The importance of establishment of newly released agents

Once permission to release has been granted, success is dependant initially on the successful establishment of the control agent. However, in many instances too little attention is given to establishment of agents.

A release cage, for releasing the Emex weevil onto Emex australis.

Successful establishment depends on:

Releasing water hyacinth moth onto Water hyacinth in Papua New Guinea.

If the researcher does not take responsibility to offer an agent the best conditions for establishment then the chances of establishment and of subsequently controlling the weed are reduced.

Releasing salvinia weevil onto Salvinia in Papua New Guinea.

The weed, in its exotic range, may have a wider tolerance of the environment than the agents being released. Releases made into areas unsuitable for the agent are doomed to failure. Release strategies should be planned so that the agent is liberated into a wide range of habitats, ecoclimatic conditions and different seasons to assist establishment and increase the likelihood of successful control. For example, salvinia weevils released in temperate climates in mid and late summer had insufficient time to develop viable populations and survive winter. Releases made in early and mid spring resulted in establishment and eventual control of the weed.

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