Effect of Various Herbicides on Warm-season Grass Weeds and Switchgrass Establishment

Switchgrass (Panicum virgatum L.) is typically slow and difficult to establish. Field experiments evaluated switchgrass establishment and the response of warm-season grass weeds (large crabgrass [Digitaria sanguinalis (L.) Scop.], broadleaf signalgrass [Urochloa platyphylla (Munro ex C. Wright) r.D. Webster], Johnsongrass [Sorghum halepense (L.) pers.], and Texas panicum [Urochloa texana (Buckley) r.D. Webster]) to a preemergence (cloransulam) or postemergence (foramsulfuron, pendimethalin, quinclorac, foramsulfuron + pendimethalin + quinclorac, nicosulfuron, nicosulfuron + pendimethalin + quinclorac, nicosulfuron + quinclorac + atrazine, and monosodium methanearsonate [MSMA]) herbicides. Experimental design was a split-split-plot design with presence/ absence of preemergence herbicide cloransulam as main plot, weed species as subplot treatment, and postemergence herbicides as sub-subplot treatments. Herbicides foramsulfuron + pendimethalin + quinclorac was applied at the 1to 2and 2to 3-leaf stage, whereas nicosulfuron was applied at 2to 3-leaf stage and nicosulfuron combinations and MSMA were applied at 3to 4-leaf stage. Using cloransulam as a preemergence herbicide resulted in lower switchgrass seedling numbers and generally did not improve establishment. Interseeding Johnsongrass allowed for the greatest number of switchgrass seedlings and was the least competitive weed, whereas interseeding large crabgrass resulted in the least amount of switchgrass and proved to be the most competitive weed. Foramsulfuron + pendimethalin + quinclorac resulted in effective weed control (>70%) for all four species evaluated and improved switchgrass establishment (13–26%) compared to the untreated control (0–3%); however, greater improvement in stand establishment is needed. M.K. Kering, C. Huo, S.M. Interrante, and T.J. Butler, The Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401; D.W. Hancock, Univ. of Georgia, Athens, GA 30602. Received 25 Apr. 2012. *Corresponding author ([email protected]). Abbreviations: 2,4-d, 2,4-dichlorophenoxyacetic acid; DAP, days after planting; DAT, days after treatment; MSMA, monosodium methanearsonate; MSO, methylated seed oil; PLS, pure live seed. Published in Crop Sci. 53:666–673 (2013). doi: 10.2135/cropsci2012.04.0252 Freely available online through the author-supported open-access option. © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.