Efficacy of Current Organic Postemergent Weed Control Options in Lawns.

A common question from lawn care companies and homeowners is “What organic herbicides or non-pesticide products are available for weed control?” An organic herbicide is one that can be used in USDA Organic farming. There are few organic herbicides available in turf. The objectives of this experiment were to determine the efficacy of various organic control products on common weed species, and also to determine the herbicide injury caused by various organic control products on Kentucky bluegrass. Turf injury was highest for the flame thrower treatment in both yeras applied in late October although turf had completely recovered by April the following spring. Scythe, Organic Weed & Grass Killer, BurnOut Weed & Grass Killer, vinegar, octanoic acid, octanoic acid + clove oil, and clove oil all also caused unacceptable injury to Kentucky bluegrass in the initial weeks after application in both years. No product provided ground ivy control in either year of the experiment. Dandelion coverage varied by treatment (P=0.07) with the Ortho Weed-Be-Gon (RTU) reducing dandelion coverage to 1% in the spring of 2011 with organic herbicides not providing any appreciable control. Dandelion coverage was not rated in 2012. Weed control without herbicides remains difficult in turfgrass systems due to undesirable turf injury and low efficacy of organic products. Homeowners wishing to control weeds with organic products need to make multiple spot treatments for improved control and be willing to accept some turf injury.