Read time: 6 minutes

Never cut the herbicide application rate

Applying sub-lethal herbicide rates to save money is a high-risk strategy.

Reducing the application rate of herbicides increases a weed’s ability to evolve resistance. Any saving in chemical costs is significantly outweighed by the risk of the low dose causing faster herbicide resistance evolution.

Scientific studies have demonstrated that resistance can rapidly evolve in weeds subjected to low doses of herbicide. Some weeds can develop resistance within a few generations.
Full rates when mixing herbicides too!

When mixing herbicides it is important that each product is still applied at the full label rate to ensure high mortality.

Applying different chemicals in one mix can provide an additive advantage. It is important to understand the mode of action of each herbicide on the plant when preparing a herbicide mix. This is just as important for pre-emergent grass weed mixes as it is for post-emergent mixes aimed at broadleaf weed control. ALWAYS READ THE LABEL.

Surrounding weed seeds with a combination of pre-emergent herbicides with different modes of action can give a high level of control and help extend the useful life of all the chemicals used. The high level of control must be supported with additional control measures for all survivors. All products with different modes of action must be applied at full label rates for this to be an effective strategy.



Mixing two chemicals with the same mode of action can achieve some additional efficacy, however, the mix should deliver the combined full rate to ensure a lethal dose. The amount of stubble present and crop safety are all important considerations when mixing chemicals. For example, when using a tank mix of Avadex® and trifluralin to control ryegrass in wheat, the rates used will vary depending on the sowing system and level of stubble retention. Be sure to get good advice.

Many herbicides on the market are a combination of two or more modes of action within the one product. These products must be applied at the full label rate to be effective. Having dual action does not negate the need to change herbicide products and rotate modes of action. Repeated use of any single strategy will reduce the effectiveness of that strategy over time.



Related Articles

Related Articles

View all
Article
News

Measuring the value of weed control expenses

Chris Davey, WeedSmart's southern extension agronomist, suggests three ways to reassure yourself that a weed control tactic is worthwhile. Read More...
Article
News

Testing optical sprayer technology return on investment

The economic benefits often outweigh the upfront cost of weed detection technology for both green-on-green and green-on-brown systems. Read More...
Article
News

Investment in holistic weed management pays off

WeedSmart is a catalyst for real on-farm practice change in farm management, crop rotations and chemical use. Read More...

Webinars

View all
Video
Webinar

Making Every Drop(let) Count – An International Perspective on Spraying Efficiencies

WeedSmart southern extension agronomist Chris Davey and Canadian spray technology expert Tom Wolf discuss efficient and effective spray application. Read More...

Videos

View all
Video
Webinar

Making Every Drop(let) Count – An International Perspective on Spraying Efficiencies

WeedSmart southern extension agronomist Chris Davey and Canadian spray technology expert Tom Wolf discuss efficient and effective spray application. Read More...

Factsheets

View all
Fact Sheet

Hazardous inversions and spray drift

Current regulations prohibit spraying of agricultural chemicals when hazardous temperature inversions exist. Read More...
Fact Sheet

Mixing and batching for agricultural chemical application technical guide

Avoid chemical mixing errors and see how growers are setting up their batching systems for added efficiencies. Read More...

Subscribe to the WeedSmart Newsletter