An approach to investigate the costs of herbicide‐resistant Alopecurus myosuroides

Abstract

Herbicide resistance in Alopecurus myosuroides causes severe problems in Western European cropping systems. Costs of herbicide resistance were investigated in this study by analysing variable production costs and sales revenues. Three farms were selected for this study, with winter wheat as the dominating crop in all farms. Resistance in A. myosuroides populations was verified at all locations. Four farming approaches were simulated over a period of 20 years: (i) continuing the actual cropping system without increase of resistance, (ii) continuing the actual cropping system with increase of resistance, (iii) changing cropping practice to overcome resistance and (iv) changing cropping practice to prevent resistance. Contribution margins representing the proportion of sales revenue that is not consumed by variable costs were calculated for all approaches. Comparative static simulations showed that average contribution margins in a cropping system with more than 60% winter cereals and reduced tillage practice dropped from 807 € ha À1 a À1 without herbicide resistance to 307 € ha À1 a À1 with herbicide resistance. Alopecurus myosuroides population densities increased to more than 1000 plants m À2 . Diverse crop rotations, including spring crops, clover-grass leys and intensive tillage, suppressed A. myosuroides populations, and average contribution margin was 630 € ha À1 a À1 . Preventive methods with rotations of winter cereals and spring crops with less clover-grass leys resulted in an average contribution margin of 691 € ha À1 a À1 . In conclusion, rotations of winter cereals and spring crops combined with inversion tillage and herbicides provide stable yields and can prevent weed population increase.

The challenge of herbicide resistance around the world: a current summary

“…Weed‐control decisions are heavily influenced by economics and utilize systems that provide the greatest measurable, near‐term economic return. In many cases, proactive resistance management comes at a short‐term cost, even though it may enhance long‐term profits …”

“…Some simulations have indicated that, if left unchecked, resistant A. myosuroides may eliminate profitability for some European farmers. 69 The same study indicates that a proactive approach that utilizes a greater diversity of crops, tillage and herbicides may reduce net profitability by 4-24% compared with an intensive cropping system without resistance, but in the long term will be more profitable compared with resistance development. 70 The consequence of evolution of resistance to ACCase and ALS inhibitors in grass species in small grain crops has been an increase in the adoption of pre-emergence herbicides, along with greater use of cultural practices such as occasional inversion tillage and use of false seedbeds, in order to reduce resistance selection pressure and eventually exhaust the seedbank.…”

“…Some countries in Europe have virtually lost the use of ACCase inhibitors to control A. myosuroides , and resistance to ALS is steadily increasing. Some simulations have indicated that, if left unchecked, resistant A. myosuroides may eliminate profitability for some European farmers . The same study indicates that a proactive approach that utilizes a greater diversity of crops, tillage and herbicides may reduce net profitability by 4–24% compared with an intensive cropping system without resistance, but in the long term will be more profitable compared with resistance development .…”

“…Because of a scarcity of new products in the pipeline and the withdrawal or enforced dose rate reduction of many active ingredients resulting from the re‐registration process, resistance cases are likely to increase in the near future . The biggest problems are encountered where simplified and standardized agronomic practices are adopted, such as monoculture and the use of herbicides with the same SOA . It is not surprising that the most affected cropping systems with major HR issues are those where a limited number of SOAs are used, for example, winter cereals.…”

“…70 The biggest problems are encountered where simplified and standardized agronomic practices are adopted, such as monoculture and the use of herbicides with the same SOA. 69 It is not surprising that the most affected cropping systems with major HR issues are those where a limited number of SOAs are used, for example, winter cereals. The adoption of conservation agriculture, which has major benefits for the soil, also has a side effect of promoting the occurrence of species germinating from the surface (i.e.…”