By the year 2050,the population of the United States is expected to reach over 418 million,while the global population will reach 9.6 billion.To provide safe food and fiber,agriculture must balance pesticide usage against impacts on natural resources.Challenges arise when storms cause runoff to be transported to aquatic receiving systems.Vegetated systems such as drainage ditches and constructed wetlands have been proposed as management practices to alleviate pesticide runoff.Twelve experimental mesocosms (1.3 × 0.71 × 0.61 m) were filled with sediment and planted with a monoculture of one of three wetland plant species (Typha latifolia,Leersia oryzoides,and Sparganium americanum).Three mesocosms remained unvegetated to serve as controls.All mesocosms were amended with 9.2 + 0.8 μg/L,12 + 0.4 μg/L,and 3.1 ± 0.2 μg/L of atrazine,metolachlor,and diazinon,respectively,over a 4 hr hydraulic retention time to simulate storm runoff.Following the 4 hr amendment,non-amended water was flushed through mesocosms for an additional 4 hr.Outflow water samples were taken hourly from pre-amendment through 8 hr,and again at 12,24,48,72,and 168 hr post-amendment.L.oryzoides and T.latifolia had mean atrazine,metolachlor,and diazinon retentions from 51％-55％ for the first 4 hr of the experiment.Aside from S.americanum and atrazine (25％ retention),unvegetated controls had the lowest pesticide retention (17％-28％) of all compared mesocosms.While native aquatic vegetation shows promise for mitigation of pesticide runoff,further studies increasing the hydraulic retention time for improved efficiency should be examined.