Chemical Weed Control in Winter Cereals

While this article focuses on chemical control, it must be remembered that best practise weed control in winter cereals also includes:
• Choice of cultivation techniques (ploughing versus non-inversion etc.)
• Crop rotation
• Sowing date

Chemical Control Strategies
Controlling both broad-leaved weeds (BLWs) and grasses in winter cereals has strong yield and profit benefits while it also facilitates trouble free harvesting.  Once the crop is sown, winter cereal weed control is highly dependent on herbicides.  The key requirements for cost-effective herbicide programs are listed below.
1. The type of weeds present-Correctly identifying the weeds present (field history is very important) and knowing the importance of these weeds are critical.  Some weeds are more competitive than others (see table 1 below) and relatively small numbers of highly competitive weeds can cause large yield losses. 

Some weeds germinate mainly in the autumn, some mainly in the spring, and others will germinate throughout both times of the year. The following lists contain the germinating times of the more commonly found weeds:

2. Timing, weed size and population-Higher rates of herbicides are required for larger weeds and for dense weed populations.  There are significant opportunities to save money when field conditions are good and herbicides are applied pre-emergence or where the weeds are small.  There are three typical scenarios:
• For early sown crops or where there is a history of grass weed problems, herbicides should ideally be applied pre-emergence.  Good soil moisture levels and fine firm seedbeds will dictate the success of these products, and the seed should be well covered by soil to ensure crop safety. 
• For most crops early post-emergence treatment at the 2-3 leaf stage, offers very effective weed control relatively cheaply, and the opportunity to combine with an aphicide. 
• Generally not the best policy to leave everything until the spring as the spray window is quite short and weeds will be larger and hardier making them more difficult to kill.  Spring treatment may however be the best option for late sown crops or where autumn control wasn’t possible.  In addition, follow-on herbicides may be required in the spring to pick up any weeds not controlled in the autumn e.g. Wild Oats. 

3. Sprayer Setup and spraying conditions-Water volumes, boom height above the crop/ground, forward speed, nozzles used, pressure and general sprayer condition all play their role in achieving a good kill of weeds.  Weather and seedbed conditions also have an impact on the success of winter cereal weed control.  It does not pay to spray when crops are under stress, e.g. after a cold or wet spell. This can cause crop damage and/or unsatisfactory weed control.  Good growing conditions usually produce the best results.

4. Product Selection-The objective is to choose the herbicide product combination that will successfully kill the weeds, particularly the most important weeds, present (or likely to be present) for the lowest cost.  However, it is wise to build in some level of insurance with the product rates without increasing costs too much.

Product selection will be limited by crop safety, crop growth stage and label restrictions.  There is a large array of suitable products for use in winter wheat, slightly less for winter barley and winter triticale, and only a very limited selection for winter oats (many growers will choose spring herbicide applications for oats, particularly for competitive crops).  The main herbicide options recommended by Dairygold for winter cereals are outlined in table 3 below.  Note rates may need to be altered depending on timing, conditions and field history.

Get in touch 

For further help and advice contact your local Agri representative

Meet all our representatives