Prevention and Early Detection
The most effective, economical and ecologically-sound approach to managing invasive plants is to prevent their invasion in the first place. Often limited resources are directed to fight firmly established infestations, but by that stage management is expensive and eradication is probably impossible. Certainly it is necessary to manage infestations to limit the spread of invasive plants into non-infested areas. However, limited resources might be spent more efficiently on proactive invasive plant management that controls existing infestations but also focuses strongly on prevention or early detection of new ones.
Prevention and Early Detection Guidelines
Plant invasions often follow a typical pattern. Seeds or plant fragments arrive by various mechanisms and become established; however, the persistence of these new individuals is tenuous because of unsuitable habitat or low population levels. If the plant invaders persist, it takes some time (the lag phase) for the population to increase in size. Only after a time specific to species and habitat has elapsed does the population suddenly expand. Control efforts are most cost-effective and likely to succeed during this lag phase. Thus the early detection of newly arriving exotic plant species is an important component of a control program. Unfortunately, these newly establishing populations are rare and consequently difficult to detect.
Prevention and early detection activities can be focused at different scales. A land manager of a 2,000-acre state park may be limited to focusing prevention efforts on that specific landscape. Invasive species may be well established in other parts of the region or state, but may be new to the 2,000-acre state park. On the other hand, land managers may have the ability to work beyond the borders of their state forest or state park. Having this larger focus will result in greater success in keeping unwanted species off protected natural lands.
Prevention techniques may include:
- Checking soil, mulch, or other materials that may be brought to a new site for invasive plant presence.
- Cleaning equipment, gear and clothing when moving between sites where invasive plants may be present.
- Moving your activities from the least infested site to the most infested site to avoid bringing in invasive plant propagules to a new area.
- Use certified seed for restoration, landscaping, and lawns to decrease bringing in unwanted invasive plant seed.
Watch List Species
Another focus for prevention and early detection activities is on species that are not yet well-established in Pennsylvania or a region of Pennsylvania (e.g., eastern PA or western PA). In addition to known species, there are a number of species that experts believe may be future problems for Pennsylvania’s natural areas. These species have been observed acting invasively in natural settings in other parts of the Mid-Atlantic region. Of greatest concern are invasions in bordering states with similar habitats. These species are included on the DCNR Watch List and should be a major focus of any EDRR efforts in the state. Recording the presence of these species on shared networks like EDDMapS allows other concerned land managers to view the introduction of a new invasive plant.
Getting Started on EDRR
Early detection of non-native species should be based on a system of regular surveys to find newly established species. However, not all species will become established, and only a small percentage of those that do will become invasive, presenting threats to biodiversity and the economy. Thus, some surveys will need to focus on specific target species known to be invasive under similar conditions or species that have been successfully eradicated before.
In addition, site-specific surveys looking for non-native species in general can be carried out. They should be targeted at key sites, e.g. areas of high conservation value, within the range of highly endangered species, and at high-risk entry points such as airports and harbors (logging roads, trail heads, parking lots). The drawback of these general surveys is that only well-trained staff will be able to identify non-native species in many taxonomic groups.
A crucial part of early detection is a contingency plan, which determines the action to be taken when a non-native species is been found. Given the diversity of potential new incursions, an initial plan will be rather general. It should summarize the stakeholders and experts who need to be contacted for a more detailed action plan. Contingency plans targeted at specific high-risk species can be very efficient, with an exact schedule for what to do.
Please refer to the Monitoring and Evaluation Section for important information on monitoring for potential new invasive species.
1. The National Invasive Species Council has developed general guidelines for the establishment of invasive species EDRR systems, which can be downloaded here.
2. The National Park Service has developed an Early Detection of Invasive Species: Surveillance, Monitoring and Rapid Response document that can be downloaded here.
3. Factsheets on avoiding transporting invasive plant hitchhikers during your recreational activities can be viewed here under "Characteristics and Impacts".
Contract and Bid Language
For all projects, general prevention measures can have a great effect on keeping invasive plants out. The following activities will help with preventing the introduction or spread of invasive plants and you can build them into your contract as requirements by the operator:
- Inventory the site for presence of invasive species prior to disturbance. If invasive plants are present, pre-treat with appropriate control methods to ensure they won’t spread during project activities.
- Wash all equipment prior to bringing it on site to be sure it is free of any soil or plant parts from previous work areas. Equipment may be inspected before entering a site to be sure it is clean and ready for use. Truck powerwash stations may be used to clean equipment; provide addresses or locations of the facilities in your area.
- Be sure to require only weed-free soil, mulch, gravel and other materials used in the project. Often, invasive plants can be introduced through the materials brought onto the site. You can inspect source materials for presence of invasive species or use reliable sources. Mulching with straw rather than hay can reduce the chance of unintended invasive species introductions.
- Seed all disturbed areas and exposed soil with suitable mixes that do not contain invasive species and are suitable for soil and erosion control. Depending on what the long-term use of the site may be, you can incorporate native grasses and herbaceous plants to occupy the site and provide wildlife habitat. Keep in mind that invasive species contamination can occur during seeding activities and be sure the equipment being used to spread seed is clean and free of any previously-used seed “hitch-hikers”.
- Monitor the site while it is being revegetated to ensure desired species are growing and invasive species have not come in. If invasive plants are present, treat with early detection methods.
Depending on your project, you may be able to require the contractor or operator to do long-term inspections of the site to be sure desired vegetation is growing and invasive species are not introduced. This can be done where the contractor may have benefits gained on the site even after construction is complete, such as oil or gas development projects or rights-of way. Requiring the contractor to monitor the site for invasive plants and treat any invasive plants that may appear for a length of time after construction, say five years, may help in keeping these unwanted plants from establishing. This can be as detailed as requiring annual formal monitoring with reporting to simply requiring treatments when you notice invasive plants on the site.