Astron was engaged by the client to determine whether its current management actions were reducing the instances of weed populations, weed spread and whether current activities were likely to result in the future eradication of the subject weed species.
Our approach was to use a) a matrix population model to evaluate management of the weed species and b) use a dispersal model to evaluate conditions that may be contributing to the proliferation of the species at the site and to map risks of weed spread. Matrix population models describe the life-stages of an organism and the probability of transition or survivorship from one life-stage to the next and fecundity. Our matrix population model specified 15 life-stages with transition probabilities estimated from values in the literature or informed opinion of those familiar with the weed species. A spatially-explicit matrix population model was then constructed by placing a variable resolution covering grid over the site, running the matrix population model separately in each grid cell and allowing seed dispersal between grid cells. Three key seed dispersal modes were explored.
The study recommended a revised herbicide strategy and emphasised the threat posed by multiple modes of dispersal. As a result the client was able to adapt its weed management program for better future efficacy.