Strawberry guava biocontrol
Frequently-asked questions (FAQ) about biocontrol (general)

Q. What is biological control of invasive plants?

A. Biological control, or biocontrol, is the introduction of a plant-feeding insect or disease to control the growth or spread of an invasive plant. These natural predators of the plant are from its home range and are part of the web of life that keeps the plant in check for a balanced environment. Biocontrol can help us to sustainably reduce the abundance of weedy plants gradually, but it will not eliminate them completely.

Q. Is biocontrol commonly used to control invasive plants?

A. Yes. Biocontrol is used all around the world. Over 100 countries use biocontrol as a natural management practice to protect the environment and local agriculture from invasive species. In Hawaii, biocontrol has been used for over a century, resulting in successful control of invasive plants such as prickly pear cactus, lantana, pamakani, emex, Klamath weed, and ivy gourd.

Q. Why use biocontrol when other methods to control invasive plants are available?

A. When weeds are widespread and in remote or rough terrain, it is difficult to rely solely on conventional methods of hand pulling and herbicide. Biocontrol is a useful tool with many advantages. It is a sustainable solution that is also more economic for long-term management.

Q. Is biocontrol safe?

A. Biocontrol of invasive plants has been practiced worldwide for over a century. Since the 1970s, the state of Hawaii has developed a strict and careful process to assure that the natural predators used for biocontrol are always host-specific. This means that they are highly specialized to survive only on the particular species that we are trying to manage. Host-specificity tests require rigorous testing and observation. Before a natural predator can be released, it must pass extensive scrutiny and scientific review at the state and federal levels. Post-release monitoring also keeps track of the natural predator's progress. Since the required testing began in the 1970s, there have been over 50 natural predators released to manage invasive plants and insects in Hawaii and not one has switched hosts to another non-target species or become invasive themselves.

Q. What about the mongoose and other disastrous introductions in Hawaii?

A. Mongooses were introduced by a private landowner in the 1800s, not by a state or federal agency. It was done without any scientific or regulatory review and is not at all representative of the modern practice of biocontrol. Today, biocontrol introductions are based on very careful research and testing. Animals like mongoose and cane toad, which feed on a broad range of prey, would never be considered for biological control. The only acceptable organisms are highly host-specific--those that have a single host or very narrow range of hosts and that are unable to survive on other species.

Q. Won't a biocontrol natural predator move on to other plants after killing off its target host plant?

A. Although some natural predators are capable of killing their host plants, biocontrol never results in complete eradication of the weed's population. Instead, as the weed population declines, so does the population of the natural predator. Highly host-specific natural predators are so closely dependent on their host plant that they cannot use other plant species, even when faced with starvation. Biocontrol is reuniting a natural and very specific relationship between the plant and the natural predator.

Q. What about the possibility of the natural predator adapting to attack new plants?

A. Rapid evolution of host switching by a host-specific plant feeder is extremely unlikely because of the many genetic changes that would have to occur. Organisms that depend on plants for their food adapt and change over time, as do their host plants. This process is gradual over thousands to millions of years. Such newly evolved host-switching has never been observed in over 1,000 cases of invasive plant biocontrol worldwide over the past 100 years.

Q. What good is biocontrol given the constant onslaught of new invasive species?

A. Biological control is not a cure-all. Solving invasive species problems in Hawaii requires the integration of a variety of approaches. We need to prevent new introductions of invasive species, rapidly respond to new invasions, and work together on long-term solutions to widely established invasive species that continue to have an impact on our environment, agriculture, health, economy and quality of life. We will need many tools in our tool box in order to address invasive species, and biocontrol offers a natural, sustainable solution to manage some our worst weeds on an island-wide scale.

The Hawaiian Ecosystems at Risk (HEAR) project is currently funded by the Pacific Basin Information Node (PBIN) of the National Biological Information Infrastructure (NBII) through PIERC (USGS) with support from HCSU (UH-Hilo). More details are available online.

This page was created on 23 June 2010 by PT, and was last updated on 23 June 2010 by PT.