Job's tears (Coix lacryma-jobi)

Also known as: Chinese pearl barley

Job’s tears is a robust, clumping grass up to 2 m tall with distinctive, shiny, oval seeds. It invades wet areas and outcompetes native plants.

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How does this weed affect you?

Job's tears forms dense infestations that:

• compete with native plants in and on the edges of waterways
• alter water flows
• restrict access to water for people and livestock
• can compete with crops such as sugar cane or rice
• limit recreational activities such as boating.

What does it look like?

Job's tears is an erect clumping grass up to 2 m tall. It is an annual plant in subtropical and temperate climates. In warmer climates with no or only mild frosts it can be a perennial plant. There are two main types of Job’s tears. Cultivated types have soft fruit cases, which are easy to remove to get to the seeds and wild types that have hard shiny fruit cases. The following description is for a wild type that has naturalised in NSW.

Leaves are:

• green with a white midrib
• flat and lance shaped with a pointed tip
• up to 45 cm long and 2–5 cm wide
• rough along the margins.

Flowerheads:

• Numerous flowers are produced on stalks 3–6 cm long in clusters at the base of leaves during summer.
• The flowerheads are very distinctive and unlike most grasses there are separate male and female flowers.
• Female flowers are partly enclosed in a round green bead-like structure and 2 feathery, red or white stigmas protrude from the hole in the bead.
• Male flowers are on a stalk that protrudes out of the same hole in the bead as the stigmas. They are in clusters up to 4 cm long, green and leaf-like with yellow stamens. The male flowers drop off as the fruit forms.

Fruit are:

• a dry, one seed fruit that looks like a bead
• white to blue-grey and sometimes reddish or black
• 6–12 mm long
• hard, smooth and shiny
• oval to egg shaped when mature.

Stems are:

• thick and upright
• green
• branched
• often supported by prop roots that protrude outwards near the base of the plant.

Where is it found?

Job's tears has escaped cultivation and grown in several locations on the North Coast over many decades. The most recent infestations are near Lismore and Kyogle. Plants have also been found in the Greater Sydney region. 

It is native to southern and eastern Asia. People have grown Job's tears for thousands of years as a cereal, fodder and forage crop. They have also used the fruit as beads and for ornaments.

What type of environment does it grow in?

Job's tears grows in tropical, sub tropical and warm temperate climates. Most plants grow in moist humid areas and disturbed sites.  Plants can grow from sea level up to 2000 m.

Job's tears grows in a wide range of soil types from sandy to heavy clay. Although it prefers neutral to alkaline soils it can tolerate acidic soils. 

Job's tears often grows along waterways, in shallow water, along forest edges and in wetlands and swamps.

Maps and records

• Recorded presence of Job's tears during property inspections (Map: Biosecurity Information System - Weeds, 2017-2023)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

Seeds

Job's tears produces up to 100 seeds per plant per year. Plants can mature and start producing viable seed after only 4 months. The seeds float and are mainly spread downstream by water. Plants grown from seeds have deeper roots than plants grown from rhizomes. 

Plant parts

New plants can grow from rhizomes. These can be broken off in floods and spread downstream.

References

Areces-Berazain, F. & Rojas-Sandoval, J.  (2017) CABI Invasive Species Compendium Coix lacryma-jobi (Job's-tears). Retrieved 19 July 2021 from https://www.cabi.org/isc/datasheet/15648#toriskAndImpactFactors

Corke, H., Huang, Y., & Li, J. S. (2016). Coix: overview. In Wrigley, C. W., Corke, H., Seetharaman, K., & Faubion, J. (Eds.).  Encyclopedia of food grains. pp184-189. Academic Press. 

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 31/05/2022 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Coix~lacryma-jobi

Technigro, (2010). Weed Watch Job's tears (Coix lacryma-job). Retrieved 31/05/2022 from: http://technigro.com.au/documents/WW%20Jobs%20tears.pdf

More information

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Control

Successful weed control relies on follow up after the initial efforts. Using a combination of control methods is usually more successful.

Prevention

Check sites downstream from known infestations every 4 months so that new plants will not have time to produce seeds. Reinspect controlled sites regularly and kill any regrowth or new seedlings.

Hand removal

Dig up small immature plants if the infestation is small. Remove all of the roots and remove the plants from the site because the rhizomes can regrow.

Collect all of the seeds if mature plants are being removed by hand.

Disposal

Contact your local council for information about how to dispose of Job's tears plants and seeds.

Chemical

Spraying

Spray actively growing plants and ensure that all the foliage is covered with the herbicide. As most infestations are near the water, ensure that the appropriate herbicides are used and avoid run off or spray drift into the waterways.  If plants are fruiting, remove all the fruit before spraying if possible. Dispose of the fruit.

Splatter gun

Splatter guns can be used for dense infestations of weeds that are difficult to reach. The specialised nozzle produces large droplets that allow plants up to 10 m away to be sprayed with limited chance of spray drift. Spray small amounts of concentrated herbicide onto the weeds. It is not necessary to cover all of the foliage.

Herbicide options

See Using herbicides for more information.

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PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: 1 part herbicide per 9 parts water
Comments: Splatter gun application. See permit for conditions.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L with Metsulfuron-methyl 600 g/kg (Various products)
Rate: Tank mixes of up to 2 L glyphosate + 15 g metsulfuron methyl per 100 L water.
Comments: Spot spraying application. See permit for conditions.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: Rate of up to 1:50 herbicide to water.
Comments: Spot spray. See permit for conditions.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
North Coast	Regional Recommended Measure* (for Regional Priority - Eradication) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
	*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here

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Reviewed 2023