Foreign Exploration For Biological Control Agents

Biological control of weeds is mainly done by using herbivores or pathogens from the weeds natural environments.  It is within this native range that a large number of natural enemies, herbivores and pathogens, are found, and have had millions of years to adapt to the plant.  Thus the first step in a biological control program is the search for natural enemies to control the target weed that has been introduced.  These foreign explorers filter among the enemies and look for species to control the weeds.

A lengthy process must be followed and approved by the International Code of Best Practices for Classical Biological Control of Weeds, which includes the plant being labeled a noxious weed and being targeted for biological control.  Then foreign exploration starts and may continue for years.  The goals for this experimental period are to thoroughly observe the native environment of the plant targeted and then collect and define the host range of herbivores and pathogens.  Sometimes release agents are approved within 18 months, but usually the process is much more extensive.

State and federal agencies as well as miscellaneous stake holders help to fund this expensive foreign exploration.  An estimated $250,000 for each target weed per year is the minimum amount needed for this type of biological control research.  Research laboratories are located overseas and nationwide in order to find these agents in their native habitats.

Process of Exploration
The first step in the exploration process involves an extended survey of available material on the plant species and a climate comparison between the plant here and in its native range.  Next, the exploration begins over the entire area where the target plant is native (many of our Montana weeds come from Eurasia).  Such things as moisture, temperature range, altitude, etc., are then studied.  Surveys are done to look at many things including; the season, soil type, and even do night surveys to try and cover all aspects of the studied species.  Right at the site the natural enemies are searched either from plants, or samples of collected plants. 

When they think they have found a possible biological control agent, the agents are collected right from the plants.  This may be done using hands, or an aspirator (bug sucker).  Next, these specimens are sent to taxonomists.  There they are identified and molecular geneticists characterize them.  When the agents are labeled as a new species a representative specimen is made as the holotype.  During each collection field data, site descriptions and field data sheets are filled out.  These include:  name, locality, latitude/longitude, topography, vegetation, collection date, time, and many other categories. 

These agents are then sent to laboratory colonies (still on the continent of origin).  Here they can be studied and observed.  At these laboratories, many detailed studies are done such as:  host range, impact assessments, and exportation to U.S. quarantine facilities. 

Usually in a 2 to 3 year span, the agents are monitored.  During this time the information is used to know the growth stages of the weed and the agent.  This allows us to know when the next biological control release should be, and how successful the agent has been. 

To sum up foreign exploration, it can be done in 7 steps.  First, there are observations for the host range.  Next, the agents are taken to laboratories where they are looked at as biological control agents.  Then, there are many studies done which include:  biological studies, starvation studies and weed impact studies.  Finally, the agent is released and observed on how well it is working.  As soon as these steps are done, the USDA Animal and Plant Health Inspection Service Plant Protection and Quarantine can approve the agent.  Right after this is done arrangements to ship the agent to North America and do more studies and trial releases, are made.

Clark, Janet K. Biological Control of Invasive Plants in the United States. N.p.: Oregon State
University Press, 2004.

By M. Battaiola, WHS student, 2/2005.

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