What risks can occur when an organism is introduced to control a weed?

While biological control is often considered more ecologically desirable than chemical methods, introducing organisms to manage weeds carries significant risks. The primary danger is that the introduced agent may become an invasive species itself, causing unintended harm to the new environment.12

Key risks include:

• Non-target impacts: Introduced organisms may fail to restrict their feeding to the target weed and instead begin attacking native plant species, potentially threatening local biodiversity.3
• Ecological disruption: As seen with the introduction of cane toads for pest control, introduced species can cause population declines in native prey, compete with indigenous animals, or poison predators that consume them.1
• Secondary pest status: An organism introduced for a specific purpose may spread into unintended areas, such as crops or turf, where it becomes a serious weed or pest itself, as occurred with Kikuyu grass in California.2
• Limited or cyclical effectiveness: Biological control is often only periodically effective; weed populations may recover once the control agent dies off due to a lack of food, leading to unstable, reciprocal cycles rather than permanent eradication.2

Because of these hazards, any release of nonnative organisms requires careful, rational management and rigorous consideration of potential long-term ecological consequences.12