When to Apply Pre-Emergent Fertilizers and Herbicides this Spring

By Derrick Wozniak- Golf Course Superintendent Radley Run Country Club

The early onset of spring like day time temperatures has everyone questioning when to apply pre-emergent fertilizers and herbicides in order to prevent crabgrass and other broadleaf weed emergence within your lawns later this summer? Sometimes using phenological indicators, such as forsythia bloom, are the best way to monitor the timing of your application if you are not keeping track of soil temperatures, but this can be misleading. As you are driving around, take notice of where these plants are in bloom along the roadside or driveway. Ambient temperatures next to the road or driveway are significantly higher than other locations in your lawn. Yes, you could apply your pre-emergents to these specific locations, but realistically, overall soil temperatures are still too cool.

Initial emergence of crabgrass will begin when the soil temperatures, not the air temperatures reach the middle to high 50’s. You will not see a significant crabgrass emergence until soil temperatures reach the mid 60’s. Currently we are experiencing very cool nighttime temperatures which are keeping the soil temperatures relatively low, so holding off your application for a few weeks will only benefit you later in the summer, as the longer you wait, the longer residual you will have in your soil.

A well-timed application is the difference between having a weed free or weed infested lawn later this summer. A little early is much better than too late, but applying something is always better than applying nothing at all. By the middle of April at the latest, I would recommend having granular pre-emergents applied to your lawn. Responsible application before a rain event this time of year, will give the herbicide time to disperse into the soil and create the barrier needed to prevent the weed seeds from germinating. Even if you see small plants emerging right now, a pre-emergent will kill these smaller plants before they become too large to manage. Fortunately, there are many post emergent crabgrass options at your local hardware store if your timing is slightly off.

Derrick Wozniak
4+ years as golf course superintendent at Radley Run Country Club
18+ years of experience in the turfgrass industry
Vice President of the Philadelphia Association of Golf Course Superintendents
Member of the Golf Course Superintendents Association of America
Member of the United States Golf Association

When to Apply Pre-Emergent Fertilizers and Herbicides this Spring
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