Practitioners in biological control of weeds agree that there are a
number of steps which should be followed in a biological control program.
Initially it is important to have agreement that the target plant is a
weed and should be controlled. In the past, many weeds were selected as
targets for biological control because mechanical and chemical methods had
proven ineffective or too expensive to apply repeatedly. It is now common
for biological control to be assessed as an option for weed control in
parallel with other control methods. The regulations to import and release
biological control agents differ between countries. Some countries have
few regulations while others have a system where several departments may
have to be convinced that the risks are minimal before a biological
control program can proceed.
The following is a summary of the crucial steps involved in a classical biological
control program. Details on each of the major procedures are presented in
other sections of this CD and in Harley and Forno (1992).
Click on the name of the step you are interested in to see a drop down summary
of that section, or click on the link beside the name to go to that section of
the CD.
 | 1. Project initiation (go
to section)
 | Select the target weed, identify any conflicts of interest as to why
it is a weed rather than a useful plant and, if possible, resolve
issues before the program commences. |
| Review the literature on the target weed to find out all that is
known on the biosystematics, distribution, economic importance and
management strategies. |
| Review the literature on the natural enemies of the plant, their
biology, host range and use as biological control agents against the
weed in other countries. |
| Compile data. |
| Determine whether any other institution worldwide is working or has
worked on biological control of the target weed. |
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| 2. Approval to work on the weed (go
to section)
| Prepare an application, using data assembled, to seek approval
and/or funds from the target country to work on the weed. |
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| 3. Foreign exploration (go
to section)
| If an exploratory phase is necessary, find out the procedures for
working in the country/s of the native range of the weed and for
exporting insects and pathogens from these countries, and
establish connections with appropriate institutions. Permission to work on and/or export insects and pathogens may require formal linkages with institutions within the country to be explored. It may take more than a year to obtain the necessary documentation to export. |
| Establish a base within the native range which is close to an international airport or which has good connections to international services and, if possible, close to institutions which may be of assistance. |
| Search for potential control agents through well planned surveys which take account of the distribution and centre of origin of the target weed, closely related plants and seasonal variation in the abundance of natural enemies of the target weed. |
| Have specimens determined by specialist taxonomists. |
| Prepare an inventory of insects, mites and pathogens that attack the weed. |
| Assess those which have potential as biological control agents (See Prioritising
Weed Biological Control Agents). |
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| 4. Surveys in introduced range (go
to section)
| Survey the weed in the introduced range to determine the fauna using
the plant as a host. |
| Establish whether the fauna are native to the target country,
whether there are species apparently not native attacking the plant
and in particular, check the identity of fungal pathogens and compare
with those found in the native range. |
| Have specimens determined by specialist taxonomists. |
| Compile data. |
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| 5. Ecological study of the weed and its natural enemies
(go to section)
| Study and, if possible, compare the ecology of the weed in its introduced and native range. This may give some indication as to why it is a weed outside its native range and whether it is a good candidate for biological control. |
| Study the ecology of potential biological control agents including their use of related plants. Knowing the ecology of potential agents before introduction to the target country may assist in predicting how and where they should be released to ensure establishment and likelihood of having an impact on the weed. |
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| 6. Host specificity studies (go
to section)
| Seek approval of the list of plants to be screened to determine the
host range of an agent by submitting the list to the regulatory
authorities in the target country (See Compiling
a Plant List). |
| If possible carry out some preliminary host testing of potential
biological control agents in the native range. Document the presence,
feeding, oviposition and development of these agents on the host and
other related plants in the field. This information will assist in the
interpretation of laboratory host screening tests. |
| Either complete the host testing outside the target country or seek
approval to import the agent into an approved quarantine facility for
completion of the host screening trials. |
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| 7. Approval to import agents (go
to section)
| Prepare and submit to the regulatory authorities in the target country a report containing all available information on the biology and host range of a particular biological control agent. |
| If host screening has been completed outside the target country, then the regulatory authorities may approve importation of an agent and grant approval for release of the agent at the same time. Often the authority will request that the agent be taken through one generation in a quarantine facility to overcome the risk of importation of unwanted contaminant organisms before release. |
| If host screening has been partially completed outside the target country, then approval may be given to import the agent into a quarantine facility for completion of the host screening tests; a separate approval will be required for field release of the agent.
If host screening has not been done outside the target country, then approval may be given to import the agent into an approved quarantine facility for host screening. Again, separate approval must be sought for field release. |
| Sometimes an agent has been host screened by another country and then approval may be granted to import the organism either without further testing or with further testing using a much reduced plant list. |
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| 8. Importation for release (go
to section)
| Upon importation, each agent is usually reared through at least one
generation to eliminate parasitoids and insect pathogens. |
| Where the agent is certified as being disease and parasitoid free by
the supplier, it may be released in the field but only after transfer
from any packaging or plant material which has been imported. |
| All imported plant and packaging material must be destroyed,
preferably by autoclaving or incineration. |
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| 9. Rearing and release (go
to section)
| Upon completion of quarantine procedures, compile a report for the regulatory authorities. The report should contain detailed information on the biology and host range of the biological control agent and an assessment of any risk to other flora. After receipt of approval for release, the agent is mass-reared and released in the field. |
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| 10. Distribution (go
to section)
| Collaboration with other institutions is often essential to ensure
rapid and widespread distribution of agents. Distribution may be from
laboratory colonies or from field sites where the agents are abundant. |
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| 11. Establishment (go
to section)
| We can only be confident an agent has become established
after monitoring shows not only that the liberated insects have survived, but
also that new generations have appeared. |
| Under some conditions there may be a lengthy period before we can be
confident of establishment. If liberations are performed in a region with
extremes of climate, the agent's population must also have survived the
less favourable period before we can be confident of agent establishment. |
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| 12. Evaluation (go
to section)
| Field studies are undertaken to determine establishment, spread and
effect of the biological control agent on the weed. Complementary
laboratory studies may be undertaken to assist in the interpretation
of field data. |
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