Einfluss von Pflanzenschutzmitteln einer Zuckerrüben-Spritzfolge auf biologische Aktivitäten und auf den Abbau von Chloridazon im Boden. II. Gefäss-und Laborversuche

Effect of carious pesticides of a sugar-fact spray programme on biological activities and chloridazon degradation in soil. II Pot trials and laboratory experiments In pot trials and laboratory experiments degradation and plant availability of Chloridazon (Pyramin) in soil, applied alone and in combination with other pesticides of a sugar-beet spray programme were investigated and also the influence of these treatments on soil dehydrogenusc activity and straw decomposition. After an initial lag-period chloridazon degradation was rapid, and obviously was unaffected by plant growth and other pesticides. The average lime for 50% decrease of the initial concentration was 10 days. The water-extractable portion of chloridazon in soil was not affected by the presence of other pesticides and was about 43% 1 week after application and decreased to 0% during the following week. Pyramin alone did not influence straw decomposition, and the spray programme was slightly stimulatory. In pot trials with and without plains, dehydrogenase activity was not significantly inhibited by Pyramin, whereas with the spray programme and bare soil, slightly reduced enzyme activities were observed. Under laboratory conditions the spray programme was more inhibitory than Pyramin alone. There was no correlation between biological soil activities and chloridazon degradation.     

Untersuchungen zum Einfluss einer Pflanzenschutzmittelspritzfolge auf das Rückstandsverhalten von Terbutryn und die mikrobielle Aktivität im Boden. Teil II. Beeinflussung der mikrobiellen Aktivität

Studies on the effect of a pesticide spray sequence on the behaviour of terbutryn residues and on soil microbial activity. Part II. Influence on microbial activity In laboratory incubation experiments (at 10 and 20°C and 30 and 60% soil water-holding capacity) soil microbial activities (dehydrogenase, respiration after glucose amendment and nitrogen transformations) were scarcely affected by 20·9 and 28·0 mg kg^?1, respectively, of terbutryn in two soils of different sorption properties. In contrast, dinosebacetate, alone or mixed with terbulryn, triadimefon or parathion, inhibited dehydrogenase activity and respiration even at a low rate of application (2·87 mg kg^?1). Following application of a 10 times higher rate to a highly adsorbent soil there was an initial inhibition of nitrification followed by an enhanced rate of nitrogen mineralization. Triadimefon and parathion, alone and in combination with other pesticides, caused both stimulation and inhibition of microbial activity; the reason is not clear. The effects on dehydrogenase and respiration were confirmed in field experiments. Dehydrogenase activity was the most sensitive and so could be a useful test for the side-effects of pesticides on soil micro-organisms. Additional work on nitrogen transformations is needed to interpret the results.     

Untersuchungen Zum Einfluss einer Pflanzenscutzmittelspritzfolge auf das Rückstandsverhalten von Terbutryn und die mikrobielle Aktivität im Boden. Teil I. Rückstandsverhalten von Terbutryn

Studies on the effect of a pesticides spray sequence on the behaviour of terbutryn residues and on soil microbial activity. Part I. Behaviour of terbutryn residues In laboratory incubation studies (at 10 and 20°C and 30 and 60% soil water-holding capacity) terbutryn dissipated with half lives of 19–113 days at a standard rate of application (2·09 or 2·8mg kg^?1) and 62–258 days at a 10-fold higher rate. There was little difference between two soils of different sorptive properties. The water-extractable residues showed that terbutryn was extensively adsorbed by both soils with only 12–18%‘plant-available'. Persistence of terbutryn in the field was consistent with the laboratory results and was predicted satisfactorily with a mathematical simulation model. In the laboratory, terbutryn breakdown was inhibited by the simultaneous application of dinoseb acetate and stimulated by triadimefon and parathion but these results were not confirmed in the field.     

Characterization of Spatial Variability Structure in Three Separate Field Trials on Pesticide Dissipation

Experiments were carried out on three Italian farms to assess the degree of spatial variation of pesticide field concentration during treatment and during dissipation trials. Test pesticides were chloridazon and metamitron (both sugar-beet herbicides) applied as a tank mix. The classical statistical technique and geostatistics were used to summarize and evaluate variable spatial data. The results show that the actual values of pesticide concentration for application rate and initial concentration in all three areas are lower than expected, thus indicating that under field conditions only a part of the pesticide reaches the soil during the distribution. The actual values for both herbicides in all three areas expressed as percentage of expected values ranged from 44·1% to 64·2% for application rate and from 40·5% to 99·5% for initial concentration. The coefficient of variation was similar for both pesticides and ranged from 23·8 to 74·1 for application rate, 24·1 and 58·8 for initial concentration and 11·1 and 110·0 for dissipation half-lives. The high variability in application rate and initial concentration could be ascribed to an uneven herbicide distribution, and in dissipation studies to variation in half-lives for the rate of herbicide loss from soil in different parts of the field. Geostatistic analysis indicated little spatial correlation, probably because the sampling sites were widely spaced on the field. In all cases, the data were not sufficient to estimate the range of influence, probably because of the size of the experimental fields and the sampling strategy. © 1997 SCI.     

In situ bioremediation of organochlorine‐pesticide‐contaminated microcosm soil and evaluation by gene probe

BACKGROUND: Pesticide‐formulating industries are contaminating the environment through various activities. Bioremediation is the best method for decontamination, as chemical and physical methods are not only costly but also not very effective in open field systems. In the present study, in situ bioremediation of organochlorine‐contaminated soil was demonstrated by combined biostimulation and bioaugmentation strategies, followed by evaluation using a molecular method. RESULTS: Three parameters were monitored: microbial biomass (colony‐forming units (CFU) g^?1 soil), residual pesticides after treatment and catabolic genes from microcosm soil. Both the biostimulation and the bioaugmentation treatments showed an initial lag phase of 80 days towards colony‐forming units. Gas chromatography of soil samples showed that concentrations of residual pesticides in the soil declined by up to 85–90% after 80 days, indicating their utilisation with time. On dot‐blot hybridisation of the total DNA from the same soil samples, it was observed that catabolic genes tfdC (catechol 1,2‐dioxygenase) and cm genes (chlorophenol monoxygenase) were predominant, whereas other catabolic genes such as catechol 2,3‐dioxygenase (xylE) were negligible. CONCLUSION: The strategy of in situ bioremediation and its evaluation by gene probe and also by conventional methods was demonstrated for organochlorine‐pesticide‐contaminated soil in open microcosms. It showed that bioaugmentation along with biostimulation was effective, although initial acclimatisation for a period of almost 2–3 months was required in the open field systems. Copyright © 2009 Society of Chemical Industry     

Determination of sugarbeet herbicides in soil samples by hplc

Determination of sugarbeet herbicides such as chloridazon, metamitron and phenmedipham in soil samples is described. After extraction with acetone, pesticides were determined by HPLC on an RP-18 column using methanol/water as mobile phase. Average recoveries were 82% for chloridazon, 93% for metamitron and 77% for phenmedipham. Quantification limits were 3·5 μg kg^?1 for chloridazon, 6·3 μg kg^?1 for metamitron and 3·6 μg kg^?1 for phenmedipham.     

Response of spring cereal crops to soil residues of ethofumesate*

For evaluation of soil residues of ethofumseate [(±)2-ethoxy-2,3-dihydro-3,3-dimethylbenzofuran-5-yl-methylsulphonate], spring barley (Hordeum vulgare L.) and spring wheat (Triticum aestivum L.) were sown in soil planted 11 months previously with sugar-beet (Beta vulgaris L.) and previously treated with band or broad-cast applications of the herbicide at rates of 1.68-4.48 kg/ha. The height of barley and wheat was suppressed only where ethofumesate was applied broadcast and the soil was not ploughed after sugar-beet harvest. Three months after sowing, the 4.48 kg/ha rate suppressed the height of barley 18% and wheat 34%. In another experiment, barley grew normally on soil treated the previous year with pre-planting and post-emergence applications of ethofumesate where ploughing followed sugar-beet harvest. For all treatments, yields of straw and grain were not significantly lower than those of the untreated check plots. The dissipation of ethofumesate 24 weeks after application to sugar-beet was 89–100% when applied on a band compared to 85-95% when applied broadcast.     

Accumulation and distribution of pp′-DDT and related compounds in an apple orchard. II. Residues in trees and herbage

DDT residues in or on the roots and leaves of the herbage and the roots, bark, leaves and fruit of the trees are given for an apple orchard sprayed annually (1953–1969). The distribution of DDT in both the grass and the grass roots was in circular areas of residues, with maximum values at each trunk and decreasing radially to each alley. Of the spray applied at the green cluster stage 80% was deposited on the grass sward and very little, if any, directly on the soil surface. The pp′-DDT content of the grass fell rapidly with successive mowings (from which the cuttings remained in situ) from 400 μg/g at spraying to 2 μg/g after nine months. 33 g/ha pp′-DDT was found in the herbage roots (0.87% of the total residues in the soil). The residues in the bark (87.5 g/ha) were much lower than expected after 13 years spray application. There were increased amounts of pp′-DDE, pp′-TDE and pp′-TDEE relative to pp′-DDT, indicating some breakdown on the bark, but the chief losses were attributed to volatilisation and to removal by wind and rain. The residue content of root bark varied from 3 μg/g near the emerging trunk to 0.05 μg/g at a depth of 90 cm. The pp′-DDT content of leaves at leaf fall rose from <1 ng/g after a single spring spray to 8.33 μg/g following an additional spray in late June. There was a large loss of DDT from the canopy between the June spray and leaf fall (440–480 g/ha down to 25 g/ha), attributed to volatilisation. The amount of pp′-DDT on the fruit, after a single spray, was 3 ng/g fresh weight (80.9 mg/ha out of a total of 1.0–1.5 kg/ha used).     

The effect of the annual use of some pesticides on soil microorganisms,pesticide residues in soil and carrot yields

The study deals with the effect of common, annually-used pesticides on soil microorganisms, pesticide residues in soil, and carrot (Daucus carota) yields in Central Finland. Linuron residues in carrot roots were also analysed. Thiram+lindane and dimethoate were applied from 1973–1981 at the commercially recommended doses on experimental plots of carrots, linuron was applied at twice the recommended rate from 1973–1979 and at the normal rate thereafter and in addition TCA was applied in 1978. Maleic hydrazide was used in the years 1973–1976, and glyphosate after 1977. The numbers of different soil microorganisms, their activities and the pesticide residues were studied from autumn 1978 to 1981. The pesticide treatments reduced the growth of soil algae but increased the total number of microorganisms and the number of aerobic spore-forming bacteria. Linuron residues in the soil were 0.9–2.8 mg kg^?1 in the growing season and 1.2–1.7 mg kg^?1 in the autumn, 3 months after application. The residues of glyphosate in the soil were 0.7 mg kg^?1 in the autumn, 41 days after the treatment, and had declined to a level of about 0.2 mg kg^?1 by the following summer. In the pesticide-treated plots the carrot yield was only 20–60% of the yield in the hand-weeded plots. The herbicide programme controlled most of the annual weeds but not couchgrass Elymus repens and milk sow-thistle Sonchus arvensis.     

Prognose-Modell zur Erfassung des Rückstandsverhaltens von Metribuzin und Methabenzthiazuron im Boden und deren Auswirkungen auf Folgekulturen

A predictive model for the assessment of metribuzin and methabenzthiazuron residues in soil and their effects on succeeding crops Aus der simulierten Abbaukurve lassen sich somit für jeden beliebigen Zeitraum nach Applikation eines Herbizids die maximalen pflanzenverfügbaren Wirkstoffanteile ableiten, aus denen die Auswirkungen auf mögliche Folgekulturen prognostiziert wurden. Die relative Empfindlichkeit (im Bereich der ED₅₀) der untersuchten Kulturpflanzen in Hydroponik war bei Metribuzin: Möhre < Bohne = Salat < Erbse = Spinat und bei MBT: Bohne = Erbse = Salat < Spinat = Möhre. Weiterhin konnte gezeigt werden, dass unter Labor- und Freilandbedingungen evtl. auftretende Schäden in fast allen Fällen in den gleichen Aktivitäskategorien lagen. The degradation of the herbicides metribuzin and methabenzthiazuron (MBT) was simulated under outdoor conditions in a sandy soil by a computer model based on the dominating influence of temperature and moisture on degradation, which is measured in preceding laboratory experiments. Depending on the conditions of incubation (10–30°C, 20–90% water holding capacity) the half-life of metribuzin was 11–60 days and of MBT 42 > 1200 days. Knowing the plant available soil water, the fraction of a total herbicide residue potentially available to plants can be calculated from the distribution coefficient (K_d-value). In the soil under investigation, for metribuzin 77% and for MBT 16% of the total residue was available to plants. Thus, the maximum residue available to plants can be calculated from the simulated degradation curve for any period after the application of a herbicide and in combination with a predictive model the effect on succeeding crops can be predicted. The specific susceptibility of the crops in question has to be established in preceding hydroponic culture experiments. The relative susceptibility (about ED₅₀) of the plants in hydroponic-culture was earrot相似文献   

Dégradation de l'isoproturon et disponibilité de ses résidus dans le sol

Degradation if isoproturon and availability of residues in soil The availability and degradation of ¹⁴C-ring-labelled isoproturon in soil was investigated over 140 days under controlled laboratory conditions. Degradation of the active ingredient followed and 65 days later only a minor fraction (0.6%) of the parent molecule remained extractable. A demethylated-isoproturon metabolite was detectable in soil from day 15 (2.6%). The amount of ¹⁴CO₂ derived from the ¹⁴C benzene ring label and liberated over time indicated that a total of 13.6% isoproturon was mineralized during the incubation period. In parallel, the amount of ¹⁴C residue extracted from the soil by water followed by methanol or remaining within the soil—analysed by combustion—was also determined at intervals. After 140 days, 72% of the radiolabel added remained in the soil as non-extractable residue. The degradation half-life of extractable isoproturon was an estimated 14 days.     

Effects of herbicide-fertiliser interactions on nitrogen and phosphorus transformations and herbicide persistence in soil

The effects of seven herbicides, alone or combined with a commercial compound fertiliser, on nitrogen and phosphorus transformations in soil, were investigated in the laboratory. No significant effect was observed without the fertiliser. When the fertiliser (N:P:K ratio 20:14:14) was applied (2 gkg^?1 of soil), asulam markedly reduced nitrification, while increasing the mineralisation of nitrogen; chloridazon, glyphosate, isoproturon and paraquat all prevented the reduction in available phosphate that occurred in the control soil in the first 2 weeks. The rates of degradation of dalapon and isoproturon were greatly reduced in fertilised soil. The importance of these results is discussed in the context of the requirements of registration authorities.     

Management of the yellow beet cyst nematode with crop rotation,soil fumigation and granular nematicides

A trail field was managed for six years to test effects of short crop rotations, soil fumigation and granular nematicides on the population dynamics of the yellow beet cyst nematode (Heterodera trifolii f. sp.beta) and sugar-beet yields.In the two-year rotation, the cyst nematode population before planting varied from about the tolerance level (5 eggs per millilitre of soil) to 25 eggs per millitlitre of soil, leading to losses of sugar yield. Soil fumigation with metam-sodium effectively reduced the nematode density before planting, resulting in a 15 and 25% increase in sugar yield in the first two crops, respectively, but was insufficient to protect the third sugar-beet crop from yield-reducing nematode attack. This was attributed to the wet soil at the time of application and accelerated disappearence of the chemical in the soil through biological adaptation to repeated fumigation. Oxamyl or aldicarb granular nematicides applied as a side-dressing to the rows had insufficient effect to protect the sugar-beet from yield-reducing nematode attack. An overall treatment with aldicarb rotavated into the soil, alone and in addition to soil fumigation, increased sugar yield significantly. However in the two-year rotation, yield of the third sugar-beet crop treated with soil fumigation and granular nematicide was still lower than that of the untreated second crop in the three-year rotation.In the three-year rotation, thecyst nematode population before sugar-beet varied from hardly detectable to about the tolerance level. Here sugar-beet could be protected from yield-reducing nematode attack by soil fumigation or an overall treatment with granular nematicide. In the threeyear rotation with soil fumigation an increase ofRhizoctonia crown rot was observed in the second sugar-beet crop.Samenvatting Om de effecten na te gaan van korte rotaties, grondontsmetting en nematicide granulaten op het populatieverloop van de gele bietcystenematode (Heterodera trifolii f.sp.beta) en de opbrengsten van suikerbieten werd gedurende zes jaren een proef uitgevoerd op een natuurlijk besmet perceel van de proefboerderij Vredepeel.In de tweejarige rotatie variëerde de cystenematodepopulatie vóór het bietegewas boven de schadedrempel, wat resulteerde in verlaging van de suikeropbrengst. Grondontsmetting met metam-natrium veroorzaakte een effective vermindering van de dichtheid van de nematoden vóór de bieten en een verhoging van de suikeropbrengst van respectievelijk 15 en 25% bij de eerste twee gewassen, maar was onvoldeende om het derde bietegewas te beschermen tegen een opbrengst verminderende aantasting door nematoden. Dit was een gevolg van natte bodemomstandigheden bij het injecteren en het versneld verdwijenen van het middel door biologische adaptatie van de grond na herhaalde ontsmetting. Nematicide granulaten (oxamyl of aldicarb) naast de rij toegepast hadden onvoldoende effect om de bieten te beschermen tegen een opbrengstverminderende aantasting door nematoden. Een volvelds toepassing van in de grond gefreesde aldicarb alleen en toegevoegd na grondontsmetting verhoodge de suikeropbrengst beduidend. De opbrengst van het derde suikerbietegewas in de tweejarige rotatie was echter na toepassing van grondontsmetting en nematicide granulaten nog beduidend lager dan die van het onbehandelde tweede suikerbietegewas in de driejarige rotatie.In de driejarige rotatie variëerde de cystenematodepopulatie vóór het bietegewas van nauwelijks aantoonbaar tot nabij de tolerantiegrens. Hier kon het suikerbietegewas worden beschermd tegen een eventueel opbrengst verminderende nematodenaantasting door grondontsmetting of volveldstoepassing van nematicide granulaten.     

哈茨木霉菌对水稻幼苗根际土壤微生物和酶活性的影响

采用钵盘育苗试验,研究了哈茨木霉菌在调节水稻苗床土壤微生物群落及土壤酶活性中的作用。研究结果表明：哈茨木霉菌能有效调节水稻幼苗根际土壤微生物群落组成;哈茨木霉菌对细菌、真菌和放线菌数量的影响程度明显不同,播种28天后,哈茨木霉菌接种处理的水稻幼苗根际土壤细菌和放线菌数量较对照分别增加50.70%和48.56%,而真菌数量较对照减少16.15%,并且哈茨木霉菌数量较刚播种时增加了138.46%;哈茨木霉菌也能显著提高土壤脲酶、磷酸酶和蔗糖酶的活性,分别较对照提高8.55%、18.31%和49.61%。研究表明,哈茨木霉菌具有改善土壤微生态环境的作用。     

植保无人机飞防助剂与杀虫剂配伍方式对其防治稻纵卷叶螟效果的影响

为探究不同类型飞防助剂与杀虫剂配伍方式对其防治稻纵卷叶螟Cnaphalocrocis medinalis效果的影响,以杀虫剂、飞防助剂和施药液量为因素设计3因素4水平的正交试验,通过方差分析(analysis of variance,ANOVA)对各因素的显著性水平进行分析,确定对稻纵卷叶螟具有理想防效的配伍方式。结果表明,杀虫剂和飞防助剂对防治稻纵卷叶螟的效果均有极显著影响,施药液量对防治稻纵卷叶螟的效果无显著影响。施药后第15天,杀虫剂选择10%甲维·茚虫威悬浮剂、飞防助剂选择有机硅、施药液量选择30.0 L/hm²的配伍方式对稻纵卷叶螟的防效较好,达84.32%。飞防助剂并非对所有杀虫剂都具有同等增效,其中聚合物助剂对5%氯虫苯甲酰胺悬浮剂的增效显著高于对其他3种杀虫剂的增效,植物油助剂对12%甲维·虫螨腈悬浮剂的增效显著低于对其他3种杀虫剂的增效,有机硅助剂对4种杀虫剂的增效均较好。     

The phytotoxicity of narrow distillation range petroleum spraying oils to valencia orange trees in South Australia. Part III: The influence of distillation temperature and spray timing on leaf and fruit drop

Petroleum oil sprays are used as pesticides on citrus to control California red scale (Aonidiella aurantii Maskell), but may have phytotoxic effects on trees and fruit. As part of a programme to establish improved specifications for spray oils for South Australia, three oils with different 50 %-distillation temperatures were applied to trees each month from October to May to observe their effects on leaf and fruit drop. The 50%-distillation temperatures of the three oils were 211, 224 and 240°C at 10 mmHg (in order of increasing molecular weight). The oils caused significant leaf drop. The higher the 50%-distillation temperature of the oil, the greater the leaf drop. Most leaf drop was caused when natural leaf drop was greatest. Oils applied from October to February caused severe leaf drop for periods of about 1–2 months, while oils applied from March to May caused severe leaf drop for up to 6 months or more. There was also a tendency for oils with a lower 50%-distillation temperature to cause leaf drop sooner after spraying than oils with a higher 50%-distillation temperature. Significant fruit drop was caused in only a few treatments, but the maximum fruit drop was less than 5% of the total fruit number and of little consequence when compared with the effects of oils on yield through reduced fruit set. Visually, a significant proportion of the total number of leaves present fell in many of the oil spray treatments, and the rate of disappearance of the oil film was directly related to the 50%-distillation temperature of the oil, and to the spraying date.     

Combined effects of solarization and organic amendment on charcoal rot caused by<Emphasis Type="Italic">Macrophomina phaseolina</Emphasis> in the sahel

The effects of soil solarization combined or not with millet residues or paunch contents amendments, on the survival ofMacrophomina phaseolina (Tassi) Goid. and development of charcoal rot of cowpea (Vigna unguiculata), were assessed in a naturally infested soil. Solarization increased the soil temperature to 50°C for at least 4 h per day during June, leading to a significant reduction (44%) in soil inoculum ofM. phaseolina. Paunch contents or millet residues amendment (3 t ha⁻¹) caused 16% or 35% reduction of initial inoculum density, respectively. The combination of paunch contents or millet residues amendments followed by solarization, resulted in the strongest effects on inoculum density, with reductions of 46% or 66%, respectively. The reduction in disease severity, as expressed by the area under the disease progress curve, was 78% or 96% for the combination of millet residues or paunch contents amendments and solarization, respectively. The stronger effect of the treatments on disease severity than on inoculum density may be explained by a weakening effect caused by the treatments on the remaining inoculum. Our results suggest that in the Sahelian zone the combination of solarization and organic amendment can be a credible alternative to pesticides for managing charcoal rot disease and improving cowpea yield in fields with heavy infestations withM. phaseolina.     

Spray treatments combined with climate modification for the management of Leveillula taurica in sweet pepper

The effects of several spray and climate treatments on Leveillula taurica were tested under controlled and commercial greenhouse conditions either alone or combined with a climate treatment. Ampelomyces quisqualis AQ10 inhibited the germination of conidia on leaves, but not on glass. Trichoderma harzianum T39 inhibited germination on both surfaces. Neither the examined biological control agents (BCAs) nor the two tested mineral oils (AddQ and JMS Stylet-Oil) affected the viability of conidia. Sulphur drastically limited the germination and viability of L. taurica. In experiments at 15–25°C, AQ10 alone reduced hyphal leaf colonisation at 25°C. T. harzianum T39 significantly reduced leaf colonisation at all temperatures but significantly reduced disease only at 20–25°C. The oils significantly reduced leaf colonisation and sulphur reduced both leaf colonisation and disease at all temperatures. Results were confirmed in an experimental greenhouse. In a field experiment, azoxystrobin, polyoxin AL, neem extract, and T39 were effective; sulphur was superior to them. Under severe epidemic conditions the disease had a negative impact on yield; late fungicide treatments at spring-time were found unnecessary. Chemical sprays applied in alternation was compared with the ‘friendly’ spray regime (alternation of Heliosoufre, T. harzianum T39 + JMS Stylet oil, A. quisqualis AQ10+AddQ oil and Neemgard) in two climates i.e. (i.) day warm climate and (ii.) regular (cool) day climate regimes. In the warm climate, there was no significant difference in the performance of the ‘friendly’ spray regime and the chemical spray regime. However, in the cooler climate, the ‘friendly’ spray programme was not as effective as the chemical spray programme. It was concluded that a change in the greenhouse climate may affect the development of powdery mildew and, at the same time, promote the activity of BCAs and render a pathogen more vulnerable to these control agents, allowing for better disease suppression.     

Predicting Avena spp. control with clodinafop

Previous analyses of two independent data sets, one generated by industry and the other involving purpose-designed field experiments, showed that the factors relating to Avena spp. control with clodinafop in Australia are fairly consistent. This article details the combination of those, together with additional new industry data, into an overall set that was subject to linear mixed model and covariate analyses for the purpose of developing a predictive model. Cross-validation methods were used to assess the potential for agronomic and environmental variables at the time of spraying clodinafop to predict Avena spp. mortality. The analyses showed that clodinafop dose, available soil moisture, cumulative minimum temperatures, maximum temperature on the day of spraying, spray water volume and the spray water volume by maximum temperature interaction at spraying were useful predictors and these were subsequently incorporated into a model. This model allows growers and agronomists to use knowledge of weather conditions on the day of application to tailor clodinafop dose and water volume accordingly, or to avoid spraying if they are adverse. The model's potential to improve herbicide efficiency and be used as part of a long-term Avena spp. management programme are briefly discussed.     

Movement of pesticides to surface waters from a heavy clay soil

A field experiment at Cockle Park, Northumberland on a clay loam soil (Dunkeswick series) cropped with winter wheat investigated the effects of drainage and season of application on pesticide movement. Isoproturon, mecoprop, fonofos and trifluralin were applied in two consecutive seasons at normal agricultural rates to three hydrologically isolated plots each of 0.25 ha. Two of the plots were mole-drained and the third was an undrained control. Surfacelayer flow and drainflow from each plot were monitored at 10-min intervals. Samples of flow were analysed for pesticides to evaluate transport of applied chemicals from the site. Despite widely differing properties (K_oc 20–8000 ml g^?1, t_1/2 10–60 days), all four pesticides were found in surface-layer flow and mole drainflow from the site. Maximum concentrations of pesticides in flow ranged from 0.1 to 121 μg litre^?1 (aqueous phase) and < 0.2 to 48 μg litre^?1 (particulate phase). Over two contrasting seasons, total losses of pesticides in flow followed total amounts of flow and were approximately four and five times larger, respectively, in 1990/91 than in 1989/90. The maximum loss occurred from the undrained plot and was 2.8 g isoproturon (0.45% of that applied). Total losses of autumn-applied pesticides from an undrained plot were up to four times greater than losses from a mole-drained plot. Mole drainage decreased movement of pesticides from this slowly permeable soil by reducing the amount of surfacelayer flow. Maximum concentrations of mecoprop and isoproturon in drainflow were 10–20 times larger following spring application than after application in autumn. Bypass flow down soil cracks was an important process by which pesticide was lost from the site, with transport to the drainage system via mole channels (55 cm depth) after less than 0.5 and 6.7 mm net drainage in the two winters.