How to Combat Weeds with Preemergents and Cultural Controls

As temperatures warm, weed control should be top of mind. Both the use of preemergent products and cultural controls are important for keeping a lawn looking lush and healthy. The more opportunities weeds are given to thrive, the harder it could be to reduce future problems. Read further to learn about the best time to apply and the effectiveness of a preemergent, as well as cultural controls to help fight against turf weeds.

When is the Best Time to Apply Preemergent Products?

Preemergent herbicides are best applied during early spring but can vary based on climate and geographical region. For example, in warmer parts of California and Arizona, January through March are ideal times to apply whereas, in colder regions with longer winters, this can range anywhere from March through May depending on the growing season. Regardless, it can be hard to determine an exact day that a preemergent should be applied. Soil temperatures will be the best indicator. Checking with a local university extension is also a good way to know the best application timing for each region.

What is the effectiveness of Preemergent Products?

Applications of preemergents typically have an effectiveness of 6 to 8 weeks. Relying on this number though is not ideal, since it is possible for the applied product to lose efficiency and not work throughout its lifetime. Therefore, it is important to continue checking soil temperatures that ensure an application is closest to the appropriate time. Applying at the correct time not only is efficient but also less wasteful, since the product will be at its full potential.

A 1/2 inch of water to the lawn should be applied after using preemergent products. This will help the product reach the seeds within the soil to ensure it blocks germination. Before applying, check weather conditions for the following days. Do not apply when expecting heavy rain to avoid dilution, leaching, and runoff. It is best to confirm the exact amount of time or water needed for the product by referring to the product label. Some products might indicate at least waiting 1 to 2 days after application due to the active ingredients within the product and how they react. (example below from BEST® ONE-SHOT™ which also includes a postemergent component, further adding to irrigation requirements for optimized weed control).

The effectiveness of preemergent products can also change based on the amount applied. To ensure proper application refer to the product’s label. The label will give directions on the amount needed and any other special instructions (e.g., calibration settings, when to apply after overseeding, and any ornamental landscape details). Be careful to follow application instructions, as an over or under-application of preemergent products have the potential to cause issues. Not only is overapplication wasteful and a label violation, but it will potentially damage the turfgrass. And although underapplying might seem like a good idea to save money, doing so could reduce the efficacy of the preemergent’s active ingredient, resulting in future costs to combat the issue.

Remember, Federal and State laws prohibit the use of herbicides outside of the scope of their label to protect applicators and the environment. Following the directed rates and timings provides the proper dose needed while also helping to minimize the possibility of harm to you or the surrounding environment.

Cultural Controls to Help Fight Against Turf Weeds

Preemergent products can aid the fight against weeds, but you can help reduce this problem by making changes to your landscape program. Below are a few cultural controls that might improve turfs fight against weeds.

Regular feeding

A stressed lawn that is missing the nutrients it needs could result in turfgrass being taken over by weeds. According to Penn State University, “Inadequate fertilization lessens the competitiveness of turfgrasses, resulting in reduced density and subsequent weed invasion.” To reduce this issue, proper fertilization can help improve turf vigor and provide growth for a lush lawn, making it harder for weeds to thrive. Therefore, it is important to have routine soil tests and ensure the turf you manage is at its best all year round. 1

Water Scheduling

Infrequent and deep watering can help turfgrass grow deeper roots. Not only could deeper roots aid in competing for space against weeds, but they might also help during periods of drought. 2

Mowing Height

According to Penn State University, “As turf grows in height, and in density, it is shading out the sun from reaching the soil. As you know, weed seeds need proper temperatures and sunlight (along with water) to germinate. If sunlight is not penetrating the turf canopy, many weeds are unable to germinate, allowing for the turf to grow better. Studies have shown that increased mowing height alone reduces weed pressure significantly, even in the absence of pre-emergent herbicides.” 3

Regularly Scheduled Aeration

Increased soil compaction creates an unfavorable environment for turfgrass to thrive. Because of this weeds have less to compete with and are more likely to form. This is why regular aerations are important for lawns once or twice a year. It is recommended to use a preemergent herbicide after this process since some weed seeds might be present in the soil cores lifted out during aeration. 4

Benefits of BEST® Granular Preemergent Products

BEST® provides a handful of granular preemergent products. The benefits of a Granular preemergent include convenience, ease of use for unpredictable weather, and 2 in 1 application of a preemergent and fertilizer.

A granular preemergent can be easier to use with minimum preparation since it is simply loaded into the spreader, whereas liquid forms often require measuring and mixing of components. Granular might also be less of a hassle to use during the spring. Because of the season's unpredictable weather, liquid equipment needs to be kept warm during this time to reduce the chances of freezing pumps. You can also save time by not having to worry about other equipment issues, such as blowing out lines. With granular forms, you simply need to put the product into the spreader. In addition, BEST® preemergent products offer dual benefits of a preemergent herbicide and a fertilizer mixed in one. This is convenient for turf managers during the cool season to provide a boost of nutrients to the turfgrass. Adding these nutrients could result in the Growth of a more competitive turfgrass that can help choke out future weeds.

For a complete list of preemergent and fertilizer products that can help you combat weeds for your turfgrass this season, contact your BEST® Sales representative or local BEST® distributor today.

Sources

  1. “Control of Summer Annual Grass Weeds in Turfgrasses.” Penn State Extension, 1 Jan. 2022, https://extension.psu.edu/control-of-summer-annual-grass-weeds-in-turfgrasses.
  2. “How to Manage Pests.” UC Healthy Lawns-Irrigation: How to Water, https://ipm.ucanr.edu/TOOLS/TURF/MAINTAIN/irrhow.html.
  3. “The Impact of Mowing on Weed Pressure.” Penn State Extension, 11 June 2015, https://extension.psu.edu/the-impact-of-mowing-on-weed-pressure.
  4. “How to Manage Pests in Gardens and Landscapes.” UC IPM Online, Mar. 2016, https://ipm.ucanr.edu/PMG/PESTNOTES/pn74113.html.