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.     

Movement and rate of decomposition of ethoprophos in soil columns under field conditions

The rates of degradation and downward movement of ethoprophos (O-ethyl SS-dipropyl phosphorodithioate) were measured under field conditions in four soils in aluminium columns (40 cm long). A 10% granular formulation was incorporated in the top 10 cm at a rate of 10.0–10.5 kg a.i./ha. Under outdoor conditions during spring and summer, loss of ethoprophos approximated to first order kinetics; the half-life was about 87 days in a humic sand and a peaty sand, with pH values of 4.5 and 4.6, respectively. In a sandy loam and a loam soil with pH values of 7.2 and 7.3, respectively, the half-life ranged between 14 and 28 days. Under experimental conditions with fallow soils and 35.3 cm rainfall, the downward movement of substantial concentrations of ethoprophos by leaching and diffusion was restricted to a few centimetres.     

Lysimeter study to investigate the effect of rainfall patterns on leaching of isoproturon

The influence of five rainfall treatments on water and solute leaching through two contrasting soil types was investigated. Undisturbed lysimeters (diameter 0.25 m, length 0.5 m) from a sandy loam (Wick series) and a moderately structured clay loam (Hodnet series) received autumn applications of the radio-labelled pesticide isoproturon and bromide tracer. Target rainfall plus irrigation from the end of November 1997 to May 1998 ranged from drier to wetter than average (235 to 414 mm); monthly rainfall was varied according to a pre-selected pattern or kept constant (triplicate lysimeters per regime). Leachate was collected at intervals and concentrations of the solutes were determined. Total flow (0.27-0.94 pore volumes) and losses of bromide (3-80% of applied) increased with increasing inputs of water and were larger from the Wick sandy loam than from the Hodnet clay loam soil. Matrix flow appeared to be the main mechanism for transport of isoproturon through the Wick soil whereas there was a greater influence of preferential flow for the Hodnet lysimeters. The total leached load of isoproturon from the Wick lysimeters was 0.02-0.26% of that applied. There was no clear variation in transport processes between the rainfall treatments investigated for this soil and there was an approximately linear relationship (r2 = 0.81) between leached load and total flow. Losses of isoproturon from the Hodnet soil were 0.03-0.39% of applied and there was evidence of enhanced preferential flow in the driest and wettest treatments. Leaching of isoproturon was best described by an exponential relationship between load and total flow (r2 = 0.62). A 45% increase in flow between the two wettest treatments gave a 100% increase in leaching of isoproturon from the Wick soil. For the Hodnet lysimeters, a 35% increase in flow between the same treatments increased herbicide loss by 325%.     

Formulation affecting alachlor efficacy and persistence in sandy soils

BACKGROUND: The development of controlled‐release formulations of alachlor to extend the period of weed control was studied. This extended duration reduces the need for high herbicide application rates that could lead to environmental contamination. For this purpose, the influence of formulation, as well as the influence of soil characteristics, on alachlor efficacy and persistence in soil of a commercial formulation (CF) and different ethylcellulose microencapsulated formulations (MEFs) was evaluated. RESULTS: Higher alachlor rates yielded an enhanced initial herbicidal activity. The prolonged release of alachlor provided by the MEFs resulted in a higher herbicidal efficacy and a longer period of weed control compared with the effects of CF in the two soils tested (at 40 days after treatment, oat growth inhibition for CF and MEFs was 1.96% and 93.5% respectively). Soil characteristics strongly influenced alachlor efficacy and weed control by MEFs. The highest alachlor efficacy and persistence were observed in the soil with lowest microbial activity and clay and organic matter content. CONCLUSIONS: The use of MEFs can be advantageous because they permit the maintenance of the desired concentration of the herbicide in the soil for longer periods of weed control. Copyright © 2009 Society of Chemical Industry     

土壤环境因子对毒死蜱两种剂型持效性的影响

以暗黑鳃金龟Holotrichia parallela幼虫为生物试材,研究了含水量、温度和泥炭质量分数3种土壤环境因子对毒死蜱30%微囊悬浮剂(CS)和30%乳油(EC)持效性的影响。结果显示:在相同土壤介质环境下,毒死蜱乳油的持效期随土壤含水量的提高而缩短,同时土壤含水量的提高减缓了微囊悬浮剂囊内有效成分的释放;在土壤中其他影响因子相同时,土壤温度越高,毒死蜱微囊悬浮剂和乳油的持效期越短;土壤中的泥炭对毒死蜱的吸附作用使得其对暗黑鳃金龟幼虫的初始毒力降低,同时也延长了毒死蜱在土壤中的持效期。对于3种土壤环境因子的不同处理,除泥炭质量分数为1.0%的处理中毒死蜱微囊悬浮剂和乳油对暗黑鳃金龟幼虫的持效性相差不大外,其他各处理中毒死蜱微囊悬浮剂的持效性均优于乳油。     

Activity,adsorption, mobility and field persistence of sulfosulfuron in soil

Petri dish bioassays, based on root response of corn grown in soil or in perlite, were used to study the activity, adsorption, mobility and field persistence of sulfosulfuron in a silty clay loam and a sandy loam soil. Both bioassays indicated that activity of sulfosulfuron increased with increasing herbicide concentration, and to a slightly greater degree in sandy loam soil than in silty clay loam soil. More sulfosulfuron was adsorbed on the sandy loam (not biologically available) than on the silty clay loam soil. Consequently, slightly greater amounts of sulfosulfuron were leached through the silty clay loam than through the sandy loam soil. Biologically available sulfosulfuron was not detected at depths below 40 cm after application in sandy loam, but this was not the case for the silty clay loam soil. In 2002, all sulfosulfuron rates showed field persistence of less than 5 months. On the other hand, in 2003, biologically available sulfosulfuron was detected in the 0–10-cm soil depth 150 days after application. http://www.phytoparasitica.org posting May 6, 2004.     

Leaching of pesticides and a bromide tracer through lysimeters from five contrasting soils

In each of two seasons, undisturbed lysimeters 0.8 m in diameter and 1.05 m in length taken from five soil types were cropped with winter wheat. They received autumn applications of the pesticides isoproturon and linuron as well as a bromide tracer and spring applications of dimethoate and MCPA. Leachate was collected at regular intervals and concentrations of the various solutes determined. Rainfall from December to March was 290 and 191 mm in the first and second seasons, respectively. Both springs were exceptionally dry with less than 50% of the mean April‐to‐June rainfall of 138 mm. Total flow from the lysimeters ranged from 335 to 477 mm (and from 0.78 to 3.95 pore volumes) over the two seasons. Leaching to drainage of bromide highlighted soils where preferential flow was influential with total losses ranging from 24% of applied for a strongly structured, alluvial clay loam to 79% for an unstructured sand. Leaching to drainage of isoproturon (K_oc ≈ 100 ml g⁻¹) was observed from all but a peat soil with losses greater (0.31–1.01% of applied) from the clay loam and a deep medium loam, where patterns of leaching clearly indicated preferential flow mechanisms, than from the sand and a light loam over gravel (0.04–0.18% of applied) where a broad breakthrough curve indicated that matrix flow was more important. Linuron (K_oc ≈ 500 ml g⁻¹) was detected in occasional samples of leachate from the clay loam, the light loam over gravel and the medium loam during the first season only (maximum loss 0.12% of applied). The sandy soil, often considered most vulnerable to leaching, gave the smallest total losses of pesticide of the four mineral soils, whilst significant preferential flow in the deep, medium loam was believed to result from a compacted topsoil. Neither of the spring‐applied pesticides was detected in the leachate, as flow following application was very small and relatively slow. © 2000 Society of Chemical Industry     

Evaluation of the bioefficacy and leaching of a controlled–release formulation of chlorsulfuron

A controlled–release formulation of chlorsulfuron (DT26B) and a conventional granular formulation were compared for their initial bioefficacy and leaching in laboratory and field experiments. Three alkaline soil types, representative of farm soils in SE Australia, were used for these experiments. Laboratory tests of initial bioefficacy using a Mallee sand (pH 7.2) were able to detect, within ED_05–95 limits, that approximately 50% of active ingredient remained as a non–available reserve in DT26B immediately after spraying, when compared with the granular formation. There was also an indication that the bioavailable component of active ingredient in DT26B would be sufficient for weed control. This was confirmed at field sites on a Kattyoong sand (pH 7.9) and a Wimmera Grey clay (pH 8.4), after using recommended application rates of chlorsulfuron during the 1994 winter growing season. The formulations produced only marginal differences in control of Lolium rigidum Gaud. The field leaching trials at these sites showed that there can be rapid leaching of chlorsulfuron with only small amounts of rainfall. Under these conditions, there was an overall trend of reduced leaching by DT26B at both trial sites, although these reductions were not significant when compared with the granular formation, A laboratory system designed to measure the mobility of herbicides is described. It was used to impose upon each formulation a greater level of leaching than in the field trials, using Mallee sand columns irrigated with 50 mm day^–1 under –50 kPa suction. This test revealed a negligible reduction in leaching of chlorsulfuron by DT26B as compared with the granular formulation. Therefore, although the controlled–release formulation DT26B demonstrated that it could provide a viable alternative for weed control under conventional spraying conditions in arable farming, the agricultural usage of DT26B for the purpose of reducing leaching could not be warranted at its current stage of development.     

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     

阿维菌素乳油和微囊悬浮剂的光解及其在土壤和小麦中的消解动态

通过光解动态研究、土壤消解试验和小麦种皮消解试验,研究了1.8%阿维菌素乳油和2%阿维菌素微囊悬浮剂在3种不同环境下的光解及消解动力学。结果表明:阿维菌素乳油与微囊悬浮剂在3种环境中的消解均符合一级反应动力学规律;微囊悬浮剂抗光解能力强,光化学分解缓慢,而乳油则在紫外光下分解较快;5、20 mg/kg的阿维菌素微囊悬浮剂和乳油在土壤中的消解半衰期分别为88.86、157.52 d和22.14、82.51 d。阿维菌素微囊悬浮剂在小麦种皮上的残留量明显高于乳油,有较长的持效期。     

Persistence and mobility of tebufenozide in forest litter and soil ecosystems under field and laboratory conditions

A field microcosm study was conducted to determine persistence of tebufenozide, an insect growth regulator, in sandy litter and soil. Litter and soil plots (c. 4·5 m² each) were sprayed with an aqueous suspension concentrate formulation of tebufenozide at rates of 35, 70 and 140 g AI ha^-1. Samples were collected at intervals up to 408 days after spraying, and analyzed for tebufenozide residues. The data were subjected to regression analysis and half-life (DT₅₀, the time required for 50% of the initial residues to disappear) values were computed. The DT₅₀ was c. 62 days for both substrates treated with the two lower dosage rates. At the highest dosage rate, the DT₅₀ was 115 days for the litter and c. 52 days for the soil, indicating irregular variations in persistence. Downward movement in soil occurred only in trace amounts, suggesting strong adsorption. Laboratory microcosm studies were conducted to investigate the relative importance of rainfall, exposure to light and volatilization on persistence. Vertical movement occurred in litter and soil (both sandy and clay types) during rainfall. The amount moved increased with the amount of rainfall, but decreased with the rain-free period. The larger the rain droplets, the greater the downward movement. When the rainwater could move laterally along the surface of the substrate (as would occur on a slope), more lateral movement than vertical movement of tebufenozide occurred. The photolysis study indicated that disappearance of tebufenozide was directly related to the duration of exposure to radiation and radiation intensity. Volatilization of tebufenozide depended upon the ambient temperature and the duration of air passing through the substrates. Nonetheless, the amount lost by volatilization was much lower than the amount lost after rainfall or exposure to radiation, thus indicating the greater influence of rainfall and sunlight on persistence. In the laboratory microcosm studies, more tebufenozide was lost from the sandy substrates than from the clay substrates. This behaviour was attributed to the greater adsorptive capacity of the clay substrates, thus providing a greater protection against downward mobility and loss due to radiation. © 1997 SCI     

Combined effects of termiticides and mechanical stress on chlorinated polyvinyl chloride (CPVC) pipe

BACKGROUND: CPVC pipe failures have recently been reported beneath structures as a result of termiticide soil treatments. To determine whether these CPVC failures were actually caused by termiticides, CPVC tubes were filled with 50 mL of either termiticide concentrate, dilutions or treated builder's sand and sealed. Mechanical stress was added to these sealed tubes by hanging bricks from their ends.RESULTS: As concentrates, eight of nine emulsifiable concentrates tested caused failure within 8 weeks. None of the three suspensible concentrates tested caused failure over this period. Dilution of emulsifiable concentrates caused progressively fewer CPVC tube failures. No treated soils caused tube failures. Excessive CPVC glue applications in combination with chlorpyrifos 440 g kg(-1) EC (Dursban(trade mark) TC) degraded the CPVC. All volatile organic compounds (VOCs) found in the termiticide formulations caused CPVC tube failure within 1 week as pure chemicals. The VOC 1,3,5-trimethylbenzene caused CPVC tube failure within minutes of exposure. This VOC was found in all termiticides that caused failures as concentrates.CONCLUSION: It is highly improbable that a properly conducted preconstruction soil treatment, where termiticide is completely adsorbed to the soil, would be solely responsible for CPVC pipe failure. Manufacturers should consider removing 1,3,5-trimethylbenzene from termiticide formulations to minimize the risk of CPVC pipe failure.     

Sulcotrione soil persistence and mobility in summer maize and winter wheat crops

Sulcotrione soil persistence in spring maize ( Zea mays L.) crops grown on a sandy loam soil was greater at pH 5·5 and 6·0 (soil half-life T _1/2≈58 days) than at pH 7·1 ( T _1/2 = 44 days). Sulcotrione was also applied as recommended on a summer maize crop at the five- to six-leaf growth stage, grown on a sandy loam soil. Sulcotrione soil half-life was 44 days, and the herbicide remained mainly in the 0- to 5-cm surface soil layer during the cropping period, in spite of the high water solubility and the heavy rains at the end of August; lower sulcotrione concentrations (10–18% of the total during the 2-month period after sulcotrione application) were detected in the 5- to 10-cm surface soil layer. The herbicide was applied pre-emergence to winter wheat ( Triticum aestivum L.) at four sites that differed in their soil texture and composition: loamy sand, sandy loam, loam and clay loam. Persistence was greater in the soils containing more organic matter. In soils having similar organic matter contents, persistence was lower in the soil containing more sand relative to loam and clay. During the winter crops, sulcotrione moved down to the 10- to 15-cm soil layer, in spite of the fact that the rains were lower in winter than in summer. Sulcotrione most generally was not detected in the 15–20 cm soil layer of the maize and winter wheat crops.     

静电自组装法制备阿维菌素纳米囊悬浮剂及其对黄瓜根结线虫病的防治效果

为提高阿维菌素在土壤中的移动扩散能力,改善其对作物根结线虫病的防治效果,采用静电自组装法制备了3%阿维菌素纳米囊悬浮剂,测定了其贮存稳定性和释放性能,并通过土壤淋溶试验与土壤薄层层析试验评价了其在土壤中的移动性,验证了其对南方根结线虫Meloidogyne incognita 2龄幼虫(J₂)的室内毒力和田间防治效果。结果显示：阿维菌素纳米囊为球形,平均粒径(D₅₀)为276.81 nm,在释放液中,60 min时纳米囊悬浮剂中阿维菌素的累积释放率为57.59%,而对照乳油制剂中阿维菌素的累积释放率为94.53%。阿维菌素纳米囊悬浮剂在土壤中横向和纵向的移动距离均明显大于阿维菌素乳油,二者对根结线虫J₂在24 h时的LC₅₀值分别为0.257与0.427 mg/L。田间试验中,相同用量下分别采用漫灌法与混土法两种方式施药,药后60 d,3%阿维菌素纳米囊悬浮剂处理比3%阿维菌素乳油处理的防治效果分别高21.82%与4.81%;而药后100 d,前者比后者分别高28.98%与19.79%。表明将阿维菌...     

Movement and conversion of aldicarb and its oxidation products in potato fields

In Spring, the insecticide and nematicide aldicarb in the granular formulation Temik 10G (supplied by Union Carbide) was broadcast on three potato fields and incorporated by rotary cultivation. Ridges were formed by repeated runs with ridging implements. The soil was sampled in layers of 0.1 m up to 0.8 m depth three to four times during the growing season. Aldicarb itself was almost completely converted on a humic sand soil and two loam soils within one month. During the growing season, its sulphoxide and sulphone, which are toxic and are formed by oxidation, were retained mainly in the top 0.3 m of all three soils. Relatively high concentrations were measured only in the top 0.2 m, indicating limited redistribution by leaching.Low to very low contents were found up to 0.8 m depth especially on one of the loam soils where the highest total rainfall was measured from May to October (328 mm). In a humic sand soil, leaching in the furrow was deepter than below the ridge. At the end of the growing season, the sulphoxide plus sulphone corresponded to a mass fraction of 5.7 to 6.7% of the dosage in the two loam soils and to 17% in the humic sand soil. These residues were mainly concentrated in the centre of the ridges.Samenvatting In het voorjaar werd op drie aardappelvelden het insecticide en nematicide aldicarb als Temik 10G breedwerpig toegediend en met een frees ingewerkt. Ruggen werden opgebouwd door herhaalde bewerkingen met aanaardwerktuigen. Gedurende het groeiseizoen werd de grond drie tot viermaal bemonsterd in laagjes van 0,1 m tot op 0,8 m diepte. Aldicarb zelf was binnen een maand bijna geheel omgezet zowel in een humeuze zandgrond als in twee zavelgronden. Gedurende het groeiseizoen bleven het sulfoxide en het sulfon, welke produkten eveneens toxisch zijn en door oxidatie van aldicarb worden gevormd, voornamelijk in de toplaag van 0,3 m bij alle drie gronden. Relatief hoge concentraties werden alleen gemeten in de bovenste 0,2 m, wat wijst op een beperkte herverdeling door uitspoeling.Lage tot zeer lage gehalten werden tot 0,8 m diepte gevonden, met name in één van de zavelgronden waar ook de grootste hoeveelheid neerslag van mei tot oktober (328 mm) werd gemeten. In een humeuze zandgrond was de uitspoeling in de voor groter dan die beneden de rug. Aan het eind van het groeiseizoen kwam de hoeveelheid resterend sulfoxide plus sulfon in de twee zavelgronden overeen met een massafractie van 5,7 tot 6,7% van de dosering en in de humeuze zandgrond met 17%. Deze residuen waren voor het grootste deel geconcentreerd in het centrum van de ruggen.     

Some aspects of tri-allate volatility

The volatility of tri-allate from different formulations when mixed with 2 soils containing water at 2%, 6% and field capacity was estimated in the laboratory. Volatility increased with increasing water content in each case. It was generally highest from an emulsifiable concentrate and lowest from a granule formulation with that from unformulated tri-atlate intermediate. In a greenhouse experiment rates of loss of tri-allate from a dry soil were similar for both emulsifiable concentrate and granule formulations, but from a wet soil and an aluminium foil dish losses were much greater from the emulsifiable concentrate. The persistence of trii-allate from granules applied in the field was virtually the same for granules containing 2.5, 5 or 10% active ingredient.     

Factors affecting the performance of granular insecticides applied to field beans

Factors influencing the performance of various granular formulations of disulfoton and phorate after foliar application to field beans were investigated by bioassay in controlled environment rooms. Frequent rainfall and high temperature increased activity considerably but humidity had little effect. With disulfoton formulation on pumice rather than fuller's earth, and toxicant concentrations of 7.5% rather than 10% increased toxicity, but effects of formulation were small with phorate. The influence of rainfall and formulation were confirmed in a field experiment. There was evidence for an initial fumigant effect, particularly for phorate, in both laboratory and field experiments. The detailed effects of the various factors at different intervals after applying the granules are discussed in relation to the physical properties of the insecticides and granular carriers. It is suggested that the possibilities of controlling performance by influencing release rates from granules are limited for chemicals such as phorate and disulfoton which are appreciably adsorbed by soil.     

吡虫啉在土壤中的稳定性及其在白蚁防治中应用探讨

为了明确吡虫啉对白蚁的持效性,研究了室内与野外模拟施工条件下降解半衰期。室内研究发现,在壤土中,吡虫啉初设浓度分别为20、50mg／kg其降解半衰期分别为157．5、198．0d;在砂壤土中,吡虫啉初设浓度分别为20、50mg／kg其降解半衰期分别为187．3、433．1d。同一初设浓度下,吡虫啉在壤土中比在砂壤土中降解得快。在同一种质地土壤中,浓度高者其降解半衰期相应变长。在野外试验中,初设浓度分别为0．05％、0．1％、0．15％,在0～5cm层土壤中吡虫啉的降解半衰期分别为123．8、130．8和133．4d：在5～10cm层分别为216．6、210．0和216．6d。这与建筑物预防15年的要求差距相差甚远。建议实际施工中要注意跟踪补施。     

Leaching of Alachlor from Alginate-Encapsulated Controlled-Release Formulations

The mobility of alachlor from alginate-encapsulated controlled-release (CR) formulations was investigated in two contrasting soil profiles. Two CR formulations of alachlor were prepared with the following components (1) base—sodium alginate+kaolin+‘Tween’ 20 (1+10+0·5 by mass) and (2) base+40 g kg⁻¹ linseed oil. These were compared to technical grade alachlor and to a commercial alachlor EC formulation (‘Lasso’ 4EC). All herbicide treatments were labeled with [¹⁴C]alachlor and were applied to duplicate soil columns that were composed of a surface and a subsoil horizon. Each horizon was packed to a depth of 12·5 cm, giving a total column length of 25 cm. The columns were leached with 21 cm (420 ml) to 30 cm (600 ml) of 0·01M calcium chloride for a period of 7 to 10 days. Alachlor leaching from the EC formulations was the same as that from the technical material in both soils: 33% in the Evesboro and 10% in the Conover soil. The CR-Oil formulation leached 4 and 2% of the applied [¹⁴C]alachlor, compared to 12 and 3% for the CR-N formulation for the Evesboro and Conover soils, respectively. The CR-Oil formulation also increased the amount of [¹⁴C]alachlor retained in the soil surface horizon (105–114%), compared to CR-N (39–45%), technical material (14–23%) and EC (12–17%).     

Droplet Dynamics and Initial Field Tests for Microencapsulated Pesticide Formulations Applied at Ultra Low Volume Using Rotary Atomisers for Control of Locusts and Grasshoppers

The physical properties and field efficacy of microencapsulated acridicides (ME) were investigated to determine their suitability for application at Ultra Low Volume (ULV) rates in Sahelian conditions. Microcapsules were not damaged during application using Micronair AU7000 rotary atomisers. Drop size was dependent upon microcapsule size, smaller microcapsules tending to form dense aggregates within large droplets. The aggregation effect was counteracted by larger microcapsule sizes and by dilution of the concentrated formulation. There was a tendency for microcapsules to land dry at increasing distances from the point of application and at high temperatures and low humidities. In the field in Mali (W. Africa) diluted ME formulations were found to be suitable for ULV application by Berthoud C8 hand-held sprayers, vehicle-mounted Micronair AU7000 pest control kits and helicopter-mounted Beecomist rotary atomisers. ME formulations of fenitrothion, chlorpyriphos and diazinon all suppressed grasshopper populations in annual grassland and were as effective as fenitrothion applied at the standard ULV rate. The spatially heterogeneous and shifting nature of the grasshopper populations prevented the relative efficacy or persistence of the different products to be quantified and the potential for reduced environmental impact could not be tested.