Assessing strategies for Orobanche sp control using a combined seedbank and competition model

Infection with the parasitic weed crenate broomrape (Orobanche crenata Forsk.) causes considerable yield losses in legumes grown in Mediterranean climates. Strategies to control the parasite must include the long-term containment of its soil seedbank. This requires a better understanding of seedbank and competition dynamics. Hence, we built a model of crenate broomrape seedbank dynamics and combined it with a model of broad bean (Vicia faba L.)-crenate broomrape competition within the simulation framework of the Agricultural Production Systems Simulator (APSIM). Parasite seed production is modeled as a function of parasite dry weight, which is an output of the competition model. Newly produced seeds are progressively added to the topmost of three vertically organized seed classes and vertically redistributed by tillage. Seed viability loss follows negative exponential functions, with the rate of seed decay depending on soil moisture status. Effects of further external factors, such as temperature, are not yet included. Viable parasite seeds present at sowing of a host crop serve as input to the next run of the competition model. We quantified effects of environment, rotation, tillage, hand-pulling, and combined strategies on parasite seedbank dynamics and broad bean yield through multiseason simulations. Modeled responses compared well with previously reported field observations. Results suggest that only by combining several management approaches, such as delayed sowing, no-till, and hand-pulling, can parasite populations be contained.