The evaluations of the following methods for the control of exotic and invasive plants in natural areas are based on experiences gleaned since 2004. Over these years, we’ve been across a tremendous amount of acres and have performed all of these activities at one time or another. We have had the opportunity to perform all initial and follow-up work through to the eradication level on a significant portion of the area mentioned. This has allowed for the rapid advancement of our understanding of the subject and provided the privilege of watching how well these natural areas mend and maintain themselves once the invasive pressure is eliminated. The intent of this writing is not to criticize, but rather to promote a reexamination of commonly used approaches in addressing this problem of extreme magnitude. In order for efforts to be successful in maintaining a healthy, diverse ecosystem across the totality of affected (infected) area, it is essential that those efforts are fruitful.
Unfortunately, we have also encountered too many previously failed attempts at control in our travels. It is essential to match methods, herbicide choices, and site specific concerns in order to maximize effectiveness and the efficient utilization of available resource conservation dollars. The most common error observed in the evaluation of invasive control projects has been that humans seem to interpret their ability to see further and walk around more easily as an improvement, whereas the offending plant populations may be the same or greater, just shorter. A “cleared” area or defoliated shrubs often produce the illusion of control, only to have the infestation again become more evident in a year or two. Another frequently observed flaw in the evaluation of previous treatment is the interpretation of the “acceptable” collateral damage incurred during the treatment process in that although the targeted invasive plants may have been killed, an environment is yielded that has native flora and fauna being impacted in a manner only conducive to future infestations and a reduction in overall forest health.1 The old phraseology of “not throwing out the baby with the bathwater” seems applicable here. The net effects of ineffective treatment techniques or implementation are often not apparent until one or sometimes more subsequent growing seasons have occurred.
It is hoped that as time allows, more detail and photo documentation can be published here that support these observations, but for now I hope some basic guidance in method selection by this outline can be conveyed.
1 Some of the potential collateral damage may not yet be accurately identified as related to the overall effect of the introduction of toxins. (Read more under herbicides link)
Manual pulling
Advantages:
-low initial cost
-no potentially hazardous chemicals utilized
-can be effective on some herbaceous species in small areas
-can serve to limit seed dispersal if plant development is too advanced for other methods
Disadvantages:
-treatment is limited to the growing season
-slow
-physically demanding on participants due to repetitive bending
-requires management/disposal of pulled material
-results in disturbed soil, favoring further establishment of invasive species
-can result in increased populations (stem count) if utilized on the wrong species
Foliar Treatment
Advantages:
-potentially allows for large areas to be treated rapidly
-allows for reliable, effective control of herbaceous species if performed appropriately
Disadvantages:
-treatment is limited to the growing season
-always produces some collateral damage to native plants with potential for catastrophic damage
-only affects susceptible species at the time of application
-exposes all organisms to herbicides within sprayed areas and to those animals moving through or eating in areas of treatment (above and below the soil surface) exacerbated with aerial foliar applications
-results in operator exposure in most all extensive applications
-requires substantial volume of herbicide solution
-creates an avenue for the development of herbicide resistant invasive plants
-frequently results in compromised effectiveness on “woody” species if the scale of the targets is too large for the herbicide(s) selected, rate, and volume utilized
-risks of damage to offsite plants (potential for drift)
-when utilized on woody species, this method makes future dormant season treatment difficult
-results in standing skeletons that tend to impede future needed follow-up treatments
-can result in aesthetically unappealing “brown out” conditions
Cut Stem Treatment
Advantages:
-can be performed in any season
-precise, targeted herbicide application is afforded
-can be utilized with low risk of operator exposure
-results in effective control of all woody species if performed appropriately
-enhances degradation of cut materials
-requires less total volume of herbicide solution
Disadvantages:
-impractical on high population herbaceous species
-more time consuming than some types of foliar applications in some situations
Prescribed Fire
It is the current position of Rock Road Ecological LLC that prescribed fire should not be implemented in our region prior to an initial invasive plant control pass. Although it may visually improve the appearance of a site, little control is actually afforded relative to a reduction in the populations of invasive plants present and the fire serves to increase the stem count by producing a greater number of stems sprouting from the root crown. Some of the invasive species that have become much more common to nearly all sites in this region are stimulated to produce root suckering that will increase the costs and severity of an infestation as well as limiting future management decisions with regard to their control.
Advantages: (when implemented after an initial control pass)
-large areas can be handled in one day
-seeds and some seedlings can be controlled provided enough high value fuels are available
-necessary maintenance tool when feasible
-candling provides den trees
-enhanced native plant emergence
-reduces physical impediments to follow-up treatments
Disadvantages:
-subject to weather conditions
-risks of escaped fire
-generally requires trained and experienced personnel
-extremely high insurance costs
-may increase soil erosion potential on some sites
Basal Bark Treatment
Advantages:
-??????? maybe less strenuous than some?
Disadvantages:
-slow
-operator exposure from at least vapors
-expensive materials
-highly toxic material usage
-vapor drift
-potential for water contamination
-carry over likely
-remaining killed plant material unsuitable for habitat
-difficult to ensure complete treatment of an area
-limited to less than 6” DBH by label
-requires careful monitoring to ensure herbicide maximum per acre rates are not exceeded
Mastication:
Advantages:
-can be performed in any season
-fairly rapid
-provides major structural change
Disadvantages:
-limited in challenging topography
–does not provide control without additional treatment
-produces major soil disturbance favoring further infestations
-very difficult to clean equipment adequately to avoid propagule transmission
-often results in major collateral damage to native species
-high equipment cost
-highly skilled operators required
-transportation challenges
Best utilized when:
-rapid structural change is needed
-starting over in an area that was formerly abandoned with negligible native presence, (IE. ag fields, oil fields, postindustrial areas, electrical distribution easements)
-a treatment plan is in place to address resulting regrowth