Search

Search Results

• 1. [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

• 2. [Article] The soil persistence and crop selectivity of 3, 6-dichloropicolinic acid

  Field studies were conducted in 1973 and 1974 to determine the soil persistence of the herbicide M-3785 (containing 0.5 lb a.e. Dowco 290 + 2.0 lb a.e. 214D/gallon). under cropping situations. Spring barley ...

  Citation × Citation Citation Abstract Copy Title: The soil persistence and crop selectivity of 3, 6-dichloropicolinic acid Author: Olson, David Lloyd Field studies were conducted in 1973 and 1974 to determine the soil persistence of the herbicide M-3785 (containing 0.5 lb a.e. Dowco 290 + 2.0 lb a.e. 214D/gallon). under cropping situations. Spring barley (Hordeum distichon L. 'Hannchen') was grown at Corvallis, Oregon and winter wheat (Triticum aestivum L. 'Nugaines.') was planted at Pendleton, Oregon. Both the barley and the wheat were treated with M-3785 in the spring of 1973. The M-3785 treatments produced no significant reductions in grain yield from the check in either 1973 or 1974 Crops sensitive to Dowco 290 [peas (Pisum sativum L.), soybeans (Glycine max L. 'Merit'), and safflower (Carthamus tinctorius L.)) were planted in the spring of 1974 to areas treated with M-3785 in 1973. The susceptible crops showed no signs of injury symptoms. Bioassays were conducted in growth chambers on soil samples collected 16 weeks, 8 weeks, 4 weeks, 2 weeks, 1 week, and immediately after spraying from the Corvallis field trial and on soil sprayed and stored in the greenhouse. Safflower was used as the bioassay crop. Safflower injury was visually detectable at a concentration of 0.0039 ppmw. Safflower was not injured when grown in soil collected in the field 16 weeks after treatment with M-3785. The greenhouse samples were still causing safflower injury at 8 weeks after treatment; however the 1/16 1/4 lb/A rate was causing much less injury at 8 weeks then at earlier sampling times. Several greenhouse experiments were conducted to compare the sensitivity of several crops to different rates of Dowco 290, M-3785, 214-D and dicamba applied as foliar sprays. Dowco 290 decreased growth more on broadleaf plants than on grasses. It caused growth reductions similar to those of dicamba and 2,4 -I) in several crops, but on some crops there were significant differences between the herbicides. Dowco 290 caused significantly less growth at lower rates of application on peas and alfalfa (Medicago sativa L. 'DuPuits'). At theligher rates significantly less growth reduction was observed on sugarbeets (Beta vulgaris L. 'SL9100363x2161)x SP6322-0') and watermelons (Citrullus lanatus [Thumb.] Mansf. 'Striped Klondike') when compared with 214-D and dicamba. The M-3785 treatments tended to cause more growth reduction than Dowco 290 or 2,4-D applied alone; however, this difference was usually not significant. M-3785 applied to winter wheat in the greenhouse caused greater growth reductions compared to 214-D applied alone. A field experiment was conducted to study the decreased growth of winter wheat growing under field conditions. No significant differences were found for the 1/16 + 1/4 lb/A rate. M -3785 at 1/8 + 1/2 lb/A caused a highly significant reduction in yield when com pared to Dowco 290 at 1/8 lb/A and 214D at 1/2 lb/A. Title: The soil persistence and crop selectivity of 3, 6-dichloropicolinic acid Author: Olson, David Lloyd Field studies were conducted in 1973 and 1974 to determine the soil persistence of the herbicide M-3785 (containing 0.5 lb a.e. Dowco 290 + 2.0 lb a.e. 214D/gallon). under cropping situations. Spring barley (Hordeum distichon L. 'Hannchen') was grown at Corvallis, Oregon and winter wheat (Triticum aestivum L. 'Nugaines.') was planted at Pendleton, Oregon. Both the barley and the wheat were treated with M-3785 in the spring of 1973. The M-3785 treatments produced no significant reductions in grain yield from the check in either 1973 or 1974 Crops sensitive to Dowco 290 [peas (Pisum sativum L.), soybeans (Glycine max L. 'Merit'), and safflower (Carthamus tinctorius L.)) were planted in the spring of 1974 to areas treated with M-3785 in 1973. The susceptible crops showed no signs of injury symptoms. Bioassays were conducted in growth chambers on soil samples collected 16 weeks, 8 weeks, 4 weeks, 2 weeks, 1 week, and immediately after spraying from the Corvallis field trial and on soil sprayed and stored in the greenhouse. Safflower was used as the bioassay crop. Safflower injury was visually detectable at a concentration of 0.0039 ppmw. Safflower was not injured when grown in soil collected in the field 16 weeks after treatment with M-3785. The greenhouse samples were still causing safflower injury at 8 weeks after treatment; however the 1/16 1/4 lb/A rate was causing much less injury at 8 weeks then at earlier sampling times. Several greenhouse experiments were conducted to compare the sensitivity of several crops to different rates of Dowco 290, M-3785, 214-D and dicamba applied as foliar sprays. Dowco 290 decreased growth more on broadleaf plants than on grasses. It caused growth reductions similar to those of dicamba and 2,4 -I) in several crops, but on some crops there were significant differences between the herbicides. Dowco 290 caused significantly less growth at lower rates of application on peas and alfalfa (Medicago sativa L. 'DuPuits'). At theligher rates significantly less growth reduction was observed on sugarbeets (Beta vulgaris L. 'SL9100363x2161)x SP6322-0') and watermelons (Citrullus lanatus [Thumb.] Mansf. 'Striped Klondike') when compared with 214-D and dicamba. The M-3785 treatments tended to cause more growth reduction than Dowco 290 or 2,4-D applied alone; however, this difference was usually not significant. M-3785 applied to winter wheat in the greenhouse caused greater growth reductions compared to 214-D applied alone. A field experiment was conducted to study the decreased growth of winter wheat growing under field conditions. No significant differences were found for the 1/16 + 1/4 lb/A rate. M -3785 at 1/8 + 1/2 lb/A caused a highly significant reduction in yield when com pared to Dowco 290 at 1/8 lb/A and 214D at 1/2 lb/A. Close

• 3. [Article] Weed management in sweet corn and other rotational crops: Research report to the Oregon Processed Vegetable Commission, 2007

  SUMMARY • Impact and Laudis herbicides were evaluated for wild proso millet and broadleaf weed control in sweet corn. • The most effective treatments were Impact and Laudis applied with Outlook and atrazine ...

  Citation × Citation Citation Abstract Copy Title: Weed management in sweet corn and other rotational crops: Research report to the Oregon Processed Vegetable Commission, 2007 Author: Peachey, Ed SUMMARY • Impact and Laudis herbicides were evaluated for wild proso millet and broadleaf weed control in sweet corn. • The most effective treatments were Impact and Laudis applied with Outlook and atrazine at V2-3. • Increasing the methylated seed oil (MSO) rate from 0.25% to 1 % was more important for improving weed control efficacy than adding UAN (Figure 1). • Impact + Outlook + atrazine (Tr. 14) provided yields above 11 t/A with exceptional wild proso millet control (Table 2). • Predicting the optimum rate of atrazine to use with these herbicides will be difficult if the objective is optimizing yield. The data suggest that a tankmix of both 2 lbs/A or none will give the same yield of sweet corn when there is a high density of both wild proso millet and broadleaves. • The symptoms normally associated with Impact injury (bleaching) have not been observed on crops planted in the fall or spring following sweet corn. Crop stand and yield may have been reduced in a few sensitive crops such as table beets. However, this only occurred at the 2x rate. There is very little risk of crop injury caused by Impact herbicide carryover. • Insecticides reduced the activity and density of the ground beetle P. melanarius from 2.0 beetles to 0.3 in the strip-till plots and from 1.5 to 0.2 beetles in conventional tillage. There was no effect of the tillage systems on beetle activity-density. • Seed loss due to predation by ground beetles averaged 20% during the month of August. Predation of wild proso millet seeds was influenced by the tillage-insecticide treatments. Insecticide use was the most important factor regulating predation of wild proso millet. Title: Weed management in sweet corn and other rotational crops: Research report to the Oregon Processed Vegetable Commission, 2007 Author: Peachey, Ed SUMMARY • Impact and Laudis herbicides were evaluated for wild proso millet and broadleaf weed control in sweet corn. • The most effective treatments were Impact and Laudis applied with Outlook and atrazine at V2-3. • Increasing the methylated seed oil (MSO) rate from 0.25% to 1 % was more important for improving weed control efficacy than adding UAN (Figure 1). • Impact + Outlook + atrazine (Tr. 14) provided yields above 11 t/A with exceptional wild proso millet control (Table 2). • Predicting the optimum rate of atrazine to use with these herbicides will be difficult if the objective is optimizing yield. The data suggest that a tankmix of both 2 lbs/A or none will give the same yield of sweet corn when there is a high density of both wild proso millet and broadleaves. • The symptoms normally associated with Impact injury (bleaching) have not been observed on crops planted in the fall or spring following sweet corn. Crop stand and yield may have been reduced in a few sensitive crops such as table beets. However, this only occurred at the 2x rate. There is very little risk of crop injury caused by Impact herbicide carryover. • Insecticides reduced the activity and density of the ground beetle P. melanarius from 2.0 beetles to 0.3 in the strip-till plots and from 1.5 to 0.2 beetles in conventional tillage. There was no effect of the tillage systems on beetle activity-density. • Seed loss due to predation by ground beetles averaged 20% during the month of August. Predation of wild proso millet seeds was influenced by the tillage-insecticide treatments. Insecticide use was the most important factor regulating predation of wild proso millet. Close

• 4. [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

• 5. [Article] Influence of weed density on efficacy of two soil-applied herbicides

  Several studies were conducted to determine the effect of weed density on herbicide efficacy. Diuron [3-(3, 4- dichlorophenyl) -1, 1- dimethylurea] was tested on various densities of Italian ryegrass (Lolium ...

  Citation × Citation Citation Abstract Copy Title: Influence of weed density on efficacy of two soil-applied herbicides Author: Burrill, L. C. Several studies were conducted to determine the effect of weed density on herbicide efficacy. Diuron [3-(3, 4- dichlorophenyl) -1, 1- dimethylurea] was tested on various densities of Italian ryegrass (Lolium multiflorum Lam. ) under greenhouse and field conditions. Cycloate (S-ethyl N-ethylthiocyclohexanecarbamate) was tested on green foxtail (Setaria viridis (L. ) Beauv. ) in the greenhouse. Under both greenhouse and field conditions, control of Italian ryegrass decreased as plant density was increased. This trend was observed at extremely high densities and also at densities commonly observed in the field. Similar results were obtained from cycloate on green foxtail. Not all experiments showed this trend, however, and further research is needed to determine the reasons for this inconsistency. Diuron is a nonvolatile herbicide that enters the plant primarily through the roots and inhibits photosynthesis. Cycloate is a volatile herbicide that is taken up by the shoot and affects the meristematic region of the grasses. These differences suggest that the observed results may not be limited to the herbicides and plants studied. Title: Influence of weed density on efficacy of two soil-applied herbicides Author: Burrill, L. C. Several studies were conducted to determine the effect of weed density on herbicide efficacy. Diuron [3-(3, 4- dichlorophenyl) -1, 1- dimethylurea] was tested on various densities of Italian ryegrass (Lolium multiflorum Lam. ) under greenhouse and field conditions. Cycloate (S-ethyl N-ethylthiocyclohexanecarbamate) was tested on green foxtail (Setaria viridis (L. ) Beauv. ) in the greenhouse. Under both greenhouse and field conditions, control of Italian ryegrass decreased as plant density was increased. This trend was observed at extremely high densities and also at densities commonly observed in the field. Similar results were obtained from cycloate on green foxtail. Not all experiments showed this trend, however, and further research is needed to determine the reasons for this inconsistency. Diuron is a nonvolatile herbicide that enters the plant primarily through the roots and inhibits photosynthesis. Cycloate is a volatile herbicide that is taken up by the shoot and affects the meristematic region of the grasses. These differences suggest that the observed results may not be limited to the herbicides and plants studied. Close

• 6. [Article] The influence of magnesium on the toxicity of atrazine

  Atrazine is an asymmetrical s-triazine herbicide used pre- and post emergence for weed control in many crops. Triazine herbicides have been used in the Pacific-Northwest for weed control in orchard crops. ...

  Citation × Citation Citation Abstract Copy Title: The influence of magnesium on the toxicity of atrazine Author: Brenchley, Ronald Glenn Atrazine is an asymmetrical s-triazine herbicide used pre- and post emergence for weed control in many crops. Triazine herbicides have been used in the Pacific-Northwest for weed control in orchard crops. Under certain conditions where trees were grown in nutrient deficient areas, it was noted that toxic symptoms due to the herbicide appeared on the leaves of the trees. It was also noted that these symptoms were apparently overcome by the addition of foliar sprays containing the nutrient which was deficient in that area. This study was conducted to determine whether nutrients might have a significant effect in reducing the toxicity of herbicides. Magnesium and atrazine were chosen to study this interaction since it was known that both affected the photosynthetic processes of the plant. Plants were grown in sand cultures to avoid the complex interactions which occur between soils and herbicides. Nutrient solutions were used to provide a nutrient supply to plants grown in sand. Three different nutrient solutions were used containing zero-magnesium, medium-magnesium, and high-magnesium levels. These three nutrient solutions contained the same amount of all the other essential elements. Tomato plants were grown in sand cultures under three magnesium levels. Three weeks after planting, atrazine rates of 0, 1/16, 1/8, and 1/4 ppm were added to pots containing the plants. Plants were harvested six weeks after planting. Results of the experiment showed a significant growth increase due to the addition of magnesium. The statistical analysis also showed that the addition of magnesium helped overcome the toxicity of atrazine. A similar experiment using oat plants was carried out. Two weeks after planting, atrazine treatments of 0, 1/32, 1/16, and 1/8 ppm were added to the plants. Plants harvested five weeks after planting showed that the magnesium treatment had no significant effect on the dry weight of the oat plants. The interaction between magnesium and atrazine was also insignificant. The difference between the results of this experiment and the experiment involving tomatoes was probably due to seed size and the duration of the experiment. Small-seeded plants grown over a longer period of time allowed the magnesium and atrazine effects to appear. Tomato plant material from the magnesium-atrazine interaction experiment was used in the laboratory to determine the effects of magnesium and atrazine on the uptake of other plant nutrients. Results showed that atrazine had a significant effect in reducing the uptake of the thirteen nutrient elements analyzed. Ambient magnesium concentrations significantly influenced the uptake of magnesium and molybdenum. Preliminary research was conducted to determine the nutrient-supplying capability of the sand used in the experiment. Results from the laboratory showed that the macro-nutrient supply of this sand was extremely low. Plants growing in this sand would have to obtain their nutrients from an external source. Title: The influence of magnesium on the toxicity of atrazine Author: Brenchley, Ronald Glenn Atrazine is an asymmetrical s-triazine herbicide used pre- and post emergence for weed control in many crops. Triazine herbicides have been used in the Pacific-Northwest for weed control in orchard crops. Under certain conditions where trees were grown in nutrient deficient areas, it was noted that toxic symptoms due to the herbicide appeared on the leaves of the trees. It was also noted that these symptoms were apparently overcome by the addition of foliar sprays containing the nutrient which was deficient in that area. This study was conducted to determine whether nutrients might have a significant effect in reducing the toxicity of herbicides. Magnesium and atrazine were chosen to study this interaction since it was known that both affected the photosynthetic processes of the plant. Plants were grown in sand cultures to avoid the complex interactions which occur between soils and herbicides. Nutrient solutions were used to provide a nutrient supply to plants grown in sand. Three different nutrient solutions were used containing zero-magnesium, medium-magnesium, and high-magnesium levels. These three nutrient solutions contained the same amount of all the other essential elements. Tomato plants were grown in sand cultures under three magnesium levels. Three weeks after planting, atrazine rates of 0, 1/16, 1/8, and 1/4 ppm were added to pots containing the plants. Plants were harvested six weeks after planting. Results of the experiment showed a significant growth increase due to the addition of magnesium. The statistical analysis also showed that the addition of magnesium helped overcome the toxicity of atrazine. A similar experiment using oat plants was carried out. Two weeks after planting, atrazine treatments of 0, 1/32, 1/16, and 1/8 ppm were added to the plants. Plants harvested five weeks after planting showed that the magnesium treatment had no significant effect on the dry weight of the oat plants. The interaction between magnesium and atrazine was also insignificant. The difference between the results of this experiment and the experiment involving tomatoes was probably due to seed size and the duration of the experiment. Small-seeded plants grown over a longer period of time allowed the magnesium and atrazine effects to appear. Tomato plant material from the magnesium-atrazine interaction experiment was used in the laboratory to determine the effects of magnesium and atrazine on the uptake of other plant nutrients. Results showed that atrazine had a significant effect in reducing the uptake of the thirteen nutrient elements analyzed. Ambient magnesium concentrations significantly influenced the uptake of magnesium and molybdenum. Preliminary research was conducted to determine the nutrient-supplying capability of the sand used in the experiment. Results from the laboratory showed that the macro-nutrient supply of this sand was extremely low. Plants growing in this sand would have to obtain their nutrients from an external source. Close

• 7. [Article] Bioherbicide use of plant defensive compounds in meadowfoam seed meal

  Meadowfoam (Limnanthes alba Hartw. ex Benth) seed meal (MSM), a by-product of meadowfoam oil extraction, has a plant defensive compound known as glucosinolate glucolimnanthin (GLN). Myrosinase enzymes ...

  Citation × Citation Citation Abstract Copy Title: Bioherbicide use of plant defensive compounds in meadowfoam seed meal Author: Intanon, Suphannika Meadowfoam (Limnanthes alba Hartw. ex Benth) seed meal (MSM), a by-product of meadowfoam oil extraction, has a plant defensive compound known as glucosinolate glucolimnanthin (GLN). Myrosinase enzymes present in soil microbes and meadowfoam seeds can convert GLN to glucosinolate breakdown products (GBPs), which demonstrate herbicidal activity and have the potential to be used as bioherbicides. The goals of this research were to evaluate the effectiveness of MSM on weed control and to explore the optimal timing, rate, and application method for further use of MSM as a bioherbicide. Adding active myrosinase from freshly ground meadowfoam seeds to MSM increased its phytotoxicity. In a greenhouse study, no lettuce emergence was observed for six days in soil amended with 3% by weight activated MSM. In a field application, MSM provided a nitrogen source and promoted lettuce growth when lettuce seedlings were transplanted seven days after MSM incorporation. Co-occurrence of herbicide and fertilizer effects was observed with all MSM concentrations. MSM concentrations of 5% and 7% provided greater weed emergence suppression than the 3% concentration but no difference in weed biomass was observed between MSM concentrations. A split MSM application resulted in a significant benefit for weed control, similar to a single MSM application; however for the split application, the concentration and time should be adjusted to prevent residual crop injury. Activated MSM inhibited spiny sowthistle (Sonchus asper (L.) Hill) greater than 95% for emergence and 80% for biomass compared to the untreated control. Soil microbes reallocated carbon input from MSM application to biomass and enzyme production. The reallocation occurred quickly, within 7 to 14 days, after MSM application. Microbial biomass increased by at least 85% for carbon and 95% for nitrogen with MSM application compared to the untreated control. β-N-acetylglucosaminidase activity was highly correlated with microbial biomass nitrogen and was involved in the acquisition of nitrogen from organic sources. Isothiocyanate showed potent herbicidal activity and was detected only in activated MSM. 3-Methoxyphenylacetic acid (MPAA), a previously unidentified GBP with herbicidal activity, was discovered in soil amended with non-activated and activated MSM. A single MSM application at 2.86 kg m⁻² as a pre-emergent soil amendment benefited crop yield, weed suppression, and soil carbon and nitrogen inputs. Title: Bioherbicide use of plant defensive compounds in meadowfoam seed meal Author: Intanon, Suphannika Meadowfoam (Limnanthes alba Hartw. ex Benth) seed meal (MSM), a by-product of meadowfoam oil extraction, has a plant defensive compound known as glucosinolate glucolimnanthin (GLN). Myrosinase enzymes present in soil microbes and meadowfoam seeds can convert GLN to glucosinolate breakdown products (GBPs), which demonstrate herbicidal activity and have the potential to be used as bioherbicides. The goals of this research were to evaluate the effectiveness of MSM on weed control and to explore the optimal timing, rate, and application method for further use of MSM as a bioherbicide. Adding active myrosinase from freshly ground meadowfoam seeds to MSM increased its phytotoxicity. In a greenhouse study, no lettuce emergence was observed for six days in soil amended with 3% by weight activated MSM. In a field application, MSM provided a nitrogen source and promoted lettuce growth when lettuce seedlings were transplanted seven days after MSM incorporation. Co-occurrence of herbicide and fertilizer effects was observed with all MSM concentrations. MSM concentrations of 5% and 7% provided greater weed emergence suppression than the 3% concentration but no difference in weed biomass was observed between MSM concentrations. A split MSM application resulted in a significant benefit for weed control, similar to a single MSM application; however for the split application, the concentration and time should be adjusted to prevent residual crop injury. Activated MSM inhibited spiny sowthistle (Sonchus asper (L.) Hill) greater than 95% for emergence and 80% for biomass compared to the untreated control. Soil microbes reallocated carbon input from MSM application to biomass and enzyme production. The reallocation occurred quickly, within 7 to 14 days, after MSM application. Microbial biomass increased by at least 85% for carbon and 95% for nitrogen with MSM application compared to the untreated control. β-N-acetylglucosaminidase activity was highly correlated with microbial biomass nitrogen and was involved in the acquisition of nitrogen from organic sources. Isothiocyanate showed potent herbicidal activity and was detected only in activated MSM. 3-Methoxyphenylacetic acid (MPAA), a previously unidentified GBP with herbicidal activity, was discovered in soil amended with non-activated and activated MSM. A single MSM application at 2.86 kg m⁻² as a pre-emergent soil amendment benefited crop yield, weed suppression, and soil carbon and nitrogen inputs. Close

• 8. [Article] Response of downy brome (Bromus tectorum) and Kentucky bluegrass (Pao pratensis) to primisulfuron

  Glasshouse and growth-chamber experiments were conducted to evaluate primisulfuron phytotoxicity and the influence of adjuvants on downy brome and Kentucky bluegrass. GR₅₀ (50% growth reduction) values ...

  Citation × Citation Citation Abstract Copy Title: Response of downy brome (Bromus tectorum) and Kentucky bluegrass (Pao pratensis) to primisulfuron Author: Hendrickson, Paul E. Glasshouse and growth-chamber experiments were conducted to evaluate primisulfuron phytotoxicity and the influence of adjuvants on downy brome and Kentucky bluegrass. GR₅₀ (50% growth reduction) values were 0.97 ± 0.57 and 8.07 ± 1.85 g/ha for downy brome and Kentucky bluegrass, respectively. Primisulfuron was applied to downy brome and Kentucky bluegrass at 3 placement sites; foliar, soil, and foliar plus soil. Foliar or foliar plus soil applications were more effective at reducing downy brome dry weights than the soil application of primisulfuron, while Kentucky bluegrass was injured more from the soil or foliar plus soil applications than from the foliar application of primisulfuron. Primisulfuron at 5 g/ha applied alone reduced downy brome dry weights by 5%, whereas, when an adjuvant was added, dry weights were reduced by 52 to 83%. Primisulfuron was more phytotoxic to downy brome at alternating temperatures of 8-16 C and 16-24 C than at 0-8 C. Phytotoxicity of primisulfuron was less when downy brome plants were stressed for soil moisture after herbicide treatments than when the plants were not stressed or only stressed before treatment. Title: Response of downy brome (Bromus tectorum) and Kentucky bluegrass (Pao pratensis) to primisulfuron Author: Hendrickson, Paul E. Glasshouse and growth-chamber experiments were conducted to evaluate primisulfuron phytotoxicity and the influence of adjuvants on downy brome and Kentucky bluegrass. GR₅₀ (50% growth reduction) values were 0.97 ± 0.57 and 8.07 ± 1.85 g/ha for downy brome and Kentucky bluegrass, respectively. Primisulfuron was applied to downy brome and Kentucky bluegrass at 3 placement sites; foliar, soil, and foliar plus soil. Foliar or foliar plus soil applications were more effective at reducing downy brome dry weights than the soil application of primisulfuron, while Kentucky bluegrass was injured more from the soil or foliar plus soil applications than from the foliar application of primisulfuron. Primisulfuron at 5 g/ha applied alone reduced downy brome dry weights by 5%, whereas, when an adjuvant was added, dry weights were reduced by 52 to 83%. Primisulfuron was more phytotoxic to downy brome at alternating temperatures of 8-16 C and 16-24 C than at 0-8 C. Phytotoxicity of primisulfuron was less when downy brome plants were stressed for soil moisture after herbicide treatments than when the plants were not stressed or only stressed before treatment. Close

• 9. [Article] Effect of chlorpropham on vegetative and reproductive development in chewings fescue (Festuca rubra L. subsp. commutata Gaud.)

  Experiments were conducted under field and greenhouse conditions to investigate the effects of chlorpropham (isopropyl mchlorocarbanilate) on vegetative and reproductive development in Chewings fescue ...

  Citation × Citation Citation Abstract Copy Title: Effect of chlorpropham on vegetative and reproductive development in chewings fescue (Festuca rubra L. subsp. commutata Gaud.) Author: Akobundu, I. O. Experiments were conducted under field and greenhouse conditions to investigate the effects of chlorpropham (isopropyl mchlorocarbanilate) on vegetative and reproductive development in Chewings fescue (Festuca rubra L. subsp. commutata Gaud.) and to determine the time of induction and initiation under natural conditions. Chewings fescue was found to be very susceptible to chlorpropham treatment and the use of this herbicide for weed control in Chewings fescue caused seed yield reduction. Time of chlorpropham application in relation to environmental factors of temperature and photoperiod was more important than the actual toxicity of the herbicide. Chlorpropham used at the recommended rate of 2 lbs/A was lethal to all tillers that were exposed to the herbicide irrespective of time of application. Seed production from treated plants depended on development of new tillers from axillary buds and on prevalence of environmental conditions conducive to induction and initiation. Extent of chlorpropham injury was dependent on type and maturity of tissue, state of activity of the organ, soil temperature, and length of time after treatment. Apical meristems of the shoot were little affected during the initial stages of injury to the shoots and remained intact even after necrosis of surrounding tissues. When plants were grown at low and high temperature levels and treated with varying herbicide concentrations, tiller production proved to be a more sensitive measure of herbicide-temperature effects than dry matter production. High temperatures favored tiller production and enhanced herbicide toxicity. Time of induction and initiation under natural conditions were determined. Induction was found to occur late in the fall (December) and initiation takes place in February. Plants taken to the field as late as February were induced but seedhead production was reduced because environmental conditions were inhibitory to initiation. Title: Effect of chlorpropham on vegetative and reproductive development in chewings fescue (Festuca rubra L. subsp. commutata Gaud.) Author: Akobundu, I. O. Experiments were conducted under field and greenhouse conditions to investigate the effects of chlorpropham (isopropyl mchlorocarbanilate) on vegetative and reproductive development in Chewings fescue (Festuca rubra L. subsp. commutata Gaud.) and to determine the time of induction and initiation under natural conditions. Chewings fescue was found to be very susceptible to chlorpropham treatment and the use of this herbicide for weed control in Chewings fescue caused seed yield reduction. Time of chlorpropham application in relation to environmental factors of temperature and photoperiod was more important than the actual toxicity of the herbicide. Chlorpropham used at the recommended rate of 2 lbs/A was lethal to all tillers that were exposed to the herbicide irrespective of time of application. Seed production from treated plants depended on development of new tillers from axillary buds and on prevalence of environmental conditions conducive to induction and initiation. Extent of chlorpropham injury was dependent on type and maturity of tissue, state of activity of the organ, soil temperature, and length of time after treatment. Apical meristems of the shoot were little affected during the initial stages of injury to the shoots and remained intact even after necrosis of surrounding tissues. When plants were grown at low and high temperature levels and treated with varying herbicide concentrations, tiller production proved to be a more sensitive measure of herbicide-temperature effects than dry matter production. High temperatures favored tiller production and enhanced herbicide toxicity. Time of induction and initiation under natural conditions were determined. Induction was found to occur late in the fall (December) and initiation takes place in February. Plants taken to the field as late as February were induced but seedhead production was reduced because environmental conditions were inhibitory to initiation. Close

• 10. [Article] Chemical and physical factors in the kinetics of herbicide penetration into plants

  Penetration has long been recognized as an important factor in the action of chemicals on plants. The effectiveness of herbicides on such plants as blackberries is often thought to be limited by the failure ...

  Citation × Citation Citation Abstract Copy Title: Chemical and physical factors in the kinetics of herbicide penetration into plants Author: López, Hernán Penetration has long been recognized as an important factor in the action of chemicals on plants. The effectiveness of herbicides on such plants as blackberries is often thought to be limited by the failure to obtain adequate penetration through the cuticular barrier. A number of factors, among them relative humidity, temperature, polarity of the compound, additives and physiological factors of the plant are known to be important. This study was concerned with obtaining more precise estimates of the quantitative relationships of temperature, humidity and other factors in the penetration of picloram and 2, 4, 5-T into plants. Measured quantities of chemicals were placed on the adaxial surface of the leaves of beans held under carefully controlled conditions of temperature, humidity, and light intensity and the amount of chemical penetrating the plant measured. Radio labeled compounds were used and the difference between the amount applied and that removed by washing at predetermined intervals, was taken as the amount penetrating the plant. It was found that the more nonpolar derivatives of these acids penetrated most readily. The addition of surfactants also enhanced the rate of penetration. Substantial differences in the effectiveness of different surfactants in enhancing penetration were observed. These differences can be accounted for in part by the lowering of surface tension but other chemical factors relating to the surfactant appear to be important. Further the mixture of four parts of 2, 4, 5,-T and one part picloram resulted in a significant increase in the rate of penetration of 2, 4, 5-T. The quantitative relationship of relative humidity and temperature in penetration was also determined. As either temperature or relative humidity or both increase, the rate of penetration for all chemical derivatives increased. Analysis of the quantitative relation of penetration revealed the overall process to follow a first order rate law. There is in fact, two or more rate processes each appearing to follow first order rate laws and in overall obeys a first order rate model. Application of Arrhenius equation to these data yields reproducible values of energy of activation. The energy of activation may be derived either directly from thermal energy available or an increase of the entropy of the system. The data suggest involvement of the process of diffusion and also the process of partitioning. Diffusion coefficients in waxes of various substances were determined and partition coefficients calculated. The understanding provided by this study should be of value in overcoming problems of penetration encountered under field conditions. Application of this type of data would permit more intelligent selection of the proper adjuvants or a more suitable mixture of chemicals to enhance penetration. Title: Chemical and physical factors in the kinetics of herbicide penetration into plants Author: López, Hernán Penetration has long been recognized as an important factor in the action of chemicals on plants. The effectiveness of herbicides on such plants as blackberries is often thought to be limited by the failure to obtain adequate penetration through the cuticular barrier. A number of factors, among them relative humidity, temperature, polarity of the compound, additives and physiological factors of the plant are known to be important. This study was concerned with obtaining more precise estimates of the quantitative relationships of temperature, humidity and other factors in the penetration of picloram and 2, 4, 5-T into plants. Measured quantities of chemicals were placed on the adaxial surface of the leaves of beans held under carefully controlled conditions of temperature, humidity, and light intensity and the amount of chemical penetrating the plant measured. Radio labeled compounds were used and the difference between the amount applied and that removed by washing at predetermined intervals, was taken as the amount penetrating the plant. It was found that the more nonpolar derivatives of these acids penetrated most readily. The addition of surfactants also enhanced the rate of penetration. Substantial differences in the effectiveness of different surfactants in enhancing penetration were observed. These differences can be accounted for in part by the lowering of surface tension but other chemical factors relating to the surfactant appear to be important. Further the mixture of four parts of 2, 4, 5,-T and one part picloram resulted in a significant increase in the rate of penetration of 2, 4, 5-T. The quantitative relationship of relative humidity and temperature in penetration was also determined. As either temperature or relative humidity or both increase, the rate of penetration for all chemical derivatives increased. Analysis of the quantitative relation of penetration revealed the overall process to follow a first order rate law. There is in fact, two or more rate processes each appearing to follow first order rate laws and in overall obeys a first order rate model. Application of Arrhenius equation to these data yields reproducible values of energy of activation. The energy of activation may be derived either directly from thermal energy available or an increase of the entropy of the system. The data suggest involvement of the process of diffusion and also the process of partitioning. Diffusion coefficients in waxes of various substances were determined and partition coefficients calculated. The understanding provided by this study should be of value in overcoming problems of penetration encountered under field conditions. Application of this type of data would permit more intelligent selection of the proper adjuvants or a more suitable mixture of chemicals to enhance penetration. Close