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I sprayed but I didn’t kill the weed!

(By Jared Hoyle, KSU Turfgrass Research and Extension)

“I sprayed but I didn’t kill the weed!” I get this comment many times throughout the year and there could be may possible reasons why, other than saying that herbicide doesn’t work. What I have found is that the most common reason is human error. So, here are a couple questions you should ask yourself to help determine what went wrong.

  1. Did you correctly identify the weed?
  2. Was the weed listed on the label?
  3. Did you use the correct rate?
  4. Did you have uniform spray coverage?
  5. Did you apply it at the appropriate growth stage?
  6. What was the temperature when you applied? Was it within the label recommendation?
  7. Was there adequate soil moisture for weed growth?
  8. Did you tank-mix?  Could have an antagonistic effect!
  9. Where you suppose to make two applications (according to the label)?
  10. Did it rain or did the irrigation run soon after application?
  11. Did you add an adjuvant or surfactant that was recommended on the label?
  12. If you applied a PRE, did you water it in, within the next few days? or has the weed already germinated or emerged?

These are just a couple questions used to help figured out what happened if you sprayed and didn’t kill the weed.

Always remember to READ THE LABEL for the correct rate, turfgrass tolerance, and specific instructions before application!!!

***Mention of trade names or commercial products in this article is solely for identification purposes and does not imply recommendation or endorsement, nor is criticism implied of similar products not mentioned by Kansas State University.***

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