The realization of the need for the use of herbicides in the management of invasive plants was difficult for me in that previously my interests had been in organic agriculture and our own dairy/crop operations had been trending in that direction. Manual non-chemical control may be a viable option in some situations when addressing herbaceous (non-woody) species and we are still pursuing non-herbicide options that can demonstrate effectiveness. On woody plants however, site data gleaned from Rock Road Ecological LLC’s project history indicates that manual control of invasive shrubs (hand pulling or the use of “poppers”) results in double to triple the subsequent control cost. Except in soil conditions when shrubs can be removed easily with all roots intact (rarely occurring on some soil types) the underground portion(s) of these shrubs remain viable and will subsequently produce growth that exhibit an increased number of stems and in some circumstances yield additional shrubs which may not be apparent for a year or possibly more. This can only be fully verified by the excavation of the root structure although above ground clues are provided in the altered growth form of the resulting shrubs as compared with those generated from seed. Some increase of the number of shrubs present around the site of the pulling may be associated with the soil disturbance (functional tillage) which is likely to enhance germination and new seedling development. (see more on this subject and images here) When following these manual attempts, the volume of herbicide (and time) required for true control is increased substantially over other methodologies. The same was true when we have been involved with following goat grazing activity in that the regrowth which occurs will present a number of stems to treat directly correlated with the number of times a particular shrub is bitten off (just like pruning a hedge). Many of these practices may create a visual impression of control, but with short term results and minimal true control. On some species (IE. winged burning bush, euonymus alatus. and numerous others) the resulting root suckering eliminates control options that minimize collateral damage to valuable native species. Prescribed fire, although necessary and highly desirable in the maintenance “toolbox” may also lead to increased costs of control if introduced prior to control of species prone to root suckering in addition to making cut stem treatment more difficult (see options).
Our goal is to use the least toxic effective herbicides available and to minimize the area where application is needed. Efforts are geared to eliminate the exotic and invasive plants while maintaining the desirable vegetation. Attempts to minimize rates of application in the attempt to reduce cost or reduce the total active ingredients applied are to be avoided as they will lead to herbicide resistance and the utilization of herbicides of greater toxicity in the future. This phenomena has been well documented in agricultural production.