THE HERBICIDAL ACTIVITY OF 2-AMINO-3-CHLORO-1,4-NAPHTHOQUINONE

Summary. An investigation was made of a now herbicide, 2–amino-3–chloio-1,4–naphthociuinone (ACNQ,), which appears to be promising for the control oi Echinochloa crus-galli (L.) Beauv. in transplanted paddy rice [ Oryza sativa L.).
In pot experiments in the glasshouse, seedlings of Echinochloa at different stages of growth were killed by ACNQ, at doses equivalent to 2–4 kg/ha (applied as granules) if they were submerged, but not if the shoots emerged above water. Activity was increased more by raising the level of water in the pot than by increasing the dosage. Emergent rice seedlings were little affected by ACNQ, up to 8 kg/ha, and the observed selectivity is considered to be due mainly to differences in plant height in relation to depth of water.
In laboratory experiments with rice seedlings grown without soil, the activity of ACNQ again increased with the depth of solution. Conversely, at a standard solution depth, there was a reduction in damage with advancing stage of growth, and the chemical had little effect once the leaf tip was above the solution surface.
The rate of leaching of ACNQ. through a sandy soil was slow and, at a dose of 2 kg/ha, persistence was about 15 days.
In evaluating new herbicides for paddy rice it is suggested that screening tests arc necessary on submerged as well as non-submerged plants.
Activité herbicide de la 2–amino-3–chloro-1,'4–naphtoquimne. I. Activité herbicide et profondtur de de l'eau     

EFFECTS OF TEMPERATURE AND SOIL TYPE ON THE PHYTOTOXICITY OF TRIFLURALIN

Summary. Wheat, oats, and green foxtail were grown at day-night temperatures of 32–16, 27–16, or 16–16°C in the growth chamber. The caryopses were planted at depths of 2·5 or 6·3 cm, and trifluralin was incorporated in the surface 5 cm of soil. The results indicated that the phytotoxicity of trifluralin was somewhat greater when plants were grown at day-night temperatures of 32–16°C than at a temperature regime of 16–16°C. A further study in the greenhouse indicated that the phytotoxicity of trifluralin was dependant upon soil properties. In general, the toxicity of trifluralin to both wheat and green foxtail appeared to decrease with an increase in the organic matter content of the soil.
Effets de la température et de la nature du sol sur la phytotoxicité de la trifluraline     

THE PERSISTENCE AND PENETRATION OF LARGE DOSES OF SIMAZINE IN UNCROPPED SOIL

Summary. The residues remaining in the soil from repeated annual application of simazine at 2–8, 5–6, and 22–4 kg/ha to uncropped plots on a loam soil were measured by chemical or bioassay methods at various intervals after treatment.
The total simazine residue present 12 months after the last of three treatments with 2–8 kg/ha and 8 months after the last of five treatments with 5–6 kg/ha was less than 10% of the annual dose. This rapid decomposition is considered consistent with the soil and climatic conditions. In contrast a much larger residue (a mean value of 1·7 kg/ha) was found on plots sampled 21/2 years after the last of two annual applications of simazine at 22·4 kg/ha and the reduction in the amount of residue during the next 12 months was only of the order of 25%.
In all treatments the highest concentration of simazine was found in the surface layers of the soil but measurable residues were detected to 60 cm depth, 31/2 years after the last 22·4 kg/ha application.
There was considerable variation in the total residues recovered between replicate plots and between different positions on the same plots in all treatments regardless of the depth of the sample. The possible causes of this variation are discussed.
Persistance et pénétration de fortes doses de simazine dans un sol non cultivé     

STUDIES ON THE DEGRADATION OF 4-AMINO-3,5,6-TRICHLOROPlCOLINIC ACID IN SOIL

Summary. Picloram was incubated at concentrations of 0, 0·25, 0·5 and 1 ppmw in Regina heavy clay topsoil maintained at moisture-holding capacity and a t 25° C The herbicide was quantitatively bioassayed at regular intervals. There was a lag period prior to degradation at all concentrations. The duration of the lag period increased as the concentration of picloram in the soil was increased. Al the end of each lag period, the degradation of picloram occurred as a first-order reaction, i.e. the rate of degradation was independent of the concentration of picloram in the soil. Due to the pronounced variations in the duration of the lag periods with concentration, the assignment of half-value or half-life periods to picloram degradation in soil is considered to be of doubtful significance.
Etude de la degradation de t'acide 4-amino-3,5,6-trichloropicolmique dans le sol     

THE EFFECTS OF SUB-LETHAL DOSES OF MCPA ON THE MORPHOLOGY AND YIELD OF VEGETABLECROPS

Summary. The effects of sub-lethal doses of MCPA-sodium on the morphology and yield of red beet, turnip and onion and on the morphology of spinach were studied in field and glasshouse experiments. Epinastic responses of beet were seen at 0.003 lb/ac a.c., but no serious formative effects or yield reductions occurred below 0–07 lb/ac and plants were only killed by doses above 0–1 lb/ac. Spinach was affected at 0–06 lb/ac, the lowest dose used, but the plants were not killed at 0–33 lb/ac. Epinasty in turnip occurred at 0–002 lb/ac, and at 0–01 lb/ac many of the roots were abnormal, while spraying with 0–1 lb/ac and above resulted in severe distortion or death of the plants. Onion was the least affected of all the crops studied. When a welting agent was included in the spray epinasty occurred at 0–3 lb/ac, but there were no serious formative effects or yield reductions below 1–0 lb/ac. The symptoms of injury in onion were often transitory because the affected parts were replaced as the bulb developed.
Effets de doses sub-léthatles de MCPA sur la morphologie et If rendement des cultures légumiéres. V. Betteraves, Epinards, Navets et Oignons     

INFLUENCE OF SOIL PROPERTIES ON PHYTOTOXICITY OF 4–AMlNO-3,5,6–TRICHLOROPICOLINIC ACID (PICLORAM)

Summary. Effective dosages of picloram (4–amino-3,5,6–trichloropicolinic acid) required to reduce fresh weight of sunflowers ( Helianthus annuus L. var. Menonite) were determined for seven Saskatchewan soils under controlled environmental conditions. The relationships between ED₅₀ value and clay content, organic matter content and cation exchange capacity were evaluated by correlation and regression analysis for possible usefulness in predicting dose requirements. ED₅₀ values were also determined for Weyburn loam and in culture solutions adjusted to various pH levels.
There Was no significant correlation between ED₅₀ values of picloram and soil clay content or cation exchange capacity. ED₅₀ values were highly correlated with soil organic matter content, and they increased as the soil pH was lowered or raised from pH 6.5. The increase in ED₅₀ values in the acidic range was attributed to adsorption of the unionized molecules of picloram on the organic matter in the soil. The increase in ED₅₀ values in the alkaline range may be mainly due to reduced uptake of the ionized acid by plant roots.     

DEGRADATION OF DICAMBA IN PRAIRIE SOILS

Summary. Electron-capture gas chromatography was used to detect dicamba residues in three prairie soils, and the breakdown under different moisture conditions was studied. At rates equivalent to 1·1 kg/ha degradation was rapid in all soils at 25°C and at moisture levels in excess of the wilting point, with over 50% of the applied dicamba being dissipated in 2 weeks. Negligible breakdown occurred in the sterile soils, over a 4–week period, indicating that microbial decomposition could be an important factor contributing to dicamba degradation.
The persistence of dicamba was investigated under field conditions at three locations using small plots. Applications equivalent to 1·1 kg/ha were made in October 1971 for analysis in May 1972, and in May 1972 for analysis in August 1972. At both sampling dates no dicamha residues were detected in any of the treatments at the 0–5, 5–10 or 10–15 cm soil levels.
Degradation du dicamba dans les sots de prairies     

THE INCIDENCE OF DORMANCY IN TWO-NODE STEM AND RHIZOME FRAGMENTS OF POLYGONUM AMPHIBIUM L.

Summary. Monthly samples of field-grown rhizomes and aerial stems of Polygonum amphibium were tested for innate dormancy during parts of 2 years in England and during 5 months of a third year in southern Germany. All stems and rhizomes were cut into two-node fragments, planted in soil in a warm glasshouse, and the new shoots counted after 3 weeks. Dormancy per month for different categories of stems varied from 0 to 23%, averaging 4–3% for all fragments tested but only 1–3% for mature buds. No evidence of a dormant period was found in either country.
Incidence de la darmance dans une tige à deux noeuds et des fragments de rhizome de Polygonum amphibium L.     

FACTORS AFFECTING THE LOSS OF TRI-ALLATE FROM SOILS

Summary. Electron-capture gas chromatography was used to detect tri-allate residues in persistence studies with two soils. At rates equivalent to 0–75, 15 and 3 Ib/ac, 50% of the amount applied was degraded in 8–11 weeks at 25°C in moist Regina heavy clay and Weyburn loam. No loss occurred in sterile soils, indicating that microbial degradation may be a, major factor contributing to tri-allate breakdown.
When aqueous solutions buffered at pH 4–8 were held at 25° G, only 10–15% of the tri-allate was chemically degraded during 24 weeks.
At the normal field rate of 1·25 Ib/ac, tri-allate was not readily leached. From soil columns of Weyburn loam, 5–7% was eluted by 9 in. of water; with clay the corresponding value was 12–13% of the amount applied. When field plots were sprayed with 125 lb/ac in April, tri-allate could still be detected until the soil froze in November.
Facteurs agissant sur la perte de tri-allate dans les sots     

Lateral loss of picloram and 2,4-D from a forest podsol during rainstorms

Losses of picloram (4-aniino-3,5,6-trichloropicolinic acid as the triisopropanolamine salt) and 2,4-D (2,4-dichloropheno-xyacetic acid as the triisopropanolamine salt) from a Tordon 101-sprayed podsol in a Great Lakes forest clearcut were measured for one year following spraying. Less than 1.0 % of the picloram and much less than 0.1% of the 2,4-D applied was lost during seven runoff events. Even an event less than 24 h after spraying failed to release significant quantities of either herbicide. Pertes simultanées de piclorame et de 2,4- D à partir d'un podzol forestier, pendant les tempêtes de pluie Les pertes de piclorame (acide 4-amino-3,5,6-trichloropicoli-nique sous forme de sel de triisopropanolamine) et de 2,4-D (acide 2,4-dichlorophénoxyacétique sous forme de sel de triiosopropanolamine) à partir d'un podzol traité au Tordon 101 dans une coupe à bianc de la forêt des Grands Lacs, ont été mesurées cours de I'année qui a suivi le traitement. Dans sept cas oú il y a eu ruissellement, la perte de piclorame a été inférieure à 1% et celle de 2,4-D très inférieure à 0,1 %, et même dans un cas qui s'est produit mo ins de 24 heures aprés le traitement, it n'a pas pu être trouvé des quantités significatives de pertes pour aucun des deux herbicides. Die laterate Verlagerung von Picloram und 2,4-D in einem Waldpodsol während Regenfätlen Nach der Anwendung von Tordon 101 in einem Kahlschlag (Podsolboden) des Forstgebietes der Grossen Seen, wurde eIn Jahr lang das Verschwinden von Picloram (4-Amino-3,5,6-trichlorpicolinsSure als Triisopropanolaminsalz) und 2,4-D (2,4-Dichlorphenoxyessigsaure als Triisopropanoiaminsalz) gemessen. Weniger als 1% des Piclorams und wesentlich weniger als 0,1% der ausgebrachten 2,4-D-Menge, waren infolge von sieben Regenfällen und dem damit verbundenen abfliessenden Oberflächenwassers verloren gegangen. Sogar ein Regen der weniger als 24 Stunden nach der Spritzung fiel, vermochte keine nennenswerten Mengen von beiden Herbiziden aus dem Boden zu lösen.     

A RAPID BIOASSAY FOR SIMULTANEOUS IDENTIFICATION AND QUANTITATJON OF PICLORAM IN AQUEOUS SOLUTION

Summary. When seeds of lettuce ( Lactuca sativa L.) were placed on small squares of filter paper moistened with solutions of picloram (4-amino-3,5,6-trichloropicolinic acid), the degree of inhibition on of root and hypocotyl elongation 72 hr later was related to picloram concentration. Inhibition was a useful parameter in determining quantities of picloram ranging from 0·03 to 7·2 μg. (Growth stimulation occurred from 0·00072 to 0·0072 μg. After paper chromatography of plant exudates containing ¹⁴C-labelled picloram, location and quantities of picloram on the chromatograms were determined by the lettuce bioassay and compared with determinations by the methods of ultraviolet light sensitivity, ¹⁴C 4π strip scanning and 14 C dilution calculations. R_f values determined lay all methods were identical, and the quantitative determination by the bioassay agreed closely with the calculations based on the amount of ¹⁴C detected by liquid scintillation counting.
Un essai biologique rapide d'idntification et de dosage de piclorame en solution aqueuse     

ABSORPTION, TRANSLOCATION AND METABOLISM OF DICHLOBENIL IN BEAN SEEDLINGS

Summary. A quantitative study was carried out on the absorption, translocation and metabolism of 2,6–dichlorobenzonitriie-¹⁴G (dichlobenil) in seedlings of Phaseolus vulgaris L. From an aqueous solution dichlobenil is absorbed by the roots and accumulates about three-fold; metabolism in the roots is of minor importance. From the roots the herbicide is translocated throughout the plant. In the leaves two competitive processes take place: the main part (90%) of the dichlobenil evaporates and another part is metabolized. The principal metabolic pathway is hydroxylation, followed by conjugation, 3–hydroxy-2,6–clichlorobenzonitriIe and 4–hydroxy-2,6–dichlorobenzonitrile analogues being formed in a ratio of about 4:1. Hydrolysis of dichlobenil into 2.6–dichlorobenzamide and 2,6–dichlorobcnzoic acid is only a minor metabolic route.
From a saturated atmosphere dichlobenil is taken up rapidly through the leaves but little translocation occurs to the roots. Following foliage application more of the applied dichlobenil Is metabolized because evaporation of dichiobenil as a competitive process is virtually eliminated.
Absorption, migration ei métabolisme du dichlobenil dans les plantules de haricot     

EFFECT OF TEMPERATURE ON THE ACTIVITY AND PERSISTENCE OF AMITROLE AND 2,4-D

Summary. One leaf of each of several tomato plants 5–6 weeks old maintained at 55, 70 or 85° F was dipped in 0.05 M amitrole or 0.005 M 2,4-D solution. The treated leaf was removed 1 week later. Scions taken from untreated plants were grafted to the treated plants at intervals up to 4 months after treatment.
Amitrole-treated plants maintained at 55° F were killed within 1 month but those at 70 and 85° F recovered.
Plants treated with 2,4-D showed typical symptoms when maintained at 70 and 85° F but no symptoms at 55° F. Scions grafted on plants maintained at 55, 70 and 85° F for 60 days after 2,4-D treatments exhibited typical symptoms. Grafts made more than 60 days following the 2,4-D application did not exhibit symptoms except a slight malformation on the plants held at 55° F.
New growth on the scions grafted up to 103 days after amitrole treatment on plants which had been maintained at 70 and 85° F exhibited typical amitrole symptoms (i.e. white foliage) but scions grafted after this lime did not. New shoots developing from buds on the treated plants also produced green growth 115 days after treatment but produced white foliage prior to that time.
Effet de la température sur l'activi'ité et la persistance de l'aminotriazole et du 2,4-D     

CHEMICAL CONTROL OF FERTILE SPARTINA TOWNSENDII (S.L.) ON THE CHESHIRE SHORE OF THE DEE ESTUARY I. FIELD TRIALS ON SPARTINA SWARD

Summary. Trials with dalapon, paraquat and fenuron in 1963 and 1964, and with bromacil and amitrole-T in 1964, were carried out on mature Spartina sward. Dalapon, paraquat and fenuron all gave complete kill on some plots in 1963. In 1964, paraquat gave variable results and lower percentage kills than in 1963, whereas dalapon and fenuron were more consistent. Fenuron allowed a greater degree of regeneration than dalapon and was uneconomic at the high dose (60 lb/ac) required for complete kill. Dalapon gave the best results and with 100 lb/ac there was 98–100% kill 2 years after treatment. At 50 lb/ac results were initially good, but there was more regeneration in the second season after spraying. Bromacil at 5 and 20 lb/ac and a mixture of 5 lb/ac bromacil and 4 lb/ac amitrole-T maintained more than 99% kill lor 2 years after application.
La lutte chimique contre les formes fertiles de Spartina townsendii (s.l.) sur la cóte du Cheshire dans l'esluaire de la Dee I. Essais au champ sur des pelouses de Spartina     

THE EFFECTS OF SUB-LETHAL DOSES OF MCPA ON THE MORPHOLOGY AND YIELD OF VEGETABLE CROPS

Summary. The effects of sub-lethal doses of MCPA-sodium on the morphology, yield and maturity of French beans, and on the morphology of broad beans, were studied in field and glasshouse experiments. Epinasty in French beans developed at 0.002 lb/ac a.e., but formative effects were not seen at less than 0–1 lb/ac. With doses up to 0.4 lb/ac there was no significant reduction in yield or haulm weight, but at 1.0 lb/ac and above, yield was reduced and some of the plants sprayed at an early stage of growth were killed. There were characteristic modifications of the roots and stems and of those leaves which were at a susceptible stage of development when sprayed. Broad beans were only slightly injured by 0.2 lb/ac but were generally killed by 2.0 lb/ac. Abnormalities were noted in the germination of seed produced by affected plants.
Effets de doses sub-léthales de MCPA sur la morphologic et le rendement des cultures légumières IV. Haricots verts et fèves     

THE EFFECT OF MCPA ON THE AMINO ACID AND SUGAR COMPOSITION OF VICIA FABA LEAVES

Summary. The effect of spraying Vicia faba leaves with 5000 ppm MCPA is described. Three to 4 days after spraying, a marked increase (× 5 approx.) was found in the concentrations of leucine iso -leucine and valine in the leaves. No significant changes were detected in the other amino acids. Treatment with MGPA also caused a significant increase (× 4 approx.) in the glucose and fructose content of the leaves. Detached leaves (sprayed and unsprayed), when kept in a moist atmosphere for 3–4 days, exhibited very similar increases in amino acids and sugars to sprayed intact plants. Experiments using ¹⁴CO₂ revealed that in short term photosynthesis (30 min) of sprayed and unsprayed plants, 80–90% of the radioactivity was incorporated in sucrose, with about 5% in each of glucose and fructose. Over photosynthelic periods of 4 days, glucose and fructose were found to be almost as heavily labelled as sucrose in sprayed plants, but in the controls the distribution of radioactivity was similar to that in short term photosynthesis. It is suggested that the build up of amino acids and sugars in plants treated with MCPA is due to an interruption of the translocatory flow from the leaves, and that this build up of metabolites may be a contributory factor in the toxic action of this herbicide.
Effet du MCPA sur la composition en amino-acides et en sucre des feuilles de Vicia faba     

THE PHOTOLYTIC DEGRADATION OF PICLORAM

Summary. The effects of sunlight and ultraviolet light (253.7 nm) on 4-amino-3,5,6-trichloropicolinic acid (picloram) in a basic aqueous solution were investigated. Electron-capture gas chromatography determinations showed that approximately 20% of a 2 × 10⁻² M concentration of picloram was degraded for each 48-hr exposure to ultraviolet light of an intensity of 200 μW/cm². Decomposition by sunlight was slower and more variable.
Precipitation of the degradation products with AgNO₃ indicated that two chloride ions were liberated for each molecule of picloram that was degraded. Titrations indicated that acids were formed in the degradation process, and ultraviolet spectra showed that the pyridine nucleus was destroyed. Chromatograms of the methylated decomposition products showed that at least five products were formed.
The effect of the addition of a free radical scavenger, hydroquinone, on the rate of decomposition was investigated but no definite conclusions could be drawn.
La dégradation photolytique du piclorame     

THE EFFECT OF JULY APPLICATIONS OF DALAPON ON THE GROWTH AND BOTANICAL COMPOSITION OF AN AGROSTIS/LOLIUM PASTURE

Summary. Dalapon–sodium at 3.3–7.5 Ib ac/a.e. was applied in early, mid– and late July 1964 to an Agrostis/Lolium pasture for selective control of the weed grasses Agrostis stolonifera, Poa trivialis and Holcus lanatus. These species were significantly more susceptible than Lolium perenne to dalapon at all doses regardless of the time of spraying. The most promising treatment was 33 lb/ac applied on 4th July, which increased the ground cover of L. perenne and substantially reduced Agrostis stolonifera and Poa trivialis. The total yield of herbage 12 weeks after spraying was only 50% of that from the unsprayed control, but the yield of Lolium perenne was not affected. When cut on 21st May and 5th August 1965, total yield was only slightly reduced and that of L. perenne was increased by 60–90%. The successful practical utilization of this selectivity is likely to depend largely on the spacing of the plants of L. perenne in the pasture. Simazine at 0.75 Ib/ac applied to half of each plot 3–4 weeks alter dalapon treatment had no lasting beneficial effect on the composition of the sward.     

ON THE REGENERATION OF ROOT FRAGMENTS OF LEAFY SPURGE (EUPHORBIA ESULA L.)

Summary. The roots of leafy spurge ( Euphorbia esula L.) normally produce shoot buds abundantly near the soil surface but with decreasing frequency at increasing depths. By placing Fragments of roots collected from various depths in the soil in shallow flats in a glasshouse, it was demonstrated that root Fragments from all depths down to 2–8 m do not differ appreciably in rcgenerative capacity and this capacity is not dependent upon the presence of performed shoot buds. By collecting root fragments from the same stand throughout the growing season it was shown that regenerative capacity is lowest in June at the time of maximum flowering. The implications of these findings arc discussed in relation to the control of this species.
Sur la régénération des fragments de racines de Euphorbia esula L .     

STUDIES ON HERBICIDE CONTENTS IN ROOTS OF SKELETON WEED (CHONDRILLA JUNCEA L.) FOLLOWING LEAF APPLICATIONS

Summary. The herbicides studied were 2,4-D, 2,4-DB, dicamba and orthoarsenic acid. Herbicide content in the roots was taken as an overall measure of penetration into and absorption by the leaves, and of translocation to the roots.
A significantly greater 2,4-D content resulted from foliar application at pH 3–5 than at higher values, though at pH 8–5 the inclusion of triethanolamine significantly increased the 2,4-D content. No evidence was obtained that a greater 2,4-D content should result from foliage applications of 2,4-DB than from 2,4-D. Dicamba gave a greater herbicide content than 2,4-D when applied at high concentration at 20° C but not at 25° C, probably because of less injury at the lower temperature.
Concentrations of Tween 20 up to 2% had no deleterious effect on the 2,4-D content; on the other hand 2,4-D content was lowered by 0–25% or more of cetyltrimethyl-ammonium bromide. Poor wetting is not the cause of the variable herbicide contents sometimes obtained.
Orthoarsenic acid, which has given better control of the weed than 2,4-D, was very poorly translocated; its effectiveness is due to its high intrinsic toxicity.
Etudes sur la teneur en herbicide des racines de Chondrilla juncea L. á la suite d'applications sur les feuilles