During containerized plant production pesticides may move from application site in runoff water created by overhead irrigation systems. In this study, four pesticides, isoxaben (V-|3-( 1-cthyl-1-methylpropvl)-5-isoxazolyl]-2,6-dimethoxybenzamide), trifluralin ((2,6-dinitro-AWdipropyl-4-trifluoromethylaniline), chlorpyrifos (0,O-diethyl O-3,5,6trichloro-2-pyridyl phosphorothioate) and thiophanate-methyl {dimethyl 4,4'-o-phenylene bis(3-thioal)ophanate), were applied at a commercial plant nursery. Overhead irrigation after application generated runoff water which was channeled into waterways of clay/gravel or hybrid bermudagrass [Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt-Davy], Isoxaben was detected in runoff water through 4 d after application (DAA). Other pesticides were detected primarily on the day of application (DOA). Thirteen percent of applied thiophanate-methyl was recovered from the clay/gravel waterway and 11% from the grass waterway. Total amounts of isoxaben lost were 23% of total applied in both treatments. Less than 0.01% of applied chlorpyrifos and trifluralin were detected. Isoxaben amounts recovered from the grassed waterway on the DOA were 16% lower than from the clay/gravel treatment. Thiophanate-methyl amounts were 18% lower from the grassed treatment on the DOA. The results suggest that vegetated waterways can reduce pesticide losses from application site in runoff water.

The ability of grassed waterways to remediate herbicide loads in runoff water was evaluated using simulated and on-site nursery research. Isoxaben plus oryzalin and isoxaben plus trifluralin were applied to model grassed (zoysiagrass or ‘Tifway 10’ hybrid bermudagrass) and nongrassed, metal and clay loam waterways, and runoff samples were collected. Grassed waterways reduced runoff volume an average of 47% and herbicide residues an average of 56% compared to nongrassed waterways. The smallest herbicide residues were from the clay/grass waterways. In a nursery study, isoxaben and trifluralin were applied to containerized landscape plant production beds. Overhead irrigation was applied and runoff water was channeled into either a clay/gravel waterway or a hybrid bermudagrass waterway. Samples were collected for 22 d following application. Isoxaben persisted through 15 d after application. Trifluralin was detected through 2 d after application. Total isoxaben recovered from the clay/gravel waterway was 32% of applied, and total trifluralin recovered was 0.9% of applied. The grass waterway reduced residues of isoxaben and trifluralin by 22 and 66%, respectively, compared to the clay/gravel waterway.

Beach vitex is a salt-tolerant, perennial, invasive shrub that has naturalized in coastal areas of the southeastern United States. Since its introduction in the 1980s, this Pacific Rim native has invaded many fragile beach-dune ecosystems along the Mid-Atlantic, Southern Atlantic, and Gulf of Mexico. Large-scale monocultures of beach vitex supplant native species through rapid vegetative reproduction and seed production. Fruits are capable of water-based dispersal, allowing for potential rapid range expansion in coastal areas. Ecosystem damage resulting from exclusion of native plant species by beach vitex and fears associated with potential negative effects on sea turtle nesting have served to promote the control and survey efforts presently underway in coastal areas of the Carolinas, Virginia, and Maryland.

Herbicides play an important role in the production of nursery crops by reducing weed problems and improving production efficiency. Herbicides applied to nursery crops may move in runoff water into retention basins, which are used to irrigate container plants. Studies investigated the growth and development of containerized landscape plants subjected to irrigation water containing herbicide residues. Containerized dwarf gardenia, Snow azalea, Buccaneer azalea, Hellers Japanese holly, fountain grass, and daylily were grown in fine pine bark medium in the greenhouse and were irrigated with water containing 1 mg/L and 10 mg/L of oryzalin, oxyfluorfen, and isoxaben. Fountain grass and daylily were the most sensitive to herbicide application with reduced root and shoot growth. Oryzalin was the most phytotoxic to fountain grass followed by oxyfluorfen and isoxaben. Oryzalin and oxyfluorfen at 10 mg/L reduced the growth index of fountain grass. Oryzalin was the most phytotoxic herbicide to daylily, followed by isoxaben and oxyfluorfen. Only the high rate (10 mg/L) of oryzalin reduced the growth index of daylily. Among woody species, the root weights of Hellers holly were reduced by 10 mg/L of isoxaben. The growth of other woody species was not affected by the herbicides.

Sprayable and granular formulations of isoxaben and trifluralin were applied to container plant nursery beds to determine formulation effects on herbicide runoff and weed control. In 1998 herbicide application was followed by 0.8 cm of irrigation delivered in 60 min, and runoff water samples were collected on the day of application (DOA). The highest concentrations of isoxaben and trifluralin detected in runoff water were 0.50 and 0.15 μg ml−1, respectively. Total isoxaben in runoff water was greater from the granular than from the sprayable formulation, but no differences attributable to formulation were detected for trifluralin. In 1999 herbicide application was followed by irrigation applied in three pulse cycles of 30 min each (0.8 cm per cycle). Runoff water samples were collected daily through 2 d after herbicide application (DAA). The highest herbicide concentrations were found in the first runoff sample on the DOA. Isoxaben was detected at 1.6 μg ml−1 from both formulations, and trifluralin concentrations were 0.8 and 0.2 μg ml−1 from the sprayable and granular formulations, respectively. Isoxaben concentrations were similar between formulations on the DOA, higher from the granular formulation 1 DAA, and higher in five of the nine runoff samples 2 DAA. Trifluralin concentrations were higher from the sprayable formulation for the first pulse cycle on the DOA and higher from the granular formulation in three of the nine samples 1 DAA and in four samples 2 DAA. The total amount of isoxaben recovered was 9.1% of applied from the granular formulation and 7.3% of applied from the spray formulation. The total amounts of trifluralin found were similar among formulations (0.5% of applied). Weed control was effective for both formulations in both years.