Runoff and pond water samples from a container nursery that recycles water for irrigation were tested for movement of herbicides from the site of application. Residues of oryzalin [4‐(dipropylamino)‐3,5‐dinitrobenzene‐sulfonamide], pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzamine]), and oxyfluorfen [2‐chloro‐1‐(3‐ethoxy‐4‐nitrophenoxy)‐4‐(trifluoromethyl)benzene], active ingredients in the granular formulations of Rout [2‐chloro‐1‐(3‐ethoxy‐4‐nitrophenoxy)‐4‐(trifluoromethyl)benzene+3,5‐dinitro‐N4,N4‐dipropylsulfanilamide] and OH‐2 (Ornamental Herbicide‐2), were evaluated. Herbicides were applied at labeled rates and followed by irrigation. Water samples were collected, herbicides were extracted by solid phase extraction and analyzed by reverse phase high pressure liquid chromatography with ultraviolet (UV) detection. Maximum herbicide residues were detected within the first 15 min of water runoff; oryzalin residues were the greatest of the three herbicides evaluated (4 mg L−1 water at 15 min) and showed rapid decreases thereafter. Herbicide residues detected in pond samples decreased over time until the detection limit was reached (2 wk following application). A microplot study was conducted to evaluate the effects of plastic, woven fabric or gravel bedcovers on herbicide movement. Plastic and fabric allowed greatest movement of oryzalin and pendimethalin, while gravel significantly retained and retarded movement of all three herbicides. Results indicate that bedcover composition plays a significant role in the movement of herbicide from the site of application. Release of active ingredient from granular formulations was evaluated; dinitroanilines (oryzalin and pendimethalin) release faster than oxyfluorfen. Oryzalin in Rout was the most rapidly released, is the most water soluble, and 71% of total active ingredient was accounted for after 3 wk.

A two-year herbicide residue study was conducted at a commercial nursery to determine the presence of herbicide residues in pond water and sediment following normal production cycles. The runoff water from irrigation and rainfall was contained on the nursery and reused for irrigation. The nursery site was approximately 60 ha with two interconnected ponds, one for containment of runoff water and one serving as a source of irrigation water. The most commonly used herbicides were oxyfluorfen plus pendimethalin (granular formulation-Ornamental Herbicide 2); approximately twice as much herbicide was applied during the second year of the study. Herbicide levels found in pond water and sediment were approximately two-fold greater during the second year corresponding to the increase in active ingredients applied. The highest concentration of oxyfluorfen found in water and sediment was 0.04 μg/ml and 4.0 μg/g, respectively. The highest concentration of pendimethalin found in water and sediment was 0.008 μg/ml and 14.3 μg/g, respectively. In irrigation water samples, the highest concentration of oxyfluorfen and pendimethalin detected was 0.005 μg/ml and 0.002 μg/ml, respectively. The herbicides did not accumulate in water or sediment over the two-year period. No landscape plant phytotoxicity problems are likely at the herbicide levels detected in irrigation water samples.

Herbicide movement from broadcast granular applications via runoff waters into containment ponds was monitored over a two-year period. The nursery site was approximately 20 ha (50 A) and contained all runoff waters and recycled it for irrigation. Levels of pendimethalin, oryzalin and oxyfluorfen applied as either OH-2 or Rout herbicides were determined in containment pond water and sediment. Herbicides were extracted by a solid-phase column method and analyzed by HPLC with confirmation by GC-MS. Generally, low herbicide levels (highest level detected was 0.013 μg/ml in water and 12 μg/g in sediment) were detected compared to quantities applied [12 to 50 kg (26 to 110 lb) ai per year]. Results showed that herbicide levels did not accumulate in containment ponds following repeated applications and there was no correlation of herbicide levels detected with amount or timing of herbicide applications.

Solid phase extraction (SPE) procedures were used to determine the recoveries of herbicides typically used in containerized ornamental plant production from water samples. Recoveries from C18cartridges and disks were compared for each of 12 herbicides with variations in elution solvent and volume of elution solvent tested. Recoveries for nine of the herbicides from the cartridges and disks using acetone as an elution solvent were not affected by SPE matrix. Fluazifop recovery was greater with the disks, while napropamide and oxadiazon recoveries were greater with cartridges. Both cartridges and disks yielded low recoveries (23 to 47%) of benefin and prodiamine. Changing the elution solvent from acetone to acetonitrile resulted in 10% improvement for the recovery of benefin and a three- to four-fold increase in recovery of prodiamine. Acetonitrile decreased recoveries of napropamide, oryzalin, oxadiazon, oxyfluorfen, and pendimethalin from cartridges. For the disks, oxyfluorfen, prodiamine, and trifluralin had increased recovery, while fluazifop, oxadiazon, and simazine had decreased recovery with acetonitrile as the elution solvent. Increasing the amount of acetone eluting solvent increased the recovery of prodiamine and oxyfluorfen while decreasing the recovery of fluazifop, pendimethalin, simazine, and trifluralin. Binding capacities of oryzalin on cartridges and disks averaged 13.2 and 7.8 mg, respectively. The advantage of the disk lies in the greater volume of water that can be processed, while the higher cost and greater variability are disadvantages. Cartridge extraction yielded good recoveries with lower standard deviations, and used less organic solvent. Selection of an SPE extraction method depends upon the herbicides under evaluation, expected levels, and the water volume being processed. Both SPE techniques offer advantages over traditional liquid-liquid extraction methods such as reduced requirements for organic solvent and sample preparation.

SUMMAR'tGinkgo biloba L. is an important landscape tree, is resistant to insect, tungi and other pests, and produces a number of chemicals that have pharmaceutical properties (termed ginkgolides). Studies were initiated to establish an in vitro culture protocol for Ginkgo. Explants (intact embryos, embryos with cotyledons removed, and cotyledon tissue) were removed from disinfested seeds and cultured on Murashige and Skoog minimal organics medium with various combinations of either 2,4-dichlorophenoxyacetic acid (2,4-D) or naphthaleneacetic acid (NAA) and either kinetin or benzyladenine (BA), Cultures were incubated in the light and morphological development was recorded. Both embryo and cotyledon explants produced callus (cotyledon tissue produced the most callus). Ginkgolides A and B were detected in callus tissue extracts. Intact embryo cultures initiated on media with 2,4-D plus NAA for 5 wk produced shoots and roots when transferred to media with 4.5 p.M 2,4-D alone for an additional 5 wk. Plants were transferred from the 2,4-D media to pots and maintained in the greenhouse.