The five Weed Research Themes
The European Weed Research Society (EWRS) considers weed scientists as people that focus their research on all aspects of weeds, defined as plants that impact both positively and negatively on economic, aesthetic or environmental aspects of any agroecosystem. Topics of their research include, amongst others, weed biology and control, herbicides, invasive plant species in all environments, population and spatial biology, modelling, genetics, biodiversity and parasitic plants.
We have clustered the wide variety of research themes in five groups that are not exhaustive but will provide you with an idea of what we do.
Theme 1 Weed biology and ecology - Weeds are interesting plants
To an outsider, weeds may seem plants like all others. They may belong to the group of grasses, or sedges, or flowering plants, with the only difference that they live in areas where we want to perform determinate human activities and where their presence is thus not appreciated, such as fields cultivated by farmers, our gardens, railway tracks and roadsides. These areas all possess characteristics that are convenient on the one hand, but stressful on the other hand. For example, road and railway tracks do not have a fertile soil with optimal humidity levels, but at the same time there is no competition from other plant species. Cropped fields on the other hand contain optimal growing conditions but are regularly disturbed by soil tillage and crop management. So the question is: how do these plant species manage to live and propagate under extreme conditions and despite our effort to eradicate them?
To reply to this question, we need to characterise these areas in terms of the resources needed by plants: nutrients, water, sunlight, and space to develop the root and leaf system. The places where weeds grow are often characterised by absence of competition with other plants (railways, roads and tilled soils), or very fertile soils with optimal humidity (cropped fields and gardens). Some plant species are able to grow and disseminate better than others under such conditions. It is the research area of weed ecologists and biologists to study the characteristics, or traits, of weed species that make them adapted to certain environmental conditions (humidity, temperature, soil pH, soil structure, soil fertility). And even if we change the environmental conditions the weeds are able to adapt to these changes. Scientific evidence shows that the extraordinary capacity of some plants to adapt to changing situations in a very short time, and even during their own life cycle, In other words, they possess a great phenotypic plasticity. This extra-ordinary capacity makes the difference between a ‘plant’ and a ‘weed’. The weeds are real die-hards and we are eager to unravel the pathways through which they resist our pressures in order to predict where we can expect to find certain weed species and develop the right tools to manage them.
If you want to have some examples of research taking place on this theme, please have a look at the following papers published in our Journal Weed Research:
paper 1: STILL NEEDS TO BE SELECTED
paper 2: STILL NEEDS TO BE SELECTED
Theme 2 Integrated weed management (IWM) - Clever management of weed
Weed biologists and ecologists are working hard to increase our understanding about what makes weeds so resistant to our tools and actions aimed at eradicating them. We have found out that weeds are very flexible and they are able to transform and adapt to all kinds of environmental and human stress levels that are imposed on them (phenotypic plasticity). This means that as soon as we repeat an operation in the same way, in the same time of year, the weed population will adapt to this disturbance by changing their growth form or habit. For example, if we till a soil to destroy the weeds every year in the same time, the population will adapt through selection of plants that are able to complete their life cycle and disseminate before the tillage. Based on this knowledge, we have understood that if we want to control weeds, we need to diversify all our operations and actions in such a way that the population cannot adapt to a regular disturbance regime. This is called Integrated Weed Management. We study all possible ways to disturb the life cycle of the weeds and combine as many different methods as possible. We need to reduce the abundance of the seeds in the seedbank, eradicate seedlings and reduce competition of mature plants with the crop and avoid mature plants to propagate. As a first approach we aim for mechanical, biological and cultural methods. We keep the chemical methods as a last way out, to be applied if all other approaches have failed. In this way we avoid to pollute the environment and at the same time we avoid that weeds can develop resistance to the active ingredients of the herbicides. Weeds adapt as well to chemicals and they put mechanisms in action to avoid poisoning by chemicals! Weeds have a very high plasticity, meaning that they respond and adapt quickly to stimuli in their environment, and we need scientific creativity to keep in control of our fields, gardens and infrastructures!
Weeds are mainly seen as troublesome plants that need to be eradicated in order to safeguard crop production or other functionalities of areas that are managed for human activities. However, weeds are also an important component of the entire food chain. They provide nectar and pollen for beneficial insects, seeds for farmland birds, contribute to soil fertility and protect the soil from erosion. So in the end, we need to develop strategies to manage weeds in an environmentally safe way and keep them under economic threshold levels, while taking advantage of the positive services they may provide. Researchers implicated in Integrated Weed Management aim to contribute to this challenge.
If you want to have some examples of research taking place on this theme, please have a look at the following papers published in our Journal Weed Research:
paper 1: STILL NEEDS TO BE SELECTED
paper 2: STILL NEEDS TO BE SELECTED
Theme 3 Herbicide resistance - Reactions of weeds to current management
Weeds are living organisms and as such they respond to their environment. On the one had they grow in those places that are adapted to their characteristics. On the other hand, in the course of time, they can adapt to specific environmental conditions through evolution. Individuals that are more adapted to shadow, or to drier soils, are fitter, and the proportion of these traits slowly increases in the entire population due to increased reproduction of the fittest individuals. Therefore, if environmental conditions change consistently, some individuals are able to adapt to these changing conditions and this will slowly result in a change in the characteristics of the population. If the species is not able to adapt to these changing conditions instead, it will disappear.
As we have explained also in the section of Integrated Weed Management, the capacity of many weeds to adapt to changing conditions makes them a weed, and requires diversified management practices to avoid adaptation to our management. This same principle can be applied to herbicide resistance of weeds. The use of herbicides is a strong tool to control weeds. Herbicides can be divided in groups based on their ‘Mode of Action’ (MoA). The MoA is the chemical pathway through which the herbicide inhibits plant growth. Herbicides can be divides in two main groups: contact herbicides, that affect plant growth on the tissue where the herbicide is applied, and systemic herbicides, that are absorbed by the plant from leaves or roots and then translocated to other parts in the plant. They can affect various chemical pathways inside the plant that are relevant for plant growth. The most important modes of action are Lipid biosynthesis inhibitors, Amino acid biosynthesis inhibitors, Plant growth regulators, Photosynthesis inhibitors, Nitrogen-metabolism inhibitors, Pigment inhibitors, Cell-membrane disruptors and Seedling-growth inhibitors. There are many different chemical compounds that act as a herbicide, but they all operate through this rather limited number of modes of action. The critical issues with herbicide resistance occurs when there is a repeated use of herbicides with the same Mode of Action. Some plant species have developed ways to block the damaging chemical either by isolating the chemical or by deactivating it. The consequences of this build-up of resistance are that we run out of chemicals to kill a weed in case no physical, cultural or biological methods are available. Weed scientists study how to avoid the development of resistance in weeds to herbicides. Integrated Weed Management is a very important tool to prevent the development of resistance in weeds. At the same time, IWM is needed to control the weeds that cannot be controlled by herbicides any longer.
If you want to have some examples of research taking place on this theme, please have a look at the following papers published in our Journal Weed Research:
paper 1: STILL NEEDS TO BE SELECTED
paper 2: STILL NEEDS TO BE SELECTED
Theme 4 Invasive weeds and climate change - Weeds under global change
Weeds, like all other organisms, are adapted to grow in a determinate range of pedo-climatical conditions (minimum or maximum temperature, rainfall, length of the growing season, acid or alkaline soils etc.). Some species are adapted to a wide range of conditions while others require more precise conditions. All plant species that co-occur form plant communities, and these communities interact with other biota by providing them food, overwintering sites or oviposition sites. If no major disturbances or changes occur in such a biome, a community of plants and animals that have adapted in response to a commonly shared bio-physical environment, the biome will be rather stable over time. However, if a major change occurs such as climate change, this will affect the species survival rate and other, adjacent, areas may become more adapted to the growth and development of certain species. What has been observed following the warming of the earth is a gradual shift of plant species from south to north. The result of this shift is the introduction of new species in pre-existing communities. In these communities, their growth and development may not be limited by herbivores or granivores, like in the biome of origin, and they may quickly reproduce and start to dominate the vegetation in the newly invaded area. In this case we speak about invasive species. The main problem is caused by the fact that they start to dominate the vegetation and compete with the native species, causing a decrease in biodiversity and upsetting entire food chains. These invasive species can occupy cropping systems but also forest systems, water courses, railways lines and city parks. Examples are Ailanthus altissima (Tree of heaven), Fallopia japonica (Japanese knotweed), Heracleum mantegazzianum (Giant Hogweed), Impatiens glandulifera (Himalayan Balsam). They cause economical and sometime also health damage. Their management is very challenging due to the fact that natural enemies are lacking and introduction of natural enemies in the newly invaded areas needs careful evaluation.
If you want to have some examples of research taking place on this theme, please have a look at the following papers published in our Journal Weed Research:
paper 1: STILL NEEDS TO BE SELECTED
paper 2: STILL NEEDS TO BE SELECTED
Theme 5 New technologies -New ways to deal with weeds
Despite the fact that most people rely on mobile phones and applications for many of their daily activities (home banking, health apps, maps etc.), they find it hard to imagine that also farmers become more and more reliant on modern technologies for their decision making and farming operations. Geographical information systems are at the basis of precision farming. Satellite image analysis allows farmers to obtain very detailed information about for example the soil nitrogen level inside the field, about nitrogen levels in the crop or about disease attack in the crop. This information can be elaborated instantly and together with GPS-driven machinery, fertilisation levels and fungicides can be applied at the dose that is needed by the crop plants at a very small scale, up to a couple of square meters. Up to date, satellite image analysis for detection of weed infestation in the crop is still difficult because of the wide diversity of weed species and the similarity between the crop and the weeds especially in the early crop stage when weed control is most relevant. However, the use of camera’s and sensors, or GPS-driven seeding and planting machinery, make it possible to eradicate weeds through precision spraying or automated weeding robots.
Weed control by crop management improvement is not limited to choice of the crop phenotype, particularities of new varieties or planting densities. Crop improvements to facilitate sustainable and more efficient chemical weed control can be achieved via multiple breeding technologies including traditional breeding, mutagenesis, double haploids, molecular tools (gene mapping, QTL’s, marker assisted breeding), gene-editing technologies and biotechnology methods.
These technological advances provide an important support to the development of sustainable crop management in general and Integrated Weed Management in particular because they contribute to the reduction of herbicide use.
If you want to have some examples of research taking place on this theme, please have a look at the following papers published in our Journal Weed Research:
paper 1: STILL NEEDS TO BE SELECTED
paper 2: STILL NEEDS TO BE SELECTED