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In the simplest of terms, human hazard with respect to pesticides is dependent on the toxicities of the pesticides involved and the chance for exposure to those pesticides. Many insecticides or fungicides act as surface active protectants that do not actually have to enter plant cells. However, most of the research in this area has focused on the foliar penetration of postemergence herbicides and growth regulators and to a lesser extent on other systemic insecticides or fungicides. Despite the fact that a very large and increasing number of herbicides and plant-growth regulators require foliar application to be active, the foliar penetration of these chemicals often is very limited and can vary from nearly 0 to more than 90% of the chemical that is deposited on the cuticular surface. Most of the insecticides or fungicides used on crops or landscapes are surface acting, protectant pesticides. Their protective effects on plants are related directly to their persistence on plant foliage.

White bean (Phaseolus vulgaris L.) was used to study the antagonism caused by Na-bentazon on the phytotoxic action of the sulfonylurea (SU) herbicide tritosulfuron. After 168 h, uptake and translocation of [14C]tritosulfuron were reduced by 60 and 89%, respectively, when Na-bentazon was added to the mixture. Addition of (NH4)2SO4 or replacement of Na-bentazon with NH4-bentazon completely eliminated the negative effects on [14C]tritosulfuron uptake but not on its translocation. Scanning electron microscopy revealed that a mixture of Na-bentazon plus tritosulfuron plus DASH HC (0.156%) formed a rough layer of grain-like crystals on the leaf surface, whereas the addition of (NH4)2SO4 or replacement of Na-bentazon with NH4-bentazon resulted in amorphous deposits that may be more easily absorbed. The antagonism of tritosulfuron's phytotoxicity by Na-bentazon involves two separate processes, chemical (uptake effect) and biochemical (translocation effect). Keywords: Bentazon; tritosulfuron; white bean (Phaseolus...

The large-scale commercial cultivation of transgenic crops has undergone a steady increase since their introduction 10 years ago. Most of these crops bear introduced traits that are of agronomic importance, such as herbicide or insect resistance. These traits are likely to impact upon the use of pesticides on these crops, as well as the pesticide market as a whole. Organizations like USDA-ERS and NCFAP monitor the changes in crop pest management associated with the adoption of transgenic crops. As part of an IUPAC project on this topic, recent data are reviewed regarding the alterations in pesticide use that have been observed in practice. Most results indicate a decrease in the amounts of active ingredients applied to transgenic crops compared with conventional crops. In addition, a generic environmental indicator -- the environmental impact quotient (EIQ) -- has been applied by these authors and others to estimate the environmental consequences of the altered pesticide use on transgenic crops. The results show that the predicted environmental impact decreases in transgenic crops. With the advent of new types of agronomic trait and crops that have been genetically modified, it is useful to take also their potential environmental impacts into account.

The physiological basis for MCPA resistance in a hemp-nettle (Galeopsis tetrahit L.) biotype, obtained from a MCPA-resistant field population, was investigated. Dose-response studies revealed that the resistance factor for MCPA, based on GR50 comparisons of total dry weight of resistant (R) and susceptible (S) plants, was 3.3. Resistance factors for fluroxypyr, dicamba, 2,4-D, glyphosate, and chlorsulfuron were 8.2, 1.7, 1.6, 0.7, and 0.6, respectively. MCPA resistance was not due to differences in absorption, because both R and S biotypes absorbed 54% of applied [14C]MCPA 72 h after treatment. However, R plants exported less (45 vs 58% S) recovered 14C out of treated leaves to the apical meristem (6 vs 13% S) and root (32 vs 38% S). In both biotypes, approximately 20% of the 14C recovered in planta was detected as MCPA metabolites. However, less of the 14C recovered in the roots of R plants was MCPA. Therefore, two different mechanisms protect R hemp-nettle from MCPA phytotoxicity: a lower rate of MCPA translocation and a higher rate of MCPA metabolism in the roots. In support of these results, genetic studies indicated that the inheritance of MCPA resistance is governed by at least two nuclear genes with additive effects.

It is well known that environmental conditions have an important influence on herbicide efficacy. In particular, the effect of humidity on herbicide uptake has been attributed to changes in cuticle hydration and droplet drying. As early as the 1950s, it was hypothesized that humectants such as glycerol would enhance herbicide uptake by not letting droplets dry, thus maintaining the herbicide in solution, and hence making it available for uptake. Shortly thereafter, evidence was found to support this hypothesis and humectants were used successfully in warm, dry areas to increase herbicide efficacy. However, by the mid-1980s, there was little use of humectants as research on humectants gave way to investigations on the effect of ethylene oxide (EO) content on surfactant performance to improve herbicide uptake and efficacy. While ethoxylated surfactants effectively increase the uptake of both lipophilic and hydrophilic herbicides, the suggestion that long EO chains have humectant properties is misleading, since the studies that led to this suggestion were performed at high humidity, which would prevent rapid droplet drying. Furthermore, current evidence suggests that highly water-soluble, ionic herbicides may be more sensitive to low humidity and rapid drop drying than lipophilic herbicides. Therefore, an overview is presented on the interaction of water-soluble herbicides with surfactants, the cuticle, and humidity, with particular emphasis on the impact of low humidity and humectants on herbicide uptake. It was found that when one focuses on research performed at low humidity the importance of humectants emerges, which is not in keeping with what is now commonly accepted.

Classical Mendelian experiments were conducted to determine the genetics and inheritance of quinclorac and acetolactate synthase (ALS)-inhibitor resistance in a biotype of Galium spurium. Plants were screened with the formulated product of either quinclorac or the ALS-inhibitor, thifensulfuron, at the field dose of 125 or 6 g active ingredient (a.i.) ha -1 respectively. Segregation in the F 2 generation indicated that quinclorac resistance was a single, recessive nuclear trait, based on a 1: 3 segregation ratio [resistant: susceptible (R: S)]. Resistance to ALS inhibitors was due to a single, dominant nuclear trait, segregating in the F 2 generation in a 3: 1 ratio (R: S). The genetic models were confirmed by herbicide screens of F 1 and backcrosses between the F 1 and the S parent. F 2 plants that survived quinclorac treatment set seed and the resulting F 3 progeny were screened with either herbicide. Quinclorac-treated F 3 plants segregated in a 1: 0 ratio (R: S), hence F 2 progenitors were homozygous for quinclorac resistance. In contrast, F 3 progeny segregated into three ratios: 1: 0, 3: 1 and 0: 1 (R: S) in response to ALS-inhibitor treatment. This segregation pattern indicates that their F 2 parents were either homozygous or heterozygous for ALS-inhibitor resistance. Therefore, there were clearly two distinct resistance mechanisms encoded by two genes that were not tightly linked as demonstrated by segregation patterns of the F 3 .

Relative humidity (RH) can greatly affect the uptake and efficacy of glufosinate ammonium ( d , l -homoalanine-4yl-(methyl)-phosphinate) in wild oat (Avena fatua L.). Exposure to high (>95%) RH as opposed to low (40%) RH increased glufosinate ammonium efficacy and it was high RH within 12 h of spraying that was most crucial in affecting the efficacy. Subsequent dose–response experiments at 40% RH indicated that exposure of wild oat to high RH for as little as 30 min before and after spraying significantly increased the efficacy when compared to plants grown continuously at 40% RH. Furthermore, when [14C]glufosinate ammonium was applied as a spray to wild oat plants grown at 40% RH, there was a significant increase in uptake into wild oat plants exposed to high RH for 30 min before and after treatment compared to those left continuously at low RH. Conversely, when the same experiment was conducted with [14C]glufosinate ammonium applied as ten 1-μl droplets, exposure to high RH for 30 min before and after treatment did not increase the herbicide uptake. Based on these results, we hypothesize that droplet size and hence drying time is the major factor in effecting changes in glufosinate ammonium uptake in response to exposure to high versus low RH. Applying [14C]glufosinate ammonium as large droplets resulted in an overestimation of uptake and masked the inhibitory effect of low RH on glufosinate ammonium as determined by dose–response experiments. Conversely, spray application of [14C]glufosinate ammonium produced data that correlated with those from dose–response experiments.

BACKGROUND Malnutrition is a common complication of end-stage liver disease. It is frequently not a priority of treatment before liver transplantation. The purpose of this study was to examine whether prospective preoperative nutritional assessment could predict resource utilization and outcome after liver transplantation. METHODS We retrospectively reviewed 109 sequential orthotopic liver transplants performed at our center between July 1996 and May 1999. Ten patients with fulminant hepatic failure were excluded from the study, leaving 99 patients. Nutritional status was determined at the time of transplantation using subjective global assessment. Wilcoxon rank sum test and rank analysis of variance were used to analyze the data. Results are reported as median (interquartile range). A P value

The effects of glyphosate ((N-phosphonomethyl)glycine) and triclopyr (((3,5,6-trichloro-2-pyridinyl)oxy)acetic acid) on the embryonic development of Xenopus laeviswere evaluated using Frog Embryo Teratogenesis Assay— Xenopus(FETAX). Rodeot, the isopropylamine (ipa) salt of glyphosate formulated without a surfactant was found to be the least toxic, with a LC5 and LC50 of 3,779 and 5,407 mg acid equivalent (AE)/L, respectively. The LC5 and LC50 of Roundupt, the ipa salt of glyphosate formulated with a surfactant, was 6.4 and 9.4 mg AE/L, respectively. The surfactant component of Roundup, polyoxyethyleneamine (POEA), had a LC5 and LC50 of 2.2 and 2.7 mg/L, respectively. Garlont 3A, the triethylamine salt of triclopyr, had a LC5 and LC50 of 119 and 162.5 mg AE/L, respectively. The LC5 and LC50 of Garlon 4t, the butoxyethyl ester of triclopyr, was 6.7 and 9.3 mg AE/L, respectively. Considering a theoretical worst case scenario when the highest rates recommended for glyphosate (12 L of Roundup/ha) or triclopyr (8 L of Garlon/ha) are applied to water 15 cm in depth, the expected environmental concentrations calculated on the basis of AE would be 2.8 and 2.6 mg AE/L, respectively. The margins of safety (LC5/expected environmental concentrations) for frog embryos exposed to these concentrations would be approximately 2, 2, 47, and 1,312 for Roundup, Garlon 4, Garlon 3A, and Rodeo, respectively.

L. salicaria is a troublesome invasive species in eastern North America. Control methods being considered include use of herbicides, phytophagous insects and cutting. More effective use of these methods, separately or as an integrated program, requires better knowledge of seed viability for this plant which is a prolific seed producer. Infloresences of L. salicaria were collected from an infestation over one growing season. Ten inflorescences were collected on each sampling date; five of which were examined while they were fresh and five were allowed to desiccate in a greenhouse under ambiant conditions. Germination tests were performed on seeds from both fresh and dried inflorescences. From 12 days after anthesis (DAA) up to and including 24 DAA, there were no seeds that were germinable on either the fresh or dried inflorescences. At 27 DAA, germinable seed was first found in the lower 20 nodes of the freshly cut inflorescences. Above node 20, the inflorescence was in bloom but the seed capsules were immature. From 27 DAA on, percent germination from most of the nodes up the stem increased with time. This same pattern was observed in the seeds from the dried inflorescences. Germinable seed was first detected 27 DAA on the dried inflorescences in the lower 10 nodes. As the inflorescences expanded, the upper nodes matured and germination was not significantly different between the fresh and dried inflorescences. Desiccation of the cut stems of L. salicaria did not affect the germinability of the seeds. There was no evidence of further maturation and greater seed viability on the dried stems as compared to the germinability of seeds from freshly cut stems. This indicates that cutting or chemical defoliation of L. salicaria within 3 weeks of anthesis should destroy the seed crop and prevent additions to the seed bank.

In performing risk assessments for plant protection products by applicants or regulators in relation to the registration of the products, an important aspect to take into account is the foliar interception and retention of the active substance of the product on the plant. An overview is given of the approaches to this item in several parts of the world. The relevant circumstances and influencing variables, such as growth phase, planting density, and some physicochemical characteristics (e.g., vapor pressure and Henry's coefficient) are dealt with. Finally, a proposal is presented for how to take into account the phenomenon of foliar interception and retention in the initial phase, first tier, of the risk assessment process.

Historically, studies on the nontarget aquatic effects of forest-use herbicides focused largely on fish and invertebrates despite the ecological importance of aquatic plants. Regulatory requirements and the aquatic phytotoxicity database need to be improved to reflect the importance of aquatic plants. Based on a review of the scientific literature and results from laboratory testing with the submersed macrophyte Myriophyllum sibiricum Komarov, the effects of 2,4 dichlorophenoxyacetic acid (2,4-D), glyphosate, hexazinone, imazapyr, metsulfuron methyl, sulfometuron methyl, and triclopyr on nontarget aquatic organisms were compared. Laboratory results indicate that M. sibiricum is sensitive to herbicide effects, especially those that impact root growth. For most herbicides, the inhibitory concentrations 25 and 50 (IC25 and IC50, concentrations that inhibit an endpoint parameter by 25 and 50%, respectively) for shoot and root growth were below the expected environmental concentrations (EEC). For example, the IC50 values for root dry mass were 0.000 12 and 0.000 22 mg active ingredient/L for sulfometuron methyl and metsulfuron methyl, respectively, concentrations that were approximately 3100 and 1700 times below the EEC for these compounds. Interspecies comparisons, conducted during this study, demonstrated that M. sibiricum was generally equally or more sensitive to these herbicides than other aquatic plant species (i.e., floating macrophytes and algae) and, in some cases, more sensitive than fish, zooplankton, and other invertebrates. For example, available data demonstrated that 2,4-D, imazapyr, and the sulfonylureas investigated were more toxic to rooted and floating macrophytes than to other aquatic organisms, including algae. Because of the high sensitivity and ecological significance of aquatic macrophytes, a greater emphasis should be placed on evaluating aquatic phytotoxicity in future ecotoxicological research.

The impact of glufosinate-ammonium and bialaphos on the zooplankton community in a small eutrophic lake was investigated using in situ enclosures. Concentrations inducing a 20% reduction in abundance (EC20), as interpolated from best-fit, nonlinear regression analyses were similar for both herbicides and ranged from 0.03 to 0.16 mg/L for various zooplankton taxa. Similarly, median effective concentrations (EC50) estimates ranged from 0.12 to 0.50 mg/L. Thus, toxicity endpoints overlapped and in some cases were well below expected environmental concentrations calculated for accidental direct overspray (1 mg/L) or drift events (0.25 mg/L). Significant concentration-dependent reductions were observed within the first 2 weeks following application and for a number of taxa persisted throughout the observation period (63 d posttreatment). At the highest treatment level, (10 mg/L), negative impacts were still apparent in the year following treatment. The results of this field study, which demonstrate significant negative effects on a variety of zooplankton taxa at environmentally relevant concentrations and relatively slow recovery therefrom, suggest a substantial risk of sustained adverse impacts on the zooplankton communities should these herbicides contaminate shallow lentic ecosystems. Extensive mitigative measures are required to protect such water bodies from potential impacts of phosphinothricin-based herbicides.

The distribution of nine pesticides between the juice and pulp of carrots and tomatoes during home culinary practices was investigated. Tomato and carrot pulp contained a higher percentage of all pesticide residues, except for mancozeb in tomatoes. Although there was a difference in the relative distribution of the pesticides between the commodities with greater amounts present in the pulp of tomatoes, the pesticides followed a similar trend in both. A relationship between the pulp/juice distribution and water solubility of the pesticide was apparent. Pesticides with the highest water solubility were present to a greater extent in the juice. An exception was noted in the case of diazinon and parathion, which were present in higher amounts in the pulp than their water solubility would suggest. The percent residue in the pulp ranged from 56.4 to 75.2% for carrots, and 49.7 to 95.4% for tomatoes. Residues in the juice prepared from washed commodities ranged from not detected to 0.83 microgram/g. Washing of the produce removed more residue from carrots than from tomatoes, but it did not affect the relative distribution of the residues. The behaviour and fate of the chemical varied with the pesticide as well as the crop.

The degradation and leaching potential of the herbicide [14C]glufosinate-ammonium [the ammonium salt of dl-homoalanin-4-yl(methyl)phosphinic acid] in a northern Ontario forest environment were examined. The DT50 and maximum leaching depth were 4.3 days and 10 cm (humic layer), respectively. [14C]MPPA-3 (3-methylphosphinylpropionic acid) and [14C]MPAA-2 (2-methylphosphinylacetic acid), the two main metabolites of glufosinate-ammonium, also did not leach beyond 10 cm. At 32 days postapplication, approximately 10−20% of the parent and metabolites remained in the soil, but by the following season (day 295) residue levels had declined to near zero. Keywords: Glufosinate-ammonium; forestry; persistence; leaching potential

The potential for vegetative propagation of Lythrum salicaria L. (Lythraceae) from stem and root sections, and the tissues involved in the lateral spread of L. salicaria were assessed. Only stem sections consisting of one or more nodes produced shoots and established a new root system. Internodal sections formed adventitious roots and rarely, one occurrence of 36, a new shoot. Neither woody nor non-woody root pieces formed shoot primordia. Entire root systems from which the stem was severed failed to produce new shoots, while root systems in which the stems were severed above the first node formed several new shoots arising from the remaining stem tissue. Plants excavated from field sites revealed that lateral spread of L. salicaria resulted from elongation of lateral meristems on horizontal stems, although the presence of adventitious roots on the stems and changes resulting from secondary growth of both the horizontal stems and adventitious roots gave the appearance of shoot primordia forming on roots. It is concluded that lateral spread and perennation of L. salicaria is facilitated by lateral shoot meristems in the leaf axils and not shoot primordia developing on roots.

The joint action of metribuzin and tridiphane was investigated in metribuzin-tolerant (T) and metribuzin-susceptible (S) soybean and tomato cultivars within species, respectively, under growth room studies. Maple Arrow (T) and Maple Amber (S) exhibited similar tolerance to tridiphane applied at soybean emergence. Vision (T) tomato was more sensitive to tridiphane than was Springset (S) tomato, the reverse of the relative tolerance to metribuzin. A phytotoxic interaction was demonstrated following application of tridiphane and metribuzin at the respective rates (kg ai ha−1) of 0.1 and 1.1 in Maple Arrow (T) soybeans, 0.05 and 0.25 in Maple Amber (S) soybeans, and 0.25 and 0.2 in Springset (S) tomato. Tridiphane applied 1 or 4 h before metribuzin caused the greatest phytotoxicity in Maple Amber (S) soybeans. Soybean field results generally supported those of growth-room studies. Foliar spray pretreatment with tridiphane increased total radioactivity in Springset (S), decreased the total root radioactivity and increased total shoot radioactivity in both Vision (T) and Springset (S) and decreased metabolism of metribuzin to water soluble conjugates in Springset (S) roots over 24 h following14C-metribuzin application to roots of intact tomato seedlings. The increased uptake, translocation to the shoots, and decreased root metabolism of metribuzin in Springset when pretreated with tridiphane could explain the phytotoxic interaction (which was unexpected, based only on the glucose detoxification pathway of metribuzin in tomato).

In vitro metabolism studies with excised shoots of wheat, barley, oat, and crabgrass indicate that [ 14 C]fenoxaprop-ethyl (ethyl-(±)2-[4-{(6-chloro-2-benzoxazolyl)-oxy}phenoxy]propanoic acid) was rapidly hydrolyzed to fenoxaprop in all four species. However, in oat and crabgrass the radioactivity remained mainly in the form of fenoxaprop, while in wheat and barley fenoxaprop underwent rapid displacement of the phenyl group by glutathione (GSH) and/or cysteine. resulting in production of S -(6-chlorobenzoxazole-2-yl)-glutathione (GSH conjugate), S -(6-chlorobenzoxazole-2-yl)-cysteine (cysteine conjugate), and 4-hydroxyphenoxy-propanoic acid. The GSH conjugate also may be catabolized to form S -(6-chlorobenzoxazole-2-yl)-cysteine (cysteine conjugate) which was subsequently metabolized to an unidentified metabolite (Metabolite I) which was speculated to be the N -glucoside of the cysteine conjugate ( S -[6-chlorobenzoxazole-2-yl]-cysteine N -glucoside). 4-Hydroxyphenoxy-propionic acid was further metabolized to yield a glucoside conjugate which upon hydrolysis with acid or β-glucosidase yielded 4-hydroxyphenoxy-propionic acid. The safener, fenchlorazole-ethyl (ethyl-1-(2,4-dichlorphenyl)-5-trichloromethyl-1H-1,2,4-triazole-3-carboxylic acid), had no qualitative effect on fenoxaprop-ethyl metabolism. However, it enhanced the rate of the herbicide metabolism in wheat and barley but not in oat and crabgrass. These results indicate that GSH. cysteine, and glucose conjugation have a major role in the metabolic detoxification and selectivity mechanism of fenoxaprop-ethyl in grass species.

Etiolated shoot segments of wheat ( Triticum aestivum L. cv. Fredrick) and barley ( Hordeum vulgare L. cv. Leger) were incubated in buffer amended with the herbicides fenoxaprop-ethyl (FE) or diclofop-methyl (DM) and the metabolic inhibitors tetcyclacis (Tc) or tridiphane (Tf). In the absence of the metabolic inhibitors, FE was more rapidly metabolized to polar compounds in wheat than in barley, while the rate of metabolism of DM was similar in the two grass species. Tc inhibited the metabolism of DM and FE in both wheat (98%) and barley (53%), suggesting a possible role of a cytochrome P450-dependent monooxygenase in the detoxification of the two herbicides. The inhibiting effect of Tc was stronger for DM than for FE. Tf did not affect the metabolism of FE in either barley or wheat. The metabolism of DM was reduced by Tf (27%) in wheat. However, this inhibition was significantly less than that of Tc. The herbicide safener, fenchlorazole-ethyl (FCE), enhanced the metabolism of FE in both barley and wheat without affecting the pattern of metabolism. The effect of FCE on FE metabolism was annulled by Tc and Tf in both plant species.

In growth room studies, POST applications of fenoxaprop-ethyl at 50 g ai ha-' at the fourto five-leaf stage of development were non-toxic to barnyardgrass, large crabgrass, and yellow foxtail. POST applications of fenchlorazole-ethyl at 12.5 or 25.0 g ai ha-1 were also nontoxic to these same three species. However, when the two chemicals were applied in combination at the above rates they were toxic to all three species, indicating a synergistic interaction in all three species. In additional studies, a sensitive biotype of wild oat was severely injured by fenoxapropethyl at 50 g ai ha-1 and a resistant biotype of wild oat was only slightly injured by fenoxapropethyl at rates as high as 800 g ai ha-1. However, no significant interactions were observed between fenoxaprop-ethyl and fenchlorazole-ethyl in either of these wild oat biotypes. Nomenclature: Fenchlorazole-ethyl [ethyl-i-(2,4-dichlorophenyl)-5-trichloro-methyllH-1,2,4-triazole-3-carboxylate], fenoxaprop-ethyl {ethyl-(?)2-[4-[(6-chloro-2-benzoxazolyl)oxy]propanoic acid}, barnyardgrass [Echinochloa crus-galli (L.) Beauv. #3 ECHCG], large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA], yellow foxtail [Setaria glauca (L.) Beauv. # SETLU], wild oat (Avena fatua L. # AVEFA). Additional index words: Antagonism, synergism, barley, barnyardgrass, large crabgrass, yellow foxtail, oat, wild oat, wheat, SETLU, DIGSA, ECHCG, AVEFA.

Hexazinone (3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione) is an s-triazine herbicide that is used widely to control weeds in forest plantations and on industrial rights-of-way. Under controlled environmental conditions, red pine (Pinus resinosa Ait.) has been shown to have greater tolerance to hexazinone than jack pine (Pinus banksiana Lamb.). In a whole-plant nutrient-culture bioassay, hexazinone concentrations up to 40 μM did not effect red pine root or shoot growth in terms of fresh weight; however, at the same concentrations, hexazinone was toxic to jack pine. After five different exposure times (i.e., 24, 48, 72, 96, and 192 hr), jack pine foliage contained significantly (P < 0.05) higher levels of radioactivity, applied to the roots as [14C]hexazinone, than did red pine foliage. The higher level of radioactivity in jack pine foliage was an apparent result of greater transpiration rates in jack pine than in red pine. In a separate metabolism experiment, after 192 hr of root exposure to [14C]hexazinone, approximately 27 and 2%, respectively, of the radioactivity recovered from the foliage was found to be unaltered hexazinone in jack pine and red pine. In the roots of both species, the amount of unaltered hexazinone did not differ significantly (P < 0.05), with approximately 87% of the radioactivity recovered as hexazinone. Metabolism of hexazinone was greater in the stem tissue than in the roots, but less than in the foliage. Two main factors (i.e., uptake and metabolism) were found to contribute to hexazinone selectivity in red pine and jack pine.

Total body dose received in home gardeners applying 2,4-D and bystanders living within the household, but not applying the pesticide was measured. Levels of 2,4-D were monitored in air samples both inside the home and downwind of the application site. Homeowners were divided into protective and non-protective apparel groups and applied both a granular and liquid formulation of 2,4-D on two separate dates. Analyses of urine collected from homeowners for 96 hours following applications found total body doses ranging from non-detectable to 0.0071 mg/kg of body weight. The highest exposures occurred in the non-protected group and were consistently associated with spills of the liquid concentrate or excessive contact with the dilute mixture on the hands or forearms. Residues of 2,4-D were not detected in urine samples supplied by bystanders to home applicators. Residues of 2,4-D were detected in five of the 76 air samples taken during the home applications. Two of these air samples coincided with measurable applicator exposure but it is unlikely that this was a major route of exposure.

Soil thin-layer chromatographic analysis revealed that [14C]glufosinate ammonium was slightly more mobile than amitrole less mobile than picloram in Fox sandy loam and Guelph loam soils. Two glufosinate ammonium metabolites, 3-(methylphosphinyl)propionic acid (MPPA-3) and 2-(methylphosphinyl) acetic acid (MPAA-2), were more mobile than the parent herbicide in the Fox sandy loam. In the Guelph loam, the MPAA-3 metabolite was again more mobile than the parent herbicide. However, the MPAA-2 metabolite was significantly less mobile than the parent herbicide. The adsorption coefficients for [14C]glufosinate ammonium in the Guelph loam and Fox sandy loam soils were 0.37 and 0.21, respectively. Laboratory degradation studies indicated that [14C]glufosinate ammonium was rapidly degraded to its metabolites, MPPA-3 and MPAA-2, and eventually to 14CO2. In all studies conducted, the half-life of glufosinate was between 3 and 7 days.

A static, 14 day laboratory bioassay using axenic Myriophyllum sibiricum Komarov was developed and utilized to determine the effects of two reference toxicants [zinc chloride (ZnCl 2 ) and phenol] upon the morphological and physiological development of this species. For ZnCl 2 , the highest "no observable effect concentration" (NOEC) was 4.26 mg/L for root length. Based upon IC 5 0 values, the most sensitive endpoint parameter for ZnCl 2 was root length (range = 8.2 - 17.8 mg/L), followed by fresh weight (range = 13.2 - 32.4 mg/L) and root number (range = 13.3 - 38.6 mg/L). For phenol, the NOEC was 11.76 mg/L for three endpoint parameters (root number, total root length and fresh weight). Based upon IC 5 0 values for phenol, the most sensitive endpoint parameter was root length (32.6 - 40.0 mg/L), followed by root number (45.8 - 57.0 mg/L) and fresh weight (48.2 - 75.9 mg/L). For both reference toxicants, the results were repeatable over time. As tested in this axenic culturing system, the ZnCl 2 was slightly more toxic to the M sibiricum than the phenol.

The safener, fenchlorazole-ethyl (ethyl-1-(2,4-dichlorophenyl)-5-trichloromethyl-1H-1,2,4-triazole-3-carboxylate), eliminated and reduced, respectively, the phytotoxicity of the herbicide fenoxaprop-ethyl (ethyl-(±)2-[4-[(6-chloro-2-benzoxazolyl)-oxy]phenoxy] propanoate) to wheat ( Triticum aestivum L.) and barley ( Hordeum vulgare L.). In barley the ED 50 value for foliar-applied fenoxaprop-ethyl was 150 g ai/ha. In wheat an ED 50 value could not be determined because of its tolerance to the herbicide but there was a 30% reduction in dry weight after application of 600 g ai/ha. In both wheat and barley no reduction in dry weight occurred when the same respective doses of the herbicide were applied in combination with the safener (4:1 w/w, herbicide:safener). Conversely, addition of fenchlorazole-ethyl increased the toxicity of fenoxaprop-ethyl to crabgrass ( Digitaria ischaemum (Schreb, Muhl.)). Metabolism studies on foliar-applied [ 14 C]fenoxaprop-ethyl indicated that the herbicide was deesterified to fenoxaprop in all three species. Regardless of whether the safener was present or not, three major metabolites, 6-chloro-2,3-dihydro-benzoxazol-2-one (HOE 054014), and two unidentified water-soluble metabolites, were found in wheat, barley, and crabgrass 48 hr after treatment. When [ 14 C]fenoxaprop-ethyl was applied alone, approximately 29, 63, and 9% of the applied radioactivity was metabolized to products other than fenoxaprop 48 hr after treatment, whereas 48, 96, and 8% was metabolized when the safener also was applied to wheat, barley, and crabgrass, respectively. These results indicate that fenchlorazole-ethyl may protect barley and wheat from the phytotoxic action of fenoxaprop-ethyl by increasing both the rate of deesterification of fenoxaprop-ethyl to fenoxaprop and the rate of metabolism of fenoxaprop to other metabolites. In crabgrass, deesterification of fenoxaprop-ethyl was increased by the safener but the subsequent detoxification of fenoxaprop was not increased in a manner similar to that found in the other two species.

The concept of using chemical safeners to improve herbicide selectivity became widely known in 1969 with the introduction of naphthalic anhydride (NA) to improve the tolerance of maize to thiocarbamate herbicides. Soon thereafter dichlormid was also developed as a safener for thiocarbamates in maize. At present there are at least eight different chemical safeners that have been developed commercially. Many of these safeners have been most effec­tive for chloroacetamide or thiocarbamate herbicides in monocotyledonous crops such as maize or sorghum. Some are like dichlormid and have been developed as physiologically selec­tive safeners that can be combined in the formulation with the herbicides. Others, like NA , are either less selective or less active in the soil and must be used as dressings on the crop seed. Most of the presently used safeners are for soil active herbicides. The challenge for the future will be to develop safeners that are effective for the newer postemergence herbicides in dicoty­ledonous as well as monocotyledonous crops.

In growth room bioassays, four herbicide safeners {BAS-145138: 1-dichloroacetyl-hexa-hydro-3,3,8a-trimethyl-pyrrolo(1,2a)pyrimidin-6(2H)-one, dichlormid: N,N-diallyl-2,2-dichloroacetamide, flurazole: phenylmethyl 2-chloro-4-(trifluoromethyl)-5-thiazole-carboxylate and MG-191: 2-dichloromethyl-2-methyl-1,3-dioxolane} were compared for their effective­ ness in reducing metazachlor {N-(2,6-dimethylphenyl)-N-(1-pyrazolylmethyl)-chloroacet-amide} injury to maize seedlings. Three of these compounds (BAS-145138, dichlormid and MG-191) and two different compounds (AD-67: N-dichloroacetyl-1-oxa-4-azaspiro-4,5-de-cane and DKA-24: N ,N2-diallyl-N2-dichloroacetylglycineamide) were also evaluated as safe­ners for acetochlor {N-(2-ethyl-6-methylphenyl)-N-(ethoxymethyl)chloroacetamide} in maize seedlings. Both BAS-145138 and dichlormid were highly effective as safeners for metazachlor and BAS-145138 and DKA-24 were equally good safeners for acetochlor. Metazachlor and acetochlor uptake and metabolism by maize seedlings were enhanced sig­nificantly in response to treatment with every safener examined. Rates of metazachlor and acetochlor uptake and metabolism were greatest in seedlings treated with BAS-145138 -the most effective safener. In the absence of any safener treatment, the non-enzymatic conjugation of the herbicides with glutathione either exceeded (metazachlor) or was similar (acetochlor) to enzymatic conjugation. However, the rate of enzymatic conjugation was generally increased by safener treat­ ment. This was particularly true when the herbicide (14C-labeled) was employed as a conjuga­tion substrate instead of the less specific substrate, CDNB (1-chloro-2,4-dinitrobenzene). A significant linear correlation was observed between safener effectiveness and rates of metazachlor metabolism or glutathione S-transferase activity in maize seedlings. However, a similar correlation could not be established for the five compounds evaluated as safeners for acetochlor.

Triazine-resistant (TR) biotypes of weeds normally susceptible (S) to triazine herbicides first were documented in Ontario in 1974. By 1988, at least nine weed species had TR biotypes, and at least 50% of the corn-producing areas were infested. Corn has been grown the longest in the southwestern Ontario, but TR weeds are only a minor problem there. Predominant agronomic practices in the southwest include crop rotation, atrazine use on 60% of corn land, use of other postemergence herbicides, interrow cultivation, little silage corn, and little manure returned to the land. Corn, particularly grain corn, is new as a large hectareage crop in eastern Ontario. However, more than 75% of corn land in that area is infested with two or more TR weed species. Predominant agronomic practices in the east include continuous corn, nearly all fields are atrazine treated, use of postemergence herbicides is not common, cultivation is rare, 25% of the corn is for silage, and manure from corn silage is returned to all cultivated land. Adequate herbicide programs exist to control TR weeds in corn and other crops. However, the spread from field to field and from farm to farm is often rapid, particularly in eastern Ontario.

Triclopyr [[(3,5,6-trichloro-2-pyridyl)oxy]acetic acid, Garlon 4E] was moderately persistent in sandy and clay soils at a Northern Ontario site. Times to 50% and 90% disappearance were 2 and 4 weeks, respectively, regardless of soil type. Evidence of triclopyr leaching in response to heavy rainfall was observed 7 days after application in both soils, but residues of triclopyr at a depth of 25-30 cm never exceeded 6 micrograms/kg, when present. In a study of lateral movement of triclopyr with runoff water, residues (in the range 0.01-0.96 micrograms/L) were recovered in a collection ditch 12-13 m downslope; however, there was no evidence of mass movement of triclopyr at quantifiable levels (0.54 micrograms/kg) downslope in the soil. Field studies of persistence and mobility confirmed earlier laboratory results and indicate that environmental problems are unlikely to occur as a result of excessive triclopyr persistence and/or mobility in soils typical of Northern Ontario forestry areas.

The role of the jelly coat in providing a protective barrier to chemical absorption was studied using the embryos of the amphibian, Xenopus laevis. Embryos with or without a jelly coat were water exposed to the butoxyethyl ester of 2,4-dichlorophenoxyacetic acid (2,4-D BEE) and the rates of uptake, metabolism, distribution, and excretion were determined. The water uptake clearance rates were slower for embryos with a jelly coat (1.5–4.5 mlwater·g embryo −1 ·h−1 or 0.040–0.022 mlwater·h−1 per embryo) in comparison to dejellied embryos (14–21 mlwater·g embryo −1 ·h−1 0.0066–0.021 mlwater·h−1 per embryo). This accounted for the much lower residues in embryos with a jelly coat than in dejellied embryos during 8 h of exposure. Despite quantitative differences in uptake, once 2,4-D BEE had entered the embryos, metabolism and distribution were similar between the two test groups. 2,4-D BEE was metabolized to 2,4-dichlorophenoxyacetic acid (2,4-D) with half-lives ranging from 35 to 42 minutes. The radioactive residues, as determined by whole body autoradiography, appeared throughout the embryo with a slight accumulation in the blastocoel. Furthermore, 35% of the radioactive residues were located in the jelly coat and 65% in the developing embryo. Based on a slower 2,4-D elimination in embryos with a jelly coat, the diffusive properties that decreased 2,4-D BEE uptake appeared to similarly decrease elimination of its metabolite. The common practice of removing jelly coats prior to embryonic amphibian toxicity studies, as in the widely used Frog Embryo Teratogenesis Assay–Xenopus (FETAX), is discouraged based on the kinetic differences observed in this study.

The physiological and biochemical basis for quinclorac resistance in a false cleavers (Galium spurium L.) biotype was investigated. There was no difference between herbicide resistant (R) and susceptible (S) false cleavers biotypes in response to 2,4-D, clopyralid, glyphosate, glufosinate-ammonium, or bentazon. On the basis of GR(50) (growth reduction of 50%) or LD(50) (lethal dose to 50% of tested plants) values, the R biotype was highly resistant to the acetolactate synthase (ALS) inhibitor, thifensulfuron-methyl (GR(50) resistance ratio R/S = 57), and quinolinecarboxylic acids (quinclorac R/S = 46), resistant to MCPA (R/S = 12), and moderately resistant to the auxinic herbicides picloram (R/S = 3), dicamba (R/S = 3), fluroxypyr (R/S = 3), and triclopyr (R/S = 2). The mechanism of quinclorac resistance was not due to differences in [(14)C]quinclorac absorption, translocation, root exudation, or metabolism. Seventy-two hours after root application of quinclorac, ethylene increased ca. 3-fold in S but not R plants when compared to controls, while ABA increased ca. 14-fold in S as opposed to ca. 3-fold in R plants suggesting an alteration in the auxin signal transduction pathway, or altered target site causes resistance in false cleavers. The R false cleavers biotype may be an excellent model system to further examine the auxin signal transduction pathway and the mechanism of quinclorac and auxinic herbicide action.

The growth of herbicide-resistant canola varieties increased from 10% of the canola area in Canada in 1996, when the technology was first introduced, to 80% in 2000. From 1995 to 2000, the amount of herbicide active ingredient applied per hectare of canola declined by 42.8% and the Environmental Impact (EI) per hectare, calculated using the Environmental Impact Quotient for individual herbicides and the amounts of active ingredients applied, declined 36.8%. The amount of herbicide active ingredient per hectare applied to conventional canola was consistently higher than that applied to herbicide-resistant canola each year between 1996 and 2000. Similarly, the EI of herbicide use per hectare in conventional canola was higher than that of herbicide-resistant canola during the same time period. Since 1996, herbicide use has shifted from broadcast applications of soil-active herbicides to post-emergence applications of herbicides with broad-spectrum foliar activity. The decline in herbicide use and EI since the introduction of herbicide-resistant varieties was due to increased use of chemicals with lower application rates, a reduced number of applications and a decreased need for herbicide combinations.

Using an amphibian toxicity testing protocol, comparative studies were conducted to assess the predictive precision, degree of similarity of results and efficiency of a central composite rotatable design (CCRD) in relation to a conventional complete 3x3 factorial design. Data were treated with response surface analysis using generalized linear models (glm) and application of profile deviance to generate confidence intervals. Design comparisons were based on studies conducted using the Frog Embryo Teratogenesis Assay-Xenopus (FETAX) protocol to examine the interaction of three toxicants at pH levels ranging from 4.5 to 8.5. Test substances included two commercial herbicide formulations based on glyphosate ([N-phosphonomethyl]glycine) isopropylamine salt (Vision, Rodeo) as well as a polyethoxylated tallow amine surfactant blend (MON 0818), which is a key component of the Vision formulation. The generated models from both the CCRD and the factorial designs produced toxicity estimates similar to each other and to previously published results. Trends were also similar to published results in that the surfactant, MON 0818, was comparatively more toxic than Vision, which was more toxic than Rodeo. Further, all toxicants induced higher mortality under alkaline as opposed to acidic conditions. The CCRD was between 66 and 124% more efficient in the Vision and Rodeo experiments in comparison to the complete 3x3 factorial. Thus, the factorial experiment would have required at least 66% more observations to obtain the same precision. There appeared to be no efficiency gain with the use of the CCRD for MON 0818. The CCRD had tighter confidence intervals in 9 of 12 cases across all test substances. Computer simulations using the experimental data for Vision demonstrated that the LCalpha estimates generated from the 1,000 simulated data sets were very close to the "true" value for both designs. This was based on small bias and mean squared error calculations. Coverage probabilities in both designs were between 91.6 and 95.6%, close to the nominal coverage of 95%. Efficiency comparisons of the simulated Vision data sets demonstrated that the CCRD was more efficient in 93.3% of the comparisons. We suggest that a CCRD using glm and profile deviance for statistical analyses be considered an effective and efficient alternative in toxicity studies where interactive effects are of interest.

Effects of Release® herbicide (triclopyr butoxyethyl ester, [TBEE]) on mortality, avoidance response, and growth of larval amphibians (Rana clamitans, Rana pipiens) were investigated using in situ enclosures deployed in two forest wetlands in northern Ontario, Canada. Release was applied at nominal concentrations ranging from 0.26 to 7.68 mg TBEE acid equivalents (AE)/L. No significant deleterious effects of this herbicide on larval growth were detected. However, concentration-dependent mortality and abnormal avoidance response were observed. Most mortality occurred within 96 h following treatment. Median lethal concentration (LC50) values for each species and experimental site ranged from 2.79 to 3.29 mg AE/L, while median effective concentration (EC50) values (abnormal avoidance response) ranged from 1.67 to 3.84 mg AE/L. The LC10 and EC10 endpoints approximated aqueous concentrations (0.59 mg AE/L) expected under direct aerial overspray scenarios, indicating a potential risk of impacts for a small proportion of native amphibian larvae. However, given the low frequency and limited use of this herbicide formulation in Canadian forestry, these risks are considered negligible. Changes in usage patterns would require concurrent chemical and biological monitoring of operational spray programs to accurately quantify the probability and magnitude of real-world exposures and to relate these exposure levels to concentration-response relationships including those described in this study.

Vision®, a glyphosate-based herbicide containing a 15% (weight:weight) polyethoxylated tallow amine surfactant blend, and the concurrent factor of pH were tested to determine their interactive effects on early life-stage anurans. Ninety-six-hour laboratory static renewal studies, using the embryonic and larval life stages (Gosner 25) of Rana clamitans, R. pipiens, Bufo americanus, and Xenopus laevis, were performed under a central composite rotatable design. Mortality and the prevalence of malformations were modeled using generalized linear models with a profile deviance approach for obtaining confidence intervals. There was a significant (p < 0.05) interaction of pH with Vision concentration in all eight models, such that the toxicity of Vision was amplified by elevated pH. The surfactant is the major toxic component of Vision and is hypothesized, in this study, to be the source of the pH interaction. Larvae of B. americanus and R. claimitans were 1.5 to 3.8 times more sensitive than their corresponding embryos, whereas X. laevis and R. pipiens larvae were 6.8 to 8.9 times more sensitive. At pH values above 7.5, the Vision concentrations expected to kill 50% of the test larvae in 96-h (96-h lethal concentration [LCS50]) were predicted to be below the expected environmental concentration (EEC) as calculated by Canadian regulatory authorities. The EEC value represents a worst-case scenario for aerial Vision application and is calculated assuming an application of the maximum label rate (2.1 kg acid equivalents [a.e.]/ha) into a pond 15 cm in depth. The EEC of 1.4 mg a.e./L (4.5 mg/L Vision) was not exceeded by 96-h LC50 values for the embryo test. The larvae of the four species were comparable in sensitivity. Field studies should be completed using the more sensitive larval life stage to test for Vision toxicity at actual environmental concentrations.

A competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) was developed to quantitate the herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid) in water. The CI-ELISA has a detection limit of 2.3 microg L(-1) and a linear working range of 10--10000 microg L(-1) with an IC(50) value of 195 microg L(-1). The dicamba polyclonal antisera did not cross-react with a number of other herbicides tested but did cross-react with a dicamba metabolite, 5-hydroxydicamba, and structurally related chlorobenzoic acids. The assay was used to estimate quantitatively dicamba concentrations in water samples. Water samples were analyzed directly, and no sample preparation was required. To improve detection limits, a C(18) (reversed phase) column concentration step was devised prior to analysis, and the detection limits were increased by at least by 10-fold. After the sample preconcentration, the detection limit, IC(50), and linear working range were 0.23, 19.5, and 5-200 microg L(-1), respectively. The CI-ELISA estimations in water correlated well with those from gas chromatography-mass spectrometry (GC-MS) analysis (r(2) = 0.9991). This assay contributes to reducing laboratory costs associated with the conventional GC-MS residue analysis techniques for the quantitation of dicamba in water.

A competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) was developed to quantitate the herbicide glyphosate [N-(phosphonomethyl)glycine] in water. The ELISA has a detection limit of 7.6 microg mL(-1) and a linear working range of 10-1000 microg mL(-1) with an IC(50) value of 154 microg mL(-1). The glyphosate polyclonal antisera did not cross-react with a number of other herbicides tested but did cross-react with the glyphosate metabolite aminomethylphosphonic acid and a structurally related herbicide, glyphosine [(N,N-bis(phosphonomethyl)glycine]. The assay was used to estimate, quantitatively with accuracy and precision, glyphosate concentrations in water samples. Water samples were analyzed directly, and no sample preparation was required. To improve detection limits, water samples were concentrated prior to analysis, resulting in the increase of the detection limits by 100-fold. After the sample preconcentration step, the detection limit improved to 0.076 microg mL(-1) with an IC(50) value of 1.54 microg mL(-1), and a linear working range was 0.1-10 microg mL(-1). Glyphosate concentrations determined by ELISA correlated well with those determined by high-pressure liquid chromatography (r(2) = 0.99). This assay contributes to reducing the costs associated with conventional residue analysis techniques for the quantitation of glyphosate in water.

Myriophyllum sibiricum Komarov, an aquatic dicotyledonous macrophyte with a north temperate distribution, was assessed for use in a new bioassay to determine the effect of pesticides, agricultural runoff and municipal waste upon non-target aquatic macrophytes. An axenic culturing system was developed for which an optimal growth medium is required before a bioassay will be reliable. Five media (Murashige and Skoog, Hoagland’s, Gaudet’s, modified Andrew’s, and Hard Water media), commonly used for aquatic plant culturing, were compared to determine the effect on M. sibiricum growth and development. Morphological endpoints for the assay included shoot length, total root length and number, fresh weight and plant area. Membrane integrity, chlorophyll a, chlorophyll b and carotenoid content were the physiological endpoints examined. Based upon these criteria, the modified Andrew’s medium at a pH of 5.8, without the addition of a buffer was chosen as a medium which supported rapid and consistent development of M. sibiricum during the two week assay period.

Pesticide exposure in greenhouse applicators was measured using the video imaging technique to assess exposure (VITAE) along with dermal patches, air monitoring, and biological assessment techniques. The exposure of five males to pesticides during high- and low-volume application methods in commercial greenhouse operations was evaluated. Failure to use precautionary handling methods when using low-volume applications resulted in the highest level of dermal tracer deposition. Results demonstrated nonuniform deposition of tracer/pesticide mixtures on various body regions, supporting earlier work that questioned the assumption of uniform deposition when assessing exposure with the dermal patch technique. By combining the tracer with an oil-based concentrate, it remained uniformly suspended in the spray solution, and deposition ratios remained constant. Estimates of pirimicarb exposure using the VITAE method were highly correlated with excretion of urinary metabolites (r2 = 0.93). The immediate visual results provided by the VITAE system to applicators proved to be a powerful educational tool in helping them adopt precautionary application techniques. The need to employ protective operating procedures when handling pesticides was demonstrated, no matter how brief the exposure period.

Exposure of greenhouse chrysanthemum workers to the pesticide pirimicarb was measured by the Video Imaging Technique to Assess Exposure (VITAE) along with air monitoring and biological assessment techniques. Workers at five commercial chrysanthemum operations were video imaged prior to debudding plants which had been treated with a fluorescent tracer and the pesticide, pirimicarb, 36–48 h earlier. After 1–4 h of debudding, workers were again imaged and the rates of tracer deposition determined with the VITAE system. Tracer deposition from contact with treated foliage was found to increase in a linear fashion over 4 h. Greatest deposition occurred on the hands and arms and represented 42% and 20% of total exposure, respectively. No detectable air residue samples of pirimicarb were found while workers were debudding plants. Monitoring of four workers for pirimicarb and its urinary metabolites revealed no detectable residues following 4 h of contact with foliage, which had been treated 48 h earlier.

Improvements in the calibration techniques used in a Video Imaging Technique for Assessing Exposure (VITAE) were examined. A series of standard curves measuring change in fluorescence with increased tracer deposition within narrow pre-exposure skin tone groupings on volunteer human subjects were developed. Nine highly linear curves were generated. Data from these curves were used to develop calibration curves which permitted the computerized correction of fluorescence based on the pre-exposure skin fluorescence. VITAE estimates of dermal tracer deposition were highly correlated with application rates (r2 = 0.98). The fluorescent tracer 4-methyl-7-diethylaminocoumarin was found to be stable for up to 48 h in a greenhouse environment when applied to chrysanthemum foliage or alpha-cellulose patches. The percentage of tracer which could be dislodged from chrysanthemum foliage was constant over 48 h. Improvements in the VITAE calibration techniques increase its value in providing full-body dosimetric estimates of dermal exposure to pesticides in enclosed environments.

Soil persistence and lateral movement of 2,4-D (2,4-dichlorophenoxy acetic acid) and picloram (4-amino-3,5,6-trichloropicolinic acid) were examined following their application as a stem-foliage spray for brush control on two power line rights-of-way. Ditches to collect runoff water were located 3, 10, 20, and 30 m downslope from the treated areas. Runoff water and soil samples were collected after 0.14, 0.43, 0.57, 1, 2, 4, 7, 8, 11, 15, 16, and 48 weeks and were analyzed for picloram and 2,4-D residues. Only 3 of 85 soil samples downslope from the target areas contained residues of 2,4-D, and only 1 of 85 down slope samples contained a detectable residue of picloram. Of 56 runoff water samples, only 11 contained 2,4-D residues and only 1 contained residues of picloram. The greatest distances down-slope at which residues were detected in runoff water were 20 and 10 m for 2,4-D and picloram, respectively. No residues of either herbicide were recovered in soil or water at 15 weeks or 48 weeks after spraying. Despite normal rainfall frequency and amounts in the first several weeks after spraying in mid-June, significant runoff of either herbicide was not evident at either study site.

Effects of Release herbicide (triclopyr butoxyethyl ester, [TBEE]) on mortality, avoidance response, and growth of larval amphibians (Rana clamitans, Rana pipiens) were investigated using in situ enclosures deployed in two forest wetlands in northern Ontario, Canada. Release was applied at nominal concentrations ranging from 0.26 to 7.68 mg TBEE acid equivalents (AE)/L. No significant deleterious effects of this herbicide on larval growth were detected. However, concentration-dependent mortality and abnormal avoidance response were observed. Most mortality occurred within 96 h following treatment. Median lethal concentration (LC50) values for each species and experimental site ranged from 2.79 to 3.29 mg AE/L, while median effective concentration (EC50) values (abnormal avoidance response) ranged from 1.67 to 3.84 mg AE/L. The LC10 and EC10 endpoints approximated aqueous concentrations (0.59 mg AE/L) expected under direct aerial overspray scenarios, indicating a potential risk of impacts for a small proportion of native amphibian larvae. However, given the low frequency and limited use of this herbicide formulation in Canadian forestry, these risks are considered negligible. Changes in usage patterns would require concurrent chemical and biological monitoring of operational spray programs to accurately quantify the probability and magnitude of real-world exposures and to relate these exposure levels to concentration-response relationships including those described in this study.