Getting the Most From Your Pre-seed Herbicide Application
Pre-seed herbicide application is just weeks away. What factors should you consider before you start your pre-seed herbicide application this year?
Do you need to do a pre-seed herbicide application?
If you did a late fall post-harvest herbicide application your fields may already be clean for spring. Consider a pre-seed application this year if you see weeds emerging or you noticed late season weed growth last fall.
What crops are you growing this year?
For convenience and time management, It can be tempting to go with one pre-seed herbicide for the entire farm, but that may not be the best choice for each crop. There are few pre-seed herbicide products that can be applied on every crop, so before you finalize your purchase decisions match the right product with the right crop. For example, you may use a different product or mix of products in your cereal crops as compared to your canola or pulse crops. Cereal crops are also more competitive than pulse or canola crops, and some options for cereal crops have residual control so a cereals only product makes sense. The number of choices can be overwhelming, so contact your local AgraCity representative and discuss which options might be best for every acre on your farm.
What weed problems did you see in your fields last year?
Did you notice winter annuals such as dandelion, stinkweed, narrow-leaved hawk’s beard, flixweed or other hard to control weeds? Did you observe volunteer canola, volunteer cereals, kochia, cleavers or other problem weeds? If so, take time to determine what products will give you the best control for these tough weeds, as glyphosate alone may not be enough.
Start with glyphosate – and know your rates.
Glyphosate is an outstanding tool for pre-seed application, but it makes sense to adjust your application rate depending on the weed spectrum. If there are perennial weeds like dandelion or quackgrass then increasing the rate of glyphosate to around 1 litre REL equivalent per acre is a good recommendation. Otherwise ½ L/acre of Disruptor® 360 glyphosate, or 0.33 L/acre of Disruptor 540 glyphosate should be sufficient for good control.
Check your water quality.
Glyphosate is sensitive to water quality; hard water or water containing calcium (Ca+), magnesium (Mg+), or iron (Fe+), or dirty water or water with suspended soil or organic matter will reduce control. If there have been water quality issues in the past, if you are not sure about your quality, or if you know that you have hard water, consider adding a water conditioner, such as Citrisoft from AgraCity. The slight additional cost may be worth to improve your glyphosate performance.
Add a tank mix partner to your glyphosate.
Glyphosate is a critical tool for pre-seed control but it has some gaps in performance and weeds resistant to glyphosate are becoming a problem. adding a tank mix partner can help with tough to kill weeds like kochia, narrow-leaved hawk’s-beard, volunteer canola, flixweed and more. For example if you have group 2 and 9 resistant kochia, you should consider a tank mix partner such as Revenge™ (carfentrazone), Revenge B (same actives as Nufarm’s Conquer®), Revenge M (carfentrazone + MCPA Ester), or Revenge Pro (carfentrazone + 2,4-D Ester). All these products add 1-2 additional modes of action to your glyphosate which will result in improved weed control plus improved herbicide resistance management.
If you farm in the northern parts of western Canada and have group 1 resistant wild oats you should consider adding Himalaya™ Express, Himalaya Pass, Himalaya Pro, or Himalaya Trio for an additional pre-seed mode of action on wild oats, plus excellent broadleaf control as well. Just ask your AgraCity representative about these new options.
Contact or systemic herbicides – which is better?
For some crops, you can choose either contact or systemic herbicide options. Both have strengths and weaknesses. Contact herbicides usually act quickly, but only control the part of the plant on which they were sprayed, so lots of water and warm sunny temperatures are important. Contact herbicides usually have little residual activity, so they are well suited for sensitive crops such as pulses or canola. Systemic herbicides are absorbed by the plant and taken into the root system for complete control, but rely on good growing conditions for best control, so cool conditions are not ideal. Depending on the product they can have residual activity, so they are often best suited for cereal crops. Contact and systemic herbicide combinations can sometimes be better than either product alone. For comparison, the chart below lists common pre-seed herbicide groups. The most common herbicide groups for pre-seed are 2, 4, 6, 9, 13,14 and 15. It can be confusing – if you are not sure how to choose a product, contact your AgraCity representative and they can help you choose the best products this year.
The Mode of Action, Site of Uptake and Symptoms of Different Herbicide Groups
Maintain recommended water volumes.
It is important to maintain your water volumes for pre-seed application, as many weeds are likely small, plus growth may be slower due to cool temperatures. This is especially important if you are applying a contact herbicide where coverage is critical to maintain performance.
Follow label recommended application rates.
As with water volume, application rates are important to maintain performance. Do not cut back rates as performance can be reduced.
When is it too cold to apply?
Pre-seed application can be challenging due to variable weather conditions. Below are some temperature requirements and guidelines for pre-seed application:
- If the daytime temperature is forecasted to reach a minimum 8-10°C, plan to spray once the temperature reaches a minimum 5°C. It is best to spray in the morning or early afternoon as temperatures rise throughout the day. Avoid application into the evening if the temperature is to drop below 10°C. In this case, stop spraying 1.5 to 2 hours before sunset or before it drops below 10°C. This allows time for the product to move from the leaves to the growing points of the plants
- Plants must be actively growing, with new green leaves and new growth emerging from the center of the plant.
- Overnight lows around 0⁰ to – 2⁰ Celsius: begin spraying once the temperature is +5⁰ Celsius and rising.
- Overnight low ranging from – 2⁰ to – 5⁰ Celsius: begin spraying once the temperature has been + 5⁰ Celsius for a minimum of 2 hours and rising, assuming there is active plant growth.
- Overnight low of – 5⁰ Celsius or colder: wait for at least several days of overnight lows that are 0⁰ Celsius or warmer + active plant growth.
- When temperatures start to decline at the end of the day: it is advised to stop spraying, when overnight lows will be around 0⁰
- If overnight lows ranging from 0 to – 5⁰ Celsius, stop spraying 2 to 4 hours before temperatures start to decline at the end of the day.
Spray and seed later that day or next day as long dandelions or quack grass are not the targeted weeds. If dandelions or quack grass are present wait 48 hours after application to seed.
Apply early or wait?
If you have been dealing with a particularly problematic field, or problem weeds such as kochia, Russian thistle, narrow-leaved hawk’s-beard, or other hard to kill weeds, consider delaying your pre-seed herbicide application to allow these weeds to germinate, be in a better stage for application, or for the weather to improve, which will increase the probability of getting better control prior to seeding. Some products also have after seeding application options but be careful – once the crop is emerged it can be controlled by your pre-seed herbicide, so check the label thoroughly before considering a post-seeding application.