Depending on your climate, crabgrass may already be germinating in your region. But that doesn’t mean it’s too late to apply pre-emergents. You can still use two main active ingredients for pre-emergent applications: prodiamine and dithiopyr (Dimension). We have in-stock products with both active ingredients, and we’ll help you determine which is right for you.

Prodiamine is a more cost-effective option, but your application window is closing. The initial germination of crabgrass occurs once the average soil temperature is 55ºF at a depth of two inches for three to four consecutive days. However, most crabgrass doesn’t germinate until the soil reaches an average temperature of 73ºF at a depth of one inch. 

With this emergence window, you can continue using prodiamine even after the initial germination, as it will prevent crabgrass emergence. Now’s the time to secure fertilizer with prodiamine and make applications before the window closes. You’ll spare yourself the stress of additional labor and more expensive chemistries to control crabgrass later in the season. Just don’t use high rates of prodiamine for late applications, especially if there are seeding projects later in the year.

It may be tempting to skip pre-emergent applications for new customers who sign up in round two or late in round one. But remember that a post-emergent approach to annual weeds will not make an excellent first impression. Even when you set proper expectations, most customers are not very patient. Studies show weeds are the number one reason lawn care customers cancel their service.

Often overlooked, foxtail and goosegrass germinate much later than crabgrass but are just as unsightly. Additional or later applications will help control these weeds as well. Pre-emergents can also help with summer broadleaf weeds like oxalis, spurge, and purslane. 

Now that we’re in the middle of the crabgrass pre-emergent application window, we must consider which products we use as the temperature rises, and crabgrass begins to germinate. 

Post-emergent control of annual grasses is inconsistent, expensive, and labor-intensive. Think of an additional pre-emergent application as an investment in future cost savings and improved customer retention.

Using various active ingredients is a good strategy for integrated pest management. However, Dimension consistently outperforms other pre-emergent herbicides as the second application of the year because of its post-emergent control. Dimension shows post-emergent crabgrass control with liquid and granular applications, providing flexibility around the crabgrass germination window. 

Dimension can provide post-emergent control when applied in two applications of at least 0.25 pounds of active ingredient per acre to achieve optimum crabgrass control. Depending on the formulation of your product, you can use the below application rates.

  • Fertilizer with 0.10% Dimension: 5.74 lb/1,000 sq ft
  • Fertilizer with 0.125% Dimension: 4.59 lb/1,000 sq ft

For both pre-emergent and post-emergent success, it’s best to use higher spread rates (no less than 4 lb/1,000 sq ft) to ensure particle distribution.

Making split or sequential pre-emergent applications is a great way to keep weeds at bay. Some years we have excessive precipitation, which erodes the initial pre-emergent barrier. A second application extends your protection by maintaining a strong barrier into mid-summer. 

Another aspect important to success is calibration. Especially with the changing fertilizer market, be sure that the load rate of Dimension matches the amount of NPK you are trying to put down. Cutting corners will only lead to more problems this summer.

Your Advanced Turf Solutions sales representative can help you decide between prodiamine and Dimension for your scenario. Whichever you choose, we have the products in stock for you to make pre-emergent applications before it’s too late.