THE BASIS OF THE DIFFERENTIAL PHYTOTOXICITY OF 4-HYDROXY-3,5-DI-IODOBENZONITRILE*

Summary. Retention of the spray solution was shown to be a major factor in the selectivity of ioxynil. Retention was high on mustard plants with or without surfactant(Tween 20). Very little ioxynil was retained by barley and pea plants when no surfactant was included in the spray hut inclusion of 0.1 or 1.0% Tween 20 increased retention. With 1.0% the retention on pea plants approached that on mustard, and there was then little differential toxicity. With no surfactant in the spray, mustard plants retained twenty-six times more ioxynil than barley plants. Addition of 01 or 1.0% surfactant increased retention by barley and reduced the differential to eleven times and eight times respectively. By varying the angle of barley leaves to the spray it was shown that the normal upright position results in reduced interception of a vertical spray and reflection of the drops without surfactant. It was concluded that for a given species growth reduction by ioxynil is largely conditioned by the amount retained and that apart from influencing retention, Tween 20 has no major independent action. At equivalent retention levels barley was much less susceptible than mustard or pea. Plants of mustard, pea and barley were treated either on the leaves only or over the whole exposed surface of the plant lo assess the influence of morphology on the response to ioxynil. There was no difference in the response of barley, but treatment by dipping aerial shoots of mustard and pea produced an effect twice that from treatment of the leaves alone at the same level of retention. The increased response of mustard and pea to whole shoot treatment is considered to be due primarily to the exposed stem and bud tissues of these species. Les bases de la toxicilé différentielle du 4-hydroxy-3,5-di-iodobenzomtrite I. Infiuence de la rétention de la bouillie et de la morphologie de la plante     

THE BASIS OF THE DIFFERENTIAL PHYTOTOXICITY OF 4-HYDROXY-3,5-DI-IODOBENZONITRlLE*

Summary. Entry of ioxynil-¹⁴C into portions of leaves was greater with mustard than with barley or pea and was unrelated to stomatal density. Measurement of ioxynil content of sprayed plants showed that by increasing the concentration of ioxynil and adding a surfactant, almost as much ioxynil could be made to enter barley as entered mustard from a lower concentration without surfactant. Auto radiographs showed that a limited amount of ¹⁴C was translocated to a small extent in plants following localized application of ioxynil-¹⁴C. An experiment comparing leaf removal by cutting with destruction of equivalent leaf areas by ioxynil treatment suggested a greater translocated effect of ioxynil with mustard than with pea or barley. Les principes de la phytotoxicité différentielle du 4-hydroxy-3,5-di-iodobetZonitrile II. Absorption et migration     

FACTORS AFFECTING THE PHYTOTOXICITY OF PARAQUAT*

Summary. Temperatures of 5–6° C delayed leaf necrosis of glasshouse-grown oats (Avena sativa), winter peas (Pisum sativum), huisache (Acacia farnesiana), mesquite (Prosopis julijiora var. glandutosa), live oak (Quercus virginiana) and yaupon (Ilex vomitoria) for at least 48 hr after treatment with paraquat as compared with higher temperatures. After 96 hr, oats, winter peas, huisache and mesquite at 5° C usually showed as much necrosis as plants at 24–28° C. Similar results were obtained with live oak and yaupon, and with yaupon in the field, except that longer periods were sometimes required for plants at low temperatures to develop injury comparable with that at higher temperatures. Washing yaupon and live oak leaves 1 hr after application reduced the effectiveness of paraquat regardless of temperature, but washing winter peas 10 min after application had little or no effect on phytotoxicity. Field-grown mesquite showed extensive leaf necrosis when leaves were washed after 20 min, live oak leaves similarly treated and washed were not injured, while the response of winged elm (Ulmus alata) was intermediate. Percentage leaf necrosis of mesquite, winged elm, yaupon and live oak increased with increasing paraquat concentration; 6–9 μg/leaf on mesquite and 20 μg/leaf on winged elm gave 100% necrosis after 4 days. Complete leaf necrosis of live oak and yaupon was not attained during this period even with 80 μg/Ieaf. Nursery-grown mesquite, yaupon and greenbriar (Smilax bona-nox) and natural stands of yaupon were treated at two growth stages, in March and May. Paraquat was more effective on mesquite when applied in May, but there were no differences with the other species. Facteurs affectant la toxicité du paraquat     

PHYTOTOXICITY OF PARAQUAT ON WHITE AND GREEN HIBISCUS,SORGHUM AND ALPINIA LEAVES*

Summary. Paraquat was applied to while, variegated and green leaves of Hibiscus rosa sinensis L. Visual observations and moisture loss determinations revealed that the rate of tissue kill by paraquat was reduced in while tissue. Evidence from paraquat absorption and concentration studies indicated that phytotoxic differences were not due to amount or rate of absorption or protoplasmic susceptibility, but to differences in chlorophyll Content of treated leaves. Desiccants such as dinoseb, not dependent upon chlorophyll for rapid action, were equally affective on white and green leaves. The same reduced activity of paraquat on white leaf tissue was demonstrated for other species. Phytotoxicité du paraquat appliqué sur les feuilles blanches ou vertes de l'hibiscus, du sorgho et de l'alpinia     

DETERMINATION OF THE VARIETAL TOLERANCE OF SUGARCANE TO PRE-EMERGENCE DIURON AND ATRAZINE

Summary. Six sugarcane varieties, N: Co 310, F146, F148, F152, F153 and F156, were Found in a field trial to differ in their tolerance to pre-emergence diuron with units of susceptibility of 100, 1·57, 1·20, 1·60, 11·30 and 8·07, and to pre-emergence atrazine of 0·75, 0·97, 0·59, 1·44, 2·42 and 0·78 respectively. Relative tolerance was assessed by subjecting each variety to seven rates of the herbicides in geometric series and calculating the F values for monthly measurements of the cane plants through the growing seasons of both the autumn-planting and ratoon crops. Units of susceptibility of each variety were obtained by transforming each mean F value into a proportion of the value for the standard variety N: Co 310. Any residual effect of the pre-emergence herbicides even at 20 kg/ha a.i. on cane plants was found to be small and insignificant after ploughing field ridges 5 months from cane-planting. With diuron, increasing the rate up to 10 kg/ha began to cause a significant reduction of sugar yield per hectare of cane, while atrazine gave such a reduction only with 20 kg/ha. Détermination de la résistance variétale de la canne à sucre à l'éigard du diuron et de l'atrazine appliqués en pré-levée Résumé. Six variétés de canne à sucre, N:Co 310, F146, F148, F152, F153 et F156, ont manifesté dans un essai au champ des differences de résistance au diuron en pré-levée, avec des mesures de sensibilité de 1,00, 1,57, 1,20, 1,60, 11,30 et 8,07; pour l'atrazine en pré-levée, 0,75, 0,97, 0,59, 1,44, 2,42 et 0,78 respectivement. Une résistance relative fut établie en soumettant chaque variétéà sept doses des herbicides en progression géométrique et en calculant les valeurs de F pour des mensurations mensuelles des plantes de canne, durant la saison de croissance, à la fois pour les plantations d'automne et les repousses de cannes après recépage. Des unités dc sensibilité pour chaque variété furent obtenues en transformant chaque valeur moyenne de F en une proportion de la valeur pour la variety standard N:Co 310. L'effet résiduel des herbicides appliqués en pré-levée, même à 20 kg/ha (m.a.) sur les piantes de cannes fut faible et non significatif apres labour des billons à 5 mois de la plantation des cannes. Avec le diuron l'aecroissement de la dose jusqu’à 10 kg/ha provoqua un commencement de réduction significative de rendement en sucre par hectare, alors que l'atrazine provoqua une telle reduction seulement avec 20 kg/ha. Bestimmung der unterschiedlichen Toleranz von Zuckerrohrsorten gegenüber Diuron und Atrazin bei Vorauflaufbehandlung Zusammenfassung. Im Feldversuch wurde gefunden, dass die sechs Zuckerrohrsorten N: Co 310, F 146, F 148. F 152, F 153 und F 156 sich bei Vorauflaufbehandlung in ihrer Toleranz gegenüber Diuron und Atrazin unterscheiden. Die Suszeptibilitätseinheiten waren für Diuron 1,00, 1,57, 1,20, 1,60, 11,30 und 8,07, für Atrazin 0,75, 0,97, 0,59, 1,44, 2,42 und 0,78. Die Ermittlung der relativen Toleranz erfolgte, indem jede Sorte mit sieben Aufwandmengen der Herbizide in geometrischer Reihe behandelt wurde und die F-Werte für die monatlichen Messungen der Zuckerrohrpfianzen während der Vegetationsperiode berechnet wurden. Die Messungen erfolgten sowohl an im Herbst gepflanztem Zuckerrohr als auch an Wurzelschossen. Die Einheiten der Suszeptibilität für jede Sorte wurden durch Umformung eines jeden mittleren F-Wertes in einen auf die Standardsorte N: Co 310 bezogenen Relativwert erhalten. Die Wirkung von Rücks-tänden der Vorauflaufherbizide auf die Zuckerrohrpflanzen war selbst bei 20 kg/ha Wirkstoff nach Furchenpflügen 5 Monate nach der Auspflanzung gering und nicht signifikant. Diuron begann eine signifikante Minderung des Zuckerertrages pro Hektar hervorzurufen, wenn die Aufwandmenge bis auf 10 kg/ha gesteigert wurde, wahrend Atrazin erst bei 20 kg/ha eine solche Ertragsminderung verursachte.     

THE PHYTOTOXICITY OF SOME HERBICIDES IN FIELD AND POT EXPERIMENTS IN RELATION TO SOIL PROPERTIES

Summary. The phytotoxicities in a number of soils of lenacil, linuron, prometryne and simazine to two indicator plants were determined in field and glasshouse experiments. The results were compared with estimates of the adsorption capacity of the soils obtained by two methods using dimethylaminobenzaldehyde as a model adsorbate. The possible influence of other soil properties was also considered.
One of the adsorption measurements had some predictive value for glasshouse behaviour but was not markedly superior to soil organic carbon content for this purpose. None of the factors studied was usefully correlated with field performance. Results from field experiments in spring were poorly correlated with those from similar experiments in autumn. Neither set of field results related closely to those obtained in the glasshouse. It is concluded that the influence of climate was more important than that of soil type.
La phytotoxiciti de quelquts herbicides dans des experiences en pots et en plein champ, en relation avec les propriétés du sol     

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     

两种鳞翅目幼虫对Bt敏感性的差异及其机理的探讨

本文用生物鉴定和ＳＤＳ－ＰＡＧＥ等方法研究了两种鳞翅目昆虫家蚕与菜粉蝶幼虫对４株苏云金杆菌的敏感性差异及其机理。生物鉴定结果表明菜粉蝶幼虫对Ｂｔ的敏感性比家蚕低。用两种昆虫的胃液体外活化伴孢晶体，ＳＤＳ－ＰＡＧＥ结果表明，菜粉蝶幼虫胃液对伴孢晶体的活化能力低，不能将无杀虫活性的原毒素在短时间内转化为毒性肽。将伴孢晶体称经家蚕胃液化再饲喂菜粉蝶幼虫，同样条件下死亡率提高３－５倍。当菜粉蝶幼虫胃液的ｐ     

A SPLIT-ROOT TETRAZOLIUM METHOD FOR EVALUATING EFFECTIVENESS AND PHYTOTOXICITY OF ROOT-ACTIVE HERBICIDES

Summary. Copper sulphate (GUSO₄.5H₂O) and sodium hydroxide (NaOH) were used to test the performance of a split-root method for evaluating the effectiveness and phytotoxicity of root-active herbicides. This method involves a vertical separation of the root system of weeping willow ( Salix babylonica L.) cuttings. One section is treated with the herbicide dissolved in half-strength Hewitt's medium while the other remains in medium without herbicide during the test period. Roots are assayed with 2,3,5-triphenyttetra-zolium chloride 24 h after treatment to determine their viability. Both herbicides satisfactorily reduced the viability of the treated roots as measured by the quantity of formazan extracted. Copper sulphate was systemic and injured untreated plant parts; sodium hydroxide affected only treated roots. The split-root tetrazolium method is relatively rapid and does not require sophisticated laboratory equipment.
Méthode au tétrazolium sur portions de racines pour l'évaluation de l'efficacité et de la phytotoxicité des herbicides agissant par les racines     

GROWTH AND SPRAY RETENTION OF WILD OAT AND FLAX IN RELATION TO HERBICIDAL SELECTIVITY*

Summary. The growth of wild oat (Avena fatua L.) was accompanied by an increase in the amount of spray retained per plant and per unit weight of plant, probably because the projected area (plan view) increased as the plant became larger. Flax (Linum usitatissimum L.) retained a fairly constant volume of spray per plant from the 8-leaf to the 35–40-leaf stages, so that the spray retained per unit plant weight decreased considerably as the plants grew. This was related to the decrease in projected area as a proportion of the whole. There was also a difference in retentivity between the cotyledons and true leaves; the cotyledons retained ten to twenty times more spray per unit weight. These results suggest that maximum selectivity would be achieved by spraying at an advanced stage of growth. Wild oat at the 3-leaf stage retained more than half the aqueous spray in the two leaf axils, while flax retained most on the cotyledons. Distribution was shown to be a probable reason for selectivity. Addition of a surfactant greatly increased retention by both species, but although the effect of a spray on wild oat might thereby be increased, under certain conditions injury to flax might be increased and the margin of selectivity reduced. Croissance et retention des bouillies herbicides par la folle-avoine et le lin en rapport avec la sélectivité     

EFFECT OF MINIMUM SOIL TEMPERATURE ON DIFFERENTIAL DISTRIBUTION OF CYPERUS ROTUNDUS AND C. ESCULENTUS IN THE UNITED STATES*

Summary. The response of tubers to low temperatures was investigated to gain insight into a physiological basis for the differential distribution of Cyperus esculentus L. (yellow nutsedge) and C. rotundus L. (purple nutsedge) in the United States. Only C. esculentus tubers survived the winter of 1968–69 in the field at Urbana, Illinois. Less than 10% of C. rotundus tubers survived at 2°C for 12 weeks, whereas more than 95% of C. esculentus tubers survived this treatment. Exposures to -2°C for 4 h or longer killed 50% of C. rotundus tubers, whereas - 6·5°C was required to kill 50% of C esculentus tubers. C. rotundus distribution is restricted to regions where the soil seldom freezes, whereas C. esculentus is distributed in regions where the soil temperatures often get below freezing. Survival of C. esculentus tubers in soil which frequently freezes may account for its wide distribution. Death of C. rotundus tubers in soils which freeze apparently is the reason why the species is restricted to the southeastern and southwestern regions of the U.S.A. L'Influence de la température du sol sur la répartition différentielle de Cyperus rotundus et de Cyperus esculentus aux Etats-Unis     

THE ADSORPTION OF LINURON, ATRAZINE AND EPTC BY MODEL ALIPHATIC ADSORBENTS AND SOIL ORGANIC PREPARATIONS

Summary. Model adsorbents were prepared by treating cellulose phosphate powder with a series of alkyltrimethylammonium compounds in which the size of the alkyl group was varied from C₈to C₁₈. The adsorption of linuron, atrazine and EPTC by these materials was found to increase logarithmically with increasing chain length. The extent of the adsorption was large compared with the adsorption of these herbicides by a humic acid and by a preparation made by removing the bulk of the inorganic constituents of a peat soil with a mixture of HCl and HF. Since soil organic matter is thought to contain alkyl groups, it is concluded that the possible influence of such groups should be considered in any discussion of the mechanisms involved in the adsorption of organic molecules by soils.
Adsorption du linuron, de I'atrazine de l'EPTC par des adsorbants de la série aliphatique et des préparations organiques de sol     

COMPLEX FORMATION AS AN ADSORPTION MECHANISM FOR LINURON AND ATRAZINE

Summary. Measurements were made of the effect of exchangeable cations on the adsorption of linuron and atrazine by an ion-exchange resin, cellulose phosphate powder, bentonite and a peat soil. The cations studied were Ca²⁺, Ni²⁺, Cu²⁺, Fe³⁺ and Ce⁴⁺. The results with linuron were consistent with the hypothesis that complex formation with exchangeable cations is a possible mechanism of adsorption. This was not so with atrazine due to complications arising from pH effects, and it seems unlikely that adsorption of atrazine by this process is significant.     

THE USE OF A LOW DOSE OF ATRAZINE ALONE AND IN MIXTURES WITH OTHER HERBICIDES IN THE MAIZE CROP

Summary. Linuron, 2,4-D-aniine, propachlor, pyriclor and cypromid, singly and mixture with atrazine, were compared with atrazine and fluromidine alone for effectiveness of weed control in maize on Oxford clay soil. Pre-emergence applications were made under wet conditions and atrazine, even at 0·28 kg/ha a.i. gave an excellent control of three main weeds, Stellaria media, Veronica spp. and Polygonum aviculare , and at 0·56 kg/ha also killed Aethusa cynapium. Fluromidine was comparable with atrazine, but linuron,2,4-D-amine, propachlor and pyriclor were less effective. Post-emergence treatments were less satisfactory. High doses of atrazine were needed for good weed control. Acynapium was resistant to pyriclor and cypromid and P. aviculare to fluromidine. 2,4-Daminewas ineffective, but atrazine/2,4-D-amine mixtures were more effective than the individual components for the control of P. aviculare. Pyriclor, at 0·56 kg/ha pre-emergenceand cypromid at 2·24 kg/ha post-emergence directly reduced the yield of the crop.
Utilisation de I'atrazine à faible dose, seule et en mélange avec d'autres herbicides, dans les culturesde maïs