A malathion-tolerant strain of the spiderChiracanthium mildei and its response to chlorpyrifos

Chiracanthium mildei L. Koch (Araneae: Clubionidae) spiders, from two populations, were collected and reared in the laboratory. One originated from a citrus grove at Kibbutz Afeq and the other from an experimental cotton field at the Newe Ya’ar Experiment Station. Laboratory evaluation indicated that the Afeq strain was more tolerant to malathion than the Newe Ya’ar strain (resistance factor of x3.3). When spiders of the Afeq strain were exposed to chlorypyrifos (Dursban) and malathion residues, chlorpyrifos was much more toxic.     

SELECTIVITY OF PYRAZON AND BENZTHIAZURON IN SUGAR BEET

Summary. Pyrazon (5-amino-4-chloro-2-phenylpyridazin-3(2H)-one) and benzthiazuron (N-(2-benzothiazolyl)-N′-methylurea) were compared in respect to their effects on photosynthesis and growth of sugar beet, and to their movement in soil. Benzthiazuron had a five-fold greater inhibitory effect than pyrazon on photosynthesis, and a ten-fold greater inhibitory effect on the growth of sugar beet grown in treated culture solution. On the other hand, sugar beet was more tolerant to benzthiazuron than to pyrazon when grown in soil treated pre-emergence with the herbicides. Leaching of pyrazon in clay soil appeared to be greater than that of benzthiazuron. Both herbicides entered the emerging seedlings through their roots, and hence movement of the compounds to the root zone by excess irrigation might be injurious to sugar beet. This was found to be more likely to occur with pyrazon than with benzthiazuron. Sélectivité du PCA et du benzthiazuron pour la betterave sucrière Résumé. Le PCA (5-amino-4-chloro-2-phénylpyridazine-3(2H)-one) et le benz-thiazuron (N-(2-benzothiazolyl)-N′-méthylurée) ont été compareés en ce qui concerne leurs effets sur la Photosynthèse et la croissance de la betterave sucrière et leur migration dans le sol. Le benzthiazuron manifesta un effet inhibiteur cinq fois plus grand sur la croissance de la betterave sucrière cultivée en solution traitée. En revanche, la betterave sucrière fut plus résistante au benzthiazuron qu'au PCA quand elle fut cultivée dans un sol traité en pré-levée avec ces herbicides. Le lessivage du PCA dans un sol argileux apparut plus important que celui du benzthiazuron. II a été constaté que les deux herbicides pénétraient dans les plantules, après la Ievée, par les racines et que la migration des produits dans la zone des racines sous I'effet d'une irrigation excessive pouvait provoquer des dégâts sur la betterave à sucre. II fut constaté que ce phénomène était plus probable avec le PCA qu'avec le benthiazuron. Selektivität von Pyrazon und Benzthiazuron in Zuckerrüben Zusammenfassung. Pyrazon (5-Amino-4-chlor-2-Phenylpyridazin-3(2H)-one) und Benzthiazuron (N-(2-Benzothiazolyl)-N′-methyl-harnstoff) wurden in ihrer Wirkung auf die Photosynthese und das Wachstum von Zuckerrüben sowie auf ihre Beweglichkeit im Boden verglichen. Das Herbizid Benzthiazuron hatte einen fünffach grösseren Hemmeffekt auf das Wachstum von Zuckerrüben, die in einer behandelten Nährlösung wuchsen. Andererseits waren Zuckerrüben toleranter gegenüber Benzthiazuron als gegenüber Pyrazon, wenn sie in Boden wuchsen, der im Vorauflauf mit diesen Herbiziden behandelt worden war. Die Einwaschung von Pyrazon in Tonboden war offensichtlich grösser als diejenige von Benzthiazuron. Es konnte festgestellt werden, dass beide Herbizide in die auflaufenden Keimpflanzen durch deren Wurzel eindrangen. Daher könnte die Verlagerung der Herbizide in die Wurzelzone durch Überschussbewässerung die Zuckerrüben schädigen. Dies ist bei Pyrazon offensichtlich eher zu erwarten als bei Benzthiazuron.     

THE ADSORPTION OF FOUR HERBICIDES BY DIFFERENT TYPES OF ORGANIC MATTER AND A BENTONITE CLAY*

Summary. A bioassay was used to study, adsorption of prometryne, simazine, linuron and pyrazon by fibrous peat, sphagnum moss, muck soil and bentonite as 1 % mixtures with quartz sand. Of these bentonite caused least reduction in bioactivity, and sphagnum moss reduced it only slightly more. Fibrous peat and muck soil were the most adsorptive. Prometryne, simazine and pyrazon were more highly adsorbed by fibrous peat than by muck soil, while for linuron the opposite occurred. Fibrous peat was approximately three, seven, thirteen and three times more adsorptive than bentonite for pyrazon, linuron, prometryne and simazine, respectively, while for muck soil the corresponding values were two, fourteen, seven and two. Studies with prometryne and five different soils indicated that percentage organic matter, cation-exchange capacity and specific surface area were all highly correlated with adsorption.     

Persistence of bromoxynil in three soil types

The persistence of bromoxynil octanoate has been studied in clay loam, fen peat and sand soils. Application of the herbicide at 1.12 kg/ha (16 oz/acre) active ingredient, as the octanoate, produced mean initial residues of 0.91,0.53 and 0.35 mg/ litre in the clay, peat and sand respectively, but declined to below the level of detection, 0.11, 0.09 and 0.14 mg/litre in the clay, peat and sand after 28, 44 and 14 days respectively. The rate of decline was inversely related to the sum of the organic matter and clay components of the soils.     

除草剂与安全剂混用对杂草防效及糜子安全性的影响

为探讨除草剂与安全剂混用对杂草的防治效果及对糜子安全性的影响,以'榆糜2号'为试验材料,在糜子三叶期选取两种茎叶型除草剂——阔世玛(3.6％ 二磺 ? 甲碘隆水分散粒剂)和锐超麦(20％ 双氟 ? 氟氯酯可湿性粉剂)与两种安全剂——芸苔素内酯(brassinolide,BR)和赤霉素(gibbrellic acid,G...     

Sorption-desorption of flucarbazone and propoxycarbazone and their benzenesulfonamide and triazolinone metabolites in two soils

Sorption-desorption interactions of pesticides with soil determine the availability of pesticides in soil for transport, plant uptake and microbial degradation. These interactions are affected by the physical and chemical properties of the pesticide and soil and, for some pesticides, their residence time in the soil. While sorption-desorption of many herbicides has been characterised, very little work in this area has been done on herbicide metabolites. The objective of this study was to characterise sorption-desorption of two sulfonylaminocarbonyltriazolinone herbicides, flucarbazone and propoxycarbazone, and their benzenesulfonamide and triazolinone metabolites in two soils with different physical and chemical properties. K(f) values for all four chemicals were greater in clay loam soil, which had higher organic carbon and clay contents than loamy sand. K(f-oc) ranged from 29 to 119 for the herbicides and from 42 to 84 for the metabolites. Desorption was hysteretic in every case. Lower desorption in the more sorptive system might indicate that hysteresis can be attributed to irreversible binding of the molecules to soil surfaces. These data show the importance of characterisation of both sorption and desorption of herbicide residues in soil, particularly in the case of prediction of herbicide residue transport. In this case, potential transport of sulfonylaminocarbonyltriazolinone herbicide metabolites would be overpredicted if parent chemical soil sorption values were used to predict transport.     

The phytotoxicity of various herbicides in two sandy loam soils and the effect of liming

The phytotoxicity of five soil-acting herbicides was investigated in two sandy loam soils and that of a further five herbicides in one of these soils. The effect of liming on phytotoxicity was also examined. Metoxuron, fenuron, metribuzin and fluometuron were more active in Boddington Barn soil than in Bledington soil. Prometryne was similar in effect in both soils. Liming significantly increased the effect of metoxuron in Boddington Barn soil and metoxuron, atraton, difenoxuron and metribuzin in Bledington soil. Monolinuron was less toxic in limed Bledington soil. Reasons for these differences have not been determined.     

Activity, adsorption and mobility of three acetanilide and two new amide herbicides

Activity, adsorption, and mobility of emulsifiable concentrate (EC) and microencapsulated (ME) formulations of alachlor and acetochlor as well as of metolachlor, S-metolachlor, dimethenamid and flufenacet were studied. Petri-dish bioassay, based on root response of oats ( Avena sativa L.), was used for their activity in sand and in a silty clay loam soil, and for determination of herbicide concentrations in soil solution (not adsorbed) and in column leachates of the adsorption and mobility studies respectively. Flufenacet and both acetochlor formulations showed the highest activity in both soils and ME-alachlor and metolachlor the lowest; the activity of dimethenamid, EC-alachlor and S-metolachlor was intermediate. Activity of both formulations of alachlor and acetochlor decreased with increasing organic matter content, but alachlor activity was reduced more than that of acetochlor. Lower amounts of dimethenamid and S-metolachlor were adsorbed by soil compared with the other herbicides and, consequently, greater amounts of these two herbicides were leached through that soil. None of the herbicides tested was detected below 30 cm. Less alachlor and acetochlor were biologically available in soil solution after their application as ME-formulations and, therefore, lower amounts of both ME-alachlor and ME-acetochlor were leached through the soil compared with those applied as EC-formulations.     

Mobility and persistence of four herbicides in soil of a South Australian vineyard

The use of persistent herbicides has increased the potential for contamination of soil, soil water and groundwater. The mobility, dissipation and fate of four herbicides, norflurazon, oxadiazon, oxyfluorfen and trifluralin, used in South Australian viticulture, have been studied in a typical sand‐over‐clay vineyard soil. Following herbicide application at field rates to plots up‐slope of miniature lysimeters, surface soil and soil water were sampled regularly over the period of annual rainfall. The concentration of each herbicide in the soil cores, surface soil and soil water was determined by GLC‐NPD following solid‐phase concentration procedures where necessary. Oxadiazon dissipated more quickly than the other three herbicides in the soil. Norflurazon was the most mobile of these herbicides in this soil. However all four herbicides were found in the soil water within the first year, though only norflurazon was found in the soil water in the subsequent year. Norflurazon moved laterally to a greater extent than the other herbicides. © 2000 Society of Chemical Industry     

Behavior and persistence in soil of benefin

The phytotoxicity of benefin, as assessed by sorghum on various soils and soil mixtures, was significantly correlated with the organic matter content but not with the clay or lime content of the soils. After 1 month of incubation no significant activity remained from 2 ppm benefin, and after 2 months only slight activity remained from 4 ppm. Benefin was less persistent than trifluralin and more persistent than nitralin.     

Degradation of the herbicide flamprop-methyl in soil

The degradation of the wild oat herbicide flamprop-methyl [methyl DL -N-benzoyl-N-(3-chloro-4-fluorophenyl)alaninate] in four soils has been studied under laboratory conditions using ¹⁴C-1abelled samples. The flamprop-methyl underwent degradation more rapidly than its analogue flamprop-isopropyl. However, similar degradation products were formed, namely the corresponding carboxylic acid and 3-chloro-4-fluoroaniline. The latter compound occurred mainly as ‘bound’ forms although evidence was obtained of limited ring-opening to give [¹⁴C]carbon dioxide. The time for depletion of 50% of the applied herbicide was approximately 1-2 weeks in sandy loam, clay and medium loam soils and 2-3 weeks in a peat soil.     

Residualwirkung von Chlortriazin-Herbiziden im Boden an drei rumänischen Standorten. II. Prognose möglicher Folgekulturen bei Atrazinrükständen im Boden

Residual effects of chlorotriazine herbicides in soil at three Rumanian sites. II. Prediction of the phytotoxicity of atrazine residues to following crops Total and plant-available atrazine residues in the top 10 cm soil were measured 120 days after application of 3 kg ai ha^?1 to maize (Zea mays L.) at three sites in Rumania. At one site, similar measurements were made 3?5 years after application of 100 kg ai ha^?1. Plant-available atrazine residues were estimated by extraction of soil samples with water, and by bioassay using Brassica rapa as the test plant. It was calculated that between 30 and 120μg atrazine 1^?1 was potentially available to plants in the different soils. Dose-response relationships for atrazine and the most important rotational crops with maize in Rumania—sunflower, winter wheat, soybean and flax—were determined in hydroponic culture using herbicide concentrations corresponding with the plant-available fractions measured in the different soils. ED₅₀ values were determined by probit analysis and the results showed that sunflower (ED₅₀, 22μg 1^?1) was the most sensitive crop, and soybean (ED₅₀, 78μg 1^?1) was the least. The residual phytotoxicity of atrazine to succeeding crops in the different soils was predicted using the appropriate availability and phytotoxicity data, and the results showed good agreement with those observed. The results suggest that measurements of plant-available herbicide residues afford a rapid method of assessing possible phytotoxicity to following crops.     

Soil persistence of selected sugar-beet herbicides and their combinations with lenacil

Laboratory studies on the degradation of several sugar-beet herbicides both singly and in combination with lenacil were conducted in four soils. First-order kinetics were used to describe the breakdown rates of lenacil, benzthiazuron, carbetamide, propham and phenmedipham, and their combinations with lenacil. Mean half-lives of the herbicides ranged from 14 days for propham to 191 days for benzthiazuron. There were no significant differences between the herbicides applied singly or in combination. Persistance dans le sol de plusieurs herbicides de la betterave et leurs combinaisons avec le lenacil Pour quatre types de sols, nous avons étudié, au laboratoire, la dégradation de plusieurs herbicides de la betterave appliqués seuls ou avec du lenacil. Des cinétiques de première ordre ont été utilisées pour calculer les taux de dégradation des herbicides suivants: lenacil, benzthiazuron, carbetamide, prophame, phenmediphame et de leurs combinaisons avec du lenacil. Les temps moyens de rémanence des herbicides se situaient entre 14 jours pour le prophame et 191 pour le benzthiazuron. Nous n'avons trouvé aucune difference significative entre les herbicides appliqués seuls et avec du lenacil.     

Effects of repeated applications of ten soil-active herbicides on weed population,residue accumulation and nitrification*

Ten herbicides, bromacil, chlorthal-dimethyl, diphenamid, diuron, fluometuron, neburon, prometryne, pyrazon, simazine and trifluralin at two doses were repeatedly sprayed, in autumn and in spring, for 4 consecutive years on non-cultivated, sprinkler-irrigated field plots. Herbicidal effect was assessed at 1–2 month intervals on the natural weed population and after each observation a paraquat + diquat spray destroyed emerged weeds. The response of various weed species to herbicides varied markedly but a herbicide-induced shift in the composition of weed population did not occur, presumably because of the paraquat treatment. The overall phytotoxicity to weeds present was, in decreasing order: diuron, bromacil, simazine, trifluralin, prometryne, neburon, fluometuron, pyrazon, diphenamid, chlorthal-dimethyl. Persistence of herbicides was in decreasing order: diuron = bromacil, simazine, neburon (at higher rate), fluometuron, trifluralin, prometryne. Control produced by pyrazon improved with the number of applications, but that of diphenamid and chlorthal-dimethyl remained weak and short. After repeated applications, the activity of these herbicides increased or remained at similar level, but in no case decreased. Soil samples were taken 5 months after each application and bioassayed. Phytotoxic residues were detected beneath the disturbed top-soil from bromacil, diuron, fluometuron and simazine after the first application, and from neburon after the second application; residues from trifluralin were found in the top soil only after the fifth application. After the seventh spraying, residues of bromacil were found in the 45–60-cm soil layer. Ammonia content in soil samples taken from treated plots after the fourth, sixth and seventh application was generally similar to the untreated control. In these samples, nitrate content appeared to be correlated negatively with remaining weed number; the control thus contained less nitrate than efficient herbicidal treatments. Soil samples taken after the seventh application of bromacil, diuron, fluometuron, neburon and simazine, which contained appreciable residual concentrations, did not show significant differences from control, in an in vitro nitrification test.     

Evidence for the Accelerated Degradation of Isoproturon in Soils

The herbicide isoproturon was degraded rapidly in a sandy loam soil under laboratory conditions (incubation temperature, 15°C; soil moisture potential, -33 kPa). Degradation was inhibited following treatment of the soil with the antibiotic chloramphenicol, but unaffected by treatment with cycloheximide, thus indicating an involvement of soil bacteria. Rapid degradation was not observed with other phenylurea herbicides, such as diuron, linuron, monuron or metoxuron incubated in the same soil under the same experimental conditions. Three successive applications of isoproturon to ten soils differing in their physicochemical properties and previous cropping history induced rapid degradation of the herbicide in most of them under laboratory conditions. There were, however, no apparent differences in ease of induction of rapid degradation between soils which had been treated with isoproturon for the last five years in the field and those with no pre-treatment history. A mixed bacterial culture able to degrade isoproturon in liquid culture was isolated from a soil in which the herbicide degraded rapidly.     

Influence of temperature on the volatilization of triallate and terbutryn from two soils

The rate of volatilization of the formulated herbicides triallate and terbutryn was studied in a volatilization chamber under controlled laboratory conditions using two soils with sand and loam textures, respectively. The influence of the most relevant experimental variables was investigated by measuring the amount of volatilized herbicides after their incorporation to the soils. The effect of soil temperature was studied in the range from 5 °C to 25 °C. Initial soil water content was fixed at field capacity depending on the physical characteristics of each soil. The volatilized herbicide was trapped in C18 cartridges during different time intervals and analyzed by HPLC. The volatilization losses for triallate ranged from 7 to 58%, whereas the losses for terbutryn ranged from 1 to 6%. Sorption and volatilization resulted in two coupled effects of major importance in these experiments: the sorption process was favoured as temperature decreased, whereas volatilization increased as temperature increased. © 2000 Society of Chemical Industry     

Tolerance to acetolactate synthase and acetyl-coenzyme A carboxylase inhibiting herbicides in Vulpia bromoides is conferred by two co-existing resistance mechanisms

Vulpia bromoides is a grass species naturally tolerant to acetolactate synthase (ALS) and acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicides. The mechanism of tolerance to ALS herbicides was determined as cytochrome P450-monooxygenase mediated metabolic detoxification. The ALS enzyme extract partially purified from V. bromoides shoot tissue was found to be as sensitive as that of herbicide susceptible Lolium rigidum to ALS-inhibiting sulfonylurea (SU), triazolopyrimidine (TP), and imidazolinone (IM) herbicides. Furthermore, phytotoxicity of the wheat-selective SU herbicide chlorsulfuron was significantly enhanced in vivo in the presence of the known P450 inhibitor malathion. In contract, the biochemical basis of tolerance to ACCase inhibiting herbicides was established as an insensitive ACCase. In vitro ACCase inhibition assays showed that, compared to a herbicide susceptible L. rigidum, the V. bromoides ACCase was moderately (4.5- to 9.5-fold) insensitive to the aryloxyphenoxypropionate (APP) herbicides diclofop, fluazifop, and haloxyfop and highly insensitive (20- to >71-fold) to the cyclohexanedione (CHD) herbicides sethoxydim and tralkoxydim. No differential absorption or de-esterification of fluazifop-P-butyl was observed between the two species at 48 h after herbicide application, and furthermore V. bromoides did not detoxify fluazifop acid as rapidly as susceptible L. rigidum. It is concluded that two co-existing resistance mechanisms, i.e., an enhanced metabolism of ALS herbicides and an insensitive target ACCase, endow natural tolerance to ALS and ACCase inhibiting herbicides in V. bromoides.     

Herbicide Effects on Sugarcane Growth, Pythium Root Rot, and Pythium arrhenomanes

ABSTRACT Six herbicides were evaluated for their effects on Pythium root rot and growth of sugarcane in greenhouse experiments and on in vitro mycelial growth rate of Pythium arrhenomanes. Pendimethalin and atrazine were most inhibitory to mycelial growth, but neither reduced root rot severity. Asulam, atrazine, and metribuzin were not phytotoxic to sugarcane and did not affect root rot symptom severity in clay loam or silt loam field soils. Atrazine and metribuzin increased shoot number, and atrazine increased total shoot weight for treated plants in silt loam soil. Glyphosate, pendimethalin, and terbacil were phytotoxic to sugarcane. These herbicides increased root rot severity, but the extent to which growth reductions resulted from increased disease severity or from direct herbicide injury was not clear. Adverse effects on plant growth and root rot severity were greater in clay loam than in silt loam soil. The results suggest that sugarcane injury from some herbicides is compounded by increased severity of root rot.     

DIFFERENTIAL PHYTOTOXICITY OF ATRAZINE AND AMETRYNE TO BANANAS*

Summary. In field screening trials for bananas (Musa acuminata var. Dwarf Cavendish) in Hawaii, ametryne (2-methylthio-4-ethylamino-6-isopropylamino-s-triazine) was less phytotoxic to bananas than atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine). Sand culture experiments showed that both herbicides were equally injurious to banana plants. Differential degradation of the herbicides by the plants did not account for the phytotoxicity observed. Both herbicides were partly metabolized by the plant to their common hydroxyl derivative (hydroxyatrazine) and two other unidentified metabolites after 3 and 7 days of exposure to nutrient solution containing ¹⁴C-labelled ametryne and atrazine. Phytotoxicity was directly related to leachability of the herbicides and negatively related to adsorption capacity of each soil for the herbicides. Organic matter content seemed to be correlated to the response observed. It was postulated that phytotoxicity in the field may have been attributed to differential location of the herbicide in relation to the roots.