Bellyache bush is an invasive rangeland weed of Northern Australia.

Biological control of bellyache bush

A jewel bug is the first biological control agent to be used against bellyache bush, a toxic weed in Northern Australia.

• 15 January 2008 | Updated 14 October 2011

• Background
• The project
• Biocontrol agents
• Researchers and collaborators

Background

Bellyache bush, Jatropha gossypiifolia (Euphorbiaceae) is a serious weed of Northern Australia.

It invades rangelands particularly in riparian zones, forming dense thickets which:

• eliminate useful species
• reduce productivity
• hinder mustering.

All parts of the plant, especially the seeds are toxic and ingestion causes death in grazing animals, a problem that occurs especially during drought.

In the Weeds of National Significance prioritising exercise, bellyache bush was rated as number 21. The standing committee on Agriculture and Resource Management has endorsed the weed as a target for biological control.

Bellyache bush is native to the American Tropics but has become widely naturalized elsewhere in tropical regions where it has been introduced as an ornamental and medicinal plant.

The project

Surveys for natural enemies were conducted in the native range of this weed, including tropical America and the Caribbean.

Surveys of natural enemies are one of the first steps in a biocontrol project and include:

• collection
• rearing
• curation
• identification
• cataloguing.

Eight countries in the native range of this weed were visited.

Searches were made at 177 locations, with some locations visited multiple times to generate 220 collection events.

Thousands of insect specimens were collected and sent for identification.

A relational database was designed and all data entered for secure storage and querying.

A preliminary list of phytophagous insects was compiled, consisting of 60 species in 21 families and four orders.

One species of fungus was also collected.

Higher priority potential agents were identified according to their abundance and the damage they inflict in the native range.

Biocontrol agents

The most promising agent proved to be a seed feeding Scutelleridae Agonosoma trilineatum.

This insect was first released in Australia in 2002 in Queensland and the Northern Territory, and was the first biocontrol agent for this weed to be used anywhere in the world.

Preliminary studies on Phakopsora jatrophicola, a rust fungus, also indicate its potential as an agent.

Several lines of evidence suggest the prospects for biological control of bellyache bush are good. These include:

• a moderately large suite of natural enemies attacking this plant in the native range
• the plant is less vigorous in the native range and we attribute this to herbivory
• no plant species in the tribe Jatropheae occur naturally or are economically important in Australia.

Agonosoma trilineatum is a biocontrol agent of bellyache bush.

Bellyache bush forms dense thickets crowding out other plant species.

This weed is also a serious problem in East Timor and east Indonesia.

These countries would benefit from the extension of Australian research activities.

Bellyache bush was included in the Cooperative Research Centre for Australian Weed Management (Weeds CRC) as a case study of an invasive rangeland shrub.

Researchers and collaborators

Key research staff involved with bellyache bush the project included:

• Dr Tim Heard - CSIRO Entomology, Queensland, Australia
• Mr Richard Chan - CSIRO Entomology, Queensland, Australia
• Mr Ricardo Segura - CSIRO Entomology, CSIRO Mexican Field Station, Mexico.

This project involved close cooperation between:

• CSIRO
• Biosecurity Queensland, Department of Primary Industries and Fisheries (DPIF)
• the Northern Territory government weeds branch (NRETA)
• Meat and Livestock Australia (MLA).

The biological control work is being conducted by CSIRO with funding input from the Northern Territory government.

DPIF have simultaneously been working on other management options.

In 2006, MLA initiated funding for further development of new biocontrol agents, allowing the project to re-start.

Mass-rearing and release of agents that have been approved for release is being done by DPIF and NRETA.

Evaluation of agent impact will be done by DPIF, and has already commenced with baseline ecological parameters collected for comparison with data after agents are established and damaging plants.

CABI BioScience, United Kingdom, assisted with pathogen work.

Learn more about the Steps in a weed biological control program.