Purdue News

June 19, 1998 Tolerate weeds in lawn until fall, expert advises WEST LAFAYETTE, Ind. -- Midsummer isn't the best time to try to control broadleaf weeds in lawns, says Purdue University turfgrass extension specialist Zac Reicher. Spraying broadleaf weeds at this time of year risks causing damage to landscape ornamentals, he said. "Many people think that it takes direct application to ornamentals to cause damage, but spray drift in mist or vapor can also cause damage," Reicher said. "The best way to avoid damage is to apply in October when these herbicides are most effective and when ornamentals are not susceptible to damage." In midsummer, the broadleaf weeds are pulling nutrients from the ground and sending them upward through the plant to the leaves. As fall nears, the nutrient flow reverses, as the plants begin sending nutrients from the leaves to the roots for the winter. Herbicides applied in late September or in October have a better chance of killing the entire plant. According to Reicher, if homeowners are absolutely determined to apply herbicides in midsummer, they should take these precautions: Apply early in the morning when there is little or no wind. Avoid spraying when temperature are over 80 degrees to avoid volatilization of the herbicide. Use the lowest application pressure possible, which will make the droplets as large as possible. Stay as far away from ornamentals as possible, or shield them with cardboard. CONTACT: Reicher, (765) 494-9737; zreicher@dept.agry.purdue.edu; http://www.agry.purdue.edu/agronomy/turf/zjr-bio.htm Compiled by Chris Sigurdson, (765) 494-8415; E-mail, sig@ecn.purdue.edu Purdue News Service: (765) 494-2096; e-mail, purduenews@purdue.edu To the Purdue News and Photos Page