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.
Highlights
Herbicides are an important component of weed control programmes and soil-applied herbicides are important for controlling germinating weeds in the context of the rapid evolution of resistance to foliar-applied herbicides
Our aim was to quantify the effect of variable soil organic matter on the seed return of A. myosuroides following the application of flufenacet or pendimethalin at a range of doses
We considered three different levels of organic matter, typical of arable fields in the United Kingdom (UK), and a range of herbicide dose rates applied to A. myosuroides seedlings in pots
Summary
Herbicides are an important component of weed control programmes and soil-applied herbicides are important for controlling germinating weeds in the context of the rapid evolution of resistance to foliar-applied herbicides. These pre-emergence herbicides are applied uniformly across the field at doses recommended by the manufacturer. Alopecurus myosuroides exhibits patchy distributions within fields, yet its control is often through uniform application of herbicides. 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
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