(Eg ED50) for Pesticide Droplets
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PN 0937 Review and evaluation of test species and methods for assessing exposure of non-target plants and invertebrates to crop pesticide sprays and spray drift (Desk study) DEFRA project number: PN 0937 S. J. Tones1, S. A. Ellis2, V. G. Breeze3, J. Fowbert4, P. C. H. Miller5, J. N. Oakley3 and C. S. Parkin5 D J Arnold6 1 ADAS Mamhead, Mamhead Castle, Exeter, Devon, EX6 8HD 2 ADAS High Mowthorpe, Duggleby, Malton, North Yorkshire, YO17 8BP 3 ADAS Rosemaund, Preston Wynne, Hereford, HR1 3PG 4 ADAS Woodthorne, Wergs Road, Woverhampton, WV6 8TQ 5 Silsoe Research Institute, Wrest Park, Silsoe, Bedford, MK45 4HS 6 Cambridge Environmental Assessments ,Boxworth,Cambs CB3 8NN Page 1 of 138 PN 0937 Contents Page No. EXECUTIVE SUMMARY 4 GENERAL INTRODUCTION 8 PART 1 PESTICIDE DEPOSITION 9 1.1. INTRODUCTION TO PESTICIDE DEPOSITION 10 1.2 METHODS OF DETERMINING AND QUANTIFYING SPRAY DRIFT 10 1.3 THE SPATIAL DISTRIBUTION OF DRIFTING SPRAY 12 1.4. FACTORS INFLUENCING THE RISK OF DRIFT FROM BOOM SPRAYERS OPERATING OVER ARABLE CROPS 13 1.5 REFERENCES 16 FIGURES 1-10 19 PART 2 NON-TARGET PLANTS 29 2.1 INTRODUCTION 30 2.2 LABORATORY/ GLASSHOUSE SCALE ASSESSMENTS 31 2.3 NON-TARGET PLANTS AND SPECIES SENSITIVITY 32 2.4 FACTORS AFFECTING EXPOSURE 40 2.5 ESTIMATING TIER 1 EXPOSURE CONCENTRATIONS 44 2.6 EXPOSURE IN THE FIELD 45 2.7 COMPETITION 52 2.8 SUMMARY AND CONCLUSIONS 54 2.9 RECOMMENDATIONS 55 2.10 REFERENCES 56 Page 2 of 138 PN 0937 PART 3 NON-TARGET INVERTEBRATES 60 3.1 BACKGROUND 61 3.2 AIMS 63 3.3 FACTORS INFLUENCING EXPOSURE 64 3.4 COMPARATIVE EVALUATION OF INVERTEBRATE SPECIES 73 3.5 ANALYSIS AND INTERPRETATION 78 3.6 CONCLUSIONS 82 3.7 RECOMMENDATIONS 85 3.8 REFERENCES 86 GENERAL CONCLUSIONS 93 GENERAL RECOMMENDATIONS 95 APPENDIX 1 97 COMPARATIVE ASSESSMENTS OF SELECTED NON-TARGET INVERTEBRATE SPECIES 97 ACKNOWLEDGEMENTS 138 Page 3 of 138 PN 0937 Executive summary Introduction and policy rationale Assessing the toxicity of Plant Protection Products (PPPs) to non-target organisms using a tiered testing scheme ranging from simple experiments based on conservative assumptions at tier 1 to increased realism, ultimately at the field scale, is a recognised approach within the EU. Tier-1 testing of non-target plants will involve exposing pot-grown plants of several different species to overhead sprays of the active substance. Tier-1 testing of non-target invertebrates (or non–target arthropods [ NTAs] as they are referred to in pesticde regulation ) is done by exposing A. rhopalosiphi and T. pyri adults to dried residues of the active substance on a glass plate. For NTAs, sprays are applied at a rate equivalent to the 90th percentile deposition rate on a flat horizontal surface, predicted from the data published by Ganzelmeier et al. (1995) and Rautmann et al. (2000). In interpolating this to predict spray drift deposition in off-field vegetation, it is assumed that the deposition rate on actual plant surfaces in off-field habitats is one tenth of that on a flat horizontal surface in the same position. The validity of this approach is questionable in relation to the airborne drift of small droplets. The validity of the proposed tier-1 test method for non-target plants is also uncertain, and little comparative data exists on the sensitivity to pesticides expressing herbicidal activity of the proposed tier-1 test plant species. Within the EU, and internationally, agreement on test methods and an approach to risk assessment is some way off. Tier-1 testing of non-target invertebrates is intended to represent a “reasonable worst-case” position. This may result in “false positives”, i.e., results wrongly indicating that a formulated active substance is harmful, but the risk of this is unestablished. The off-field Hazard Quotient for non-target invertebrates includes a correction factor of 10, which is intended to safeguard against the possibility that the sensitivity of the two standard test species may underestimate that of the general invertebrate biomass. The validity of this assumption is unknown. No specific allowance is made in the Hazard Quotient for the extent to which exposure in the standard glass plate bioassay may overestimate or underestimate exposure by direct contact, residual contact or feeding in natural invertebrate habitats under normal conditions. If the off-field Hazard Quotient for either or both test species exceeds a trigger value of two, the candidate active substance is referred for higher-tier testing, which can involve extended laboratory, semi-field, or field bioassays, of other invertebrate species (e.g., Orius laevigatus, Chrysoperla carnea, Coccinella septempunctata, and Aleochara bilineata). Whether or not these higher-tier species adequately represent the more general invertebrate biomass is questionable. Objectives To evaluate the extent to which exposure of non-target plants and invertebrates to pesticide drift in off-field habitats may be influenced by different factors, and to re-evaluate the current/ proposed tier-1 and higher-tier testing methods and regulatory guidelines in light of the findings. Page 4 of 138 PN 0937 Approaches The published scientific literature was searched and reviewed. Specialist opinions were obtained from recognised experts. Relevant information was collated, analysed, re-interpreted and summarised. Plant and invertebrate species representative of a broad range of ecological niches were compared with the standard test species. Non-target invertebrates were compared using an exploratory decimal indexing technique. Seventy two representative invertebrate species, including the two tier-1 and four preferred higher-tier test species, were assessed and indexed for each of the main factors likely to influence exposure. Alternative assumptions about the influence of invertebrate size and mobility were tested. Aggregate indices for exposure by direct contact, residual contact and feeding were calculated, and species rankings under different scenarios were compared. Commentaries on the draft final report were obtained from recognised experts. Results The horizontal plate sampling method used by Ganzelmeier et al. (1995) to measure spray drift deposition, does not adequately account for airborne drift of small droplets in clouds or plumes, which can occur over much greater distances than the downward deposition of large droplets (Miller, 1999). Up to five-fold differences in drift into off-field hedges can result from the use of different spray application and nozzle systems (Murphy et al., 2000; Glass et al., 1998). Drift can be doubled by increasing spray boom height. Drift deposition in off-field vegetation may be up to one order of magnitude greater than predicted by Ganzelmeier et al. (1995). Factors that influence the deposition and retention of spray-drift droplets on plant surfaces include: (1) droplet size; (2) droplet viscosity; (3) droplet velocity; and (4) droplet direction. Redistribution of an active substance within a plant depends on the lipid and water solubility of the chemical. Few data are available either on the degree of penetration of spray drift droplets into off-crop, non-target plant habitats or the influence of biological factors on droplet capture. Biological factors that are likely to influence the exposure of non-target plants include: (1) seasonality; (2) plant size and shape; (3) position within the vegetation canopy; (4) leaf and other surface micro-structure. The species composition of off-field plant assemblages depends on climate, soil type and land management practices, including those of cutting marginal vegetation or spraying it with herbicides (Andrews et al., 1999; Bunce et al., 1994). Foliage-inhabiting invertebrate communities in off-field habitats tend to be dominated by true bugs (Hemiptera), beetles (Coleoptera), flies (Diptera), butterflies and moths (Lepidoptera), sawflies, bees and wasps (Hymenoptera), mites (Acari) and spiders (Araneae). Non-target invertebrates may be exposed to pesticide drift either by: (1) direct deposition of drifting droplets on the invertebrate cuticle; (2) walking over drift residues present on solid habitat structures; (3) consuming contaminated food. Molecules of an active substance deposited on the invertebrate cuticle are either absorbed through the cuticle, or consumed secondarily during cleaning. Biological factors that have an important influence on the exposure of non-target invertebrates include: (1) seasonality; (2) phenology of the different active life-stages; (3) diurnality (4) invertebrate body size, shape and surface micro-structure; (5) cleaning habits; (6) barrier effects; (7) location of resting and feeding sites; (8) feeding habits; (9) ambulatory habits; (10) dispersal range; (11) behavioural reactions to sub-lethal doses of active substances. The quantitative relationship between invertebrate size and exposure is not clear, but may be Page 5 of 138 PN 0937 critically important because of the small size of both tier-1 test species. The influence of invertebrate mobility and of invertebrate responses to sub-lethal doses of pesticides is also poorly understood. Comparative analyses suggested that the exposure of different invertebrate species to drift in off-field habitats could vary by many orders of magnitude. A. rhopalosiphi and T. pyri, the two tier-1 test species, are unrepresentative of many invertebrates belonging to other trophic groups, and are probably much less likely to be exposed by residual contact or feeding than are many plant feeding species of invertebrate. The tier-1 bioassay