Spray application factors and plant growth regulator performance: I. Bioassays and biological response

Bioassays were adapted to investigate effects of droplet size and carrier volume on performance of daminozide, gibberellic acid (GA₃) and 2,4-D using Phaseolus vulgaris L. as a model system. Response to plant growth regulators was indexed by inhibition (daminozide), promotion of internode elongation (GA₃) or ethylene production (2,4-D). Elongation of first plus second internodes above primary leaves was evaluated 14 days after treatment of primary leaves, while ethylene production was determined from head-space samples of incubated leaves 24 h after treatment. Daminozide inhibition of internode elongation was related to decreased cell size and number in pith and epidermis (range 49–70% of the untreated control). GA₃ increased cell size and number in both tissues 2·3- to 4·8-fold. Responsiveness to daminozide and 2,4-D markedly decreased as seedling age increased from 8 to 12 days, but responsiveness to GA₃ increased. Decreasing droplet size (10–0·5 μl) and increasing carrier volume (10–200 μl per leaf) at constant dose of daminozide (100 μg per leaf) and 2,4-D (100 μg per leaf) significantly increased performance, but had little effect on performance of GA₃ (2 μg per leaf). Effects of application factors on performance were related to their effects on the interface area between droplets and leaf surface. Significant positive linear relationships were obtained between plant response and the logarithm of the droplet/leaf interface area for all growth regulators. © 1998 Society of Chemical Industry     

Spray application factors and plant growth regulator performance: III. Interaction of daminozide uptake,translocation and phytotoxicity in bean seedlings

Effects of droplet size and carrier volume on foliar uptake and transport of daminozide were investigated. A constant dose of daminozide (100 µg per leaf) was applied to both primary leaves of 10‐day‐old Phaseolus vulgaris (cv Nerina) in droplet sizes of 1–10 µl and carrier volumes of 10 to 200 µl per leaf. Decreasing droplet size or increasing carrier volume decreased daminozide penetration, but increased translocation. Plotting the logarithm of the leaf surface/droplet interface area vs daminozide uptake yielded a negative linear relationship, but for translocation an optimum quadratic type relationship was obtained. Some phytotoxicity occurred at low carrier volumes and large droplet sizes. The degree of phytotoxicity was positively related to the amount of daminozide deposited per unit wetted area above 0.7 µg daminozide mm⁻². Below this threshold, there was no visual evidence of phytotoxicity. At the breakpoint, the deposit covered an area of 276 mm² on both primary bean leaf surfaces. Since the maximum in the relationship of translocation with interface area was in close agreement with the threshold amount of deposit above which phytotoxicity occurred, the inverse relationship between daminozide uptake and translocation at low interface areas was attributed to phytotoxicity. © 2000 Society of Chemical Industry     

Effect of low temperatures on 2,4-D behaviour in maize plants

The foliar surface of 4-leaf maize plants was found to be poorly wettable and retained 106 μl g^?1 dry matter when sprayed with a U46D (2,4-D formulation) blank. The third leaf retained 141 μl g^?1. A 7-day cold spell (17/9°C) increased retention per unit dry matter by 53% (135% on the third leaf). Cold stress lowered epicuticular wax quantity by 29% on the third leaf. Contact angles of formulated 2,4-D lay between 115 and 125° and were not significantly affected by cold stress. 2,4-D rapidly entered into maize third leaf (66% in 24 h) but migration from it was less than 1.5%. 2,4-D was readily degraded in maize (80% in 72 h). The most abundant metabolite was probably an ester conjugate; little of the hydroxy derivatives were found. Cold stress reduced 2,4-D degradation, and 72 h after treatment the amount of undegraded 2,4-D was 78% higher in cold-stressed maize plants. It was concluded that 2,4-D selectivity in maize results from low spray retention per unit dry matter and active degradation of penetrated herbicide. Cold stress affects both factors.     

Studies on low-volume application of plant growth substances; Part 1: Ethylene production,induced by 1-naphthylacetic acid,as a means of evaluating spray parameters

The evolution of ethylene, induced by 1-naphthylacetic acid (NAA), was studied as a means of evaluating spray parameters using cowpea [Vigna sinensis (Torner) Savi] under defined conditions as a test system. The dose-response curve was linear over the range of 1.4-14 μg per leaf. The marked production of ethylene following treatment with an active auxin, 2,4-D (2,4-dichlorophenoxyacetic acid), and the absence of its production following treatment with an inactive analogue (3,5-dichlorophenoxyacetic acid), established that ethylene production was hormonally induced. The effect of application volumes of 10-100 μ1 and of droplet sizes of 1-10 μ1 were evaluated using a constant dose (5 μg NAA per leaf); NAA was more effective when delivered to the leaf in the larger volumes but in the smaller droplet sizes.     

Relationship between the Spray Droplet Density of Two Protectant Fungicides and the Germination of Mycosphaerella fijiensis Ascospores on Banana Leaf Surfaces

The effect of fungicide spray droplet density (droplet cm^-2), droplet size, and proximity of the spray droplet deposit to fungal spores was investigated with Mycosphaerella fijiensis ascospores on the banana (Musa AAA) leaf surface for two contact fungicides: chlorothalonil and mancozeb. When droplet size was maintained at a volume median diameter (VMD) of 250 μm while total spray volume per hectare changed, M. fijiensis ascospore germination on the leaf surface fell below 1% for both fungicides at a droplet deposit density of 30 droplet cm^-2. At a droplet deposit density of 50 droplet cm^-2, no ascospores germinated in either fungicide treatment. When both droplet size and droplet cm^-2 varied while spray volume was fixed at 20 litre ha^-1, ascospore germination reached 0% at 10 droplet cm^-2 (VMD=602 μm) for both fungicides. At lower droplet densities (2–5 droplet cm^-2 VMD=989 μm and 804 μm respectively), ascospore germination on the mancozeb-treated leaves was significantly lower than on the chlorothalonil-treated leaves. The zone of inhibition surrounding a fungicide droplet deposit (VMD=250 μm) on the leaf surface was estimated to extend 1·02 mm beyond the visible edge of the spray droplet deposit for chlorothalonil and 1·29 mm for mancozeb. The efficacy of fungicide spray droplet deposit densities which are lower than currently recommended for low-volume, aerial applications of protectant fungicides was confirmed in an analysis of leaf samples recovered after commercial applications in a banana plantation. Calibrating agricultural spray aircraft to deliver fungicide spray droplets with a mean droplet deposit density of 30 droplet cm^-2 and a VMD between 300 and 400 μm will probably reduce spray drift, increase deposition efficiency on crop foliage, and enhance disease control compared to aircraft calibrated to spray finer droplets. © 1997 SCI.     

赤霉素缓解Mn~(2+)对草甘膦拮抗效应的研究

为探索能够减轻或消除Mn2+对草甘膦拮抗效应的方法,以高羊茅为试材,将赤霉素(GA3)与草甘膦和硫酸锰(Mn2+质量分数为0.1%)混用,研究了赤霉素对Mn2+降低草甘膦药效的缓解作用。结果表明:赤霉素+草甘膦+硫酸锰处理组高羊茅比同剂量草甘膦+硫酸锰处理组叶色更黄,萎蔫更严重,与同剂量草甘膦单剂处理组比较接近,其中加入50 mg/L赤霉素处理组缓解草甘膦拮抗效应的效果最好。赤霉素+草甘膦+硫酸锰处理组高羊茅的干、鲜重及叶绿素含量均低于草甘膦+硫酸锰处理组,而丙二醛和莽草酸含量均明显高于草甘膦+硫酸锰处理组。处理后第6天,赤霉素+草甘膦+硫酸锰组莽草酸含量分别比草甘膦+硫酸锰组增加了49.8%(加入50 mg/L赤霉素)和28.8%(加入30 mg/L赤霉素),差异显著;处理后第2天,赤霉素+草甘膦+硫酸锰组丙二醛含量分别比草甘膦+硫酸锰组增加了54.1%(加入50 mg/L赤霉素)和52.9%(加入30 mg/L赤霉素),差异显著。研究表明,将赤霉素与锰肥和草甘膦混合喷施,将有可能在一定程度上缓解Mn2+对草甘膦的拮抗效应,保证草甘膦的除草效果。     

Concentration-Dependent Mobility of Chlorfenvinphos in Isolated Plant Cuticles

The mobility of chlorfenvinphos in isolated pear (Pyrus communis cv. Bartlett) leaf cuticular membranes (CM) was studied as a function of concentration of chlorfenvinphos sorbed in the cuticle. Mobilities of chlorfenvinphos increased approximately 9-fold when the amount sorbed increased from 1 to 100 μg cm⁻² pear leaf cuticle. From the amounts per area, average volume fractions of chlorfenvinphos in the cuticle were calculated ranging from 2×10⁻³ to 5·1×10⁻². The increase in mobilities was steepest at the lower and levelled off at higher volume fractions. This correlation could be described for the whole range of volume fractions investigated by an equation which assumes homogeneously dispersed chlorfenvinphos. Temperature dependence of mobilities was studied at 17, 25 and 35°C and chlorfenvinphos volume fractions of 5·5×10⁻³ and 0·12, respectively. Arrhenius graphs were linear for both volume fractions, showing that cuticles did not undergo a phase transition due to the high amount of sorbed chlorfenvinphos. However, at a volume fraction of 0·12, the activation energy of diffusion, E_D, was significantly lower (83·6 kJ mol⁻¹) than at 5·5×10⁻³ (135 kJ mol⁻¹). We interpret these findings as evidence for a plasticising effect on cuticular waxes by chlorfenvinphos. So far, such an effect had been demonstrated only for certain adjuvants (ethoxylated alcohols) but not for active ingredients. Chlorfenvinphos not only increased its own mobility in pear leaf cuticles, but also that of 2,4-D in Citrus leaf cuticles. This would be expected if plasticising of waxes was the sole mechanism responsible for increased mobilities. From these data we predict that permeabilities of cuticles to chlorfenvinphos are not constant. Depending on temperature as well as types and amounts of adjuvants, rates of foliar penetration of chlorfenvinphos can be higher if its concentration in the spray liquid is increased.     

Utilization of Parthenium hysterophorus for the remediation of lead‐contaminated soil

A greenhouse experiment was conducted to study the role of plant growth regulators, a chelating agent, and plant growth‐promoting bacteria in lead (Pb) phytoextraction and their subsequent effect on the weed plant, Parthenium hysterophorus. Gibberellic acid (GA₃) and indole‐3‐acetic acid (IAA) were used as the foliar spray. Ethylenediamine tetra acetic acid (EDTA) was applied in split doses. Bacillus and Rhizobium strains were used as a single culture and as co‐cultures. The accumulation of Pb in different parts of the plant was analyzed by using an atomic absorption spectrophotometer. The amount of lead translocation and accumulation in the stems and leaves was significantly higher in the hormonal and EDTA treatments, while the microbial treatments showed no significant difference in the amount of Pb translocation into the stems and leaves, when compared to the control. The EDTA increased the amount of translocation into the shoots, but the dry biomass declined and subsequently reduced the total Pb phytoextraction. The GA₃ treatment showed the maximum total Pb accumulation, along with a higher dry biomass. The microbial co‐inoculated plants showed a significant increase in their dry biomass but the Pb accumulation did not increase like with the GA₃ and IAA treatments. These findings encourage the use of the GA₃ application for Pb phytoextraction by P. hysterophorus. One important feature of this weed plant is its unpalatable nature to herbivores, which could help in reducing the entrance of Pb into the food chain. Gibberellic acid is environmentally friendly compared to EDTA; therefore, more investigation of GA₃ and P. hysterophorus is required.     

雾滴大小与施药液量对草甘膦在空心莲子草叶片沉积的影响

为提高草甘膦防治空心莲子草Alternanthera philoxeroides时药剂的有效利用率,用丽春红S为示踪剂研究了草甘膦药液在空心莲子草叶片的沉积特性。结果表明,用体积中径(VMD)149.5~233.7 μm的雾滴喷雾,草甘膦在空心莲子草叶片上的沉积量在体积中径为157.3 μm时最多,随着雾滴体积中径增大,沉积量减少。雾滴体积中径157.3 μm与施药液量339 L/hm2处理的沉积量是雾滴体积中径233.4 μm与施药液量694.5 L/hm2处理的1.54倍。施药液量超过382.5 L/hm2时,草甘膦药液的流失明显增多。800 mg/L草甘膦药液在空心莲子草叶片上的最大稳定持留量约为 4.92 μg/cm2。结果表明,喷雾施药时采用小雾滴和较低施药液量,可大幅度提高草甘膦在空心莲子草上的沉积量。     

A gas-liquid chromatographic method to determine size spectra of droplets of an aerially applied non-volatile spray mix deposited on kromekote® cards

A non-volatile oil-based spray mix of a low-vapour-pressure insecticide, aminocarb, containing an oil-soluble red dye was applied at a dosage rate of 70 g AI in 1-5 litre ha^?1, using a fixed wing aircraft equipped with four ?Micronair’?® AU3000 atomizers, over a 1000 × 500 m spray block selected in Bathurst, New Brunswick, Canada. Spray was applied twice, at an interval of five days, to provide a total dosage rate of 140 g AI in 3.0 litre ha^?1. Spray mass recovery was assessed on glass plates and droplets were collected on ?Kromekote’?® cards, both at ground level. The stain sizes were grouped into different categories. The area containing the stains was excised, and the aminocarb present was quantified by gas-liquid chromatography (GLC). The mass of aminocarb per droplet in each stain size category was evaluated. From the mass, the spherical droplet diameter (d), number and volume median diameters (D_N.5 and D_v.5 respectively), a new parameter [mass (of aminocarb) median diameter] (D_M.5), and the droplet size spectra were calculated. The D_M.5 for the first application was 56 μm, which was identical to the D_v.5. whereas the D_N.5 was smaller at 45 μm. The corresponding values for the second application were: D_M.5 = D_v.5 = 63 μm, but the D_N.5 was 53 μm. Because the spray mix was non-volatile, all the droplet size spectra parameters were identical both at spray release height and at ground level. The present study has provided, for the first time in the literature, a novel method to determine directly the spherical diameters of the droplets deposited on artificial samplers, without having to go through the tedious procedures of spread factor measurements under laboratory conditions. In fact, the present study has made it possible to calculate spread factors under field conditions, by using the stain diameters measured and the spherical diameters calculated from the aminocarb concentration levels.     

Spray retention, foliar uptake and translocation of glufosinate and glyphosate in Ambrosia artemisiifolia

Ambrosia artemisiifolia plants exhibit stomata on both leaf surfaces and three types of trichomes: (i) small (<50 μm) spherical or ovoid, (ii) medium‐sized (50–100 μm) and (iii) long (100–200 μm) and sharp. Only the long and sharp trichomes were stained with AgNO₃, indicating the presence of hydrophilic domains. Epicuticular waxes appeared amorphous, consistent with high levels of spray retention. Glufosinate was readily taken up by A. artemisiifolia leaves, with maximum uptake of >80% of the applied label, and half maximum uptake being reached within 6 h. The foliar uptake of glyphosate was nearly complete and half of it was attained after 3 h. Glufosinate and glyphosate were ambimobile and their translocation out of the treated leaves amounted to 13–16% and 11–15% of the absorbed radioactive label respectively. Glufosinate was mainly directed to the apical developing tissues, with less amounts reaching the tissues below the treated leaves. Glyphosate was directed towards the sink tissues (apical developing tissues and roots). The sensitivity of A. artemisiifolia to glufosinate and glyphosate can be explained by high spray retention, rapid and important foliar uptake, and appreciable migration out of the parts of the plant hit by the spray.     

STUDIEN ZUR VERTEILUNG VON 14C-MARKIERTEM 2,4-D IN VERSCHIEDEN EMPFINDLICHEN UNKRÄUTERN

Studies of the absorption and translocation of ¹⁴C-2,4-D in Chenopodium album L., Galinsoga parviflora Cav., Datura stramonium L. and Galium aparine L. in relation to their susceptibility gave the following results: In G aparine (resistant) there was little transport of 2,4-D applied to the leaves, and a probable relationship between resistance and the immediate binding of the 2,4-D in the treated leaf. D. stramonium (relatively resistant) transported 2,4-D in considerable amounts alter uptake through the leaf, while C. album (very susceptible) and G. parviflora (susceptible) were intermediate in respect of 2,4-D translocation. No relationship between susceptibility of these four species and 2,4-D uptake and translocation from the leaves could be established. After application to the root systems of the four species, 2,4-D was taken up and translocated in the shoot to varying extents. In G. aparine much 2,4-D was taken up and translocated. In contrast to leaf application, the herbicide was not immediately converted into a strongly-held immobile form. In C. album, G. parviflora and D. stramonium, however, no 2,4-D was translocated in the shoot. There was thus no correlation between susceptibility and shoot transport of 2,4-D in the four species studied. Distribution du 2,4-D marqué au ¹⁴C dans des espèces de mauvaises herbes présentant des sensibilités diverses     

Effects of formulation with different adjuvants on foliar uptake of difenzoquat and 2,4-D: model experiments with wild oat and field bean

The effect of different adjuvants on the foliar uptake of difenzoquat methyl sulfate and sodium 2,4-D was studied in wild oat and field bean plants growing under controlled environmental conditions. The ¹⁴C-herbicides were applied to leaves as c. 0–2-μl droplets, usually containing 0.5 g 1^?1 active ingredient, plus adjuvants in the range 0.05–5 g 1^?1. The addition of non-ionic polyoxyethylene surfactants to solutions of both herbicides could induce considerable foliar uptake. Aliphatic C₁₃C₁₃ alcohol surfactants generally improved uptake more than nonylphenol surfactants when used at equivalent concentrations and ethylene oxide (EO) contents. The surfactant threshold for enhancement of difenzoquat uptake in wild oat was very low (0.05 g 1^?1), whilst that in field bean was much higher (>0.5 g 1^?1). For 2,4-D, surfactants at >0–5 g 1^?1 were needed to produce substantial increases in its uptake into both species. Although surfactants of low EO content (5–6) were less efficient at promoting difenzoquat uptake than those of higher EO content (10–20), particularly in wild oat, there was little dependence on surfactant EO content for enhancement of 2,4-D uptake. Adjuvants with humectant properties also promoted penetration of difenzoquat, but less so than alcohol or nonylphenol surfactants. For formulations of both ¹⁴C-herbicides translocation was directly related to the quantity of radiolabel that had penetrated the leaf tissue. Effets de la formulation avec différents adjuvants sur l'absorption foliaire du difenzoquat et du 2,4-D: modeles experimentaux sur la folle avoine et le haricot L'influence de differents adjuvants sur l'absorption foliaire du difenzoquat methyl sulfate et du 2,4 D sodium a eétéétudiée chez la folle avoine et le haricot, cultivés sous des conditions environnementales contrôlées. Les herbicides marquees au ¹⁴C ont ete appliquées aux feuilles sous forme de gouttelettes de 0,2 μl contenant 0,5 g 1^?1 de matière active, avec en plus des adjuvants de 0,05 à 5 g ^?1. L'adjonction de surfactants polyoxyethylénes non ioniques aux solutions des deux herbicides pourrait induire un absorption foliaire importante. Les surfactants d'alcools aliphatiques C₁₃/C₁₅ ont généralement augmenté la pénétration mieux que les surfactants de type nonylphénol utilises à une concentration équivalente et que les oxydes d'éthylènes (EO). Le seuil de surfactant pour l'amélioration de l'absorption de difenzoquat sur folle avoine était très bas (0,05 g 1^?1) tandis que sur haricot, il était beaucoup plus éievé (> 0,5 g 1^?1). Pour le 2,4 D, des surfactants à une dose de >0,5 g 1^?1 sont nécessaires pour produire une amelioration de son absorption chez les deux espéces. Bien que les surfactants à faible teneur en EO (5–6) fussent moins efficace pour favoriser l'absorption du difenzoquat que ceux a forte teneur (10–20), spécialement pour la folle avoine, il y avait une petite dépendance sur la teneur en EO pour l'amélioration de l'absorption du 2,4 D. Les adjuvants avec des propriétés d'humectation ont favorisé la pénétration du difenzoquat, mais moins que les surfactants alcool ou nonylphenol. Pour les formulations des deux herbicides marqués au ¹⁴C, le transport était directement reliéà la quantité de molécule marquée ayant pénétrée dans le tissu foliaire. Wirkung verschiedener Netzmittel auf die Blattaufnahme von Difenzoquat und 2,4-D am Beispiel von Flug-Hafer und Ackerbohne Der Einfluß verschiedener Zusatzstoffe auf die Blattaufnahme von Difenzoquat und 2,4-D-Na- Salz wurde an Flug-Hafer- und Ackerbohnen-Pflanzen unter kontroUierten Bedingungen untersucht. Die ¹⁴C-Herbizide wurden auf die Blatter mit etwa 0,2 μl großen Tröpfchen einer Lösung mit 0,5 g 1^?1 AS und 0,05 bis 5 g 1^?1 des Zusatzstoffs ausgebracht. Durch Zugabe von nichtionischen Polyoxyethylen-Netzmittein zu den Lösungen der beiden Herbizide konnte die Blattaufnahme erheblich gesteigert werden. Aliphatische C₁₃C₁₅-Alkohol-Netzmittel förderten die Aufnahme mehr als Nonylphenol-Netzmittel, wenn sie mit equivalenten Konzentrationen und Ethylenoxid-(EO)Gehalten ausgebracht wurden. Die Schwelle für die Steigerung der Difenzoquat-Aufnahme durch Netzmittel lag bei Flug-Hafer sehr niedrig (0,05 g 1^?1), bei der Ackerbohne vielhöher (>0,5 g 1^?1). Bei 2,4-D wurden bei beiden Arten zur deutlichen Förderung der Aufnahme Netzmittelkonzentrationen von >0,5 g 1^?1 benötigt. Obwohl Netzmittel mit niedrigem EO-Gehalt (5–6) die Difenzoquat-Aufnahme weniger förderten als solche mit höherem Gehalt (10–20). besonders bei Flug-Hafer, ergab sich für die Förderung der 2,4-D-Aufnahme kaum eine Abhängigkeit vom EO-Gehalt des Netzmittels. Additive mit feuchtigkeitshaltenden Eigenschaften förderten auch die Aufnahme von Difenzoquat, aber weniger als alkoholische oder nonylphenolische Netzmittel. Die Translokation der Mischungen der beiden ¹⁴C-Herbizide stand in direktem Verhäitnis zur Radioaktivitätsmenge, die in das Blattgewebe aufgenommen wurde.     

TRANSLOCATION AND PERSISTENCE OF 2,4-D IN POPULUS TREMULA L.

Summary. Treatment of aspen ( Populus tremula L.) with 2,4-dichlorophenoxyacetic acid (2,4-D), using a leaf spray, basal bark spray or a stem injection method of application, resulted in some reduction of stump regrowth although downward translocation of 2,4-D was slight. Persistence of 2,4-D in dead leaf tissue and in woody tissue near the injection sites was observed. This persistence could in certain circumstances be noted 6 years after treatment.
Migration et persistance du 2,4-D chez Populus tremula L.     

Distribution and activity of spray deposits in an oak canopy following aerial application of diluted and undiluted formulations of Bacillus thuringiensis Berliner against the gypsy moth,Lymantria dispar L. (Lepidoptera: Lymantriidae)

The distribution and biological activity of spray deposits resulting from aerial applications of diluted and undiluted Bacillus thuringiensis, ‘Dipel 64AF’ against the gypsy moth, Lymantria dispar L., were examined in oak stands in south-eastern Ontario, Canada. The sprays were applied by fixed-wing aircraft equipped with four ‘Micronair AU4000’ atomizers. Application of diluted formulation at 30 BIU ha^?1 in 6.0–6.4 litre generally resulted in a higher droplet density (10–28 cm ^?2 leaf) than application of undiluted product at the same dosage rate in 1.8 litre ha^?1 (4–10 cm ^?2). However, spray deposits of undiluted product with a volume median diameter (D_v.5) of 90–130 μm caused as much mortality of gypsy moth larvae in bioassays of sprayed foliage as deposits of diluted product with a D_v.5 of 150–350 μm despite a two- to three-fold reduction in droplet density. Our data suggest that by using fine spray atomization, undiluted application of these formulations can offer the same efficacy against gypsy moth as coarsely atomized sprays of diluted product.     

Initial deposits and persistence of azadirachtin in fir and oak foliage after spray application of ‘Margosan-O’® formulation

Foliar deposits and persistence of azadirachtin were investigated after spraying ‘Margosan-O’® formulation at three dosage and volume rates on to balsam fir and oak seedlings in a laboratory chamber. Droplet-size spectra and deposits were assessed using artificial samplers, and foliar residues were measured by high-performance liquid chromatography (HPLC) at different intervals of time after treatment. Disappearance of azadirachtin from both types of foliage was rapid, and the DT₅₀ (the time required for 50% of the initial concentration to disappear) values ranged from 17 to 22 h. The initial azadirachtin concentrations varied widely from 4 to 96 μg g^?1 (fresh weight), but the rate constants 0.0311 to 0.0414, were not significantly different. The data thus indicated a poor relationship between initial concentrations and the rate of loss. The influence of spray droplet size and cuticular wax content of foliage on persistence of azadirachtin was investigated using both foliar types, and glass microscope slides without and with the foliar wax coating. Neither the type of surface nor the droplet size influenced the persistence. The rate of azadirachtin loss from the glass slides was faster than from both types of foliage, and was unaffected by the presence of wax coating. The fir foliage had higher cuticular wax content than the oak foliage, but the persistance of azadirachtin was similar in both foliar types.     

Plant growth regulators induced changes in antioxidant potential and andrographolide content in Andrographis paniculata Wall.ex Nees

In this study, 5 μM ABA and GA₃ concentration were used to study the effect of these growth regulators on the andrographolide content and antioxidant potentials of Andrographis paniculata. The growth regulators were applied by means of foliar spray during morning hours. A significant enhancement in non-enzymatic antioxidant contents was observed in all sampling days in A.paniculata plants under ABA and GA₃ treatments. Ascorbic acid and α-tocopherol content was increased significantly under the growth regulator treatments in leaves, stem and roots of A. paniculata. The activities of antioxidant enzymes such as ascorbate peroxidase, superoxide dismutase and catalase were increased by ABA and GA₃ treatments in the leaves, stem and roots of A. paniculata plants. The HPLC analysis was used to quantify the andrographolide content in control and growth regulator treated plants. The growth regulators ABA and GA₃ treated plants showed increased contents of andrographolide when compared to control.     

Influence of wetting agents on the foliar uptake and herbicidal activity of glufosinate

The influence of four different wetting agents on the foliar retention, uptake and herbicidal activity of the glutamine synthetase inhibitor, glufosinate, was examined in growth-chamber experiments on barley (Hordeum vulgare L. cv Roland) and barnyard grass (Echinochloa crus-galli (L.) P.B.) as test species. The non-formulated monoammomum salt, glufosinate-ammonium, was applied as a spray, either alone or mixed with a wetting agent. The dose rates of herbicide and wetting agent were 0.5 g a.i. litre^?1 and 2.0 g litre^?1, respectively, on barnyard grass, and 2.0 g a.i. litre^?1 and 60 g litre^?1, respectively, on barley. Herbicide damage, rated 10 days after spraying, was greatest when glufosinate was used with a sodium C₁₂/C₁₄-alcohol-diglycolether sulfate (FAEO-sulfate) and least with polyoxyethylene (POE)(8) tridecyl ether; intermediate effectiveness was obtained with a combination of herbicide and a POE(15) tridecyl ether or POE(15)-tallow amine. The activity of the target enzyme, glutamine synthetase, measured 2 h after spraying, was reduced most when FAEO-sulfate was present and least with POE(8) tridecyl ether. The behaviour of the glufosinate wetting agent solutions on plant foliage was analysed by measurements of spray retention, droplet contact angles and foliar uptake of [¹⁴C]glufosinate. The results led, for both grass species, to the conclusion that differential ability of the wetting agents to enhance the permeation of glufosinate from the leaf surface deposit into the leaf tissue was the main factor responsible for the differences in herbicidal effectiveness of the glufosinate/wetting agent combinations used in this study.     

UNTERSUCHUNGEN ÜBER AUFNAHME UND TRANSLOKATION VON 14C-MARKIERTEN HERBIZIDEN IN AGROSTEMMA GITHAGO L. UND TUSSILAGO FARFARA L.

Studies of the uptake and translocation of ¹⁴C-labelled 2, 4-D, MCPA and aminotriazole in Agrostemma githago L. and Tussilago farfara L. clarified the behaviour of the herbicides in both species. In A. githago, MCPA was more freely mobile than 2,4-D after application to the leaf; it was distributed in the plant more rapidly and in greater quantity. Similarly, following root uptake MCPA was transported in the shoot in greater amounts than was 2,4-D. There is a clear relationship between the susceptibility of A. githago to MCPA and the mobility of the herbicide in the plant. In T. farfara, 2,4-D and aminotriazole applied to the leaves were equally well absorbed and relatively rapidly translocated. During the period up to 72 h the amounts of herbicide in the plant increased to similar levels; after that, ¹⁴C activity in plants treated with 2,4-D fell slightly whereas there was further accumulation of aminotriazole. Following uptake through the roots, translocation and accumulation in the leaves were considerably greater with aminotriazole than with 2,4-D. The lack of accumulation of 2,4-D could be a factor in the resistance of T. farfara to this herbicidie. Recherches sur l'absorption et la migration d'herbicides marqués au ¹⁴ C dans Agrostemma githago L. et Tussilago farfara L.     

Adjuvants and herbicidal efficacy – present status and future prospects

The influence of adjuvants on spray liquid behaviour and herbicide performance is reviewed. Total formulation efficacy can be expressed as a function of [deposition:retention:uptake: translocation:a.i. toxicity]. Adjuvants influence the physico-chemical and plant interactions involved for each factor. Deposition efficiency of spray droplets on to a target is dependent largely on the droplet spectrum, whereas retention performance is dependent on plant leaf surface character, orientation and canopy architecture, as well as droplet volume, velocity and dynamic surface tension effects. Uptake into plant foliage is affected by the leaf surface wax, cuticle age and composition and species variability. Uptake can be improved through appropriate formulation to provide either stomatal infiltration or much greater and faster cuticular absorption of the active ingredient. The inherent translocation capability of the a.i. is not affected directly by adjuvants, which are relatively immobile, but they can increase the mass of absorbed a.i. translocated, as a consequence of improved uptake or may reduce it as a result of localized contact phytotoxicity. Considerable progress has been made in developing models of spray droplet deposition, adhesion and retention, as well as uptake. In future, individual models may be combined to provide an integrated formulation efficacy decision support system.