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Perhaps our first education about biological control came early with the nursery rhyme lines about the little old lady who swallowed organisms to catch the originally swallowed organism, (e.g. “the little old lady swallowed the spider to catch the fly and swallowed the bird to catch the spider and swallowed the cat to catch the bird”). The simple lesson from that nursery rhyme is that one seemingly simple biocontrol act may require successive unsustainable actions.  Biological control for vegetation management relies on organisms to manifest mortality, reduce health and thus reproduction and density, or out compete the undesired plants. Organisms used for this purpose can range from other desired plants to animals, insects, fish or those that cause disease in the undesired vegetation, such as bacteria, parasitoids or fungi. The most easily implemented biological control strategy on rangelands uses grazing animals (see targeted grazing) such as sheep, goats, cattle and horses (EPA 2008), for targeted grazing on the invasive plant. Humans could be considered as a biological control agent on mesquite encroachment for example (see also cultural methods), by employing alternative uses of mesquite; seed pods ground into flour or used as fodder for cattle, lumber, slash used to fill gullies or other water control structures, fuelwood, biofuel and biochar (Ellsworth et al. 2018). 

The use of biological control for woody plant encroachment is not typical, but there are some examples. Some success has been found by using mesquite seed eating insects such as bruchid beetles to control mesquite invasion in Australia and Argentina. Use of insects should be restricted if possible, to those native to the location and specialists on the target species to be controlled with rigorous testing done before introducing a non-native (Ellsworth et al. 2018). One of the most well-known introductions in the past decade was to control invasive Saltcedar. After rigorous testing and federal approval, the Tamarisk leaf beetle was successfully introduced into North America to control 1.5 million acres of Saltcedar (Tamarisk spp.) invaded and dominated riparian areas across thirteen states in the West (CATB 2012; Kauffman 2005). However, this biocontrol introduction has been so quickly successful at causing Saltcedar dieback that it has had subsequent consequences on the endangered Southwestern willow flycatcher that nests in riparian habitats. Use of such biocontrol measures require proactive monitoring and coordinated partnership restoration efforts to regain pre-invasion native vegetation to avoid a cascade of impacts on other species now relying on the invaded habitat.  

There are three primary strategies or approaches for biocontrol: classical, augmentation, and conservation. Classical biocontrol is an intentional introduction of a non-native agent for long-term control of a target organism (or plant) without the need for supplemental agent releases. Taking an augmentative approach entails a single large release of the biocontrol agent, where the agent does not reproduce or remain in an ecosystem long-term. Lastly, conservation biocontrol does not involve releasing an agent or pest, but rather supporting naturally occurring enemies of the target organism either through providing additional resources, modifying an ecosystem, or protecting the natural enemy to enhance the control. 

In the USA, any implementation of biocontrol that involves the release of a non-native agent should follow guidelines, permitting, and approvals as outlined by the US Department of Agriculture's Animal and Plant Health Inspection Service.

Brush (or shrub) encroachment is a global phenomenon whereby native and nonnative woody species displace grass species (Archer et al., 2017). The shift in a grass- to woody-dominated ecosystem results from complex interactions between many environmental drivers, physical controls, and historical land uses. A widespread conversion of grasslands to shrublands can significantly impact a variety of ecosystem processes and services such as soil erosion, water infiltration, and forage production (Archer & Predick, 2014). Range managers and land owners can employ several “brush management” treatments for reducing shrub/tree cover and help to restore encroached grasslands (Hamilton et al., 2004; Scifres et al., 1985).  

Brush management treatments are broken into four broad categories: biological, chemical, cultural, and mechanical. The following web resources details each method individually and for application in combination to maximize their effectiveness (e.g., Integrated Brush Management Systems) to meet management goals:

In 2018, a series of workshops were hosted in southeastern Arizona to discuss historical and current trends of brush cover; brush management methods and stories of application; and working collaboratively to apply their collective knowledge to meet brush cover goals. Details on this workshop series including agendas, presentations, and videos can be found here:

Much of the Western rangelands are a checkerboarded, interspersed land ownership of private, state and federal public lands. This creates difficulty in accomplishing landscape level vegetation management. One cultural tool that helps this diverse ownership with potentially conflicting opinions work together is Community-based Collaborative Conservation (Charnley, Sheridan and Nabhan 2014). These groups avert conflicts by focusing on evidence-based issues and group education (collaborative learning) in order to reach collective landscape level management decisions on shared goals regarding rangeland natural resources. Collaborative Conservation groups raise the voices of communities with concerns about impacts to their livelihoods because of environmental issues such as: landscape condition changes diminishing landscape productivity, erosion causing soil loss and water quantity and quality declines, endangered and threatened species management, wildfire mitigation and management, enforcement of regulations or fragmentation and development threats (Wilkins et al. 2020). Typically, these groups have a diverse representation of stakeholders from community members (producers, farmers and local residents) to industry and non-governmental organizations, universities as well as state and federal government agency representatives. Public land management agencies (e.g., U.S. Forest Service, Bureau of Land Management and U.S. Fish and Wildlife Service) also have cooperation and collaborative partnership policy mandates for many of their land planning processes. This brings collective action to implement rangelands maintenance and restoration solutions to often complex, cross boundary and interrelated environmental issues. 

Citations see Further Reading