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Evaluation of Alligatorweed (Alternanthera Philoxeroides [Mart.] Griseb.) Control with Nine Different Herbicides

Cox, M. C., Wersal, R. M., & Madsen, J. D. (2010). Evaluation of Alligatorweed (Alternanthera Philoxeroides [Mart.] Griseb.) Control with Nine Different Herbicides. Aquatic Plant Management Society 50th Annual Meeting. Bonita Springs, FL.


Alligatorweed (Alternanthera philoxeroides [Mart.] Griseb.) is an emergent, herbaceous perennial native to South America that has invaded over 32 countries around the world. Alligatorweed forms hollow stems that produce adventitious roots at the nodes and anchor into nearby sediment or organic matter. This aquatic invasive plant is capable of forming dense, floating mats that may impede boat traffic, harbor insects carrying pathogens, cause flooding, and reduce overall water quality. The objective of this study was to evaluate control of alligatorweed with nine different herbicides applied at both 0.5 and one times half the maximum label rate: diquat (2.24 and 4.48 kg ai/ha), glyphosate (isopropylamine salt at 2.27 and 4.54 kg ae/ha and diammonium salt at 2.10 and 4.20 kg ae/ha), 2,4-D (1.06 and 2.13 kg ae/ ha), carfentrazone (0.11 and 0.22 kg ai/ha), penoxsulam (0.05 and 0.101 kg ai/ha), imazamox (0.28 and 0.56 kg ae/ha), imazapyr (0.56 and 1.12 kg ae/ha), and triclopyr (3.36 and 6.72 kg ae/ha). Visual control ratings (0-100%) were taken every 7 days, beginning after treatment. At 28, 56, and 84 DAT plant tissue was harvested at the soil line from each pot, dried at 70 C for 7-10 days, and weighed. Carfentrazone applied at both rates and penoxsulam at half the maximum label rate showed significantly the least control 28 DAT, with all other herbicides showing similar control results. Glyphosate, 2,4-D, imazamox, imazapyr, and triclopyr showed significantly more control 56 DAT, and carfentrazone showed the least. By 84 DAT, imazapyr, triclopyr, imazamox, glyphosate, 2,4-D, diquat, and penoxsulam at the maximum label rate showed significantly better control of alligatorweed than carfentrazone, diquat (1/2 rate) and penoxsulam (1/2 rate). Carfentrazone applied at the maximum label rate did not control alligatorweed at 84 DAT.

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