Perfect Spray Timing for Better Dandelion Control

/_uploads/images/ts-weeds-WCAN.jpgSpraying multiple effective modes of action is one of the best ways to control tough and herbicide-resistant weeds.1 But for some weeds, when you spray is even more important than what you spray.

 

Here are some strategies to help you perfect your application timing and get better control of perennials like dandelion in the spring and fall.

 

SPRING CONTROL STRATEGIES

 

Expect to achieve only top-growth control in the spring. The dandelion in your field are the over-wintering perennial plants from last year, and they will have already flowered and set seed by the time you make a pre-plant burndown.2

 

Your spring weed control strategy should focus on reducing competition for the incoming crop and removing top growth to starve the root system.

 

The dandelion seeds produced by the over-wintering plants will germinate in late June to early July – after many farmers have completed their in-crop herbicide application. Control this population with a post-harvest glyphosate application.

 

FALL CONTROL STRATEGIES

 

“Dandelions are easier to control in the fall than in the spring,” says Johnathan Dierking, Monsanto Weed Management Technology Development Representative in Wisconsin. “If you wait until spring, dandelions will be much hardier after storing up moisture and nutrients in their root systems from overwintering.”3

 

In the fall, dandelion stocks up its root reserves for the winter. Systemic herbicides can move through the plant with the sugars being sent down to the roots.4 Applying a full-rate of glyphosate when the plants are actively growing will do the most damage to the roots.

 

Post-harvest weed staging

Dandelion can survive several light frosts, so it can be treated later into the fall. Watch out for hard frosts and droughts – they’ll stop weed growth, and glyphosate will not control perennials at the root level. If a hard frost has occurred, wait at least two days for plants to recover and check for leaf tissue damage before spraying. At least 60% of the plant leaf tissue should remain green for glyphosate to work effectively.5

 

Target weeds Regrowth required Rate (L/ac) Tillage interval Comments
Dandelion <15 cm diameter
>15 cm diameter
0.67 – 1.0
1.0 – 1.33
Minimum 5 days Use higher rates for larger plants. Apply pre-bloom to full-flower for best results. Dandelions covered in straw will likely not be controlled.

CULTURAL CONTROL STRATEGIES

 

Use selective, post-harvest tillage.

For dandelions, tillage must be deep enough to cut the root 4 inches below the crown. Heavy-duty cultivators and deep tillers offer the best control.6

 

Dandelion can be tilled seven days after a post-harvest glyphosate application. Following this window will ensure sufficient herbicide translocation for optimum control.

 

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1 Kniss, Andrew. “Want to reduce herbicide resistance? Spray more herbicides!” Control Freaks, Wyoming Weed Science 17 Nov. 2014. Web. Accessed 4 Apr. 2016

2 “Controlling Dandelion In The Fall.” Manitoba Agriculture, Food and Rural Development. Web. Accessed 1 May 2017. http://www.gov.mb.ca/agriculture/crops/weeds/print,controlling-dandelion-in-the-fall.html

3 “Fall is Best Time to Control Dandelions in No-Till Fields.” Roundup Ready Plus. 1 Nov. 2012. Web. Accessed 28 Apr. 2017. http://www.roundupreadyplus.com/resourcecenter/fall-is-best-time-to-control-dandelions-in-no-till-fields

4 “Dandelion.” Ontario Ministry of Agriculture, Food and Rural Affairs. Web. Accessed 1 May 2017. http://www.omafra.gov.on.ca/english/crops/field/weeds/dandelion.htm

5 “Managing Late Season Perennial Weeds.” Roundup Ready Plus. 25 Aug 2016. Web. Accessed 1 May 2017. http://www.roundupreadyplus.com/resourcecenter/managing-late-season-perennial-weeds

6 “Dandelion.” Manitoba Agriculture, Food and Rural Development. Web. Accessed 1 May 2017. http://www.gov.mb.ca/agriculture/crops/weeds/print,dandelion.html