TURF MANAGEMENT The Importance of Pre-emergent Controls Weeds come at your lawn from all angles, in all seasons-rain or shine, sleet or snow. They compete with grass for precious sunlight and soil nutrients, and they are resilient. Pre-emergent herbicides attack weeds while theyre still seeds, essentially eliminating unwanted plants before they begin to germinate. They create a seal over the topsoil acting as a weed-prevention barrier zone. When applied correctly and in a timely fashion, pre-emergents penetrate one to two inches of the soil and prevent the weeds from reaching the surface. When it comes to applying pre-emergents, geography, mother nature and soil temperature are a few of the many factors that are considered. Timing is everything and, as the name implies, pre-emergent herbicides need to be applied before the weeds begin to germinate. Due to variations in climate, application dates will vary and different species of weed will germinate at different times. The key indicator in weed germination is soil temperature. Soil temperature is like an environmental signal to most weeds to start sprouting. There is no concrete rule, but in general when the soil temperature reaches 50 degrees F most weeds will begin to germinate. Already having the pre-emergent controls in place will prevent those stubborn weeds from appearing. Pre-emergents are especially important for the prevention of crabgrass, foxtail, spurge and other hard-to-kill weeds. It is much easier to prevent them from germinating, than trying to eliminate them once theyve matured. But you cant just apply a pre-emergent once and expect a pristine lawn to maintain its gleam. No matter how well crabgrass has been controlled in previous years, there is still a tremendous seed bank in the soil and any weak spots in the lawn are likely sites to be invaded by this fast growing summer annual. Crabgrass’ rapid emergence and extremely fast growth rate allow it to get a jump start on both cool and warm-season grasses alike. It takes a calculated annual or semi-annual approach to control weeds and eliminate them from your lawn. It is also important to note that pre-emergent controls need to be watered into the ground after application. Whether by rainfall or irrigation, the watering process is essential to the formation of the weed-prevention barrier throughout the top of the soil. Return to Listing
Posted on: Mon, 19 Jan 2015 01:54:11 +0000
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