Biocontrol

Biocontrol is the use of host specific organisms to control weeds through direct predation.

This method of control is suitable where specific agents, approved by the Department of Agriculture and Fisheries, based on extensive suitability testing.

The conditions under which biocontrol will work vary greatly from one agent to the next, however it can be broadly said that this method is suitable for controlling large areas of weeds that are difficult to access otherwise or where alternate control methods cannot be applied. In individual cases it may also be singularly effective or effective in conjunction with strategic herbicide control.

Before you attempt to implement biocontrol, make sure:

  • you have identified target weeds correctly (all are host specific so if the weed is miss-identified there will be no response at all)
  • you can obtain approved agents from a reliable source
  • you have a good understanding of the likelihood of success and have considered the need to integrate biological control with other methods of control
  • that adequate measures have been implemented to prevent dispersal when transporting materials

Equipment

The equipment you will need is:

  • hat, safety eyewear, long-sleeved shirt, long pants, covered footwear
  • suitable storage (sealed containers or bags)

Now you are ready to start deploying biocontrol agents to your weed infestations. For large areas tractor slashers are most appropriate while a mower or whipper snipper may be suitable for small to medium areas. Whipper snippers are usually used in conjunction with both machines to manage areas not accessible to the larger machines, for example along fence lines.

Deploying

It is crucial to the success of biocontrol to have a good awareness of the agent’s preferences. For example Cyrtobagous salvinniae (the Salvinia weevil) is:

  • host specific (meaning it can only eat, shelter in and breed on Salvinia molesta)
  • is semi-aquatic (must have access to water)
  • and is warm climate adapted (reproduction can only occur between 20°C and 36°C)

Therefore, to establish a population of agents, the weed infestation must be: healthy and actively growing, must have reasonable depth of water and no layering of the weed and good sunlight exposure.

This means that the best place to deploy them is typically toward the middle of the water body where depth and sunlight infiltration are greatest.

Occasionally, it is also useful to spray peripheral areas to create a portion of 'clear water' to reduce layering.

More information

For more information or if you would like a copy of the fact sheet mailed to you, send an email to the Pest Plant team.