by Tom Peters, Extension Sugarbeet Agronomist
I have been traveling the countryside to complete spring planting, like many of our growers in North Dakota and Minnesota. I have traveled past beautiful freshly planted fields, enjoying the contrast between the green ditches and black fields. However, recent heat and rainfall have changed the landscape. One can now row emerged crops in fields. And to no-one's surprise, there are weeds in fields.
Growers have two options for controlling grass and broadleaf weeds in sugarbeets. First option is to implement a postemergence spray program. I suggest you start by reviewing any historical data or fields for weeds to be sure you are absolutely sure of the weed species, weed size and weed density. Use a weed identification guide or ask for help from your ag retailer or extension specialist if you are not sure about the identity of weeds. Consider the following guidelines when using glyphosate:
- Use maximum allowable rates in every application.
- Apply to small, actively growing weeds, 1-2 inches tall to maximize control.
- Know your glyphosate formulation; add a high quality nonionic surfactant at 0.25% v/v to fully loaded formulations (unless prohibited) to improve control of tough weeds. Add 0.25 to 0.50% to partially loaded formulations and add 0.5 to 1.0% to non-loaded formulations.
- Use a tank-mix partner with glyphosate for control of tough weeds such as common ragweed, giant ragweed, common lambsquarters, kochia or waterhemp.
- Scout fields and be prepared to apply a sequential application, approximately 14 days after the first application.
There are three acetamide herbicides labeled for use layby in sugarbeet. They are Dual Magnum, Outlook and Warrant and can be applied over 2 to 8 leaf sugarbeet. Consult the label for applications rates and other details. Use the following guidelines and considerations when using herbicides layby:
- There are no concerns with replanting sugarbeet in Outlook or Dual treated fields. However, Warrant is labeled for postemergence only in sugarbeet.
- Consider the preharvest interval (PHI) between application and sugarbeet harvest. The PHI for Dual Magnum, Outlook and Warrant is 60 days, 60 days and 70 days, respectively.
- Acetamide herbicides must be rainfall activated for them to provide weed control.
- Outlook, Dual Magnum and Warrant can be split-applied. The interval between sequential application ranges from 7 days (Warrant) to 10 days (Outlook). The Dual Magnum label does not stipulate a time interval between sequential sprays. Split applications generally have improved consistency of small seeded broadleaf control in NDSU and University of Minnesota trials.
- Warrant is an encapsulated formulation. I suggest application of Warrant no later than the 4-leaf stage to ensure the product gets properly activated.