Practical advice on herbicide applications and tackling resistance

Pre-emergence herbicide applications play an important role in cereal crop weed management strategies. 

How they work

Pre-emergence herbicides are applied before weed seeds germinate. Once germination occurs, the herbicide prevents weed roots and shoots from developing and creates a barrier between the soil and the surface. This prevents weeds from breaking through and becoming established in your crops. 

To get the best results from your pre-emergence applications:

Ensure optimum soil conditions

There must be adequate soil moisture to allow the active ingredients in the spray to move into the upper layer of the soil where the weeds germinate. If the soil is too dry, it can reduce the effectiveness of the herbicide, as can very wet conditions. If the soil is too wet, the active ingredients can end up in the crop rooting zone which can impact on the crop. 

Don’t spray on cloddy seedbeds

If the soil is fine and firm, you can make sure weeds come into contact with the herbicide as they emerge. Large clods can prevent the spray from reaching some areas in the soil which means weeds survive. Rolling after drilling can break down clods and make the seed bed firmer. 

Drill to the right depth

Weed roots and shoots absorb the active ingredient in the herbicide layer as they germinate which kills them. We recommend that you drill to a depth no shallower than 32mm, so you keep your cereal crop seeds out of the reach of the herbicide. 

Apply herbicides within 48 hours of drilling

Weeds can start germinating as soon as you have finished drilling, so a pre-emergence application of herbicide as soon as possible will prevent them from becoming established. 

Optimise your sprayer for best results

• A drift-reducing nozzle will help you achieve even coverage of the soil.

• Your forward speed should not exceed 12km/h.

• Use the correct water volume of 200L/ha for good soil coverage and weed uptake. 

• Maintain boom height of 50cm or less. 

• Always apply products at the recommended rate to ensure effective weed management and reduce crop effects. 

• Service, clean, and test your sprayers before application. 

Digital agronomy tools also play a part in a successful integrated weed management strategy. The Spray Assist app will provide you with the latest spray application advice and technique for 16 different crop types so you can create a spray plan that is tailored to your needs. 

Spray Assist Features and Guidance:

• Spray Forecast for hourly guidance on the best spray windows. 

• Add details of the equipment and nozzles you are using for accurate recommendations. 

• Search for information on over 600 different nozzle types from 20 leading manufacturers. 

• A drift risk calculator allows you to evaluate the drift risk rating from any nozzle, according to the pressure at which it is being operated. This enables you to optimise leaf coverage or penetration into the crop canopy, and work within safe parameters. 

Download the app for free and get tailored spray advice in the palm of your hand.

Pre-emergence applications 

Application technique: Focus on achieving consistent coverage of the soil surface to achieve the best residual activity. 

Best nozzle choice: The Syngenta 3D-ninety nozzle which offers 90% drift reduction with a droplet pattern and integrated spray angle optimised for soil surface coverage.

Peri-emergence applications 

Application technique: Target small emerged weeds as well as the soil surface. 

Best nozzle choice: In ideal spraying conditions, the nozzle of choice would be the Syngenta 3D, operated at 100 l/ha. However, if conditions are sub-optimal, the 3D ninety is the next best option and will minimise drift.   

Minimising drift 

Prioritise minimising drift because any product that fails to make contact with the weed is wasted. Don’t forget that wind gusts can shift the spray pattern leading to underdosed patches where weeds can escape control. To reduce the risk of drift and get the most from your herbicide, make this your mantra:

Go Low - keep nozzle tip height at 50cm above the target weeds.

Go Slow - Operate your sprayer at 12km/hr or less to maintain boom stability. 

Get Covered - Use a water volume of 200L/ha for optimum soil coverage.