Things to know when using preemergence herbicides

Published 4:33 pm Friday, February 10, 2017

By Ty Torrance

When planning your preemergence herbicide applications there are a couple of things to consider.  Preemergence herbicides kill weed seeds that may be present in your lawn.  The herbicide only works if the chemical is present when the weed seed attempts to germinate.  Once the herbicide is sprayed it can persist and continue to work for some time, but it does not last forever.  It is important that the herbicide is applied at the most opportune time to get sufficient control of weeds.  In South Georgia, we typically need to spray between Feb 15th – March 15th because that is when the soil warms up enough for seed to germinate. The majority of weed seed need soil temperatures near 55°F to germinate. 

As I mentioned above this temperature typically occurs between Feb 15th- March 15th, but this year has been different.  Many farmers will say they are not sure what a typical year looks like because they have never seen one.  South Georgia weather always has a way of keeping you on your toes.  The soil temperature for the past two weeks has been over 55°F.  It is likely that your lawn never went completely dormant.  Nevertheless, applying peremergence herbicides in this time frame will give you the best chance to kill weeds before they emerge. 

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There are so many products out there that can be used.  Most of the products that will serve as good preemergence herbicides will have crabgrass somewhere in the name.  To make sure you are getting the correct chemical, look at the front of the bottle near the bottom and you will see a list of active ingredients with a percentage beside them.  The following herbicide active ingredients are labeled for homeowner use: atrazine, benefin, dithiopyr, oryzalin, pendimethalin, and prodiamine.  So, no matter the large printed product name in red ink make sure you look at the bottom and read what the bottle contains.  Some of the chemicals can only be used in specific turf types like centipede or bermudagrass.  Check the label to see if your grass is listed before you apply.  Also, some products can damage shrubs and ornamentals, so be cautious where you apply the chemical. 

If you have any questions, please give us a call at the Decatur County Extension office: (229) 248-3033.