Ecological Risk Screening Summary - Mexican Primrose-willow (Ludwigia octovalvis) - High Risk

Species that are considered high risk have a well-documented history of invasiveness in at least one location globally, and a high or medium climate match to the contiguous United States.

Ludwigia octovalvis, the Mexican Primrose-willow, is an emergent aquatic plant with a nearly pan-tropical and -subtropical distribution. The species has diverse medicinal uses and has potential for use in bioremediation of heavy metal-contaminated environments. L. octovalvis is native to the southeastern United States, Puerto Rico, and the U.S. Virgin Islands, and it can occasionally be found in trade. Its status as native or introduced in Hawaii is uncertain. Other introductions of this species have been documented in southern Africa and several Pacific islands, resulting in established populations outside the native range. The history of invasiveness was classified as High due to several reports of negative impacts to taro agriculture on Pacific islands. The species is also a significant weed of rice fields within the native range. The climate match to the contiguous United States was high for Ludwigia octovalvis, with the highest matches occurring in the Southeast (where the species is native), Southwest, and Great Plains. The certainty of assessment was medium due to some uncertainty about the native range and the limited details available on impacts of introduction. However, impacts were reported from several locations where L. octovalvis has been introduced. The overall risk assessment category for Ludwigia octovalvis in the contiguous United States is High.