Autoradiographs following treatment of Cyperus esculentus L. with C14-labeled amitrole indicated that it was readily translocated from the point of application to the seed. Seed germination was significantly reduced following amitrole applications.

Amitrole-5-C14 was rapidly degraded in unsterile soil but underwent only minor modification in sterile soil. An unidentified chemical product of amitrole was formed in both sterile and unsterile soil. The principle metabolic product of amitrole was carbon dioxide; however, at least 13 additional compounds were formed. One or more metabolic compounds formed from amitrole are tenaciously bound to the soil and appear to be resistant to degradation.

In a “closed system” nutrient solution experiment, shoot growth of downy brome (Bromus tectorum L.) was: (1) more rapid during early growth, (2) accelerated earlier by nitrogen, and (3) increased more by low to intermediate levels of nitrogen than that of crested wheatgrass (Agropyron desertorum Fisch. ex Link). Shoot growth of crested wheatgrass was increased more by high levels of nitrogen and at a more mature stage of growth than that of downy brome. Root growth of crested wheatgrass was greater at all nitrogen levels than that of downy brome and was increased by the high nitrogen levels. Downy brome removed more nitrogen from solution at the intermediate nitrogen level than did crested wheatgrass and more phosphorus at both the low and intermediate nitrogen levels. At the highest nitrogen level, crested wheatgrass removed more nitrogen from solution than did downy brome.

A laboratory sprayer for precision application of herbicides to pot cultures consists of a miniature compressed-air sprayer mounted as a pendulum and equipped to automatically spray a pot placed beneath the center of its arc of swing.

During a 12-hr incubation low concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) enhance the metabolic breakdown of ribonucleic acid (RNA) whereas high concentrations of the auxin almost completely inhibit RNA breakdown after 4 hr of treatment. The data, from experiments where the incorporation of adenosine-8-C14 into RNA was followed, clearly show that the role of auxin in this system is not to appreciably alter net synthesis of RNA, but rather to alter some process(s) related to the degradative metabolism of RNA.

Amitrole (3-amino-1,2,4-triazole) was applied to purple nutsedge (Cyperus rotundus L.) clones newly established in the field in the Piedmont Plateau. Applications were made one week after initial foliar emergence, then at biweekly intervals through the 20th week. The principal results were: (1) Nutsedge was most susceptible to amitrole applied 4 weeks after initial emergence. The next most susceptible stages were at 1 or 2 weeks; (2) Six weeks after emergence, nutsedge appeared resistant to amitrole; (3) All applications after 10 weeks were relatively ineffective; (4) Chemical analyses of tubers and bulbs indicated a high ash content early in the season, particularly at 6 weeks after emergence.

Barnyardgrass (Echinochloa crusgalli (L.) Beauv.) seeds which did not germinate because of low temperature, insufficient moisture, or seed dormancy were exposed to concentrations of ethyl N,N-di-n-propylthiolcarbamate (EPTC) lethal to emerging barnyardgrass seedlings. After different periods of exposure, seeds were removed from the EPTC-treated environments and germinated in untreated soil. Seed germination was not reduced by EPTC and there was no permanent injury to the seedlings. It was concluded that rates of EPTC used for selective weed control do not injure barnyardgrass seeds prior to germination.

Spectrophotometric and chemical analyses indicated that photodecomposition of 3-amino-2,5-dichlorobenzoic acid [amiben] in water solution occurred rapidly during exposure to, sunlight or light from fluorescent sun lamps. Slow but definite photochemical alteration occurred when dry amiben on filter paper was exposed to light from the sun lamps. Several reaction products were separated by paper chromatography. Loss of herbicidal activity from 10-3 molar aqueous solutions of amiben approximated disappearance of amiben determined colorimetrically. Photochemical inactivation of the formulated triethylamine salt of amiben in aqueous solution was slower than that of chromatographically pure amiben. A method involving diazotization of amiben with nitrous acid and coupling the diazo form with chromotropic acid was suitable for quantitative determination of amiben.

Unshielded cultivation (during which soil is purposely moved into the drill row) and shielded cultivation (soil movement into drill row minimized) were compared in field plots of cotton [Gossypium hirsutum L. (var. DBES 8274)] which received no herbicide, a banded preemergence herbicide, one to three banded postemergence herbicide applications, or a combination of the banded pre- and postemergence herbicides. All plots were hoed and cultivated as needed to maintain reasonably good control of weeds. The study was a 3-year experiment replicated six times.

Unshielded cultivation was superior or equal to shielded cultivation as a weed control measure supplementary to hoeing or hoeing and herbicides as evaluated by effects on hoe-labor requirements, cotton yields, and weed infestations at harvest time. Replacing one or more postemergence herbicide applications with unshielded cultivation resulted in reduced control of weeds. Late season initiation of unshielded cultivation in plots previously shield cultivated had no detrimental effect on yield.

Significant increases in yield of cotton were obtained in plots treated with a preemergence herbicide as compared with plots receiving only hoeing and cultivation for weed control. Postemergence herbicide treatments (applied as a directed spray) did not result in significantly higher yields as compared with plots receiving hoeing and cultivation only. As measured by 3-year averages preemergence or postemergence treatments provided about 50 per cent control of weeds; combined they provided about 75 per cent control.

Rose clover (Trifolium hirtum All.), subterranean clover (T. subterraneum L.), and crimson clover (T. incarnatum L.), were sprayed at different growth stages with 2,2-dichloropropionic acid dalapon), and two formulations of 4-(2,4-dichlorophenoxy)-butyric acid [4-(2,4-DB)], in two growing seasons. Herbage yields, seed yields, and seed quality were for the most part unaffected by either formulation of 4-(2,4-DB) at the dates required for weed control. Only subterranean clover was tolerant of dalapon and then only at very low rates.

The addition of a combination of methyl cellulose, sodium acetate and an alkyl aryl sodium sulfonate (sodium petroleum sulfonate) to spray solutions increased the toxicity of 2,2-dichloropropionic acid (dalapon) to oats and Cynodon dactylon L. The most effective combination tested on oats in the laboratory was 2.25% methyl cellulose, 1.75% sodium acetate, and 0.8% of an alkyl aryl sodium sulfonate. Lower concentrations of the three materials, combinations of any two of these additives, or any one added alone were less effective. Under field conditions, the response of Cynodon dactylon L. to dalapon was more rapid, control was more uniform and regrowth slower when dalapon sprays contained the three additives. Methyl cellulose increased and maintained the spray load on the grass foliage. Alkyl aryl sodium sulfonate probably increased penetration of dalapon. Sodium acetate increased the toxicity of the spray.

Application of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) was effective in controlling quackgrass (Agropyron repens) in fields planted to corn. Corn yields were greatly improved by the treatment. Most favorable dates of application were in the fall or in the early spring before planting. Applications after corn planting were much less effective. Favorable rates of application were 2 to 4 lb/A. Rates lower than 2 lb/A were not as effective and rates over 8 lb/A were not required. Atrazine and 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) were generally superior to other triazine analogues used. Greater solubility and greater activity as a foliar spray favors use of atrazine for control of quackgrass.

For many years the disparity in values placed by different people on naturally growing plant species in both non-cropland such as in rights-of-way and in crop fields has been apparent. For example, agencies responsible for highway maintenance have preferred to destroy most growths of woody species located on roadsides because they were an obstacle to snow removal or ditch drainage. Some agriculturists have advanced land-use practices aimed at eliminating all non-crop vegetative growths whether herbaceous or woody located anywhere on the farm. Conversely, wildlife managers not only have stressed the importance of leaving all non-crop vegetation but have advocated the planting of more shrub species.

Dalapon (2,2-dichloropropionic acid) was applied to a predominantly medusahead (Elymus caput-medusae L.) community at rates of 1, 2, 3, 4, and 5 lb/A and at four stages of growth. Low rates of dalapon gave better control when applied at early growth stages than the same rates applied later. Reduction in total ground cover was less from December and February applications than from March applications.

Dalapon at 3 lb/A applied 30 days after emergence gave 100% kill of medusahead. Two lb/A gave 96% or better control when applied during the vegetative stage (December, February, March). Both 2 and 3 lb/A applied in December, and 2 lb/A in February left a favorable balance of species among the remaining forage plants.

The fate of 3-(p-chlorophenyl)-1,1-dimethylurea (monuron), 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), and 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) in Wymore silty clay loam soil at Lincoln, Bridgeport loam soil at North Platte, and Rosebud loam soil at Alliance, Nebraska, was followed during a 16-month period. Oats grown for 40 days in the field as a bioassay crop showed that simazine and atrazine were less phytotoxic in the finer textured soil where the rainfall was highest. Soybean bioassays in soil from different horizons showed a higher concentration of monuron remaining in the 0- to 3-inch soil horizons than of simazine or atrazine. There was a marked decrease of monuron phytotoxicity in the 3- to 18-inch soil layer 16 months after as compared to 4 months after the herbicide application. Atrazine showed the greatest leaching of the three herbicides in this study.

C14-ring-labeled 2-chloro-4-diethylamino-6-isopropylamino-s-triazine (ipazine) was soil-applied to young cotton plants or placed in solution cultures. C14-labeled constituents accumulated in the lysigenous glands of roots, stems, and leaves. Retranslocation of C14-labeled components into new growth after removal of C14-ipazine from solution cultures did not occur. No evolution of of C14O2 by C14-ipazine-treated plants was detected, but evolution of C14O2 occurred from C14-ipazine-treated soil. Some unaltered C14-ipazine was present in leaves and stems sampled 3 months after treatment. No C14-ipazine could be detected in seed formed on treated plants. Free hydroxyipazine did not constitute a major degradation product. However, hydroxyipazine and other basic substances appeared to be released upon hydrolysis of a chloroform-soluble, non-distillable component that accumulated in roots and leaves. An ethanol-insoluble, non-dialyzable component also accumulated in leaves and roots.

The absorption and translocation of labeled herbicides by submersed weeds was studied by sealing the immersed root system in a 60 ml polyethylene bottle and immersing the bottle and shoots in water in a 500 ml graduate. The medium for either roots or tops could be treated without affecting the other. Simazine [2-chloro-4,6-bis(ethylamino-1-C14)-s-triazine] and fenac [2, 3, 6-trichlorophenylacetic acid-1-C14 (mixed isomers)] were absorbed by both roots and shoots of waterstargrass (Heteranthera dubia) and translocated to the untreated portion (root or shoot) of the plant. The distribution patterns of C14-labeled simazine and fenac in bluegills (Lepomis macrohirus) were studied by gross autoradiography. The viscera of the fish contained the greatest amount of activity.

Application of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) generally reduced dry weight of tops and roots of corn and Pinus radiata seedlings. Simazine always increased top-root ratios of corn but generally decreased those of pine seedlings. Simazine increased significantly the uptake of N by corn in all soils; of Mg and P in limed, and of K in acidified soils. Aluminum sulfate decreased injury from simazine. Lime at 3 tons per acre mixed into the soil exerted a synergistic effect on the activity of 12 pounds per acre of simazine and killed all pine seedlings in the 7th or 8th week after sowing. The death of the seedlings was. caused by excess calcium ions and not by pH.

Rhizome sections of ironweed from which the fleshy roots had been pruned made less than half as much growth in the greenhouse as sections which had three inches of fleshy roots attached. Rhizome sections at least two inches long with portions of the fleshy roots intact should be used for asexual reproduction of ironweed. Ironweed plants in the field after 8 and 9 years of mowing treatments at 2 dates were approximately ⅔ as tall as untreated plants. No significant reduction in stand was obtained by 9 successive years of mowing.

The disodium salt of 3,6-endoxohexahydrophthalic acid (disodium endothal) and the derivative identified by the manufacturer as the di-N,N′-dimethylococoamine salt of endothal (coded as TD-47) were particularly effective upon submersed species of aquatic vegetation as contact herbicides. Disodium endothal at concentrations of 0.5 to 10.0 ppmw was effective in controlling approximately 50 per cent of the 19 species of plants involved in 270 tests. TD-47 at concentrations of 0.02 to 10.0 ppmw trolled 77 per cent of the 11 plant species in 94 tests.

Algae (Chara, Cladophora, Pithophora, and Spirogyra) were more effectively controlled by TD-47 than by disodium endothal. Although TD-47 was at least 10 times more herbicidal than disodium endothal, it was about 100 times more toxic to fish. Disodium endothal was more than 50 per cent effective on submersed aquatic plants at rates in excess of 2.5 ppmw with a wide margin of safety in fish (4- to 10-fold). Disodium endothal had a median tolerance limit ranging from 95 to 150 ppmw in the aggregate of nine fish species tested extensively. Median tolerance limits for TD-47 ranged from about 0.06 to 0.3 ppmw for five species of fish. TD-47 applied at a concentration lethal to fish (0.3 to 1.0 ppmw) was effective as a dual management tool in controlling vegetation and achieving partial or complete renovation of stunted fish populations.

Young, growing vegetation was most susceptible to control, and best results were achieved at water temperatures exceeding 60 F. Higher rates were required to kill plants as they matured and stands became dense. Endothal liquid formulations were superior to granules in controlling algal mats, floating and emergent plants. Granules were more effective on submersed rooted plants.

TD-47 residues were of short duration. The rate of disappearance depended on time and concentration. Detectable residues disappeared within 8 days following application of 0.3 ppmw and within 2 weeks for 0.6 ppmw. However, 1.0 to 3.0 ppmw took up to 25 days to disappear. Some residues were found in fish-food organisms from treated enclosures 3 weeks after application. Fish flesh showed no absorption of endothal-armeens at sublethal concentrations. Intraperitoneal injection of endothal into fish produced a disturbance of the osmoregulation. The physiological effect of endothal was measured by chemical analysis of blood serum.