Implementing Invasive Plant Prevention

Successfully preventing the spread of invasive plants on wildlands requires understanding what factors are allowing invasive plants to be successful. The success of invasive plants depends on their ability to disperse enough propagules to overcome the biotic resistance of the plant community they are trying to invade (D'Antonio et al. 2001; Davies 2008; Davies et al. 2008). With high biotic resistance the invader's propagule pressure has to be exceedingly large for successful invasion; however, at low biotic resistance even a few propagules can produce a successful invasion (D'Antonio et al. 2001). Thus, the first step in preventing invasion is to determine the biotic resistance of the plant community and propagule pressure from the invasive plant species. Determining the relationship that exists between propagule pressure and biotic resistance allows for an assessment of where prevention efforts need to be focused (Fig. 4). For example, if the plant community is fairly resistant to invasion, but propagule pressure is large from a nearby infestation, the most prudent decision would be to focus management actions on reducing propagule dispersal and early detection/eradication. It would be ineffective to expend resources and efforts to make small gains in community biotic resistance. However, if the plant community has little resistance to invasion and low invasive plant propagule pressure, then it is imperative to implement management that increases the communities' resistance to invasion and to eradicate new infestations. If the resistance of a plant community cannot be appreciably improved, then a comprehensive program to limit the introduction of invasive plants and to locate and eradicate new infestations must be implemented. The ecology of the invasive plant species and the risk of the plant communities to invasion must be considered to decide on the most appropriate course of action.

High Invasion Risk

-All three strategies should be employed

Moderate Invasion Risk

-Limit spatial dispersal of invader

-Search for & eradicate new infestations

Moderate Invasion Risk

-Increase plant community resistance

-Search for & eradicate new infestations

Low Invasion Risk

-Search for & eradicate new infestations

- Use of other methods are likely inefficient

Low High

Low High

Biotic Resistance

Figure 4. A guide to deciding which management strategies would be most effective at preventing invasive plant species infestations and where the risk of invasion is greatest based upon the biotic resistance of the existing plant community and propagule pressure of invasive plant species.

Successful implementation of invasive plant prevention programs also requires developing wide spread support among land managers and land users. Invasive plant infestations are not impeded by boundaries in land ownership, thus the most successful prevention programs will also not be limited by property boundaries or ownership categories. Cooperative weed management areas (CWMA) may be effective levels to implement multiple-landscape prevention programs, while more specific management may be refined at the watershed level. Prevention can be implemented by adopting adaptive management strategies, where invasive plant prevention across landscapes can be modified based on monitoring the success of previous management actions.

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