Assessment of management options for Salsola australis in south-west Australia by transition matrix modelling

P>A matrix model of the life cycle of Salsola australis was constructed, based on population ecology data collected from the district of Lake Grace, Western Australia. The model was used to assess potential control strategies for this summer annual weed within the Western Australian broad acre grain cropping system. The population growth rate (lambda) of S. australis in the absence of weed control strategies was 1.49 and was virtually unaffected by the dormant seedbank. However, lambda increased to 8.21 if it was assumed that a constant number of seed immigrated into the area in question from neighbouring populations of S. australis, through farm-scale seed dispersal. As a result, effective weed management depended on reducing seed dispersal. The model determined that burning all senesced, mobile plants in late autumn, combined with herbicide control of the largest cohorts of S. australis in summer and autumn, reduced population growth rate to 0.79. This control strategy resulted in a 66.1% chance of the population becoming extinct over 25 years. Management strategies are proposed based on the results of the models and further research is required to validate their effectiveness and practicality in the field.