Are You Seeing Weeds-This Could Be Why
Weeds are now active across West TN and parts of Southeast MO. So why would lawns that get treated have weeds already coming up even after they had a Fall Pre-Emergent applied? That’s a great question. The answer is actually pretty simple.
First, your selection of your Fall Pre-Emergent will ultimately determine the residual, or how long the herbicide will remain effective in the soil inhibiting weed germination. So, one must determine which weeds that they are trying to control, and then make a final decision on the Pre-Emergent to select that will prevent those weeds as well as how long that Pre-Emergent will last.
Secondly, assuming your Pre-Emergent has expired, your soil temperature must reach a certain temperature for germination. And with the recent mild temperatures that is no big surprise. That would explain why in some years, such as last, it was closer to Mid-March before we ever began to see weeds like we are now. Average temperatures were much cooler. Even though we still have cool/cold days and nights, our current weather has been strangely mild for this time of the year. Even as I write, we are supposed to break record highs again today in hitting 72 degrees! (For February 7th) That is crazy. So what does that do for our weed control strategy. Well, quite a bit actually.
We generally deal with warm season grasses, such as Bermuda grass and Zoysia grass, in West Tennessee and Southeast Missouri. Pre-Emergent Applications need to be applied, for all practical purposes, early, before weed germination. Therefore, it is ideal to get you Fall Pre-Emergent application down around Mid-September while air temperatures are between 50 and 70 degrees. However, it is impossible for professionals to be on all properties at the same given time, so we not only apply a Pre-Emergent during the fall, but also add a Post-Emergent in the same application to control weeds that are already up and active. The later you apply your Pre-Emerge the longer it will last into the late winter or early spring.
For example, the Fall Pre-Emergent of choice in 2016 for 4-Evergreen is expected to have a residual that last up to 4 months. So, if your Fall Pre-Emerge Application was applied in Mid-October, the material that was applied is beginning to lose its effectiveness. That would make perfect sense why you are starting to see this new weed pressure.
This could be the explanation for some of those who are just now starting to see the problems. If weeds are a continual problem for you in your lawn even with a steady diet of Spring and Fall Pre-Emergent Applications, there could be a more underlying issue. Remember that a thick, healthy lawn provides for a great weed defense. And a good fertilization strategy to keep your lawn thick and healthy will help with the invasion of weeds. Lawns that are under-fertilized, unhealthy, and thin will have more weeds. Also, check your soils Ph by pulling a soil sample. Lawn soils that are too acidic are also prone to have more weed problems. Weeds thrive in acidic soils.
I hope this may help shed a little light on how Pre-Emergent Applications and when they stop working. If you are a 4-everGreen (or not) customer and are seeing weed pressure, please contact us to schedule your next scheduled visit or a free consultation.
For more information about Soil Samples or our Pre-Emergent Applications, please visit our website or call our office.
Hope everyone has a great week,