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Post-Harvest Weed Control for a Better Start Next Spring

distinctThis week’s blog is brought to you by Paula Halabicki, BASF Technical Service Specialist

Distinct herbicide provides an excellent broad spectrum and alternative mode of action product for use on broadleaf annual, winter annual and perennial weeds in the post-harvest use segment.  Distinct combines two modes of action: dicamba, a Group 4 synthectic auxin and diflufenzopyr, a Group 19 that allows the weed control to glyphosate, resulting in cleaner fields in the spring and an effective herbicide resistance management strategy.

Here are some tips for the best results with Distinct applied in the fall:

  • Apply in the morning or early afternoon, as plants need two to four hours of 10 degrees Celsius or greater for effective translocation of systemic herbicides like Distinct.
  • Give weeds 1 or 2 days after frost before scouting to determine if herbicide applications are still available.
  • Leaves of weeds should have >60% green after a frost event for effective uptake of herbicides.  If more than 40% of tissue is dead due to frost, herbicides will be ineffective on weeds.
  • Perennial weeds can tolerate some frost depending on temperatures leading up to the frost event.  If daily temperature lows reach 5 degrees  or lower for multiple days prior to the frost event, perennial plants “harden off” and may with stand frosts close to -10 degrees and still be effectively controlled with post-harvest treatments.  Without these lead up temperatures, these plants can be dormant after a frost as light as -3 degrees, resulting in reduced control.  Scouting for actively growing plants is vital prior to application.

Tank mixed with glyphosate, one case of Distinct will treat 40-80 acres, depending on rate (58-115 g/ac) and is supported with Merge or MSO applied at 200 ml /ac.  Distinct applied at 80 ac/case prior to October 15 allows for all cereal and corn crops to be seeded the following spring.  Applications prior to October 1 allows for all canola systems, soybeans, field peas, and lentils to be seeded the following spring.  Applications prior to September 1, allow for all other unlisted crops to be planted the following spring.  If higher rates of Distinct are used after September 1, rotate to cereal or corn crops only.

A fall application of Distinct herbicide in combination with glyphosate allows for effective management of weeds, including glyphosate-resistant weeds, and gives growers the best chance at starting with clean fields in the spring.

Getting The Best of Both Worlds: Pre-harvest crop and weed management

~This week’s blog is brought to you by Paula Halabicki, Technical Specialist BASF

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Pre-harvest herbicide applications are an important tool for growers. According to growers, the number one reason for pre-harvest applications is for cleaner fields next spring, while speeding up crop dry down comes in second (Figure 1). By choosing the right pre-harvest management tool, growers can get the best of both worlds – a faster crop dry down with effective weed control. 

Figure 1. Grower survey results showing the number one reason for pre-harvest glyphosate applications.

 Contact vs systemic herbicides 

There are two kinds of pre-harvest herbicides – contact and systemic.  Contact herbicides, such as diquat, cause rapid dry down of the plant tissue that they come into contact with, but this may not result in complete plant death. These desiccants must also be applied at higher water volumes for improved coverage and there is risk of crop regrowth. Systemic herbicides, such as glyphosate, translocate to the growing points of the plant. This leads to complete plant death and a reduced risk of regrowth, but plants take longer to dry down. Heat LQ contains both contact and systemic properties, speeding up crop and weed dry down for both a faster harvest and cleaner fields the following season.

 

Cleaner fields next spring

When tank mixed with glyphosate, Heat LQ does not compromise the level of perennial weed control provided by glyphosate. The combination provides faster, more complete weed dry down on many annual weeds compared to glyphosate alone, leading to reduced weed pressure the following spring.  Using multiple modes of effective action in the tank is also a great way to prevent glyphosate resistance from developing.  Wherever possible, add in a second mode of action.

 

Improved harvestability

Crop dry down and the timing to harvest will be fastest when using a desiccant and slowest with glyphosate alone.  The combination of Heat LQ and glyphosate will fall somewhere in between. Although not as fast as a desiccant, tank mixing Heat LQ with glyphosate has been shown to improve crop and weed dry down, right down to the stalks, thus reducing green material that may affect harvesting efficiency, crop quality and storability.

 

Application Timing

Pre-harvest herbicide applications should be made when seed moisture is less than 30%. Earlier applications can potentially reduce yield and/or impact quality. Here are some quick tips for making sure an application is made at the correct stage:

 

Canola

  • 60 to 75% of seeds have changed colour (later is better to allow for complete pod fill)
  • Do not determine by pod colour – pods must be opened to determine percentage change in seed colour
  • Seeds on the bottom 2/3 to 3/4 of the plant are dark brown or black

Field peas

  • 70 to 80% of pods have dried down (changed colour)
  • The peas in the remaining pods should be firm
  • Peas cannot be split by squeezing

Sunflowers

  • Back of the heads have turned yellow
  • Bracts are yellow, edges of bracts are turning brown

Soybeans

  • 90% of the pods have changed colour
  • Lower pods are brown, upper pods are yellowish-brown or grey
  • 80% of leaves have dropped, remaining leaves are yellow
  • Seeds should rattle in the pods

Dry beans

  • 90% of pods have changed colour to yellow or light brown
  • 80 to 90% of leaves have dropped
  • Stems are green to brown in colour
  • The few remaining green pods are only in the top of the canopy
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