IWM involves using numerous weed control methods to try and manage a weed problem sustainably.

Whilst herbicides can still be used as part of an IWM approach, a major aim is to reduce reliance on them by also incorporating methods including, cultural, mechanical, biological, thermal and genetic control. A combination of such approaches can allow for optimal control of a specific weed problem.

Related topics on FarmPEP include herbicides and herbicide resistance. You can also view the topic pages on grass weeds and broad-leaved weeds which provide examples of suitable control methods.

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Herbicide resistance is the inherited ability of a weed to survive a rate of herbicide which would be lethal to a member of the normal population. It can develop over time based on repeated selection pressure imposed on the weed. This selection pressure changes the population from susceptible to resistant. Herbicide resistance is becoming an increasing problem in UK agriculture, in both grass weeds and broad-leaf weeds. See also the general topic on herbicides.

'Integrated Weed Management (IWM) systems in the agroecology context; new challenges.' NIAB, Cambridge, UK 24th - 26th of May 2023

Herbicides are substances (usually chemical) used to control weeds in a variety of situations including agriculture, horticulture and managed landscapes. Herbicides are classified according to their mode of action (MOA) - this is the precise biochemical mechanism in which the herbicide targets and kills the weed. The 'active ingredient' of the herbicide is the specific herbicidal compound that has the phytotoxic effect and this is formulated with a variety of other ingredients (including other active substances, surfactants, buffers, adjuvants e.t.c) to make a final product which is given a trade name by the herbicide manufacturer. With any herbicide product you will find an associated product label which explains how to use the product safely and legally. This page provides an overview of herbicides including how they are classified and used. Please link any pages or projects relating to herbicide use to this topic page.  Some widely used herbicides (e.g glyphosate) also have their own topic page. Other related topics on FarmPEP include herbicide resistance,  bioherbicides, broad leaved weeds and grass weeds.  

A 1998 study commissioned by the Pesticides Safety Directorate to assess the non-target impacts of pesticides on non-target terrestrial plants (NTTP's).  'To conserve and enhance biological diversity within the UK' was a stated aim of of the UK Biodiversity Action Plan (1994). Over 25 years later this is still a vital issue and the UK has stated its commitment to secure a post-2020 Biodiversity Framework as well as developing a 10 point plan for financing biodiversity (UK Government, 2022). However, a threat to plant biodiversity is non-target effects of pesticides - this is when pesticide materials reach areas beyond the target application area and affect the species there. Effects of pesticides on non-target plants can range from lethal (death of the plant) all the way to enhanced growth of these plants. Such varied effects depend on a range of things including the type of pesticide used, the concentration of its active ingredient and the sensitivity and spatial range of affected plants. Importantly, plants are part of complex food and pollination webs and so pesticide effects on plants can have cascading effects on the fauna that rely on them, and vice versa.

Grass weeds are a major challenge in UK agriculture and are often highly competitive in arable crops. Some of the most common grass weeds in the UK include: Black-grass (Alopecurus myosuroides), Italian rye-grass (Lolium multiflorum), Brome (Bromus sp.), wild-oats (Avena sp.), Couch grass (Elytrigia repens), annual meadow grass (Poa annua) and Rat's-tail Fescue (Vulpia myuros). You can find specific topic pages for black-grass and brome. See also related topics of: broad-leaved weeds, herbicides, herbicide resistance and integrated weed management

Broad-leaved weeds are a varied group of weeds that can grow and cause significant problems in arable fields in the UK. Some of the most common broad-leaved weeds in the UK include: Common Chickweed (Stellaria media) , Scentless Mayweed (Tripleurospermum inodorum), Common poppy (Papaver rhoeas), Charlock (Sinapis arvensis L.), Fat-hen (Chenopodium album L.), Common groundsel (Senecio vulgaris), Docks (Rumex spp) and Creeping thistle (Cirsium arvense). See also related topics of: grass-weeds, herbicides, herbicide resistance and integrated weed management.

The herbicide glyphosate was first registered in 1974 under the original trade name RoundUp (Monsanto) and has since become one of the most commonly used herbicides globally. It is a non-selective, post-emergent herbicide with a wide range of uses including arable, forestry, and horticulture.

Crop modelling is a useful tool in agriculture to improve our understanding how a crop grows in interaction with all external factors, including environmental interactions and the crop management practices in place. The idea is that by modelling cropping system factors as a mathematical representation, and incorporating real past data to 'calibrate' the model,  you can then simulate various scenarios and predict the impacts of certain changes on crop growth. One example of this would be a simulation of predicted environmental conditions under various climate scenarios to predict the impacts of climate change on crop growth and yields. Whilst models are oversimplifications of reality and can never capture all the complexity of agricultural systems, modelling has been a vital tool underpinning key agricultural developments and models are constantly being developed to be more dynamic, complex and sensitive. One particular application of modelling is in weed control. This page highlights the application of modelling in weed management and introduces a case study of a weed model from a DEFRA report.       

We are establishing a network of farms to share knowledge and data on the application and impact of IPM strategies with the aim to better understand the effectiveness of IPM approaches on farm yield and profitability, and support sustainable, productive systems with no pesticide inputs wasted. We’ve had some initial funding from Defra to design the network, and now we are moving into a pilot phase.   

Written By James Clarke - ADAS Research Director

Biofumigation involves incorporating brassicaceous cover crops into the soil.

Creeping thistle has become an increasing problem especially for organic arable farms with soils of higher organic matter content.

The IPMWORKS e-learning modules have been prepared based on successful experiences within the project network, including technical aspects of IPM strategies, farm performance or co-innovation and method for farm hub coaching, targeting both farmers and advisers.

A series of case study booklets compiled through the IPM Works project.

Docks are perennial weeds that compete with forages of nutritional importance for livestock production.

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