Threshold weed management methods have recently been elaborated to consider effects of threshold management on weed population dynamics. Such economic optimum thresholds are calculated using population-dynamics models which require detailed information about weed demography, including seed production (as affected by events between germination and seed dispersal), seed dispersal, and seed survival and movement in soil. Factors affecting any of these aspects of demography appear likely to modulate the growth rate of a sub-threshold population and therefore to influence the economic optimum threshold value. To test this conjecture and evaluate weed threshold management, including associated risk, improved understanding is particularly needed of weed seed dispersal, seedbank processes, and unpredictable demographic variation.
Plant fecundity and seed dispersal in spatially heterogeneous environments: models, mechanisms and estimation