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Texas Tech University (2011)

The response of Khakiweed (Alternanthera pungens Kunth) to herbicides, soil compaction, and mowing height

Hephner, Andrew

Titre : The response of Khakiweed (Alternanthera pungens Kunth) to herbicides, soil compaction, and mowing height

Auteur : Hephner, Andrew

Université de soutenance : Texas Tech University

Grade : Master of Science 2011

Résumé
Khakiweed (Alternanthera pungens Kunth) is a perennial broadleaf weed that readily invades managed turfgrass systems throughout the arid and semi-arid regions of the United States. The presence of this weed significantly reduces the aesthetic value and playability of desired turfgrass species. Morphological characteristics and the ability to adapt to a wide range of environmental factors have led to the increase in khakiweed prevalence in managed turf. Limited chemical control options exist for the reduction of khakiweed infestations. In fact, trifloxysulfuron is the only herbicide labeled for the postemergence control of khakiweed in turf. Therefore, investigation into the competitive response of khakiweed to cultural practices and examination of new herbicides may provide clues to long-term control. The effect of simulated compaction on the lateral spread of khakiweed was determined in field studies conducted in 2009 and 2010 in Texas over three month periods. Reduction in lateral spread was most severe in the high (9,519 N) compaction regime. At the conclusion of the experiment, khakiweed lateral spread in the high (9,519 N) compaction regime had only increased 95%. Lateral spread in the medium (6,346 N) compaction regime increased 126%, while lateral spread in the low (3,173 N) compaction regime increased 130%. Based upon these results, khakiweed can still increase in plant diameter when subjected to levels of compaction that may reduce bermudagrass quality and canopy cover. The effect of mowing regime on lateral spread of khakiweed was determined in field studies conducted in 2009 and 2010 in Texas over three month periods. Reduction in lateral spread compared to the non-mowed plots was most severe in the 1.3-cm mowing regime. At the conclusion of the experiment, khakiweed lateral spread in the 1.3-cm regime was reduced 250% compared to the non-mowed check. Lateral spread in the 2.5-cm regime was reduced 158% compared to the non-mowed check, while lateral spread in the 5.1-cm regime was reduced 118%. Therefore, khakiweed infestations may be more prevalent in bermudagrass mowing heights common to golf course roughs, athletic fields, and home lawns (≥ 2.5 cm). However, the production of a thick taproot high in carbohydrate content may enable khakiweed to regenerate from frequent defoliation common to golf course fairways. Khakiweed response to single and sequential herbicide applications was evaluated during the summer of 2009 and 2010 in Texas. Although initial khakiweed injury was observed in all treatments, effective long-term control was difficult to achieve. Excellent control (95 to 97%) was exhibited by sequential metsulfuron applications 12 WAIT regardless of rate. Sequential applications of trifloxysulfuron (0.018 or 0.028 kg ai ha-1) and single applications of metsulfuron at 0.042 kg ai ha-1 exhibited moderate khakiweed control (75 to 80%) 12 WAIT. All other treatments exhibited ≤ 57% khakiweed control 12 WAIT. The season-long (as assessed by the 12 WAIT control estimates) efficacy of sequential metsulfuron applications is a strong incentive for its adoption in place of sequential trifloxysulfuron (the only labeled herbicide) applications for the control of khakiweed in bermudagrass turf.

Mots clés : Khakiweed ; Compaction ; Mowing Height, Competition, Herbicides

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Page publiée le 18 juin 2013, mise à jour le 8 novembre 2018