Texasweed is an annual broadleaf plant belonging to the Euphorbiaceae family and is an emerging problem in southern U.S. rice fields. Field studies were conducted in 2008 and 2009 to study the effect of flood depth on Texasweed survival and growth. The trearments were five flood depths: 0, 10, 15, 20, and 30 cm and two Texasweed growth stages: two- to three-leaf stage and four- to five-leaf stage. The experiment was conducted in a completely randomized split-plot design with three replications. Flooding conditions were created by placing potted plants in 1.3 m by 0.7 m by 0.7 m polyvinyl chloride troughs. The effect of flood depth on Texasweed growth and fruit production was evaluated using ANOVA and regression analysis. Texasweed plants were able to survive in floods up to 30 cm; however, growth and fruit production were reduced. Increasing flood depths resulted in increased plant height and greater biomass allocation to stem. Texasweed plants produced adventitious roots and a thick spongy tissue, secondary aerenchyma, in the submerged roots and stem, which may play a role in its survival under flooded conditions. The recommended flood depth for rice in Louisiana is 5 to 10 cm. A 10-cm flood in the present study caused about 30 and 15% biomass reduction in two- to three-leaf and four- to five-leaf stage Texasweed, respectively. The results, thus, suggest that flooding alone may not be a viable option for Texasweed management in drill-seeded rice. However, appropriate manipulation of flooding could enhance the effectiveness of POST herbicides. This aspect needs further investigation.

Nomenclature: Texasweed, Caperonia palustris (L.) St. Hil. CNPPA; rice, Oryza sativa L. ORYSA.