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• 1. [Article] Herbicidal effectiveness of trifluralin as influenced by methods of incorporation into the soil and depth of weed seed germination

  This study was conducted to compare the effectiveness of four methods of incorporating the herbicide trifluralin into the soil, and to determine the interaction between depth of incorporation of trifluralin and ...

  Citation × Citation Citation Abstract Copy Title: Herbicidal effectiveness of trifluralin as influenced by methods of incorporation into the soil and depth of weed seed germination Author: Gargano, Don Richard This study was conducted to compare the effectiveness of four methods of incorporating the herbicide trifluralin into the soil, and to determine the interaction between depth of incorporation of trifluralin and depth of weed seed germination. Field experiments on green and dry peas were established in Oregon and Idaho. Trifluralin, applied at four rates, was incorporated by a rototiller, tine-tooth harrow, spike-tooth harrow or double-disked, prior to planting. At time of harvest, yields were taken and plots were evaluated for weed control. On dry peas, only the tine-tooth harrow gave unsatisfactory incorporation of trifluralin. Increasing the rate of trifluralin, regardless of the method of incorporation, reduced the yield of dry peas, indicating injury. On green peas, both the double-disk and rototiller satisfactorily incorporated trifluralin. However, yields from the rototiller plots were slightly less than those from the disk plots. No injury was noted with increasing rates of trifluralin. Greenhouse experiments were conducted at Corvallis to determine the effect of increasing the depth of incorporation and depth of weed seed germination on the herbicidal activity of trifluralin. Trifluralin, applied at three rates, was incorporated to four depths and planted at three depths to pigweed (Amaranthus retroflexus L.) and barnyardgrass (Echinochloa crusgalli (L.) Beauv.). Pigweed was not affected when planted below the trifluralin-treated zone. Only pigweed plants whose roots grew into the trifluralin were controlled. Shoot uptake appeared to be more effective than root uptake by barn-yardgrass. When trifluralin was incorporated over 1.5 inches, weed control was reduced, indicating a dilution effect. Results of this study indicate that the weed species to be controlled will be of major importance when determining the depth and method of incorporation of trifluralin. Title: Herbicidal effectiveness of trifluralin as influenced by methods of incorporation into the soil and depth of weed seed germination Author: Gargano, Don Richard This study was conducted to compare the effectiveness of four methods of incorporating the herbicide trifluralin into the soil, and to determine the interaction between depth of incorporation of trifluralin and depth of weed seed germination. Field experiments on green and dry peas were established in Oregon and Idaho. Trifluralin, applied at four rates, was incorporated by a rototiller, tine-tooth harrow, spike-tooth harrow or double-disked, prior to planting. At time of harvest, yields were taken and plots were evaluated for weed control. On dry peas, only the tine-tooth harrow gave unsatisfactory incorporation of trifluralin. Increasing the rate of trifluralin, regardless of the method of incorporation, reduced the yield of dry peas, indicating injury. On green peas, both the double-disk and rototiller satisfactorily incorporated trifluralin. However, yields from the rototiller plots were slightly less than those from the disk plots. No injury was noted with increasing rates of trifluralin. Greenhouse experiments were conducted at Corvallis to determine the effect of increasing the depth of incorporation and depth of weed seed germination on the herbicidal activity of trifluralin. Trifluralin, applied at three rates, was incorporated to four depths and planted at three depths to pigweed (Amaranthus retroflexus L.) and barnyardgrass (Echinochloa crusgalli (L.) Beauv.). Pigweed was not affected when planted below the trifluralin-treated zone. Only pigweed plants whose roots grew into the trifluralin were controlled. Shoot uptake appeared to be more effective than root uptake by barn-yardgrass. When trifluralin was incorporated over 1.5 inches, weed control was reduced, indicating a dilution effect. Results of this study indicate that the weed species to be controlled will be of major importance when determining the depth and method of incorporation of trifluralin. Close

• 2. [Article] Surfactant effects on bromacil and picloram adsorption by Oregon soils

  The physical and chemical properties of soils greatly affect the toxicity of bromacil and picloram. Consequently, a knowledge of the parameters which influence the soil inactivation of these herbicides is ...

  Citation × Citation Citation Abstract Copy Title: Surfactant effects on bromacil and picloram adsorption by Oregon soils Author: Gaynor, John Donald The physical and chemical properties of soils greatly affect the toxicity of bromacil and picloram. Consequently, a knowledge of the parameters which influence the soil inactivation of these herbicides is necessary to determine proper application rates for good weed control. Enhancement in phytotoxicity with the addition of surfactants or surface active agents in the spray volume has been observed for these chemicals; however, little is known concerning the effects of these additives on picloram and bromacil adsorption. The objectives of this research are: 1) to evaluate the effects of cation saturation on bromacil adsorption by montmorillonite, 2) to determine the effects of pH and organic matter on the adsorption of bromacil and picloram by soils and 3) to determine the effects of dilute solutions of four surfactants on the adsorption of bromacil and picloram by soils. The adsorption of 2-¹⁴C-labeled bromacil on Ca²⁺, Cu²⁺ and Al³⁺ saturated montmorillonite was determined after equilibration a. 0° and 25°C. Seven concentrations of 2-¹⁴C-labeled bromacil and ¹⁴C-carboxyl labeled picloram were equilibrated without surfactant with nine Oregon soils at 25°C. Labeled bromacil and picloram at 5 ppm and 10 ppm concentration in 1% and 10% surfactant solution were also equilibrated at 25°C with eight of the above soils. After equilibrium the montmorillonite and soil samples were centrifuged and analyzed on a liquid scintillation counter for bromacil and picloram remaining in solution. The adsorption of bromacil at 25° and 0°C for each cationic saturated montmorillonite and at 25°C by the nine Oregon soils increased with concentration according to the Freundlich equation, Bromacil adsorbed on the montmorillonite increased with cation saturation in the order Ca²⁺ < Cu²⁺ < Al³⁺. The overall adsorption of bromacil was reduced when the temperature was increased to 25°C. Bromacil adsorbed on the cation saturated rnontmorillonite may occur by complexation of the Cu²⁺ or Al³⁺ cations with the ring N at the one position of the bromacil or by induction through a pH effect. The increased adsorption at the lower temperature may be due to a change in water solubility or adsorption energy. The equilibration of bromacil with the nine Oregon soils indicated organic matter was the most important parameter affecting adsorption. A highly significant correlation coefficient of 0.913 was calculated between the Freundlich K value for bromacil adsorption and organic matter. Bromacil adsorption in the low organic matter soils appeared to be directly correlated with an increase in exchangeable aluminum or pH as observed in the montmorillonite study. However, the wide range in organic matter at the intermediate level limited the opportunity to correlate bromacil adsorption with aluminum or pH. The adsorption of bromacil increased in the presence of the 1% cationic and anionic surfactants and decreased in the presence of the 1% nonionic surfactant solution compared to that without surfactant. Regardless of surfactant type the 1% surfactant solutions greatly decreased the variable effects of organic matter on bromacil adsorption in the Minam and Kinney soil series but not the Woodcock soil series. Bromacil adsorption from the 10% concentration of each surfactant type was greatly reduced compared to adsorption from the 1% surfactant solution. Strangely, the adsorption of bromacil from surfactant solution was always less in the Woodcock soil series than in the Minam and Kinney soil series. Picloram adsorption increased with concentration on the nine soils according to the Freundlich equation. A significant negative correlation coefficient of 0.667 was calculated between the Freundlich K value for picloram adsorption and pH; however, the interaction between pH and exchangeable aluminum could not be isolated. Complexation of picloram with exchangeable aluminum and adsorption of the molecular species by organic matter appeared to be the principle modes of adsorption. The adsorption of picloram by soils increased in the presence of the 1% cationic and nonionic surfactant solutions and decreased in the 1% anionic surfactant solution compared to that without surfactant. Adsorption in the presence of 1% cationic surfactant solution occurred from the molecular and ionic species as indicated by equal adsorption in the Minam (pH = 7) and Kinney (pH = 5) soil series. The 10% cationic surfactant solution decreased adsorption from that in the 1% surfactant solution; however, an inverse relationship between organic matter and adsorption was evident in the Minam and Kinney soil series. Adsorption from the nonionic surfactant solution was independent of surfactant concentration but decreased as pH increased. The 1% anionic surfactant solution effectively competed with picloram for adsorption sites. However, the 10% surfactant solution increased adsorption from that in the 1% surfactant solution possibly due to the creation of adsorption sites for picloram by the adsorbed surfactant. Increased phytotoxicity of bromacil and picloram has been observed by others when a nonionic surfactant was introduced into the spray solution. The results of this study indicate that part of the increased toxicity may be due to reduced soil adsorption of the chemicals in anionic and nonionic surfactant solutions. The addition of a cationic surfactant, on the other hand, may increase adsorption and provide poor weed control at recommended rates. Further investigation is required to determine if the herbicides adsorbed by the surfactant are available for root uptake and if the soil applied surfactant is phytotoxic. Title: Surfactant effects on bromacil and picloram adsorption by Oregon soils Author: Gaynor, John Donald The physical and chemical properties of soils greatly affect the toxicity of bromacil and picloram. Consequently, a knowledge of the parameters which influence the soil inactivation of these herbicides is necessary to determine proper application rates for good weed control. Enhancement in phytotoxicity with the addition of surfactants or surface active agents in the spray volume has been observed for these chemicals; however, little is known concerning the effects of these additives on picloram and bromacil adsorption. The objectives of this research are: 1) to evaluate the effects of cation saturation on bromacil adsorption by montmorillonite, 2) to determine the effects of pH and organic matter on the adsorption of bromacil and picloram by soils and 3) to determine the effects of dilute solutions of four surfactants on the adsorption of bromacil and picloram by soils. The adsorption of 2-¹⁴C-labeled bromacil on Ca²⁺, Cu²⁺ and Al³⁺ saturated montmorillonite was determined after equilibration a. 0° and 25°C. Seven concentrations of 2-¹⁴C-labeled bromacil and ¹⁴C-carboxyl labeled picloram were equilibrated without surfactant with nine Oregon soils at 25°C. Labeled bromacil and picloram at 5 ppm and 10 ppm concentration in 1% and 10% surfactant solution were also equilibrated at 25°C with eight of the above soils. After equilibrium the montmorillonite and soil samples were centrifuged and analyzed on a liquid scintillation counter for bromacil and picloram remaining in solution. The adsorption of bromacil at 25° and 0°C for each cationic saturated montmorillonite and at 25°C by the nine Oregon soils increased with concentration according to the Freundlich equation, Bromacil adsorbed on the montmorillonite increased with cation saturation in the order Ca²⁺ < Cu²⁺ < Al³⁺. The overall adsorption of bromacil was reduced when the temperature was increased to 25°C. Bromacil adsorbed on the cation saturated rnontmorillonite may occur by complexation of the Cu²⁺ or Al³⁺ cations with the ring N at the one position of the bromacil or by induction through a pH effect. The increased adsorption at the lower temperature may be due to a change in water solubility or adsorption energy. The equilibration of bromacil with the nine Oregon soils indicated organic matter was the most important parameter affecting adsorption. A highly significant correlation coefficient of 0.913 was calculated between the Freundlich K value for bromacil adsorption and organic matter. Bromacil adsorption in the low organic matter soils appeared to be directly correlated with an increase in exchangeable aluminum or pH as observed in the montmorillonite study. However, the wide range in organic matter at the intermediate level limited the opportunity to correlate bromacil adsorption with aluminum or pH. The adsorption of bromacil increased in the presence of the 1% cationic and anionic surfactants and decreased in the presence of the 1% nonionic surfactant solution compared to that without surfactant. Regardless of surfactant type the 1% surfactant solutions greatly decreased the variable effects of organic matter on bromacil adsorption in the Minam and Kinney soil series but not the Woodcock soil series. Bromacil adsorption from the 10% concentration of each surfactant type was greatly reduced compared to adsorption from the 1% surfactant solution. Strangely, the adsorption of bromacil from surfactant solution was always less in the Woodcock soil series than in the Minam and Kinney soil series. Picloram adsorption increased with concentration on the nine soils according to the Freundlich equation. A significant negative correlation coefficient of 0.667 was calculated between the Freundlich K value for picloram adsorption and pH; however, the interaction between pH and exchangeable aluminum could not be isolated. Complexation of picloram with exchangeable aluminum and adsorption of the molecular species by organic matter appeared to be the principle modes of adsorption. The adsorption of picloram by soils increased in the presence of the 1% cationic and nonionic surfactant solutions and decreased in the 1% anionic surfactant solution compared to that without surfactant. Adsorption in the presence of 1% cationic surfactant solution occurred from the molecular and ionic species as indicated by equal adsorption in the Minam (pH = 7) and Kinney (pH = 5) soil series. The 10% cationic surfactant solution decreased adsorption from that in the 1% surfactant solution; however, an inverse relationship between organic matter and adsorption was evident in the Minam and Kinney soil series. Adsorption from the nonionic surfactant solution was independent of surfactant concentration but decreased as pH increased. The 1% anionic surfactant solution effectively competed with picloram for adsorption sites. However, the 10% surfactant solution increased adsorption from that in the 1% surfactant solution possibly due to the creation of adsorption sites for picloram by the adsorbed surfactant. Increased phytotoxicity of bromacil and picloram has been observed by others when a nonionic surfactant was introduced into the spray solution. The results of this study indicate that part of the increased toxicity may be due to reduced soil adsorption of the chemicals in anionic and nonionic surfactant solutions. The addition of a cationic surfactant, on the other hand, may increase adsorption and provide poor weed control at recommended rates. Further investigation is required to determine if the herbicides adsorbed by the surfactant are available for root uptake and if the soil applied surfactant is phytotoxic. Close

• 3. [Article] Effect of two methylcarbamates on the toxiciity of isopropyl m-chlorocarbanilate (chlorpropham) to safflower (Carthamus tinctorius L.) and common buckwheat (Fagopyrum esculentum Moench.)

  Addition of the methylcarbamate compounds p-chlorophenyl N-methylcarbamate (PPG-124) and 1-naphthyl N-methylcarbamate (carbaryl) to various herbicides has resulted in reduced rates of degradation. Carbaryl ...

  Citation × Citation Citation Abstract Copy Title: Effect of two methylcarbamates on the toxiciity of isopropyl m-chlorocarbanilate (chlorpropham) to safflower (Carthamus tinctorius L.) and common buckwheat (Fagopyrum esculentum Moench.) Author: Kirkland, Kenneth Addition of the methylcarbamate compounds p-chlorophenyl N-methylcarbamate (PPG-124) and 1-naphthyl N-methylcarbamate (carbaryl) to various herbicides has resulted in reduced rates of degradation. Carbaryl affects the degradation of certain herbicides in both plants and soils while PPG-124 has only been demonstrated to affect degradation in soils. Both these materials are effective in increasing the persistence of isopropyl m-chlorocarbanilate (chlorpropham) in the soil. No work has been published on the possible effect of these compounds on the response of plants to chlorpropham or other carbahilate herbicides. Studies were conducted in a growth-chamber to investigate the effect of PPG-124 and carbaryl on the response of two test species to chlorpropham. One species, safflower (Carthamus tinctorius L. ), was chosen for its resistance to chlorpropham; the other, common buckwheat (Fagopyrum esculentum Moench. ) for its susceptibility. Plants were grown in Hoagland's solution to which the various treatments were added. This approach was used to avoid any soil effects such as differential adsorption and degradation of the chlorpropham. Four experiments were carried out with safflower and two with buckwheat. Varying doses and exposure periods to the chemicals were included but all experiments were of the same duration. The effects of mixtures of chlorpropham with PPG-124 or carbaryl were compared with those of individual treatments of the three compounds applied at the same time. Dry weights of roots and shoots were taken as indicators of plant response. The method of Colby (1967) was used to compute the expected response of the test species to the various mixtures. Comparisons of the expected with the observed responses indicated that both PPG 124 and carbaryl had an antagonistic effect on chlorpropham activity when applied to roots of safflower. In contrast, a slight synergistic effect at certain concentrations was noted when buckwheat was used as the test species. An explanation of these effects would require uptake and metabolism studies with labeled materials. The slight alterations in response to chlorpropham noted in these experiments probably would be masked in the field by the increased persistence of chlorpropham in soil treated with mixtures of this herbicide with PPG-124 or carbaryl. Title: Effect of two methylcarbamates on the toxiciity of isopropyl m-chlorocarbanilate (chlorpropham) to safflower (Carthamus tinctorius L.) and common buckwheat (Fagopyrum esculentum Moench.) Author: Kirkland, Kenneth Addition of the methylcarbamate compounds p-chlorophenyl N-methylcarbamate (PPG-124) and 1-naphthyl N-methylcarbamate (carbaryl) to various herbicides has resulted in reduced rates of degradation. Carbaryl affects the degradation of certain herbicides in both plants and soils while PPG-124 has only been demonstrated to affect degradation in soils. Both these materials are effective in increasing the persistence of isopropyl m-chlorocarbanilate (chlorpropham) in the soil. No work has been published on the possible effect of these compounds on the response of plants to chlorpropham or other carbahilate herbicides. Studies were conducted in a growth-chamber to investigate the effect of PPG-124 and carbaryl on the response of two test species to chlorpropham. One species, safflower (Carthamus tinctorius L. ), was chosen for its resistance to chlorpropham; the other, common buckwheat (Fagopyrum esculentum Moench. ) for its susceptibility. Plants were grown in Hoagland's solution to which the various treatments were added. This approach was used to avoid any soil effects such as differential adsorption and degradation of the chlorpropham. Four experiments were carried out with safflower and two with buckwheat. Varying doses and exposure periods to the chemicals were included but all experiments were of the same duration. The effects of mixtures of chlorpropham with PPG-124 or carbaryl were compared with those of individual treatments of the three compounds applied at the same time. Dry weights of roots and shoots were taken as indicators of plant response. The method of Colby (1967) was used to compute the expected response of the test species to the various mixtures. Comparisons of the expected with the observed responses indicated that both PPG 124 and carbaryl had an antagonistic effect on chlorpropham activity when applied to roots of safflower. In contrast, a slight synergistic effect at certain concentrations was noted when buckwheat was used as the test species. An explanation of these effects would require uptake and metabolism studies with labeled materials. The slight alterations in response to chlorpropham noted in these experiments probably would be masked in the field by the increased persistence of chlorpropham in soil treated with mixtures of this herbicide with PPG-124 or carbaryl. Close

• 4. [Article] Factors influencing the herbicidal activity and persistence of isomers of 1, 1-dimethyl-diisopropyl-indanyl ethyl ketone in soil

  The purpose of this study was to evaluate the activity of Sindone (isomers of 1, 1-dimethyl-diisopropyl-indanyl ethyl ketone) under field conditions and to gain information regarding the rate of detoxification of ...

  Citation × Citation Citation Abstract Copy Title: Factors influencing the herbicidal activity and persistence of isomers of 1, 1-dimethyl-diisopropyl-indanyl ethyl ketone in soil Author: Donaldson, Dean Robert The purpose of this study was to evaluate the activity of Sindone (isomers of 1, 1-dimethyl-diisopropyl-indanyl ethyl ketone) under field conditions and to gain information regarding the rate of detoxification of Sindone in soil. A series of trials were established in sugar beet fields in California, Oregon, and Washington. Sindone was applied as a pre-plant treatment, power incorporated to a depth of 1.5 inches, at rates of 0, 1.5, and 3.0 lb /A active ingredient, and followed by sprinkler or furrow irrigation. The toxicity of Sindone to emerging sugar beets and seedling grasses was recorded. Yield data were collected where possible. Incorporated Sindone gave good grass control at rates of 1.5 to 3.0 lb /A when irrigated after application. Areas that received no irrigation within four weeks after application showed no visible weed control. Rates of Sindone that gave good grass control injured sugar beets. A series of greenhouse experiments were conducted to study the detoxification rate of Sindone in soil. The rate of detoxification was determined at soil moisture levels of 47%, 77%, and 102% field capacity. Treated soils were stored at -18, +5, +25, and +35°C. Barnyardgrass (E. crusgalli) was used as the bioassay species. The rate of detoxification was greatest at the 77% moisture level and at 35°C. Sindone degradation rates were also determined in eight agricultural soil types stored at +25°C. The rate of detoxification indicated a half-life for incorporated Sindone under these conditions of approximately six months. The results of this study indicate that Sindone offers little promise as a sugar beet herbicide because of lack of selectivity. However, the long half-life indicates potential usage in perennial crops or in turf weed control. Bioassay results indicate a strong possibility that phytotoxic metabolites are formed in the degradation process. Title: Factors influencing the herbicidal activity and persistence of isomers of 1, 1-dimethyl-diisopropyl-indanyl ethyl ketone in soil Author: Donaldson, Dean Robert The purpose of this study was to evaluate the activity of Sindone (isomers of 1, 1-dimethyl-diisopropyl-indanyl ethyl ketone) under field conditions and to gain information regarding the rate of detoxification of Sindone in soil. A series of trials were established in sugar beet fields in California, Oregon, and Washington. Sindone was applied as a pre-plant treatment, power incorporated to a depth of 1.5 inches, at rates of 0, 1.5, and 3.0 lb /A active ingredient, and followed by sprinkler or furrow irrigation. The toxicity of Sindone to emerging sugar beets and seedling grasses was recorded. Yield data were collected where possible. Incorporated Sindone gave good grass control at rates of 1.5 to 3.0 lb /A when irrigated after application. Areas that received no irrigation within four weeks after application showed no visible weed control. Rates of Sindone that gave good grass control injured sugar beets. A series of greenhouse experiments were conducted to study the detoxification rate of Sindone in soil. The rate of detoxification was determined at soil moisture levels of 47%, 77%, and 102% field capacity. Treated soils were stored at -18, +5, +25, and +35°C. Barnyardgrass (E. crusgalli) was used as the bioassay species. The rate of detoxification was greatest at the 77% moisture level and at 35°C. Sindone degradation rates were also determined in eight agricultural soil types stored at +25°C. The rate of detoxification indicated a half-life for incorporated Sindone under these conditions of approximately six months. The results of this study indicate that Sindone offers little promise as a sugar beet herbicide because of lack of selectivity. However, the long half-life indicates potential usage in perennial crops or in turf weed control. Bioassay results indicate a strong possibility that phytotoxic metabolites are formed in the degradation process. Close

• 5. [Article] Foliage applications of terbacil to peppermint (Mentha piperita) and several weed species

  Several studies were conducted to determine the feasibility of using terbacil (3-tert-butyl-5-chloro-6-methyluracil) postemergence to weeds and peppermint (Mentha piperita L.). Three nonionic surfactants, four ...

  Citation × Citation Citation Abstract Copy Title: Foliage applications of terbacil to peppermint (Mentha piperita) and several weed species Author: Radosevich, Steven R. Several studies were conducted to determine the feasibility of using terbacil (3-tert-butyl-5-chloro-6-methyluracil) postemergence to weeds and peppermint (Mentha piperita L.). Three nonionic surfactants, four nonphytotoxic oils, and a liquid fertilizer were each combined with 0.5 lb ai/A terbacil in 35 gallons of water per acre. Weed species tested include: redroot pigweed (Amaranthus retroflexus L.), lambsquarters (Chenopodium album L.), common mustard (Brassica campestris L.), barnyardgrass (Echinochloa crusgalli (L.) Beauv.), and green foxtail (Setaria viridis (L.) Beauv.). Broadleaf weeds were more susceptible to foliage applications of terbacil than grass species. However, excellent control of both broadleaf weeds and grasses was obtained when applications were made within seven days after weed seedling emergence. Less grass control always resulted when treatments were made two or three weeks after emergence. The addition of nonphytotoxic oils or surfactants to the spray solution was beneficial to terbacil activity at later stages of weed growth. Nonphytotoxic oils were usually more effective than surfactants. Solution 32, a liquid nitrogen solution, in combination with terbacil did not improve herbicidal activity. None of the terbacil treatments with or without spray solution additives, significantly reduced peppermint hay production. Bioassay of core samples to determine the amount of herbicide remaining in soil from preemergence and split applications of terbacil indicated that lower levels of herbicide remained in soils treated by split application. Foliage interception and subsequent rapid detoxification of terbacil by the peppermint plant may explain this observed decrease of herbicide in the soil. Title: Foliage applications of terbacil to peppermint (Mentha piperita) and several weed species Author: Radosevich, Steven R. Several studies were conducted to determine the feasibility of using terbacil (3-tert-butyl-5-chloro-6-methyluracil) postemergence to weeds and peppermint (Mentha piperita L.). Three nonionic surfactants, four nonphytotoxic oils, and a liquid fertilizer were each combined with 0.5 lb ai/A terbacil in 35 gallons of water per acre. Weed species tested include: redroot pigweed (Amaranthus retroflexus L.), lambsquarters (Chenopodium album L.), common mustard (Brassica campestris L.), barnyardgrass (Echinochloa crusgalli (L.) Beauv.), and green foxtail (Setaria viridis (L.) Beauv.). Broadleaf weeds were more susceptible to foliage applications of terbacil than grass species. However, excellent control of both broadleaf weeds and grasses was obtained when applications were made within seven days after weed seedling emergence. Less grass control always resulted when treatments were made two or three weeks after emergence. The addition of nonphytotoxic oils or surfactants to the spray solution was beneficial to terbacil activity at later stages of weed growth. Nonphytotoxic oils were usually more effective than surfactants. Solution 32, a liquid nitrogen solution, in combination with terbacil did not improve herbicidal activity. None of the terbacil treatments with or without spray solution additives, significantly reduced peppermint hay production. Bioassay of core samples to determine the amount of herbicide remaining in soil from preemergence and split applications of terbacil indicated that lower levels of herbicide remained in soils treated by split application. Foliage interception and subsequent rapid detoxification of terbacil by the peppermint plant may explain this observed decrease of herbicide in the soil. Close

• 6. [Article] Effect of glyphosate when applied to grass and legume seeds or preemergence to bentgrass (Agrostis tenuis Sibth.)

  Paraquat (1,11-dimethy1-4,4'-bipyridinium ion) and glyphosate [N (phosphonomethyl)glycine] are herbicides utilized for chemical seedbed preparation in the establishment of grass and legume seed crops. ...

  Citation × Citation Citation Abstract Copy Title: Effect of glyphosate when applied to grass and legume seeds or preemergence to bentgrass (Agrostis tenuis Sibth.) Author: Salazar, Luis Carlos Paraquat (1,11-dimethy1-4,4'-bipyridinium ion) and glyphosate [N (phosphonomethyl)glycine] are herbicides utilized for chemical seedbed preparation in the establishment of grass and legume seed crops. When these herbicides are applied after seeding the crop, seeds which are not protected by a layer of soil could be exposed to the herbicide. Effects of paraquat on exposed seeds have been studied previously, but more information was needed on effects from glyphosate. Greenhouse studies were conducted using direct applications of glyphosate and paraquat over exposed seeds of six grass species: Kentucky bluegrass, perennial ryegrass, bentgrass, tall fescue, fine fescue, and orchardgrass; and two legume species, alfalfa and red clover. Glyphosate tended to be toxic to all species tested, reducing germination and particularly seedling growth. Paraquat was toxic only to grasses and did not affect legumes. The major detrimental effect of glyphosate on legume seeds and seedlings was caused by direct contact of the herbicide with seeds, but a minor effect was detected when untreated seeds were transferred to treated soil, indicating that glyphosate was not inactivated in soil as fast as paraquat. These results indicate that the use of glyphosate in chemical seedbed preparation may be detrimental to the new crop if the herbicide is applied directly to exposed seeds. Glyphosate has been reported by many research workers to be inactivated almost immediately upon contact with the soil. However, a few growers in western Oregon have reported phytotoxic effects on grass seedlings when glyphosate applications were made shortly before emergence of the crop. Greenhouse studies were conducted to determine whether glyphosate could have herbicidal activity when applied directly to soil prior to bentgrass emergence (from 1 to 5 days) and to examine some soil factors involved. Soil activity of glyphosate differed considerably among three high-organic soils and one mineral soil. The soils in which glyphosate was most active contained the highest levels of organic matter (64% and 28%), but there was no strong correlation with organic matter content in the other soils or in soil blends containing various levels of organic matter. Varying phosphorus levels did not significantly influence activity of glyphosate. There was no evidence that glyphosate formed an inactive complex with Fe or Al. The two soils in which glyphosate was most active, organic soils No. 3 and 4, contained the highest levels of Fe and at least equal levels of Al. Increasing pH increased glyphosate activity markedly in the mineral soil and one high-organic soil, while slightly decreasing activity in two high-organic soils. Although none of these soil factors proved conclusively to be entirely responsible for variations in glyphosate soil activity, general results from the series of experiments indicated that glyphosate can definitely be taken up from soil by crop plants and produce injury. The herbicide remained available in the soil solution for sufficient time to cause significant plant growth reduction. Consequently, a waiting period of several days should elapse from glyphosate treatment to emergence of a crop. Title: Effect of glyphosate when applied to grass and legume seeds or preemergence to bentgrass (Agrostis tenuis Sibth.) Author: Salazar, Luis Carlos Paraquat (1,11-dimethy1-4,4'-bipyridinium ion) and glyphosate [N (phosphonomethyl)glycine] are herbicides utilized for chemical seedbed preparation in the establishment of grass and legume seed crops. When these herbicides are applied after seeding the crop, seeds which are not protected by a layer of soil could be exposed to the herbicide. Effects of paraquat on exposed seeds have been studied previously, but more information was needed on effects from glyphosate. Greenhouse studies were conducted using direct applications of glyphosate and paraquat over exposed seeds of six grass species: Kentucky bluegrass, perennial ryegrass, bentgrass, tall fescue, fine fescue, and orchardgrass; and two legume species, alfalfa and red clover. Glyphosate tended to be toxic to all species tested, reducing germination and particularly seedling growth. Paraquat was toxic only to grasses and did not affect legumes. The major detrimental effect of glyphosate on legume seeds and seedlings was caused by direct contact of the herbicide with seeds, but a minor effect was detected when untreated seeds were transferred to treated soil, indicating that glyphosate was not inactivated in soil as fast as paraquat. These results indicate that the use of glyphosate in chemical seedbed preparation may be detrimental to the new crop if the herbicide is applied directly to exposed seeds. Glyphosate has been reported by many research workers to be inactivated almost immediately upon contact with the soil. However, a few growers in western Oregon have reported phytotoxic effects on grass seedlings when glyphosate applications were made shortly before emergence of the crop. Greenhouse studies were conducted to determine whether glyphosate could have herbicidal activity when applied directly to soil prior to bentgrass emergence (from 1 to 5 days) and to examine some soil factors involved. Soil activity of glyphosate differed considerably among three high-organic soils and one mineral soil. The soils in which glyphosate was most active contained the highest levels of organic matter (64% and 28%), but there was no strong correlation with organic matter content in the other soils or in soil blends containing various levels of organic matter. Varying phosphorus levels did not significantly influence activity of glyphosate. There was no evidence that glyphosate formed an inactive complex with Fe or Al. The two soils in which glyphosate was most active, organic soils No. 3 and 4, contained the highest levels of Fe and at least equal levels of Al. Increasing pH increased glyphosate activity markedly in the mineral soil and one high-organic soil, while slightly decreasing activity in two high-organic soils. Although none of these soil factors proved conclusively to be entirely responsible for variations in glyphosate soil activity, general results from the series of experiments indicated that glyphosate can definitely be taken up from soil by crop plants and produce injury. The herbicide remained available in the soil solution for sufficient time to cause significant plant growth reduction. Consequently, a waiting period of several days should elapse from glyphosate treatment to emergence of a crop. Close

• 7. [Article] Combined Effects of Intensive Forest Management and Microclimate on Reproduction in a Cavity-Nesting Songbird

  Future scenarios of global climate change rely on large-scale climate envelope models that do not account for local climatic conditions to which organisms most closely respond. Shifts in species distributions ...

  Citation × Citation Citation Abstract Copy Title: Combined Effects of Intensive Forest Management and Microclimate on Reproduction in a Cavity-Nesting Songbird Author: Jones, Kristin N. Future scenarios of global climate change rely on large-scale climate envelope models that do not account for local climatic conditions to which organisms most closely respond. Shifts in species distributions and phenology driven by climate change are well-documented, yet we lack a strong understanding of how climate change will influence the demographic rates of animal populations, which directly determine the likelihood of species persistence. Land cover change, an agent of global change that is increasing in extent and intensity to meet the needs of a growing human population, can combine with climate change to stress animal populations by altering microclimatic conditions, as well as changing the availability of resources such as food and cover from predators. Thus, identifying the individual and combined effects of climate and land management practices is essential to accurately predict the responses of animal populations to global change. Intensive forest management results in land cover change by suppressing the growth of competing plant species in favor of commercial species and altering the abundance and composition of forest vegetation. In turn, changes in the abundance and composition of forest vegetation can modify local air temperatures. I hypothesized that herbicide application would alter the thermal environment for early-seral forest organisms (Chapter 2). If this were the case, then air temperature could be expected to increase in magnitude and variability along a gradient of herbicide treatment intensity. To test this hypothesis, I used iButton dataloggers to monitor air temperature at 160 nest boxes on 20 intensively managed early-seral forest stands (10.4 - 18.9) in the northern Oregon Coast Range, USA representing a gradient in intensive forest management (i.e., no-spray control, light, moderate and intensive herbicide application). I also measured the amount and composition of vegetation cover to test for herbicide effects on vegetation among application intensities. Using linear mixed models, I compared three measures of air temperature (mean daily minimum, mean, and maximum) and their associated coefficients of variation (CVs). Additionally, I used linear mixed models to confirm differences in total vegetation and broadleaved vegetation cover. Although mean total vegetation cover generally decreased, it did not significantly differ among herbicide treatments; in contrast, mean broadleaved vegetation cover was significantly reduced in the moderate and intensive treatments. Herbicide treatment was a significant predictor of maximum and mean temperatures, but minimum temperatures did not differ with herbicide treatment. Although there was an effect of herbicide treatment on air temperature, corrected pairwise comparisons indicated no significant differences among treatments. I note that though my power to detect statistical differences among treatments was limited, these differences were quite small (< 0.5°C) and confidence intervals were generally relatively narrow (< 1.5°C), suggesting that temperature did not differ among herbicide treatments in biologically meaningful ways. Furthermore, I did not detect an effect of herbicide treatment on temperature variability. Estimated differences in temperature variability among treatments were small (< 0.5%) and confidence intervals covered a relatively broad range of values, indicating that I did not have enough statistical power to detect effects. I found no uniform pattern in the direction (positive or negative) of the effect of herbicide treatment on temperature or CVs among treatment intensities. Daily air temperatures can strongly influence the reproductive output of early-seral songbirds if temperatures exceed physiological tolerances of offspring, decreasing physiological performance (e.g., excessively high and low temperatures can alter metabolic rates) and survival. Moreover, the abundance and composition of early-seral forest vegetation can influence songbird reproductive output through changes in nest predator communities, food resources, or both. Thus, I further hypothesized that intensive forest management practices could combine with intraseasonal air temperatures to impact reproductive output in an insectivorous cavity-nesting songbird, the House Wren (Trogolodytes aedon) (Chapter 3). If this were the case, then House Wren nest survival, the number of offspring produced, and the quality of those offspring would decline with greater management intensity and increasing air temperatures. To test these predictions, I monitored 283 nests on 24 intensively managed early-seral forest stands (8.6 - 18.9 ha) in the northern Oregon Coast Range, USA representing a gradient in intensive forest management (i.e., no-spray control, light, moderate and intensive herbicide application). I used data from Chapter 2 to test for combined effects of air temperature and herbicide-driven vegetation changes on House Wren reproductive output. Using linear mixed models within a model selection framework, I did not find support for combined effects of temperature and herbicide treatment on nest survival. After accounting for the effects of herbicide-driven vegetation changes on reproductive output, air temperature effects were negligible. My results suggest that post-harvest vegetation management likely does not influence the number of young produced nor their quality (as indicated by body condition) in intensively managed early-seral forests, but may influence nest survival. However, nest survival did not decline along a gradient of herbicide intensity as I expected. Instead, mean nest survival was greatest in the control and most intensively managed stands (failure was greatest in the light treatment); however, these effects were so variable as to not be statistically significant. My results suggest that post-harvest vegetation management in intensively managed forests may be linked to minor changes in microclimatic air temperatures, but that there is high variation in these effects and effects are likely small. Therefore, there appears to be limited potential for vegetation control strategies through herbicides to buffer expected climate change effects on organisms in early-seral forest. My results also suggest that the potential for combined effects of herbicide application and air temperature on early-seral cavity-nesting songbirds is limited. Under current local climate patterns, air temperature appears to exert negligible effects on House Wren reproductive output after accounting for changes in vegetation cover. The effects of herbicide-driven vegetation changes on early-seral songbirds may be large, though highly variable, and not an increasing function of herbicide intensity. These effects may be primarily predator-mediated, as indicated by the large effects of herbicide treatment on House Wren nest survival but not the number of offspring produced nor their quality. My finding of limited temperature effects on House Wren reproductive output compared to the effects of forest management intensity supports predictions that, despite increasing concerns over the impacts of advancing climate change on animal populations, land cover change driven by anthropogenic land use will continue to be the primary global change driver impacting animal populations in the near future. Title: Combined Effects of Intensive Forest Management and Microclimate on Reproduction in a Cavity-Nesting Songbird Author: Jones, Kristin N. Future scenarios of global climate change rely on large-scale climate envelope models that do not account for local climatic conditions to which organisms most closely respond. Shifts in species distributions and phenology driven by climate change are well-documented, yet we lack a strong understanding of how climate change will influence the demographic rates of animal populations, which directly determine the likelihood of species persistence. Land cover change, an agent of global change that is increasing in extent and intensity to meet the needs of a growing human population, can combine with climate change to stress animal populations by altering microclimatic conditions, as well as changing the availability of resources such as food and cover from predators. Thus, identifying the individual and combined effects of climate and land management practices is essential to accurately predict the responses of animal populations to global change. Intensive forest management results in land cover change by suppressing the growth of competing plant species in favor of commercial species and altering the abundance and composition of forest vegetation. In turn, changes in the abundance and composition of forest vegetation can modify local air temperatures. I hypothesized that herbicide application would alter the thermal environment for early-seral forest organisms (Chapter 2). If this were the case, then air temperature could be expected to increase in magnitude and variability along a gradient of herbicide treatment intensity. To test this hypothesis, I used iButton dataloggers to monitor air temperature at 160 nest boxes on 20 intensively managed early-seral forest stands (10.4 - 18.9) in the northern Oregon Coast Range, USA representing a gradient in intensive forest management (i.e., no-spray control, light, moderate and intensive herbicide application). I also measured the amount and composition of vegetation cover to test for herbicide effects on vegetation among application intensities. Using linear mixed models, I compared three measures of air temperature (mean daily minimum, mean, and maximum) and their associated coefficients of variation (CVs). Additionally, I used linear mixed models to confirm differences in total vegetation and broadleaved vegetation cover. Although mean total vegetation cover generally decreased, it did not significantly differ among herbicide treatments; in contrast, mean broadleaved vegetation cover was significantly reduced in the moderate and intensive treatments. Herbicide treatment was a significant predictor of maximum and mean temperatures, but minimum temperatures did not differ with herbicide treatment. Although there was an effect of herbicide treatment on air temperature, corrected pairwise comparisons indicated no significant differences among treatments. I note that though my power to detect statistical differences among treatments was limited, these differences were quite small (< 0.5°C) and confidence intervals were generally relatively narrow (< 1.5°C), suggesting that temperature did not differ among herbicide treatments in biologically meaningful ways. Furthermore, I did not detect an effect of herbicide treatment on temperature variability. Estimated differences in temperature variability among treatments were small (< 0.5%) and confidence intervals covered a relatively broad range of values, indicating that I did not have enough statistical power to detect effects. I found no uniform pattern in the direction (positive or negative) of the effect of herbicide treatment on temperature or CVs among treatment intensities. Daily air temperatures can strongly influence the reproductive output of early-seral songbirds if temperatures exceed physiological tolerances of offspring, decreasing physiological performance (e.g., excessively high and low temperatures can alter metabolic rates) and survival. Moreover, the abundance and composition of early-seral forest vegetation can influence songbird reproductive output through changes in nest predator communities, food resources, or both. Thus, I further hypothesized that intensive forest management practices could combine with intraseasonal air temperatures to impact reproductive output in an insectivorous cavity-nesting songbird, the House Wren (Trogolodytes aedon) (Chapter 3). If this were the case, then House Wren nest survival, the number of offspring produced, and the quality of those offspring would decline with greater management intensity and increasing air temperatures. To test these predictions, I monitored 283 nests on 24 intensively managed early-seral forest stands (8.6 - 18.9 ha) in the northern Oregon Coast Range, USA representing a gradient in intensive forest management (i.e., no-spray control, light, moderate and intensive herbicide application). I used data from Chapter 2 to test for combined effects of air temperature and herbicide-driven vegetation changes on House Wren reproductive output. Using linear mixed models within a model selection framework, I did not find support for combined effects of temperature and herbicide treatment on nest survival. After accounting for the effects of herbicide-driven vegetation changes on reproductive output, air temperature effects were negligible. My results suggest that post-harvest vegetation management likely does not influence the number of young produced nor their quality (as indicated by body condition) in intensively managed early-seral forests, but may influence nest survival. However, nest survival did not decline along a gradient of herbicide intensity as I expected. Instead, mean nest survival was greatest in the control and most intensively managed stands (failure was greatest in the light treatment); however, these effects were so variable as to not be statistically significant. My results suggest that post-harvest vegetation management in intensively managed forests may be linked to minor changes in microclimatic air temperatures, but that there is high variation in these effects and effects are likely small. Therefore, there appears to be limited potential for vegetation control strategies through herbicides to buffer expected climate change effects on organisms in early-seral forest. My results also suggest that the potential for combined effects of herbicide application and air temperature on early-seral cavity-nesting songbirds is limited. Under current local climate patterns, air temperature appears to exert negligible effects on House Wren reproductive output after accounting for changes in vegetation cover. The effects of herbicide-driven vegetation changes on early-seral songbirds may be large, though highly variable, and not an increasing function of herbicide intensity. These effects may be primarily predator-mediated, as indicated by the large effects of herbicide treatment on House Wren nest survival but not the number of offspring produced nor their quality. My finding of limited temperature effects on House Wren reproductive output compared to the effects of forest management intensity supports predictions that, despite increasing concerns over the impacts of advancing climate change on animal populations, land cover change driven by anthropogenic land use will continue to be the primary global change driver impacting animal populations in the near future. Close

• 8. [Article] Efficiency of forest vegetation control with herbicides

  Selective suppression of crown and root sprouting of non-coniferous cover are the keys to effective forest vegetation management. This study 1) develops insight into mechanisms of controlling root suckering ...

  Citation × Citation Citation Abstract Copy Title: Efficiency of forest vegetation control with herbicides Author: Fredrickson, Edward A. Selective suppression of crown and root sprouting of non-coniferous cover are the keys to effective forest vegetation management. This study 1) develops insight into mechanisms of controlling root suckering and top regrowth of bear clover (Chamaebatia foliolosa), and develops a broad data base for controlling broad groups of vegetation chemically. Finally, it develops a mangement guide for use of this technology to achieve certain management objectives. Four herbicides were evaluated for their ability to control post-treatment resprouting of bear clover. Sprouting was evaluated above and below ground by creating trenches to expose the rhizome network. Soil moistures were also studied to determine if their were differences due to varying levels of efficacy. They were marginally responsive in the top 60 cm of soil. Plant moisture stress measurements were obtained on ponderosa pine (Pinus ponderosa), and were found considerably more responsive than surface soil water contents. Several application parameters including volume, dose, surfactant, dropsize and product were studied to determine their influence on herbicide efficacy and efficiency on several Pacific Coast species of shrubs and grass. Sites included the Oregon Coast Range, the east side of the Oregon Cascade Range and the west side of the Sierra Nevada Mountains in California. Growth regulator products were not suitable for long-term control. High levels of sprouting were observed above and below ground. Glyphosate led to control of above-ground sprouting as well as the rhizome system of bear clover. Sprouting was found to increase with increasing distance from healthy vegetation. Glyphosate was much less effective on other evergreen species. Herbicide treatments in April were more selective between evergreen shrubs and ponderosa pine than those in June. Surfactant increased pine damage while decreasing selectivity. Drop size was related to pine damage in general but degree of effect varied with geographic location. Dose was found to be the single most important factor contributing to response. Application parameters other than dose generally did not contribute to efficacy except that large drops enhanced growth regulator effects on manzanita on the east side of the Cascades, as indicated by a second order interaction between dose, surfactant and nozzle. The addition of surfactant to growth regulator products in April and to glyphosate in June also increased absolute efficacy on Sierran brush species. Soil residual products did not respond in important ways to application technology. Salmonberry also did not respond to dropsize or surfactant. The information obtained was incorporated into a management guide for efficient herbicide use. Title: Efficiency of forest vegetation control with herbicides Author: Fredrickson, Edward A. Selective suppression of crown and root sprouting of non-coniferous cover are the keys to effective forest vegetation management. This study 1) develops insight into mechanisms of controlling root suckering and top regrowth of bear clover (Chamaebatia foliolosa), and develops a broad data base for controlling broad groups of vegetation chemically. Finally, it develops a mangement guide for use of this technology to achieve certain management objectives. Four herbicides were evaluated for their ability to control post-treatment resprouting of bear clover. Sprouting was evaluated above and below ground by creating trenches to expose the rhizome network. Soil moistures were also studied to determine if their were differences due to varying levels of efficacy. They were marginally responsive in the top 60 cm of soil. Plant moisture stress measurements were obtained on ponderosa pine (Pinus ponderosa), and were found considerably more responsive than surface soil water contents. Several application parameters including volume, dose, surfactant, dropsize and product were studied to determine their influence on herbicide efficacy and efficiency on several Pacific Coast species of shrubs and grass. Sites included the Oregon Coast Range, the east side of the Oregon Cascade Range and the west side of the Sierra Nevada Mountains in California. Growth regulator products were not suitable for long-term control. High levels of sprouting were observed above and below ground. Glyphosate led to control of above-ground sprouting as well as the rhizome system of bear clover. Sprouting was found to increase with increasing distance from healthy vegetation. Glyphosate was much less effective on other evergreen species. Herbicide treatments in April were more selective between evergreen shrubs and ponderosa pine than those in June. Surfactant increased pine damage while decreasing selectivity. Drop size was related to pine damage in general but degree of effect varied with geographic location. Dose was found to be the single most important factor contributing to response. Application parameters other than dose generally did not contribute to efficacy except that large drops enhanced growth regulator effects on manzanita on the east side of the Cascades, as indicated by a second order interaction between dose, surfactant and nozzle. The addition of surfactant to growth regulator products in April and to glyphosate in June also increased absolute efficacy on Sierran brush species. Soil residual products did not respond in important ways to application technology. Salmonberry also did not respond to dropsize or surfactant. The information obtained was incorporated into a management guide for efficient herbicide use. Close

• 9. [Article] The effect of 2,4'-dinitro-4-trifluoromethyldiphenylether (C-6989) on beans (Phaseolus vulgaris L.) under certain soil and light conditions

  Oregon is the largest producer of green beans for processing in the United States. Because the repeated use of a single herbicide may lead to changes in the weed population, build up of residues, and other undesirable ...

  Citation × Citation Citation Abstract Copy Title: The effect of 2,4'-dinitro-4-trifluoromethyldiphenylether (C-6989) on beans (Phaseolus vulgaris L.) under certain soil and light conditions Author: Pollak, Tomas Oregon is the largest producer of green beans for processing in the United States. Because the repeated use of a single herbicide may lead to changes in the weed population, build up of residues, and other undesirable factors, a continuous search for new herbicides is taking place. C-6989¹[superscript /] has been registered and used in soybeans; however, the response of green beans to the chemical has not been studied in detail. In this work the following factors were studied: The tolerance of beans and other plants to C-6989, site of uptake, type and site of action of the herbicide and the extent to which mechanical conditions of the soil surface is responsible for herbicidal injury to bean seedlings. An evaluation was made of the residual effects of C-6989 in rotation crops. Results indicated that the herbicide is taken up by roots, shoot or combination of both, depending upon species. Applied at high rates on beans, the effects observed were that of a contact type herbicide. It appeared to block the photosynthetic process by destroying chlorophyll pigments. Under field conditions, a rate of 4 lb/A applied preemergence controlled a broad spectrum of weeds without harmful effects to five varieties of bean. Delays in the application of the herbicide after bean planting, as well as delays in irrigation, tended to cause crop injury. The residual life appears to be short enough under summer conditions to allow the planting of rotation crops without injury. ¹[superscript /] Trade name is Preforan. Chemical name is 2, 4'-dinitro-4-trifluoromethyl-diphenylether. Title: The effect of 2,4'-dinitro-4-trifluoromethyldiphenylether (C-6989) on beans (Phaseolus vulgaris L.) under certain soil and light conditions Author: Pollak, Tomas Oregon is the largest producer of green beans for processing in the United States. Because the repeated use of a single herbicide may lead to changes in the weed population, build up of residues, and other undesirable factors, a continuous search for new herbicides is taking place. C-6989¹[superscript /] has been registered and used in soybeans; however, the response of green beans to the chemical has not been studied in detail. In this work the following factors were studied: The tolerance of beans and other plants to C-6989, site of uptake, type and site of action of the herbicide and the extent to which mechanical conditions of the soil surface is responsible for herbicidal injury to bean seedlings. An evaluation was made of the residual effects of C-6989 in rotation crops. Results indicated that the herbicide is taken up by roots, shoot or combination of both, depending upon species. Applied at high rates on beans, the effects observed were that of a contact type herbicide. It appeared to block the photosynthetic process by destroying chlorophyll pigments. Under field conditions, a rate of 4 lb/A applied preemergence controlled a broad spectrum of weeds without harmful effects to five varieties of bean. Delays in the application of the herbicide after bean planting, as well as delays in irrigation, tended to cause crop injury. The residual life appears to be short enough under summer conditions to allow the planting of rotation crops without injury. ¹[superscript /] Trade name is Preforan. Chemical name is 2, 4'-dinitro-4-trifluoromethyl-diphenylether. Close

• 10. [Article] The physiological effects and fate of dichlobenil (2,6-dichlorobenzonitrile) in an aquatic environment

  The amounts of residual dichlobenil (2,6-dichlorobenzonitrile) in water and hydrosoil were compared periodically following application of the wettable powder and granular formulations of the herbicide ...

  Citation × Citation Citation Abstract Copy Title: The physiological effects and fate of dichlobenil (2,6-dichlorobenzonitrile) in an aquatic environment Author: Ogg, Alex Grant, 1941- The amounts of residual dichlobenil (2,6-dichlorobenzonitrile) in water and hydrosoil were compared periodically following application of the wettable powder and granular formulations of the herbicide to separate ponds at ten pounds of active ingredient per surface acre {0.6 ppmw (parts per million by weight) }. Dichlobenil was measured by electroncapture gas chromatography. Maximum residual concentrations in the water after treatment with wettable powder or granules were 1.00 ppmw after four days and 0,68 ppmw after five days, respectively. After 15 days, the amounts of residue in the two ponds were similar, and decreased steadily to 0.001 ppmw or less after 126 days (last sampling date). The maximum concentration of dichlobenil in the hydrosoil occurred 6 days after treatment with wettable powder and was 1.47 ppmv (parts per million by volume), while the granules produced a maximum concentration of 3.70 ppmv in one day. Residues in the hydrosoil of the two ponds reached similar concentrations 34 days after treatment. After 126 days the residue levels in the hydrosoil of both ponds had decreased to less than 0.04 ppmv. The persistence of dichlobenil in pond water and hydrosoil was similar whether applied as a granular or a wettable powder formulation. The growth rates of two aquatic vascular plants, Potamogeton pectinatus and Alisma gramineum var. Geyeri, and one aquatic alga, Scenesdesmus obliquus, were measured after exposure to various concentrations of dichlobenil in laboratory studies P. pectinatus and A. gramineum were sensitive to 0.1 ppmw of dichlobenil, whereas S. obliquus was tolerant to concentrations as high as 10.0 ppmw. Several laboratory studies were conducted in efforts to elucidate the mode of action of dichlobenil. Dichlobenil did not affect photosynthesis in either P. pectinatus or S. obliquus as determined by manometric measurements of oxygen evolution. Utilization of oxygen by isolated potato mitochondria, measured by polarographic techniques, appeared to be stimulated slightly by 25 ppmw dichlobenil in the reaction medium during state 4 respiration. However, measurements of mitochondrial ATPase activity following additions of 10-5 or 10-4 M dichlobenil indicated that the action of dichlobenil in apparently stimulating respiration did not involve the uncoupling of oxidative phosphorylation. The basis for the selectivity of dichlobenil was investigated by exposing P. pectinatus and S. obliquus to 10 ppmw radioactive dichlobenil for 72 hours. Two possible explanations were found for the selective action of dichlobenil. First, S. obliquus, the tolerant species, absorbed dichlobenil at a slower rate than the susceptible species, P. pectinatus. Secondly, S. obliquus apparently metabolized a greater percentage of the .absorbed.herbicide to non-phytotoxic product(s) than did P. pectinatus. Proper standards were not available for the identification of the metabolite. Title: The physiological effects and fate of dichlobenil (2,6-dichlorobenzonitrile) in an aquatic environment Author: Ogg, Alex Grant, 1941- The amounts of residual dichlobenil (2,6-dichlorobenzonitrile) in water and hydrosoil were compared periodically following application of the wettable powder and granular formulations of the herbicide to separate ponds at ten pounds of active ingredient per surface acre {0.6 ppmw (parts per million by weight) }. Dichlobenil was measured by electroncapture gas chromatography. Maximum residual concentrations in the water after treatment with wettable powder or granules were 1.00 ppmw after four days and 0,68 ppmw after five days, respectively. After 15 days, the amounts of residue in the two ponds were similar, and decreased steadily to 0.001 ppmw or less after 126 days (last sampling date). The maximum concentration of dichlobenil in the hydrosoil occurred 6 days after treatment with wettable powder and was 1.47 ppmv (parts per million by volume), while the granules produced a maximum concentration of 3.70 ppmv in one day. Residues in the hydrosoil of the two ponds reached similar concentrations 34 days after treatment. After 126 days the residue levels in the hydrosoil of both ponds had decreased to less than 0.04 ppmv. The persistence of dichlobenil in pond water and hydrosoil was similar whether applied as a granular or a wettable powder formulation. The growth rates of two aquatic vascular plants, Potamogeton pectinatus and Alisma gramineum var. Geyeri, and one aquatic alga, Scenesdesmus obliquus, were measured after exposure to various concentrations of dichlobenil in laboratory studies P. pectinatus and A. gramineum were sensitive to 0.1 ppmw of dichlobenil, whereas S. obliquus was tolerant to concentrations as high as 10.0 ppmw. Several laboratory studies were conducted in efforts to elucidate the mode of action of dichlobenil. Dichlobenil did not affect photosynthesis in either P. pectinatus or S. obliquus as determined by manometric measurements of oxygen evolution. Utilization of oxygen by isolated potato mitochondria, measured by polarographic techniques, appeared to be stimulated slightly by 25 ppmw dichlobenil in the reaction medium during state 4 respiration. However, measurements of mitochondrial ATPase activity following additions of 10-5 or 10-4 M dichlobenil indicated that the action of dichlobenil in apparently stimulating respiration did not involve the uncoupling of oxidative phosphorylation. The basis for the selectivity of dichlobenil was investigated by exposing P. pectinatus and S. obliquus to 10 ppmw radioactive dichlobenil for 72 hours. Two possible explanations were found for the selective action of dichlobenil. First, S. obliquus, the tolerant species, absorbed dichlobenil at a slower rate than the susceptible species, P. pectinatus. Secondly, S. obliquus apparently metabolized a greater percentage of the .absorbed.herbicide to non-phytotoxic product(s) than did P. pectinatus. Proper standards were not available for the identification of the metabolite. Close