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Despite the fact that several cases of unsafe pesticide use among farmers in different parts of Africa have been documented, there is limited evidence regarding which specific interventions are effective in reducing pesticide exposure and associated risks to human health and ecology. The overall goal of the African Pesticide Intervention Project (APsent) study is to better understand ongoing research and public health activities related to interventions in Africa through the implementation of suitable target-specific situations or use contexts. A systematic review of the scientific literature on pesticide intervention studies with a focus on Africa was conducted. This was followed by a qualitative survey among stakeholders involved in pesticide research or management in the African region to learn about barriers to and promoters of successful interventions. The project was concluded with an international workshop in November 2021, where a broad range of topics relevant to occupational and environmental health risks were discussed such as acute poisoning, street pesticides, switching to alternatives, or disposal of empty pesticide containers. Key areas of improvement identified were training on pesticide usage techniques, research on the effectiveness of interventions targeted at exposure reduction and/or behavioral changes, awareness raising, implementation of adequate policies, and enforcement of regulations and processes.

Summary Background Pesticides present widespread risks to human and environmental health, yet selection criteria for end-users that factor in differences in risk between compounds are scant. We developed a system to classify pesticide risks and hazards with respect to human and environmental health and produce a minimum (lower risk) pesticide list. Methods We classified 659 pesticides by acute and chronic risks to human health (eg, respiratory and carcinogenic effects) and by environmental risks, including biomagnification and atmospheric ozone depletion and risks to aquatic life, terrestrial wildlife, and pollinators. From this analysis, we produced a guideline for selection of lower risk pesticides. The classification of highly hazardous and high-risk compounds has been tested in more than a million farm households in the tropics, and in US integrated pest management (IPM) programmes. The full classification, including the minimum pesticide list, has been used in management of the fall armyworm (Spodoptera frugiperda) throughout Africa and Asia. Findings Our analysis developed a stand-alone guideline for selection of lower risk pesticides. When classifying pesticides in current use against the fall armyworm in Africa, our guideline identified chemicals that are effective and of lower risk to human and environmental health. We argue that a minimum (lower risk) pesticides list, which meets IPM needs, could be developed from our classification system. Interpretation As far as we are aware, our analysis is the first to propose a method for implementing the idea of a minimum pesticide list and the first to outline lower risk candidate compounds. Currently accepted criteria for defining highly hazardous pesticides do not adequately protect human bystanders, aquatic life, terrestrial wildlife, and pollinators. Funding The Sustainable Agriculture Network, the Rainforest Alliance, the US Department of Agriculture-National Institute of Food and Agriculture, the US Department of Agriculture, the Foreign Agricultural Service, the US Agency for International Development, the International Maize and Wheat Improvement Center, and the UN Food and Agriculture Organization.

Pesticides present widespread risks to human health, and they contribute to global biodiversity decline. Information on the relative risks posed by pesticides is difficult to obtain, and we lack procedures for pesticide selection that factor in the differences in risk between compounds. This is perpetuating problems that require urgent solution. We have classified more than 700 pesticides by acute and chronic human health risk, environmental risk including bio-magnification and atmospheric ozone depletion, and risks to aquatic life, terrestrial wildlife, and pollinators. Our analysis is presented as a guideline that can be used to encourage selection of lower risk pesticides. It also demonstrates that currently accepted criteria for defining highly hazardous pesticides fail to adequately protect human bystanders, aquatic life, terrestrial wildlife, and pollinators. When used to classify pesticides in current use against the fall armyworm, an invasive pest that is attacking maize crops in Africa, our guideline identifies effective lower-risk chemicals. This risk and hazard-based classification system has been field tested among more than a million farm households in the tropics, and in IPM programs in the United States and Africa, with success. We have isolated a lower-risk group of pesticides, from which a minimum list could be developed in order to meet most IPM needs, while limiting risks to human and environmental health. Our analysis is the first to propose a methodology to develop and refine this concept, and the first to outline candidate compounds since the minimum list was proposed through the Lancet in 2002. Funding Statement: Funding was provided by the Sustainable Agriculture Network, Rainforest Alliance, United States Department of Agriculture (USDA) National Institute of Food and Agriculture, USDA Foreign Agriculture Service, the International Maize and Wheat Improvement Center, and the UN Food and Agriculture Organization. Funding for the international review process for HHPs, pesticides requiring risk mitigation, and mitigation methods was provided by the Sustainable Agriculture Network (SAN) and Rainforest Alliance. Development and use of this classification system in the Western USA was supported by a United States Department of Agriculture Western Sustainable Agriculture Research and Extension Professional Development Program (USDA WSARE PDP) grant EW17-019, and USDA National Institute of Food and Agriculture Crop Protection and Pest Management Extension IPM Program (NIFA CPPM EIP) grant 2017-70006-27154, and a USDA NIFA CPPM Western IPM Center (WIPMC) Signature Program Sub-award SA18-4060-01 to PCJ and KM; and a USDA NIFA CPPM Applied Research and Development (ARDP) grant 2016-70006-25868 to KM. Drafting of this publication, development of the low risk (minimum) pesticide classification, and determination of PPE requirements was supported by a USDA Foreign Agriculture Service (FAS) Agreement (FX18TA- 10960R021) to PCJ, which also funded the African case study, with additional support from the International Maize and Wheat Improvement Center (CIMMYT) and the UN Food and Agriculture Organization (FAO) to PCJ. Declaration of Interests: The authors state that they do not have conflicts of interest to declare. Ethics Approval Statement: Not required.

National Institute of Food and Agriculture, U.S. Department of Agriculture [2012-51120-20087, 2014-70006-22629, 2015-34383-23709]

Purpose: This paper examines the benefits of using an outcome-based education (OBE) method within agricultural extension outreach programmes for professional and farmer audiences. Design/Methodology/Approach: The method is elaborated through two practical examples, which show that focused, short-duration programmes can produce meaningful skill development and impacts at the farm level. Both examples addressed pressing problems that were evolving during the education programme, and we sought a method that would respond adaptively to local circumstances and unanticipated changes. Key aspects of the method include strategic planning to properly focus education programmes, and the integration of data-driven decision support tool development to reduce uncertainty associated with the use of high-risk pest management inputs. Findings: Professionals and farmers increased their knowledge and skills related to pesticide management, and follow-up evaluation documented high levels of adoption of risk reductio...

The ability to predict patterns of species dispersal across habitat edges takes on increasing conservation relevance as land-scapes become more fragmented. We assessed edge responses for four ground-dwelling arthropod taxa by measuring their distribution and movement patterns across a forest edge associated with a forested riparian buffer and an adjacent upslope clearcut at a single site. We used Spatial Analysis by Distance Indices to describe the spatial distribution of arthropods, habitat variables, and the associations between them across a 49 × 63 m pitfall trapping grid with 80 trapping stations. We used mark-release-recapture techniques to measure the distance, rate, and direction of arthropod movement within and between habitat types. Scaphinotus angusticollis (Coleoptera; Carabidae) was restricted to the cool, moist portion of the riparian buffer and was not observed to cross the forest edge. The carabids Pterostichus lattini and Scaphinotus marginatus had more eurytopic distributions ac...

BACKGROUND: Chemical dissipation and organism immigration are considered important factors that influence recovery potential from perturbation of aquatic macroinvertebrates. Experiments were conducted to investigate the effect of simulated immigration on recovery of aquatic macroinvertebrates exposed in outdoor microcosms to ecotoxicologically similar concentrations of the rapidly dissipating pyrethroid insecticide cypermethrin (70 ng L−1) or the more persistent herbicide intermediate and degradate 3,4-dichloroaniline (10 mg L−1). Microcosms were covered with light-permeable mesh to prevent recolonisation. Immigration was simulated by the regular addition of organisms after treatment. RESULTS: Microcosms exposed to 3,4-dichloroaniline treatment suffered substantial loss of taxon richness and by 10 months after treatment had only recovered where invertebrates had been added. Those treated with cypermethrin underwent an initial decline in certain crustacean and insect populations. These populations showed some signs of recovery over a period of 5 months through internal processes alone. However, rate of recovery was further enhanced where immigration was simulated, and in this case recovery had occurred around 100 days after treatment. CONCLUSION: Although not the only factors involved, simulated immigration and chemical fate clearly influence the ability of communities to recover from chemical exposure. Consideration of immigration processes and development of models will help to increase the realism of risk assessments. Copyright © 2009 Society of Chemical Industry

Procedures for the selection of species for ecotoxicological risk assessment of Bacillus thuringiensis (Bt) gene products in the epigeal and hypogeal environments are proposed. Although species can be selected on the basis of ecological realism and functional importance, the number of organisms requiring testing and the nature of the test procedures remain uncertain with such a selectively toxic material. The heterogeneity of the soil environment, the stratification of plant material at different stages of breakdown and decomposition and the aggregation and patterns of movement of the soil fauna and flora impose problems for the design of ecologically relevant test methods. Similarly, the impact upon beneficial invertebrates, if toxic effects are detected, will be mediated by the scale and pattern of transgenic plant release in the fragmented agricultural landscape. To properly assess the ecological risks posed by a widely released toxin with a narrow spectrum of effects, a combination of laboratory tests, field experiments and longer-term monitoring will be required.

An international initiative is developing a scientifically rigorous approach to evaluate the potential risks to nontarget arthropods (NTAs) posed by insect-resistant, genetically modified (IRGM) crops. It adapts the tiered approach to risk assessment that is used internationally within regulatory toxicology and environmental sciences. The approach focuses on the formulation and testing of clearly stated risk hypotheses, making maximum use of available data and using formal decision guidelines to progress between testing stages (or tiers). It is intended to provide guidance to regulatory agencies that are currently developing their own NTA risk assessment guidelines for IRGM crops and to help harmonize regulatory requirements between different countries and different regions of the world.

The use of insectary plants in agroecosystems to provide floral resources for enhancing natural enemy activity is an increasingly used practice, but candidate flowering plant species are not always screened for their attractiveness to key arthropods in the system being studied. In the work presented here, the relative attractiveness of four species of insectary plants to beneficial and pest insect species was assessed by observing the relative frequencies of flower visits to replicated blocks of the insectary flowers in two Oregon broccoli fields. The four plant species tested were alyssum (Lobularia maritima L. Desv.), coriander (Coriandrum sativa L.), buckwheat (Fagopyrum esculentum Moench), and phacelia (Phacelia tanacetifolia Benth.). Predatory hoverflies (Syrphidae) were identified to species, where possible, because of their previously observed importance as aphid predators in broccoli fields in the study area. The other beneficial insect groups observed were in the families Apidae, Coccine...

Previous work has shown that insecticide residual toxicity to arthropods on foliage varies strongly with leaf type. Although several aspects of leaf morphology could influence insecticide toxicity, the possible role of leaf waxes, which could influence bioavailability, has not previously been investigated. In this study, the influence of leaf wax cover on the residual toxicity of deltamethrin and dimethoate was investigated using the standard test arthropod Folsomia candida Willem (Collembola: Isotomidae) as a surrogate for soft-bodied leaf-dwelling insects. Sixteen leaf types were studied, representing a wide range of crop species. Deltamethrin efficacy increased with increasing leaf surface wax cover. No such relationship was observed, however, for the more polar insecticide dimethoate. Leaf surface roughness was examined using atomic force microscopy and was also observed to influence the efficacy of deltamethrin. The increased efficacy of deltamethrin may be attributed in part to the acquisit...

Summary 1. Dispersal parameters are critical for modelling spatially dynamic populations yet remain among the most difficult to quantify. Linyphiid spider aerial dispersal by ‘ballooning’ on silk threads is dependent on meteorological factors and amenable to analysis and quantification. 2. Spider aerial activity was measured during consecutive 10-min periods for up to 11 h a day. Aerial density was measured at four heights using sticky traps. The time intervals between successive flights were measured by observing spiders landing and taking-off. 3. Meteorological measurements (wind speeds and temperatures) were taken simultaneously with the collection of airborne spiders, and used to calculate Richardson numbers to estimate atmospheric turbulence. 4. Numbers of airborne spiders on any given day, and their vertical density profile on different days, were significantly correlated with Richardson numbers. 5. Single flight distances were modelled using estimates of ascent and descent rates, the vertical density profile of airborne spiders and the wind speeds they experience aloft. The distributions of single flight distances and the time spent between successive flights were combined in an alternating renewal process to model the number of flights and the total daily dispersal distances of ballooning spiders as a function of available dispersal time. 6. On a day with, for example, 6 h of suitable weather, linyphiid spiders can potentially disperse a mean distance of approximately 30 km downwind. 7. Synthesis and applications . We have developed a dispersal model of linyphiid spiders that is central to the further development of spatially dynamic population models of these spiders in agricultural landscapes. It could also be adapted for application to other wind-borne organisms. Such models have a key role in the future management of sustainable agricultural systems where natural predators are seen as major components of pest control.

This study investigated the extent to which aquatic plant and macroinvertebrate assemblages in small outdoor microcosms (cylinders 1.25-m diameter x 1.25 m deep) resembled assemblages found in natural ponds in Britain. Comparisons were made in terms of community structure, species richness, and numbers of uncommon species. Multivariate analysis indicated that, although the microcosms had no exact natural analogues, their plant and animal assemblages were most like those of deep, circumneutral ponds. Unlike natural ponds, the microcosms supported relatively species-poor invertebrate assemblages, lacking uncommon species. Among individual taxa, microcosms supported similar numbers of species of Gastropoda, Isopoda, Amphipoda, and Odonata as natural ponds but significantly fewer Coleoptera, Hemiptera, and Trichoptera species. This was most likely due to the absence of a shallow littoral area in the microcosms. Because of their vertical sides, the microcosms supported no marginal wetland plants, but submerged and floating-leaved plant assemblages were similar in community type and species richness to natural ponds. Refinements to microcosm and mesocosm designs are identified that would enable experimental systems to more closely replicate the assemblages found in natural ponds. In particular, the incorporation of natural margins would be likely to lead to experimental communities that were closer analogues of natural ponds.

Achieving food security in a ‘perfect storm’ scenario is a grand challenge for society. Unless 50% more food, 50% more energy and 30% more freshwater are available by 2030, a ‘perfect storm’ is envisaged where there would be simultaneous shortages of all of these on a global scale [[1][1]].

Summary 1 An experiment was conducted in a winter wheat field using yellow water traps at crop height and at ground level, near to and distant from flowers, to test the hypothesis that such traps are seen as a source of food by flower-feeding adult hoverflies and are therefore likely to selectively trap hungry individuals. Hoverflies caught in each trap were counted and identified and the amount of pollen in their guts was assessed. Ratios of numbers of hoverflies seen in the wheat crop to numbers caught in nearby traps were compared for the different treatments. 2 Most hoverflies were caught in crop-high traps but they included a high proportion of individuals with empty guts. The taxa were: Episyrphus balteatus (De Geer), Metasyrphus corollae (F.) (these species together accounted for over 90% of the individuals trapped), with Sphaerophoria spp., Syrphus spp., Scaeva pyrastri (L.), Melanostomini and unidentified others making up the rest. 3 Significantly fewer hoverflies were captured in low than in high traps. The ratios of numbers trapped to numbers observed, in flower and in no flower treatments would be expected to be the same if the traps were not selective. This was supported for low traps. With high traps, however, there was a highly significant difference between the ratios (71.34 and 126 : 8, respectively). 4 Flies captured in high traps had less pollen in their gut than those captured in low ones. At each distance, more E. balteatus captured in high traps were in pollen category 1 ( 5000 grains). Median pollen categories were 2 (21–200 grains) and 4 (1501–5000 grains) for flies caught in high and low traps, respectively. 5 The ecological selectivity of traps according to their height and the physiological condition of the targeted individuals is a problem likely to affect many trapping systems apart from the one described in this paper.

The morphological basis of sugarcane resistance to the sucking pest Pyrilla perpusilla was studied across a wide genetic range of sugarcane cultivars. The observed mean relative growth rate (MRGR) obtained by confining first and third instar nymphs onto leaves was compared with variation in leaf spine density, thickness of phloem fibre tissues and distance to the phloem from the epidermis. These characteristics were found to determine the growth of first instars (84.4% of the variance in growth rate explained) and third instars (32% variance explained) to a variable degree. The most important characteristics for the antibiotic resistance were spine density and thickness of the phloem fibre layer in the minor vascular bundle, which together determined up to 82.8% of the variance of MRGR in the first instar. The antibiotic resistance is described by a regression model.

Laboratory bioassays were carried out to determine the toxicity to Folsomia candida Willem (Collembola: Isotomidae) of residues of a pyrethroid insecticide, deltamethrin, and an organophosphorus insecticide, dimethoate, on different leaf surfaces. The test leaves included a range of species and leaves of different ages. Dose-response relationships were estimated for F candida walking over the various treated leaf substrates. Probit analysis was used to estimate the means and standard deviations of the associated tolerance distributions expressed as gAIha-1. Parallelism tests were undertaken to compare the susceptibilities of F candida to the two compounds applied to the different leaf surfaces. On deltamethrin-treated leaf surfaces, the LD50 values for F candida varied from 6.36 to 77.14 gAIha-1. F candida was least susceptible to deltamethrin residues when applied to leaves of dwarf bean (Phaseolus vulgarus L) and the highest susceptibility was observed following application to leaves of seedlings of barley (Hordeum vulgare L). In contrast, the LD50 values observed for dimethoate treatments did not differ significantly between leaf types, ranging from 1.35 to 8.69 gAIha-1. The laboratory data on susceptibility of F candida on different leaf types for different pesticides can be used to investigate the role of leaf surface properties in modifying the toxicity of applied pesticides to exposed invertebrates.

The recent increase in the incidence of deformities among natural frog populations has raised concern about the state of the environment and the possible impact of unidentified causative agents on the health of wildlife and human populations. An open workshop on Strategies for Assessing the Implications of Malformed Frogs for Environmental Health was convened on 4-5 December 1997 at the National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina. The purpose of the workshop was to share information among a multidisciplinary group with scientific interest and responsibility for human and environmental health at the federal and state level. Discussions highlighted possible causes and recent findings directly related to frog deformities and provided insight into problems and strategies applicable to continuing investigation in several areas. Possible causes of the deformities were evaluated in terms of diagnostics performed on field amphibians, biologic mechanisms that can lead to the types of malformations observed, and parallel laboratory and field studies. Hydrogeochemistry must be more integrated into environmental toxicology because of the pivotal role of the aquatic environment and the importance of fates and transport relative to any potential exposure. There is no indication of whether there may be a human health factor associated with the deformities. However, the possibility that causal agents may be waterborne indicates a need to identify the relevant factors and establish the relationship between environmental and human health in terms of hazard assessment.

We outline an approach to pesticide risk assessment that is based upon surveys of pesticide use throughout West Africa. We have developed and used new risk assessment models to provide, to our knowledge, the first detailed, geographically extensive, scientifically based analysis of pesticide risks for this region. Human health risks from dermal exposure to adults and children are severe enough in many crops to require long periods of up to three weeks when entry to fields should be restricted. This is impractical in terms of crop management, and regulatory action is needed to remove these pesticides from the marketplace. We also found widespread risks to terrestrial and aquatic wildlife throughout the region, and if these results were extrapolated to all similar irrigated perimeters in the Senegal and Niger River Basins, they suggest that pesticides could pose a significant threat to regional biodiversity. Our analyses are presented at the regional, national and village levels to promote regulatory advances but also local risk communication and management. Without progress in pesticide risk management, supported by participatory farmer education, West African agriculture provides a weak context for the sustainable intensification of agricultural production or for the adoption of new crop technologies.

The effects of pesticides on beneficial predatory arthropods have been widely studied; this paper however deals with their effects on Heteroptera, an important beneficial insect group and food source for farmland birds. Field trials were used to evaluate pesticide effects under realistic conditions of application on a commercial arable farm and compared with previously published laboratory findings. Fungicides were found to produce very low levels of mortality, not significantly different from control treatments. Aphicides varied in their impact, producing non-significant to highly significant mortality levels. The likely ecological impact of pesticides on various heteropteran groups found within the field and field boundary is discussed.

Dose rates of the pyrethroid insecticide deltamethrin were optimized for aphid control and the conservation of beneficial parasitoids in winter wheat. A logarithmic dose sprayer was used to apply concentrations ranging from twice the recommended field rate to a concentration representing one-fiftieth of the field rate. Volumetric analysis of colored dye deposits quantified the partitioning of pesticide through the crop canopy and was used to calculate direct exposure rates of aphid colonies and residue concentration on different plant structures contacted by foraging parasitoids. Aphid parasitoids, from the genus Aphidius, were found to be more at risk from exposure to insecticide residues than were their aphid hosts under the given bioassay conditions. However, the toxicity of deltamethrin residues on flag leaves was found to dissipate over a 5-d period after application. Deltamethrin provided significant aphid control at dose rates greater than 1 g a.i./ha (or at approximately one-sixth of the recommended field rate). At low concentrations of deltamethrin, aphids survived in the lower crop strata within low toxicity refuges. The implications of these refugia and the spatial redistribution of prey and host populations following spray application for the success of biological control agents are discussed.

Linyphiid spiders were sampled in three grass and four cereal fields, between October 1989-October 1990, and from one grass and one cereal field, from June-August 1991. Population growth and decline were characteristic of field type and pattern of management. Agricultural operations caused large population depletions: insecticide applications, cutting grass for silage and autumn cultivations reduced spider populations by 56% to 96%; heavy grazing caused virtual extinction. Aerial dispersal activity, monitored by water traps, showed high dispersal frequency with highest intensity in June, July and August. The results are discussed with reference to the large-scale spatial structure of linyphiid spider populations and the use of spatially dynamic models to predict metapopulation size as a function of patterns of crop management, land-use and landscape structure.

Laboratory bioassays were carried out to determine the toxicity of deltamethrin residues to the aphid parasitoid Aphidius rhopalosiphi DeStefani-Perez (Hymenoptera: Braconidae) on glass and foliar substrates. Residual toxicities were compared by iterating sequences of lethal dose ratios between LD10 and LD90 from the dose-response statistics for each substrate. The calculated mean ratios were termed ''toxicity factors'' (Tf). The Tf values indicated that the toxicity of deltamethrin residues on glass plates was 1.3 times greater than on cereal flag leaves. Parasitoid mortality was reduced by lowering the deltamethrin concentration and parasitoid exposure period. Individuals exposed to field concentrations for less than 1 h recovered when exposure ceased. Parasitoid emergence from hosts was reduced by deltamethrin at field concentrations; however, the fecundity of surviving females did not differ from controls. Deltamethrin applied at half rate had no effect on parasitoid emergence. Spray deposition on aphid mummies within a mature winter wheat canopy varied significantly with leaf position. Mummies located on awns and adaxial surfaces of flag leaves received the highest deposition rates, with the lowest levels recorded for mummies on stems and abaxial leaf surfaces. The low volumes of spray solution impinging upon mummies in the field indicated that current laboratory bioassays may overestimate pesticidal effects on developing parasitoids by between 3.4- and 266-fold.

The spatial and temporal effects of the pyrethroid insecticide, deltamethrin, on populations of cereal aphids and their primary parasitoids and hyperparasitoids were investigated in a large scale field experiment in winter wheat. Four hectare plots were treated at the recommended field concentration or a reduced concentration representing one twentieth of field rate. A control plot was left unsprayed. Invertebrate populations were sampled at sites within a grid layout covering the whole plots, enabling the use of geostatistical analysis. Hymenopteran populations were monitored using transparent sticky traps and suction sampling. Aphid populations were recorded by visual counts. Monitoring continued for 36 days after treatment. The full rate deltamethrin treatment resulted in initial reductions of aphid populations by 78%. Primary parasitoid and hyperparasitoid populations were reduced in suction samples by 90% and 47% respectively, when corrected for control fluctuations. The reduced deltamethrin concentration caused reductions of aphid, primary parasitoid and hyperparasitoid populations of 40, 60 and 54% respectively. Aphid population recovery over the full rate plot occurred slowly and in a ‘patchy’ manner following treatment. No significant reinvasion gradients were detected. Aphid population density recovered more rapidly in the reduced rate treatment; with initial evidence for increased densities at the plot centre. Significant patterns of reinvasion were initially detected for both groups of Hymenoptera in the full rate treatment, suggesting that reinvasion of the sprayed area was taking place from untreated surrounding reservoirs. It was concluded that experiments that examine pesticide impacts within small plots will lead to underestimates of effects on dispersive groups including parasitic Hymenoptera.

The deposition of spray applied through hydraulic flat fan pressure nozzles mounted on an Oxford precision sprayer and spinning disc Micromax atomisers were compared in wheat crops at a range of growth stages. The Micromax rotary atomisers when operating at a disc speed of 5000 r.p.m. (drop size VMD 80–90 μm) were found to be the most efficient at all the growth stages examined. The Micromax atomisers operating at 3500 r.p.m. disc speed (drop size VMD 130–140 μm) produced a similar spray deposition pattern to the flat fan nozzle although crop and ground deposits were lower up to GS59 with the Micromax atomisers. The pest control efficacy of the two nozzle types was evaluated in three aphicide trials on wheat crops. In the first two trials deltamethrin at one twentieth of the recommended dosage rate (6.25 g a.i. l −1 ) provided a similar degree of cereal aphid control to the applications at half the recommended dosage rate using both types of nozzle. In the third trial similar levels of aphid control were achieved using deltamethrin at one quarter of the recommended dosage rate applied using the rotary atomisers compared with one half of the recommended dosage rate using the flat fan nozzle. The impact of the deposition patterns on beneficial insects is discussed.

Risk assessment of pesticides for aquatic ecosystems is typically based on comparisons of exposure and effect concentrations at a variety of levels (tiers). At the highest tier, effects assessment can involve generating data under field conditions, typically in mesocosm experiments. However, interpreting the ecological significance of effects measured in these studies can be difficult because ecological factors can influence the outcome of perturbations in the real world. The influence of ecological factors is not readily addressed experimentally and so a strategic modelling approach is proposed which may aid in defining acceptability of effects.

The behaviour of Aphidius rhopalosiphi DeStefani-Perez (Hymenoptera: Braconidae) was recorded in laboratory bioassays in the presence and absence of both residues of honeydew from the English grain aphid, Sitobion avenae (F.) and the pyrethroid insecticide, deltamethrin. Insecticide concentrations ranged from the field recommended dose rate (6.25 g ai/ha in 200 l water) to 1/16th of field rate. Parasitoids responded strongly to patches of honeydew on filter papers, however the addition of increasing concentrations of deltamethrin caused increasingly early departure from the honeydew-treated areas. Parasitoids pre-exposed to field concentration residues for between 1 and 20 min showed shorter retention times and abnormal types of behaviour on honeydew-treated patches compared to control wasps. Recovery of ‘normal’ behaviour patterns occurred over a 12 h period away from the insecticide source. Further laboratory studies examined the foraging of A. rhopalosiphi and one of its associated hyperparasitoids, Dendrocerus carpenteri (Curtis), on mature wheat plants treated with an artificial honeydew solution and deltamethrin. Wasps exposed to deltamethrin residues were observed to spend shorter visit times, to groom more frequently and to rest less frequently than those on insecticide-free plants. Differences were found between the distribution of parasitoids on insecticide-treated and untreated plants, with D. carpenteri showing greater movement down insecticide-treated plants accompanied with an increase in time spent on abaxial leaf surfaces compared to A. rhopalosiphi. The results are discussed in terms of the repellency of deltamethrin and the implications for integrated pest management of differing sub-lethal insecticide effects on primary parasitoid and hyperparasitoid behaviour.

The opposing effects of attraction to host-derived kairomones and repellency from the pyrethroid insecticide deltamethrin were investigated with aphid parasitoids from the genus Aphidius (Hymenoptera: Aphidiinae). The spatial distribution of female parasitoids was recorded in a series of experiments conducted in a small glasshouse containing wheat plants either infested with cereal aphids, Sitobion avenae (F.) (Homoptera: Aphididae), uninfested or treated with the recommended field concentration of deltamethrin. The number of parasitoids per plant were counted at 0.5 h, 1 h and then at one hourly intervals up to 8 h after release. Parasitoids showed a strong aggregation response to aphid-infested plants compared to adjacent uninfested plants. With the introduction of insecticide-treated plants around the aphid-infested plants, parasitoids showed a greater tendency to disperse away, resulting in fewer parasitoids on plants and significantly lower rates of aphid parasitism. The degree of aphid fall-off from plants was a good indicator of parasitoid foraging activity. In field studies, using sticky traps to measure the activity of parasitoids in plots sprayed with water, deltamethrin and/or an artificial honeydew solution, repellent properties were evident for up to 2 days after application. The attraction/arrestment stimuli associated with the honeydew solution were sufficient for parasitoids to continue searching insecticide-treated areas. The implications of these findings for parasitoids searching crops contaminated with aphid-derived kairomones and insecticides are discussed.

The acute and chronic toxicities of three benzoylphenyl ureas, diflubenzuron, hexaflumuron and teflubenzuron were assessed under laboratory conditions against two-day-old second (II) instar Desert Locust, Schistocerca gregaria (Forskal) nymphs. Following exposure by ingestion of a single precise dose applied to short pieces of spring barley, nymphs were monitored for two moults until the fourth (IV) instar. Analysis of acute response data gave three significantly different LD 50 statistics (P < 0.05), 68.0, 26.6 and 0.71 μg per nymph respectively for diflubenzuron, hexaflumuron and teflubenzuron. The probit regression slopes also differed significantly, indicating distinct tolerance distributions for the three compounds, the narrowest response being to diflubenzuron and the widest range of response being to teflubenzuron. The timing of death was found to vary between the compounds ; most nymphs died during the first moult following treatment with either hexaflumuron or teflubenzuron. However, the majority of nymphs that died after exposure to diflubenzuron did so after completing the first moult after treatment, but before the second. The mean development times of nymphs during the II and especially third (III) instars were significantly longer (P < 0.05) than those of the controls following exposure to diflubenzuron and hexaflumuron. Teflubenzuron had no significant effect (P < 0.05) on the duration of the II instar. The potential of the three compounds to control S. gregaria populations in the field is discussed with particular reference to the timing and nature of acute and chronic responses.

Second-instar (II) nymphs of the Desert Locust, Schistocerca gregaria (Forsk.) were exposed to three benzoylphenyl ureas (BPUs), diflubenzuron, hexaflumuron and teflubenzuron. Nymphs were treated with precise doses by allowing them to ingest treated barley leaves at varying stages of the II instar. They were exposed to the same total quantity of active ingredient over one (Days 1, 2, 3 or 4), two (Days 1-2, 2-3 or 3-4) or four days (Days 1-4) of the four-day inter-moult period. The total amounts applied were 60 μg per nymph of diflubenzuron, 30 μg per nymph of hexaflumuron or 0.25 μg per nymph of teflubenzuron. The nymphs were then monitored for two moults after treatment until they reached the fourth (IV) instar, to observe both the acute and chronic effects of treatment. The timing of the exposure during the inter-moult period and the duration of exposure were both found to result in significantly different acute responses for each BPU. Treatment over one or two days showed that the closer to the moult II instars were treated, the greater the mortality. This indicated that locust pharate cuticle is predominantly synthesised late in the instar. Treatment over four days resulted in higher mortality than exposure to the same quantity of active ingredient over one or two days, suggesting that BPUs are highly toxic to locust nymphs but non-cumulative within their bodies. The timing of death was also significantly affected by both the timing and duration of treatment. A significant proportion of the mortality occurred after the first moult following treatment when nymphs were dosed on Day 1 and Day 2 with hexaflumuron and diflubenzuron respectively. Mortality following all other treatments occurred during the first moult after treatment. The duration of the II and third (III) instars were significantly prolonged in many cases following treatment with BPUs. The implications of increased mortality following prolonged exposure to BPUs and extended development periods are discussed in relation to the use of BPUs as barrier-sprayed insecticides for the control of mobile locust nymph populations.

Experiments were conducted in 1989 and 1990 to investigate the mechanism underlying patterns of invertebrate population recovery in winter wheat following treatment with the broad-spectrum insecticide dimethoate. Predation of Drosophila pupae and artificially induced aphid populations was monitored at different distances into plots treated with dimethoate. An initial drop in predation was recorded in all positions following treatment. Predation rate then showed a period of recovery, which progressed from the edge to the centre of the treated plots. This pattern of recovery corresponded to the numerical pattern of recovery of the predatory invertebrate groups; Carabidae, Staphylinidae and Linyphiidae. The results are discussed in terms of mechanisms to explain observed patterns of recovery of invertebrate 'prey' groups such as aphids. It is concluded that the ranking of pesticides by their toxicity alone would fail to take into account ecological processes that determine the different patterns of population change following treatment.

We consider ways in which laboratory-delived toxicity data might be used to predict the safety of insecticides to beneficial invertebrates. A model test system consisting of a predator, the convergent lady beetle, Hippodamia convergens Guerin-Meneville (larvae and adults); a parasitoid, Aphidills ervi Haliday; and the bee species Apis mellifera L., Megachile rotundata (F.), and Nomia melanden (Cockerell) was tested with diazinon, imidacloprid, and RH-7988 [ethyl (3- tert -butyl-1-dimethyl carbamoyl-1 H -1,24-triazol-5-ylthio) acetate]. We also tested the pea aphid, Acyrthosiphon pisllm (Harris), to calculate selectivity ratios for these beneficial species, which coexist with the aphid pest in Washington State pea and alfalfa ecosystems. Topical toxicity was estimated for all species and ranged 0.0002-0.45 micro grams per insect for diazinon, 0.000031-0.04 micro grams per insect for imidacloprid, and 0.0015-6.11 micro grams per insect for RH-7988. Selectivity ratios based on these values spanned 0.02-47.4, 12.9-1,290.3, and 13.3-4,073 for diazinon, imidacloprid, and RH-7988, respectively. Risk assessment indices based on probit substitution (estimate of mortality of beneficial species at LD90 for tile pest) and 2 standard methods for bees, a sequential testing scheme and a hazard index gave variable predictions of the compatibility of these compounds with integrated pest management. We conclude that predictive methods must advance to consider relative exposure rates to pesticides, aspects of chemical fate, and behavior of the organisms concerned if they are to be useful. Above all, predictions must be validated with field data.

The toxicity of the pyrethroid insecticide deltamethrin to a cereal aphid and a coccinellid beetle predator was assessed. Deltamethrin gave effective aphid control in winter wheat at dose-rates of 6.25, 3.13 and 1.56 g a.i./ha. The direct exposure of adult Coccinella septempunctata L. (Coleoptera: Coccinellidae) to spray drops was estimated at a range of positions in a cereal crop canopy from volumetric analysis of fluorescent tracer deposits. These measurements were used to calculate exposure to deltamethrin at the three experimental dose-rates. Observations of coccinellid beetle distribution through a cereal crop canopy permitted a realistic range of direct contact doses to be calculated and the toxic effects of these levels of exposure to be predicted from laboratory dose-response data. Estimated beetle mortalities from direct exposure were 19, 8 and 3% at the three experimental dose-rates. In situ bioassays with adult C. septempunctata which exposed beetles continuously to deltamethrin residues on flag leaves, resulted in 100, 94 and 39% mortality respectively at these dose-rates during the 10 days after spray application. Additional in situ bioassays exposed beetles to deltamethrin residues on flag leaves for 24 h and then transferred surviving beetles to the soil under the cereal crop canopy for a further 9 days. This resulted in 89, 69 and 29% beetle mortality respectively at the three dose-rates. Mortality predictions combining both direct contact and residual exposure were made for the three dose-rates to determine the maximum impact of summer sprays of deltamethrin on adult coccinellid populations in cereals. These worst case predictions suggested that a reduction in dose-rate by as much as three quarters of the recommended application rate in UK cereals may be necessary to preserve approximately 60% of adult C. septempunctata in the crop over the 10 days after a deltamethrin spray application. The methodology described may be appropriate for estimating selective dose-rates for key enemies in a range of crops.

Ergosterol biosynthesis-inhibiting fungicides have been found to synergize the toxicity of pyrethroid insecticides to the honeybee (Apis mellifera L.). The mechanism by which the fungicide prochloraz enhances the toxicity of the pyrethroid insecticide λ-cyhalothrin was investigated. In vitro incubations with honeybee midguts were used to study the metabolism of [14C]λ-cyhalothrin. The principal metabolite was identified as 4-hydroxy-3-phenoxybenzyl alcohol (4′-OH-3-PBAlc) with small amounts of 3-phenoxybenzoic acid (3-PBAc). Both are products of ester bond cleavage, but microsomal oxidation was implicated in the formation of 4′-OH-3-PBAlc. After treating midguts with prochloraz, metabolism was predominantly to 3-PBAc, with little formation of 4′-OH-3-PBAlc, strongly indicating an inhibition of microsomal monooxygenase activity. In vivo investigations showed the major metabolic products of [14C]λ-cyhalothrin extracted from frass of treated honeybees were 4′-OH-3-PBAlc, 2′-hydroxy-3-phenoxybenzyl alcohol, and 4′-hydroxy-3-phenoxybenzoic acid. However, when bees were simultaneously dosed with prochloraz, there was an absence of metabolites detected in the frass of bees for 16 hr post-treatment Thus, prochloraz delayed the metabolism, detoxication, and excretion of λ-cyhalothrin by inhibition of microsomal oxidation, effectively enhancing the toxicity of the pyrethroid to the honeybee.

A database analysis of pesticide impact upon entomophagous arthropods was undertaken to assist in risk analysis for chlorpyrifos, malathion, fenitrothion, deltamethrin and diflubenzuron when used as acridicides in the Sahel. Eight test methods were included in the analysis to give a comprehensive assessment of toxicity, recorded in both laboratory and field. Initial analysis of all taxa (100 family-pesticide combinations) showed diflubenzuron to be significantly less hazardous than the other insecticides. There was evidence that chlorpyrifos was less hazardous than other organophosphates and significantly less so, compared with deltamethrin. A three-stage toxicity classification was developed (1, >30% effect; 2, 30–90% effect and 3, >90% effect). When >50% of records were in toxicity class 3 or mean toxicity class exceeded 2.24, the chemical could be classified as significantly hazardous and possibly rejected for integrated pest management purposes or subjected to further testing. The toxicity class values are, however, not predictive and should be viewed as indicating the potential for harm. Once this potential has been established, relevant laboratory and field-based test methods will be required in the developing world.

The behaviour and distribution of adult Coccinella septempunctata L. (Coleoptera: Coccinellidae) were recorded in two plots of winter wheat infested with the cereal aphids Sitobion avenae (F.) and Metopolophium dirhodum (Walk.) (Homoptera: Aphididae). One plot was sprayed with the pyrethroid insecticide deltamethrin at a rate of 6.25 g a.i./ha and the other was left unsprayed. Single ladybird beetles were released sequentially on the ground at the centre of the sprayed and unsprayed plots and their behaviour and position in the crop canopy were recorded at 30 second intervals for a total of 15 min per beetle. Assessments, with fresh beetles, continued for four days after spray application with a total of eighty ladybird beetles observed. The 15 min period was selected to avoid lethal effects and no ladybird beetles were killed or knocked down as a result of exposure to deltamethrin residues during this period. Significant differences were found between the overall behaviour patterns of C. septempunctata in the untreated and deltamethrin treated plots up to three days after the spray application. Ladybird beetles exposed to deltamethrin residues were observed to walk and groom significantly more frequently and to rest significantly less frequently than those in the unsprayed plot. Significant differences were also found between the observed distribution of ladybird beetles in the sprayed and unsprayed crop canopies, with higher numbers of observations towards the bottom of the crop canopy and on the ground in the deltamethrin treated plot than in the untreated plot during the first two days after deltamethrin application. Upon the foliage itself, ladybird beetles were observed significantly more frequently on the abaxial leaf surface in the deltamethrin treated crop compared with the untreated crop. The results are discussed in terms of possible evidence for the repellency of deltamethrin to C. septempunctata and also the implications for integrated pest management of changes in predator behaviour and crop distribution resulting from sub-lethal uptake of insecticides.

The responses of female Aedes aegypti (Linnaeus) to a variety of stimuli were studied using an olfactometer bioassay. Mosquitoes responded significantly to convection currents produced by a human hand. The addition of water vapour to convection currents enhanced significantly the mosquitoes' response. Lactic acid, either alone or in combination with water vapour or/and convection currents however, did not increase the response level. Sweat extract elicited higher response than convection currents, water vapour and lactic acid. Human hands elicited significantly higher responses than any other stimuli. The presence of active chemicals other than lactic acid in human odour extract is discussed.

Barrier treatments of diflubenzuron were applied in advance of mobile hopper bands of Dociostaurus maroccanus in grassland and cereal crops in Morocco. Bands entering wheat and barley crops (69–120 tillers m −2 ; ear emergence stage), treated with diflubenzuron barriers (50 m deep) at a rate of 60 g a.i. ha −1 within the treated area, experienced high levels of mortality at subsequent moults. There was a significant positive correlation between the proportion of the treated groups moulting and the level of population decline; this did not occur in the control bands. Bands entering barrier treatments in cereals also demonstrated reduced rates of displacement compared with a control band and, although hopper densities remained similar to the control, the band area declined relative to the untreated population. A treatment on low-density annual grassland was less effective, possibly as a result of low vegetation density.

Pesticide applications were made to sparse, ephemeral grasses that supported a sedentary population of grasshoppers and locusts. Areas of 100 m × 100 m were sprayed with either diflubenzuron at 60 g a.i. ha−1 in 21 of diluent or with malathion at 600 g a.i. ha−1 in 0.5 of diluent, with three replicates of each treatment and unsprayed controls. Population assessments of nymphs and adults were made in 20 quadrats (each 1 m2) at the centre of each plot in a grid pattern. Age structure was monitored by taking sweep-net samples from around the edges of the plots. The malathion treatment showed a rapid and significant reduction of both nymphs and adults, followed by a slow recovery that started 10 days after spraying. The diflubenzuron treatment showed a slower decline in nymphal and adult numbers but the populations remained low from day 10 after spraying until the end of monitoring. Malathion- and diflubenzuron-treated nymphal populations differed significantly for the first 10 days after treatment (p 0.05) but diverged significantly from days 20 to 30. Adult populations were also reduced in both treatments but the effects were less because immigration into the plots by adults was observed at the end of the trial. The potential uses and limitations of diflubenzuron as a blanket insecticide against sedentary locust and grasshopper populations are discussed.

Batches of adult Nebria brevicollis (F.) (Coleoptera: Carabidae) were provided with freeze-killed aphids, Metopolophium dirhodum (Walk.) (Homoptera: Aphididae), that had been treated topically with 30 ng a.i. deltamethrin. Beetles in different hunger states were found to consume contaminated aphids, but they consumed significantly fewer aphids than control beetles. The mean numbers of contaminated aphids eaten increased with hunger-level, from 2.5 aphids per beetle for those provided with food 24 h before exposure, to 4.5 aphids per beetle for those provided with food 120 h prior to exposure. The highest mortality that occurred over the following six days after consumption of contaminated aphids was 27% for the beetles that had been fed 120 h before exposure and the lowest was 13% for the beetles that had been fed 24 and 48 h prior to exposure. A regurgitation response was observed in 53–80% of the beetles that had consumed deltamethrin-treated aphids. The beetles that survived consumption of treated aphids showed a short-term reduction in mean numbers of untreated aphids consumed relative to the control beetles. Dietary and topical dose-response data for deltamethrin and N. brevicollis were compared by probit analysis and maximum likelihood procedures. The dietary exposure probit line had a significantly steeper slope than the topical exposure probit line but the two lines occupied similar positions along the dose axis. The steepness of the dietary exposure probit line may be partly explained by the regurgitation response shown by the beetles, which causes water loss and may amplify toxic effects. The results indicated that the consumption of deltamethrin-contaminated prey may be an important cause of predator mortality soon after pesticide application.

Laboratory bioassay and spray deposition data were used to predict the levels of mortality that may result from the exposure of the carabid beetle Nebria brevicollis to the synthetic pyrethroid, deltamethrin, sprayed at a rate of 6.25 g Al/ha in a cereal crop insecticide in the 72-h after spray application. Mortalities from direct contact with spray droplets, uptake from spray deposits and dietary intake of spray-contaminated prey were considered. At decimal growth stage 73 the predicted direct contact mortality was 1–3% for N. breaicollis; mortality via uptake from deltamethrin residues on soil was 4–5%; and mortality from dietary intake was between 13 and 27%, depending on the state of beetle hunger. The integration of these findings to predict toxic effects in the field is discussed.

Ecotoxicology addresses a vast array of pollution problems that span all classes of habitats, chemical pollutants and organisms. In order to manage this complexity and develop a more predictive and less descriptive approach, general methods of ecotoxicological risk analysis are needed which incorporate appropriate ecological theory with toxicology and environmental chemistry. The current emphasis on toxicological criteria, at the expense of ecological factors, has led to methodologies that describe local toxic effects in great detail, but which fail to consider the importance of these effects for populations of the organisms that are suffering them. Application of ecological ideas to risk analysis will lead to a more probabilistic approach, which predicts ranges of possible outcomes for a given pattern of exposure to a pollutant: this should indicate that there is no single concentration of a pollutant that guarantees protection to a particular community of organisms. It may also tell ecotoxicologists that they should be measuring different things in order to estimate risk. This paper describes qualitative and quantitative approaches to ecological risk analysis for the short and long-term effects of pesticides on non-target arthropods. Criteria for identifying sensitive indicators for short-term effects and indicators of longer-term effects are given. Research into the spatial dynamics of predatory invertebrates in farmland is then used to argue that the probability of local extinction may be an appropriate endpoint for long-term risk analysis. This analysis indicates that the pattern and frequency of exposure to the toxic chemical and the landscape structure are important determinants of risk for pollutants with short persistence, pollutants in temporary habitats or pollutants affecting dispersive invertebrates.

A simple methodology to predict the risks posed to Episyrphus balteatus larvae exposed to direct spraying and residues of the pyrethroid insecticide λ-cyhalothrin in wheat crop canopies is described. Data describing the deposition of pesticide through the crop canopy following application at 200 1/ha and laboratory assessments of topical and residual toxicity were integrated to provide the initial risk estimates which may be tested in the field to set optimum dose-rates.

Summary A fluorescent spray tracer was used to measure the profile of spray deposits through winter-wheat crop canopies and upon beneficial insects, placed in fixed positions which approximated to their natural distributions. Tracer deposition profiles were recorded on a series of occasions between G.S. 47 to G.S. 90. Deposition levels declined through the canopy on each occasion but the proportion of the spray reaching the ground varied between growth stages. Deposition rates upon insects followed the same trends but insects on the aerial parts of the plant received a higher volume of tracer per unit area than the part of the crop that they were placed upon. Insects placed on the ground received a dose equivalent to their ground area. For a given distribution of insects, these data permit direct spray exposure to be estimated. The general application of the method to a wide range of crops, to the calculation of risk indices, to the standardisation of field tests and to the development of selective spray placement methods are discussed.

The intrinsic toxicity of deltamethrin to the grain aphid Sitobion avenae (F.) (Hemiptera: Aphididae) and a range of its important natural enemies was determined by laboratory topical bioassay. The natural enemies included polyphagous predators such as Pterostichus melanarius (Illiger), Harpalus rufipes (Degeer), Nebria brevicollis (F.), Agonum dorsale (Pont.), Demetrias atricapillus (L.), Trechus quadristriatus (Schrank), Bembidion obtusum (Serville), and B. lampros (Herbst.) (Coleoptera: Carabidae), Tachyporus hypnorum (F.) (Coleoptera: Staphylinidae) and Erigone atra (Blackwall) (Araneae: Linyphiidae), as well as the aphid-specific ladybird Coccinella septempunctata (L.) (Coleoptera: Coccinellidae). Dose–response relationships were compared between species by probit analysis and maximum likelihood procedures to determine trends of susceptibility, measured in terms of ng a.i. arthropod−1 and μg a.i. g−1 body weight. The range of LD50 values varied between 0.8 and 232 ng arthropod−1 and 0.76 and 66.17 μg g−1 body weight for the species tested. The linyphiid spider E. atra (♀) was the most intrinsically susceptible species and had the narrowest tolerance distribution of the predators tested, whereas the small carabid beetle D. atricapillus was the least intrinsically susceptible predator species. There were significant differences in susceptibility between species of different orders, i.e. the Araneae, Hemiptera and Coleoptera. Differences within the Coleoptera were closely related to body weight, with the exception of the carabid beetle D. atricapillus, which seemed to be tolerant to deltamethrin. Knockdown time studies indicated that D. atricapillus had a higher survival rate after being knocked down than other species of predator. Aphid susceptibility per unit body weight was not significantly different from that of the predators. The aphid did, however, demonstrate a broader tolerance distribution than most of the predators, which may be related to its herbivorous nature. The use of laboratory susceptibility data to determine selectivity and to predict pesticide hazard is discussed.