Turf Weeds at Virginia Tech

Turf Weeds was developed to provide weed management information and newsearch reports to turfgrass managers. This site contains information on weed identification, chemical and cultural management of weeds, and current topics relevant to weed management in lawns and professional turf. Turf Weeds was created by Dr. Shawn Askew, Assistant Professor of Turfgrass Weed Science at Virginia Polytechnic Institute & State University.

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A Hard to Control SOB “Star-of-Bethlehem”

Description:
Author:	Shawn D. Askew
Author Org:	Virginia Tech
Date:	01/05/2006
Presenter:
Conference:	Virginia Turfgrass Journal
Location:
File Formats:
Abstract:	Introduction: Star-of-Bethlehem (Ornithogalum umbellatum, L.) (SOB) is a bulbous perennial that resist mowing and is difficult to control. Plants reproduce primarily by small bulbs that are spread by plowing and watershed. Plants are poisonous and disrupt turfgrass uniformity and reduce sod value. SOB grows vegetatively from January to June but plants are not evident in summer and fall and may be overlooked on land rented for sod production until it is too late and turfgrass seed have already been planted. SOB is tolerant to most herbicides, including glyphosate, and Virginia Tech researchers have tested over 30 chemicals for its control in the past five years. Early research suggest that Gramoxone (paraquat) applied twice at 2.5 to 3 pints per acre effectively controls SOB. However, selective control measures are still not available. Our work suggest that rates of dicamba (Clarity) as high as one gallon per acre controls the majority of SOB plants without harming tall fescue and research conducted in Tennessee reported partial control with bromoxynil (Buctril) at normal labeled rates. Better selective controls are needed. Our goal was to evaluate a new herbicide, carfentrazone (Quicksilver) and Buctril in various combinations with Clarity to improve selective SOB control. Research Methods: Experiments were conducted in April 2005 in Nelson County, VA to evaluate combinations and rates of Banvel, Buctril, and Quicksilver. Banvel was applied at 2 or 4 quarts per acre, Buctril at 2 pints per acre, and Quicksilver at 2 or 4 ounces per acre. Various combinations, such as Banvel followed by Buctril, were also evaluated. Plots were visually rated for effects on tall fescue turf and SOB weeds one month later and plots have been marked for evaluation next year. Our comparison treatments included Gramoxone applied twice at 3 pints per acre, Velocity applied twice at 45 g active ingredient per acre, and aminopyralid applied once at 3.8 ounces per acre or twice at 1.7 ounces per acre. Experiments were conducted in April 2005 in Nelson County, VA to evaluate combinations and rates of Banvel, Buctril, and Quicksilver. Banvel was applied at 2 or 4 quarts per acre, Buctril at 2 pints per acre, and Quicksilver at 2 or 4 ounces per acre. Various combinations, such as Banvel followed by Buctril, were also evaluated. Plots were visually rated for effects on tall fescue turf and SOB weeds one month later and plots have been marked for evaluation next year. Our comparison treatments included Gramoxone applied twice at 3 pints per acre, Velocity applied twice at 45 g active ingredient per acre, and aminopyralid applied once at 3.8 ounces per acre or twice at 1.7 ounces per acre. Research Results: As in previous years, Gramoxone controlled SOB 96% but also injured tall fescue 95%. Treating with Clarity one week before treating with Buctril did increase the level of SOB control by 20% compared to either a single treatment of Clarity or Buctril but the best control observed with this combination was 63% at one month after initial treatment. An unexpected result of this research was that Quicksilver at 4 fluid ounces per acre controlled SOB 96% one month after treatment. Combinations of Clarity followed one week later with two treatments of Quicksilver, each at 2 fluid ounces per acre, also controlled the weed 96%. Quicksilver, Clarity, and Buctril did not injure tall fescue. Velocity and aminopyralid did not control SOB. As in previous years, Gramoxone controlled SOB 96% but also injured tall fescue 95%. Treating with Clarity one week before treating with Buctril did increase the level of SOB control by 20% compared to either a single treatment of Clarity or Buctril but the best control observed with this combination was 63% at one month after initial treatment. An unexpected result of this research was that Quicksilver at 4 fluid ounces per acre controlled SOB 96% one month after treatment. Combinations of Clarity followed one week later with two treatments of Quicksilver, each at 2 fluid ounces per acre, also controlled the weed 96%. Quicksilver, Clarity, and Buctril did not injure tall fescue. Velocity and aminopyralid did not control SOB. Recommendations: After five years of research and the trial conducted in 2005, we can make the following recommendations: After five years of research and the trial conducted in 2005, we can make the following recommendations: • To avoid SOB problems, scout rental fields in April, avoid tillage of infested areas, and don’t attempt to renovate infested areas with glyphosate (Roundup). • To control SOB selectively, apply Quicksilver at 4 fluid ounces per acre in late March. • To renovate areas infested with SOB, use paraquat (Gramoxone) at 3 pints per acre applied twice at a three-week intervals starting in late March. • To get more information on SOB, visit Dr. Askew’s Web site at www.turfweeds.net and enter its name in the search box.

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