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Title: Distribution of wild taro (Colocasia esculenta) in subtropical Texas, growth of young colonies, and tolerance to simulated herbivory

item Moran, Patrick
item Yang, Chenghai

Submitted to: Subtropical Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2012
Publication Date: 12/1/2012
Citation: Moran, P.J., Yang, C. 2012. Distribution of wild taro (Colocasia esculenta) in subtropical Texas, growth of young colonies, and tolerance to simulated herbivory. Subtropical Plant Science. 64:18-28.

Interpretive Summary: Non-native, invasive weeds that grow in wet places along rivers and lakes in subtropical Texas cause a great deal of damage by reducing water resources, pushing out the native plants that are supposed to be growing there, reducing recreational enjoyment of waterways, and costing millions of dollars per year to control with chemicals or mechanical removal. One such weed is wild taro or elephant ear, a plant originally from Malaysia and the Pacific Islands that has very large leaves and is used in yards and gardens as an ornamental plant in the southern U.S., but that also has taken over shorelines along rivers and lakes from southern Florida to central Texas. In this study, we used observations posted online and our own road-based surveys to determine that nine rivers and 14 counties in Texas have known populations of elephant ear, with at least 600 km or 370 miles of river shoreline potentially invaded by this plant. In test tanks with wet, nutritious soil, a single plant placed in each tank increased its size by three- to fivefold in five months, with most of the increase in weight going to build a large, potato-like underground storage organ. Each single plant also produced 20 copies of itself in five months by sending out runners-no flowering was needed for reproduction. In a separate test, we simulated feeding damage by insects that could be used in the future for biological control of wild taro, by punching holes in all of the leaves on young wild taro plants, and we shaded some plants under a tent. Both with and without shade, damaged wild taro plants recovered lost foliage and attained the same size as undamaged plants, showing that wild taro is tolerant of insect feeding on leaves. Taken together, the results suggest that wild taro has spread across a wide area along the Rio Grande and in central and southeastern Texas, and has the potential to become a significant invasive plant along subtriopical and warm temperate rivers and lakes by rapidly developing large 'colonies' of plants that will not be damaged substantially by insects.

Technical Abstract: Non-native wild taro (Colocasia esculenta) is an ornamental plant that is an emerging invasive weed in moist riparian areas in subtropical and warm temperate river systems in Texas, with potential impacts on native plant species, habitat quality and water use in the Lower Rio Grande Basin. Observations from an online database and survey data indicate that wild taro is distributed or has the potential to invade at least 600 km of riparian habitat in Texas. In a five-month growth study in tanks, wild taro founder plants collected from the Rio Grande and San Marcos River watersheds increased their total weight by 2.6 to 5.6-fold, with most of this increase invested in corms, while also developing colonies containing over 20 asexual progeny arising from stolons. Plants damaged artificially with 20 hole punches per leaf recovered lost foliage and attained similar size as undamaged plants in a five week study. Wild taro has the potential to increase its distribution in subtropical riparian habitats such as the Rio Grande due to its colony growth potential and ability to recover from damage. Integrated chemical and biological control approaches may be needed to manage populations of this invasive plant species.