Introduction

The most effective invasive weed removal techniques consider: species involved, climate, terrain, size of infestation, available resources, and many other factors. The type of control strategy and method(s) vary dramatically from project to project. It is best to evaluate the project area and create a removal plan, using a variety of control methods that best suit the area and infestation involved for both short and long-term success. The following are general descriptions of control techniques used in invasive plant control, for specific weed control recommendations, refer to invasive plant fact sheets.

Strategy

IPM: Integrated Pest Management (IPM) incorporates an ecosystem based control strategy with a long-term goal of preventing invasive exotics. IPM integrates a combination of techniques including biological control, habitat manipulation, manual control, mechanical removal, chemical control and cultural practices to ensure long term prevention of invasive plant species in site-specific situations (LeBlanc, 2001).

IPM is recommended to remove and control most invasive plant infestations, but the combinations of techniques will vary from case to case, depending on species, location, size and many other factors. There is no single successful method when dealing with the removal and control of invasive species. Instead, we will a combination of techniques will target specific issues with each situation.

Methods

No Control: This technique is recommended when the ecological threat from an invasive species is insignificant, or if no further action is needed to achieve or maintain control of the species.

Prevention: Preventing the ability of invasive exotics to enter an area is the most effective method of conserving native species. This includes taking several precautions in areas vulnerable to invasive weed infestations. For example, most invasive plants thrive in areas where ground disturbance has occurred, the key is to seed a recently disturbed area with native plant seeds to encourage regeneration by desired rather than exotic species (NPS, 2001). Educate your community about plant species that are SAFE to use in gardens and yard. Teach your community to identify and handle (if needed) aggressive plants that pose a threat to your area. It is always important to ensure that people check shoes, backpacks, dogs, etc. for invasive plant seeds when before hiking or recreating in wilderness areas.

Manual Control: This method generally involves hand-pulling and digging up weeds using a few simple tools such as weed wrenches, shovels, loppers and pulaskis. This can be an effective technique when infestations and plant species are young and root systems have not fully developed. If repeated diligently over the recommended period of time, manual techniques can also be successful in controlling and eradicating certain invasive non-native plants, such as Scotch broom, Bull thistles, etc.

Mechanical Control: Mechanical control involves the use of machinery such as bulldozers, backhoes, cable yarders and loaders may be used in areas where exotic plant density is high, native species are absent and impacts to other natural or cultural resources are negligible (NPS, 2002).

Prescribed Burning: This technique consumes above-ground vegetation and may kill seeds of invasive plant species or break their dormancy, which also assists in later removal of plants. Fire also affects the composition of native flora, and this may be manipulated to re-establish and support its natural resistance to invasion by non-native species. Personnel working in invasive plant management will work closely with prescribed burn staff to accomplish the multiple objectives of each burn, (NPS 2002).

Biological Control: Introducing natural predators (often insects) is often a successful control method and been effective with many species. FDA testing and approval is necessary, and it is not recommended for all species. Like most control techniques, biological control is most successful when combined with other techniques, such as habitat manipulation.

Waipuna Organic Hot Foam/Water Weed Treatment System: This system consists of a machine with a single or double burner that heats water with organic foam to just under 212 F. The system also has insulated hoses of varying lengths, a 300-gallon water tank, and a generator to power the entire system. The foam sits on top of the water and acts like a lid to hold the heat long enough to penetrate the topsoil and kill seeds in the seedbank. Multiple treatments are often recommended to deplete the energy reserves contained in most infestations (pers. Comm.Jennifer Wheeler).

The BLM Resource Center in Arcata uses this technique on Bermuda buttercup (Oxalis pers-caprae) in the Samoa Dunes Endangered Plant protection area. BLM has leased the machine for 2 years for a cost of $17,000, and states that the technique is very cost effective, but the targeted weeds must be within reach of a trailer and the length of hoses. Removal crews using the Waipuna Hot Foam Application need training to maintain the machine and must have a vehicle that can handle four or five thousand pounds (pers. comm. Jennifer Wheeler).

Habitat Manipulation: Habitat manipulation refers to altering or re-establishing ecological processes in habitats in an attempt to discourage or prevent re-growth of invasive species. Prescribed burns can control large-scale infestations, but this must take place after proper research, in a professional manner with CDF approval, and with close monitoring. Flooding, mulching, or revegetation are other types of habitat manipulation that may be effective.

Grazing: Intentional use of grazing livestock to control infestations of invasive exotic species can be effective. This technique is not recommended for every species since many are toxic and/or undesireable to livestock. Mules and horses can also be used for plowing or pulling out large individual plants.

Chemical Control: The use of herbicides, though not recommended for use in the Mattole watershed, is a commonly used technique for controlling invasive exotics. However, this technique is most successfully used and with minimal negative ecological impact, when combined with other methods and not used as the primary control method.