10 Tips for Improving Herbicide Efficacy Under Difficult Conditions


Jun 07, 2024

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While spring weather typically can be unpredictable, this year’s El Niño and La Niña are bringing pronounced temperature fluctuations that are impacting growers. In particular, the above-average temperatures in Canada are making chem spraying more challenging.

Spraying under difficult conditions can be manageable with the right strategies, though. 

Below are 10 tips to help ensure effective and safe spraying. But first, let’s discuss specific recommendations for two of the popular herbicides, glyphosate and glufosinate

Click to jump directly to the section that’s most relevant to your ag operation or continue reading below:

Spraying Glyphosate Under Difficult Conditions

Products like Smoke 540 Glyphosate contain glyphosate in the form of potassium salt, which is soluble in water, making it easy to apply as a foliar spray. However, there are several conditions that may reduce glyphosate efficacy, including: 

  • Temperatures higher than 25℃

  • Dry soil conditions

  • When relative humidity percentage (RH%) is lower than 40%

  • Water quality: water is hard or has a high pH. (Optimum pH range for Glyphosate is 5-6)

  • Weeds out of stage 

For hot weather and dry soil conditions, consider:

  • Increasing water volumes

  • Adding a non-ionic surfactant (NIS) like ICON or Falcon® 

  • Spraying early in the morning when temperature are favourable for plant uptake and when RH% is the highest during the day

For challenges related to water quality, consider:

For weeds out of stage, consider:

  • Using higher rates of glyphosate

  • Using surfactants

  • Applying a pre-seed burn off

  • Spraying on time

  • Scouting and knowing the most dominant weeds in the field and planning accordingly

Shop for Glyphosate 540 Value Pick on FBN to get it delivered directly to your farm.

Spraying Glufosinate Under Difficult Conditions

Glufosinate works primarily as a contact herbicide, requiring thorough coverage of the plant tissue for effective control. It is important to apply it to young, actively growing weeds for the best results. However, several environmental conditions may reduce glufosinate’s efficacy, including:

  • When RH% is lower than 40-50%

  • Cloudy, foggy, or heavy dew conditions

  • Temperatures higher than 25℃ 

  • Dry soil conditions

  • Water volume

  • Weeds out of stage or not on label

For low RH%, hot weather, and dry soil conditions, consider:

  • Increasing water volumes

  • Adding surfactants like Accu-Spray ®

  • Spraying in the morning when it’s sunny and the RH% is high during the day 

For cool and cloudy conditions, consider: 

  • Adding adjuvants such as  ACCU-SPRAY® to heat up the herbicide

For foggy and heavy dew conditions, consider: 

  • Waiting until it dries up a bit or 1-2 days if it is raining

Glufosinate is a contact herbicide. Therefore, requires a relatively higher water volume that is no less than 12-15 US gal/Ac to ensure good coverage and efficacy. 

For weeds out of stage, consider:

  • Using higher rates of glufosinate

  • Using surfactants

  • Applying  a pre-seed burn off

  • Spraying on time. 

  • Scouting and knowing the most dominant weeds in the field and planning accordingly

Shop for Glufosinate 150 VP on FBN to get it delivered directly to your farm.

10 Tips for Spraying Under Difficult Conditions

1. Monitor Weather Conditions

Always check the local weather forecast before planning your spray applications. Avoid spraying during windy conditions — generally wind speeds over 10 mph — to minimize drift, and during temperature inversions, which can also cause drift and poor pesticide performance.

Read FBN®’s free guide How Will El Niño Impact Canadian Farmers This Year? to learn about weather patterns across Canada and crop yield forecasts.

2. Choose the Right Time

Early morning or late evening can be ideal times for spraying because winds are typically lighter and temperatures are cooler, reducing the volatility and evaporation of pesticides.

3. Adjust Spray Equipment

Use spray nozzles that produce larger droplets to reduce drift. Lowering the boom height can also help minimize drift. Ensure that the equipment is well-calibrated and the pressure is appropriate for the type of chemical and the target.

Learn how to choose the right type of spray nozzle in this blog.

4. Select Appropriate Formulations

Use formulations that are less prone to drift and volatilization. Water-based formulations may be preferable over volatile organic solvent-based ones in windy or hot conditions.

5. Incorporate Adjuvants

Consider using adjuvants that improve the sticking properties and efficacy of the pesticide under challenging conditions. This can help reduce the amount of active ingredient needed and minimize environmental impact.

Get adjuvants delivered directly to your farm when you shop online at FBN.

6. Increase Efficacy

Adjust the concentration of the pesticide according to the label instructions for different conditions. Sometimes, a higher concentration might be necessary to combat reduced efficacy due to rapid drying or other factors.

7. Buffer Zones

Maintain buffer zones to protect sensitive areas from drift. This is especially important near water bodies, residential areas, and non-target crops.

8. Keep Records

Keep detailed records of all applications, including weather conditions, product used, rate, and any observations. This can help in assessing the effectiveness and any potential issues that may arise.

9. Follow Safety Protocols

Ensure that you wear appropriate personal protective equipment (PPE) and follow safety guidelines, especially under adverse conditions. Be mindful of your surroundings and ensure that there are no people, animals, or sensitive areas like water bodies nearby that could be affected by drift.

10. Consult Product Labels

Always refer to the product label for specific guidance on application rates, timing, and weather restrictions. Labels can provide crucial information tailored to the product you are using.

To find this information on FBN, click on the Product Labels link at the top of the product page.

Shop for Glyphosate and Glufosinate on FBN

By shopping for glyphosate and glufosinate on FBN, farmers can benefit from a wide selection of products, competitive pricing, detailed product information, and a convenient online shopping experience.

Shop now for:

Don’t forget to add an adjuvant to your cart to make the most of your herbicide purchase:

Related Resources

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Written by Norm℠, reviewed and edited by Stephanie Nikolopoulos.

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Jun 07, 2024

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