by slashing, fire, and vehicle hygiene (Mackey et al. 1997; Land Protection 2006).

Chemical control: Herbicide is only effective on seedlings and new regrowth as the cuticle on mature plants is thick and provides protection from herbicides (Mackey et al. 1997; Land Protection 2006).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au .

Non-chemical control: Slashing does not kill the plants but can be undertaken to reduce old plants to a manageable size, and/or to obtain a fair percentage kill if certain conditions are met. Sharp slasher blade cuts will encourage the plant to reshoot so blunt blades should be used to shatter the stems of the plant. Slashing should always be done prior to seed set preferably when plants are flowering. Repeated slashing over a number of years may cause the plants to become procumbent, in which state they can still produce seed. A combination of slashing and spraying regrowth has been successful (Mackey et al. 1997; Land Protection 2006).

Rotary hoeing or discing infested areas and immediately sowing with improved pastures can be effective, provided that the grasses are well managed. Ploughing can be unsuccessful as it can cause scarification of the seed and a proliferation of plants (Mackey et al. 1997; Land Protection 2006).

All machinery should be cleaned on site following mechanical control in order to reduce possible seed spread into clean areas (Mackey et al. 1997; Land Protection 2006).

Fire is only used in controlled management plans as fire scarifies the seed and can cause a proliferation of plants. If used strategically over a number of years it can be a valuable tool for managing sicklepod (Mackey et al. 1997; Land Protection 2006).

Sicklepod and Foetid Senna have also been recognised as a target for biological control through a cross-jurisdictional government process. This allows activities to be undertaken to develop effective biological controls.

Does it have a biological control agent?

YES

When does it grow? (lifecycle/growth calendar)

Both Sicklepod and Foetid Senna are usually annuals but can sometimes reshoot from the rootstock and persist for a further year (Land Protection 2006). Flowering and fruiting occurs from February to August (Smith 2002).

Where Is It Found?

Which states and territories is it found?

NT, QLD, WA

What areas within states and territories is it found?

Sicklepod and Foetid Senna are distributed mainly in coastal and sub-coastal areas of northern Queensland and the Northern Territory. They have also been recorded in central and southern Queensland and in the northern parts of Western Australia (Navie 2004).

Ecoclimatic modelling suggests that Sicklepod could spread along the entire east coast of Queensland and Foetid Senna could grow across the base of Cape York and into the country around the Gulf of Carpentaria (Mackey et al. 1997).

Where does it originate?

Sicklepod is native to the Caribbean region and tropical America while Foetid Senna is native to Asia, from India to China and Polynesia (Navie 2004).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NT, QLD, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Senna obtusifolia

Other scientific names (synonyms)?

• Cassia obtusifolia L.
• Cassia tora var. obtusifolia (L.) Haines
• Cassia tora L. (misapplied by Bentham, G. 1871, Transactions of the Linnean Society of London. 27: 535-536., p.p.)

Does it have other known common name(s)?

Java Bean, Foetid Senna, Sicklepod Senna, Sickle Senna, Chinese Senna, Coffee Weed, Habucha, Arsenic Weed, Foetid Cassia, Wild Senna, Stinking Cassia, Peanut Weed, Low Senna