Searching for and Eradicating

Strategically searching for and eradicating new infestations is a critical component of a successful prevention program because uncontrollable and random events may still lead to new infestations even with the best management of community biotic resistance and invasive plant dispersal. Searching for and controlling new invasive plant infestations is a more effective strategy than trying to control large infestations (Moody and Mack 1988; Smith et al. 1999). However, time and resource limitations coupled with the vast nature of wildlands make searching all areas for new infestations untenable. This suggests a critical need to employ a strategic approach for planned searches. Areas where invasions are likely to occur should receive priority for planned searches. One of the most logical ways to systematically search for new infestations is to search around established infestations and along potential vector pathways. For example, horses using recreation trails can be major long-distance dispersal agents of invasive plants (Wells and Lauenroth 2007), suggesting recreation trails are a potential vector pathway and a logical choice for planned searches. If an invasive species is primarily wind dispersed, searching downwind of established infestations would provide the most return on resources expended. Searching areas that have been heavily disturbed should also receive priority because only a few propagules are required to establish a new invasive plant infestation when biotic resistance is low (D'Antonio et al. 2001).

An economical tool for increasing detection of new infestations is to capitalize on opportunities where inventory of new infestations can occur as a secondary activity with other planned activities. For example, in rented grazing allotments, livestock producers could be educated about existing invasive species infestations and/or new invasive plant threats. Livestock producers and/or their employees could then document any new infestations located during normal livestock management activities. When livestock are removed from the grazing allotment, livestock producers would be contacted to obtain any information gathered. This is just one example of several existing opportunities to search for new infestations across large areas while expending few resources. Other opportunities include using recreationists, wildland fire fighters, university students, and road maintenance personal to inventory invasive plant infestations during their normal activities. This highlights the need for public education and awareness of invasive plants.

Once new infestations are located, eradication should be attempted. The smaller the infestation and earlier it is detected, the greater the chance for successful eradication. Eradication efforts are usually confined to infestations smaller than one hectare (DiTomaso, 2000); however, larger scale eradication projects are possible. Larger scale eradication projects are usually attempted on invasive species that have relatively few populations but threaten economic and ecological losses across vast areas. The goal of eradicating new invasive plant infestations is to limit reproduction and subsequent development of a seed bank. Intensively managing small infestations for eradication can protect much larger areas (Pokorny and Krueger-Mangold 2007). Eradication should be viewed as an iterative approach in which the original treatments are monitored for several years and retreated if necessary. Follow-up monitoring, even if the eradication effort appears successful, will be required to ensure that invasive plants do not return from the seed bank and to prevent other invaders from occupying the spaces vacated by the eradicated invasive plant and/or non-target plants that suffered mortality from the eradication treatment.

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