[ARCHIVED CONTENT] Defra, UK - Farming - Environmental management - Land Management

Farming

Weed control

There are three main issues around controlling weeds. First, the general methods of control, second the occurrence of herbicide resistance and finally weeds termed injurious.

Each of these are dealt with below:

method of control
herbicide resistance
injurious weeds

Controlling agricultural weeds

You can minimise weed problems using cultural control methods – such as ploughing, mechanical weeding and crop rotation - or through the use of chemical herbicides.

Changing cultural practices can often have a greater impact on weeds than adjusting herbicide usage. It is also encouraged to minimise the risk of herbicide resistance developing (see below).

When using chemical herbicides to control weeds you should do so responsibly and safely, referring to the Defra advice product on pesticides which covers:

preparation and planning
application
protecting the environment
storage and disposal

In addition, you should refer to advice and guidelines produced by the Pesticides Safety Directorate (PSD) and the Pesticides Forum which includes:

Code of practice for using plant protection products (on PSD website)
Pesticides and integrated farm management

These documents include guidance on crop rotations, sowing dates, wildlife and water protection, equipment loading and cleaning advice.

Herbicide-resistance

Herbicide-resistant weeds have developed an ability to survive herbicides originally designed to kill them. Resistance typically increases production costs and limits options for herbicides, cultivations and rotations.

As weeds are relatively immobile, the development of resistance is frequently due to practice on individual farms. The leaflet Managing and preventing herbicide resistance in weeds advises on ways you can managing resistance in common cereal weeds. The leaflets can be downloaded from the PSD website.

You can carry out a simple audit on your farm using the PSD’s Herbicide-resistant grassweeds - Are you at risk? The leaflet will take you through the key risk factors that influence the development of grassweed resistance and show you the areas at risk on your farm.

Further practical advice is available from the Home Grown Cereals Authority Practical topic sheet Dealing with herbicide-resistant wild oats.

Injurious weeds

Under the Weeds Act 1959, there are five weeds, called injurious weeds, which if present on your land you may be required to prevent spreading to neighbouring land. The five weeds specified in the Weeds Actare:

common ragwort
spear thistle
creeping or field thistle
broadleaved dock
curled dock

The Act allows Defra to carry out inspections of land to see if these five weeds are growing. Where there is a risk of the weeds spreading to land used for agricultural activities, including grazing horses and livestock, Defra may serve an enforcement notice requiring you to take action to clear the weeds within a set timescale.

An Identification guide to harmful weeds (969 KB) has been published by Defra, along with a Guidance note on methods that can be used to control harmful weeds.

In particular, common ragwort (268 KB) is poisonous to horses and other livestock and can have potentially fatal consequences if ingested.

A Code of practice to prevent the spread of ragwort (180 KB) provides comprehensive guidance on developing a strategic approach to ragwort control. It includes advice on identification, priorities for control, control methods, environmental considerations and health and safety issues.

Effective disposal of ragwort is a key factor in control and further advice leaflet Guidance on disposal options for common ragwort (383 KB) supplements the code of practice .