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What is Pre-emergent?

Ask any turf specialist this question and you will get a simple response, "It is your crabgrass control." But how does this seemingly miracle product work, and what does it mean to my family? These are the most common questions that follow. The answers to these questions are more complex, but that is what your Loyalty Lawn Care specialists are here for.

The pre-emergent herbicide is a pro-active control measure of many annual weeds. Often applied in many practices of the agricultural community, this product is used in turf management programs to prevent many difficult annual weeds like crabgrass. It will create a barrier in the soil that prevents germination of seeds by prohibiting the cell walls organization. It does this by blocking specific enzymes crucial to plant development. This just means that the seed cannot mature, and so the process will have a minimal, if any, effect on a plant that has already been established or made it through its seedling stage. This process is effective on crabgrass, but it does mean that a successful seeding in the spring may be difficult.

Since the process prevents the germination, it needs to be in place before the soil temperatures are right for the young seedling to grow. In the St. Louis area, that is typically in late February to mid-March, however that often varies with the weather. In many southern lawns, due to the warmer climate, a fall application can often be beneficial.

The need for spring seeding is sometimes a concern for many homeowners, however the spring months do not provide a very effective window for the young turf to mature prior to its exposure to the summer heats. For this reason, a fall seeding is going to be most beneficial for cool season turfs in our area. In addition to being more effective for a successful seeding, waiting until fall allows the pre-emergent to break down in the soil. The two most common pre-emergent herbicides used in turf management throughout the Mid-West are Barricade and Dimension. Both products last anywhere from 3-6 months, depending on the application rate and environmental conditions. A great way to achieve season long control is to over-lap two treatments of pre-emergent in the spring, with a divided rate, to achieve optimal control through the summer months.

As the world around us evolves, so do the concerns of many homeowners. The questions of safety and environmental effect are often in all of our minds. Pre-emergent herbicide is a product that seems scary to some, but the facts are that they are less toxic than common house hold aspirin. The EPA has a way of measuring the toxic dose of chemicals that they label as the LD50 number. This is the lethal dose of a substance that can cause death in 50% of the tested population. Aspirin has a LD50 of >1600, where the common pre-emergent Barricade has a LD50 of >5000. Now, that number seems much more dangerous if you don't know what the numbers mean, however the larger number means that you would have to consume a much larger dose to achieve a fatal result making it less toxic.

Understanding Pre-emergent herbicides is a big step in developing your own turf management program. Your turf specialist is trained to understand the proper timing, rates, and any factors that may alter the effectiveness of this product. Call your Loyalty Lawn Care professional today to set up your free evaluation and get started toward a beautiful, crabgrass free, lawn today!