tools as described herein in one mode of managing target watermilfoil plants in a lake 10 samples of the plants 11 are obtained and packaged e g in a container to preserve the samples as appropriate for subsequent testing the packaged plant samples 11 are shipped to a processing facility 12 such as by overnight courier the processing facility 12 processes the samples to extract dna 13 followed by obtaining genetic information from the extracted dna 14 the thus obtained genetic information is input to a processor 15 along with stored genetic information 16 from previously characterized watermilfoil plants at least some of which are identified as herbicide tolerant hybrid northern u00d7 eurasian or other watermilfoil plants the computer processor runs a routine to generate a genetic comparison such as a phylogenetic tree showing genetic relationships among the target watermilfoil plants and the previously characterized watermilfoil plants a visible display 17 is generated such as a printout or electronic image depicting the genetic comparison for example a phylogenetic tree this display is transmitted to an entity e g a product technical support specialist a treatment service provider or the lake owner or manager responsible for developing herbicide treatment recommendations or otherwise involved in the management of the watermilfoil in the lake 10 in one optional embodiment the processing facility 12 also designs a recommended herbicidal treatment.