Herbicidal strategies to control Phalaris brachystachys in a wheat-sunflower rotation: a simulation approach

Abstract

Phalaris brachystachys is a common and troublesome weed in winter cereals in Mediterranean countries. A deterministic model was developed to simulate P. brachystachys seedbank dynamics in the wheat-sunflower rotation, a commonly practiced cropping system in southern Spain, under different herbicide-based management scenarios: no herbicide application, full herbicide dose (standard rate) and two reduced dose rates (75 and 50% of the standard rate). Without treatment, a steady increase of the seed bank is predicted up to an equilibrium level of 54,859 seeds m -2 (575 plants m -2 ) after 25 years. Full dose herbicide applications in wheat years resulted in a progressive seed bank decline over years. Reducing the efficacy of the herbicide by using 50% or 75% of the recommended rate resulted in no long-term seed bank decline. Instead, a population increase until equilibrium densities is predicted. A sensitivity analysis showed that seedling survival and fecundity were the most sensitive demographic parameters under the full dose strategy, whereas fecundity and seedbank mortality were the most sensitive parameters under reduced dose strategies. Reduced dose strategies tended to be less sensitive than the full dose strategy. Simulations indicated that longterm control of this weed may be attained under full dose, highly effective, herbicide applications. Unless effectiveness could be maintained at very high levels, reduced herbicide doses may not be a recommendable option for the long-term control of this species in a wheat-sunflower rotation.Additional key words: population model; seed bank; sensitivity analysis; short-spiked canarygrass; simulation; sunflower-wheat rotation. Resumen Estrategias para el control con herbicidas de Phalaris brachystachys en una rotación trigo-girasol: un modelo de simulaciónPhalaris brachystachys es una de las malas hierbas más importantes en el cultivo de trigo en los países mediterráneos. Un modelo determinístico fue desarrollado para simular la dinámica del banco de semillas de P. brachystachys en una rotación trigo-girasol, un sistema de cultivo utilizado frecuentemente en el sur de España, bajo diferentes escenarios de manejo basado en el uso de herbicidas: sin herbicidas, dosis completa (recomendada por el fabricante), y dos dosis reducidas (75% y 50% de la dosis recomendada). Al usar el tratamiento sin herbicidas, el banco de semillas alcanza un nivel de equilibrio con 54.859 semillas m -2 (575 plantas m -2 ) a los 25 años. La aplicación de la dosis completa en el año de trigo resultó en una reducción progresiva del banco de semillas. El uso de dosis reducidas no resultó en una disminución en el banco de semillas a largo plazo. El análisis de sensibilidad mostró que la supervivencia de plantas y la fecundidad son los parámetros demográficos más sensibles al aplicar la dosis completa del herbicida, mientras que la fecundidad y la mortalidad en el banco de semillas fueron los parámetros más sensibles al aplicar las dosis reducidas de herbicidas. De acuerdo con el análisis de...

Economical Evaluation of Reduced Herbicide Doses Application Rates to Control Phalaris brachystachys (Short-Spiked Canary Grass) in a Biennial Wheat–Sunflower Rotation in Mediterranean Dryland: A Modelling Approach

“…The bioeconomic model integrates three sub-models: population dynamics, weedcrop competition and economic [13]. This study expands a previous population dynamics model for P. brachystachys [12], including weed-crop competition and an economic analysis.…”

“…This result is similar to that obtained in a field experiment carried out by Garcia [ 17 ] to control P. brachystachys in wheat, where an average value of EUR 123.23 ha −1 was obtained with a full dose application of clodinafop. Not controlling this species leads to an economic loss of EUR −31.45 ha −1 year −1 ( Figure 1 ) and the establishment of an important seed bank [ 12 ]. Previous results on this species indicate that effective population control can only be achieved by applying the full herbicide dose [ 4 , 12 ].…”

“…Not controlling this species leads to an economic loss of EUR −31.45 ha −1 year −1 ( Figure 1 ) and the establishment of an important seed bank [ 12 ]. Previous results on this species indicate that effective population control can only be achieved by applying the full herbicide dose [ 4 , 12 ].…”

“…The population dynamics sub-model for P. brachystachys in the wheat–sunflower rotation has already been described [ 12 ]. It combines life-cycle population dynamics models for P. brachystachys during the wheat and sunflower growth stages [ 13 , 32 ] ( Figure 2 ) and is described by the following mathematical structures: P. brachystachys population dynamics model in wheat …”

“…By simulating different scenarios and considering various factors, these models provide valuable insights into the effectiveness of weed control programs and help guide sustainable management practices. Population dynamic models have been employed to explore the long-term impact of weed management tactics [ 11 ], including the application of low herbicide doses on P. brachystachys in wheat [ 5 ] and in wheat–sunflower rotation [ 12 ]. However, there is a lack of information on the economic implications of these approaches.…”