The implications of spatially variable pre‐emergence herbicide efficacy for weed management

Abstract

BACKGROUNDThe efficacy of pre‐emergence herbicides within fields is spatially variable as a consequence of soil heterogeneity. We quantified the effect of soil organic matter on the efficacy of two pre‐emergence herbicides, flufenacet and pendimethalin, against Alopecurus myosuroides and investigated the implications of variation in organic matter for weed management using a crop–weed competition model.RESULTSSoil organic matter played a critical role in determining the level of control achieved. The high organic matter soil had more surviving weeds with higher biomass than the low organic matter soil. In the absence of competition, surviving plants recovered to produce the same amount of seed as if no herbicide had been applied. The competition model predicted that weeds surviving pre‐emergence herbicides could compensate for sublethal effects even when competing with the crop. The ED50 (median effective dose) was higher for weed seed production than seedling mortality or biomass. This difference was greatest on high organic matter soil.CONCLUSIONThese results show that the application rate of herbicides should be adjusted to account for within‐field variation in soil organic matter. The results from the modelling emphasised the importance of crop competition in limiting the capacity of weeds surviving pre‐emergence herbicides to compensate and replenish the seedbank. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Developing hierarchical density‐structured models to study the national‐scale dynamics of an arable weed

“…This article is protected by copyright. All rights reserved León et al, 2014), soil type (Colbach et al, 2006;Metcalfe et al, 2017Metcalfe et al, , 2018, herbicide resistance status (Moss, Perryman and Tatnell, 2007b;Moss et al, 2011;Hicks et al, 2018) and more specific management options (Holst, Rasmussen and Bastiaans, 2007;Harker and O'Donovan, 2013;Metcalfe et al, 2017) are obvious areas where the predictive performance of these models could be improved, and should form the basis for future applications.…”

“…Numerous studies have investigated how the role of spatial structure in weed populations influences the persistence, spread, and control of weed populations (Rew and Cousens, 2001;Holst, Rasmussen and Bastiaans, 2007;Metcalfe et al, 2017;Somerville et al, 2017;Gonzalez-Andujar, Perry and Moss, 2018). It is possible that the greater influence of field-level effects compared to rotational management in our simulations is partly due to specific spatial…”

Spatial Modelling of Within-Field Weed Populations; a Review

“…For example, fertiliser application, crop orientation, and crop establishment rate may vary across the field, and can affect weed composition and fitness [70,74,75]. Herbicide application and efficiency may also vary within a field, due to drift, soil properties, or crop residues, which can influence weed spatial distribution within a field [76][77][78]. In addition, weed detection and cross pollination can be affected by temporal differences in plant growth patterns.…”

Modelling the effect of spatially variable soil properties on the distribution of weeds

“…Pre-emergence herbicide efficacy is known to be reduced with increasing organic matter, this can have an indirect effect on the life-cycle of the weed as on some soils there will be an increased number of survivors (Pederson et al, 1995, Metcalfe et al, 2018a). So to model the proportion of plants surviving pre-emergence herbicide application the value of p used to draw from the binomial distribution (Eq.…”

“…We modelled the survival rate of A. myosuroides after the application of pre-emergence herbicides using data from Metcalfe et al (2018a). We took the data points for the proportion of seedlings surviving an application of pre-emergence herbicide at a dose equivalent to field rate on different soils and plotted this against the organic matter (%) in the soil and fitted Eq.…”