Redefining weeds for the post‐herbicide era

Abstract

AbstractIn the 50th edition of Weed Research the Editor‐in‐Chief introduced the concept of ‘the post‐herbicide era’. This appears increasingly prescient as herbicides continue to face ever‐increasing legislative restrictions and evolved resistance. They are also an important enabler of intensive agriculture which is a key contributor to the planetary crises, such as climate change and biodiversity loss. Integrated weed management (IWM) is the clear direction of travel for both weed science and practice, and is increasingly being holistically integrated into overall crop management. However, most definitions of ‘weeds’ date from the era of intensive agriculture, so may not be suitable for the post‐herbicide era and IWM. It is argued that deciding if a plant is a weed is fundamentally a ‘value judgement’, so weeds are, therefore, ethical and social constructs, and not a scientific concept. The proposed definition is ‘A plant, or population of plants, in a specific time and place, causing significant harm, either immediately or in the longer term, based on a holistic analysis of both their positive and negative attributes’. Thus, plants are defined as weeds on a case‐by‐case basis, that is, at a specific time and place, which counters the belief that a particular plant species are weeds. Significant harm is the value statement at the heart of the definition. As seedbanks and living plants persist from year to year and plants can become invasive, a caveat about the harm being in the future is required. The analysis of harm must also be holistic, for example, consider all ecosystem services that the plants provide. ‘Other plants’ or ‘aliae plantae’ are suggested to describe non‐crop plants that are not weeds that this definition creates.