Detlef Schenke

Spatial and temporal exposure patterns in non-target small mammals during brodifacoum rat control

Worldwide pest rodents on livestock farms are often regulated using anticoagulant rodenticides (ARs). Second generation ARs in particular can cause poisoning in non-target species due to their high toxicity and persistence. However, research on exposure of small mammals is rare. We systematically investigated spatial and temporal exposure patterns of non-target small mammals in a large-scale replicated study. Small mammals were trapped at different distances to bait stations on ten farms before, during and after brodifacoum (BR) bait application, and liver samples of 1178 non-target small mammals were analyzed for residues of eight ARs using liquid chromatography coupled with tandem mass spectrometry. BR residues were present in 23% out of 742 samples collected during and after baiting. We found clear spatial and temporal exposure patterns. High BR residue concentrations mainly occurred within 15m from bait stations. Occurrence and concentrations of residues significantly decreased with increasing distance. This pattern was found in almost all investigated taxa. After baiting, significantly more individuals contained residues than during baiting but concentrations were considerably lower. Residue occurrence and concentrations differed significantly among taxa, with the highest maximal residue concentrations in Apodemus species, which are protected in Germany. Although Sorex species are known to be insectivorous we regularly found residues in this genus. Residues of active agents other than brodifacoum were rare in all samples. The confirmation of substantial primary exposure in non-target small mammals close to the baiting area indicates considerable risk of secondary poisoning of predators, a pathway that was possibly underestimated until now. Our results will help to develop risk mitigation strategies to reduce risk for non-target small mammals, as well as their predators, in relation to biocidal AR usage.

Relation between Intensity of Biocide Practice and Residues of Anticoagulant Rodenticides in Red Foxes (Vulpes vulpes)

Anticoagulant rodenticides (ARs) are commonly used to control rodent infestations for biocidal and plant protection purposes. This can lead to AR exposure of non-target small mammals and their predators, which is known from several regions of the world. However, drivers of exposure variation are usually not known. To identify environmental drivers of AR exposure in non-targets we analyzed 331 liver samples of red foxes (Vulpes vulpes) for residues of eight ARs and used local parameters (percentage of urban area and livestock density) to test for associations to residue occurrence. 59.8% of samples collected across Germany contained at least one rodenticide, in 20.2% of cases at levels at which biological effects are suspected. Second generation anticoagulants (mainly brodifacoum and bromadiolone) occurred more often than first generation anticoagulants. Local livestock density and the percentage of urban area were good indicators for AR residue occurrence. There was a positive association between pooled ARs and brodifacoum occurrence with livestock density as well as of pooled ARs, brodifacoum and difenacoum occurrence with the percentage of urban area on administrative district level. Pig holding drove associations of livestock density to AR residue occurrence in foxes. Therefore, risk mitigation strategies should focus on areas of high pig density and on highly urbanized areas to minimize non-target risk.

Prey composition modulates exposure risk to anticoagulant rodenticides in a sentinel predator, the barn owl

Worldwide, small rodents are main prey items for many mammalian and avian predators. Some rodent species have pest potential and are managed with anticoagulant rodenticides (ARs). ARs are consumed by target and non-target small mammals and can lead to secondary exposure of predators. The development of appropriate risk mitigation strategies is important and requires detailed knowledge of AR residue pathways. From July 2011 to October 2013 we collected 2397 regurgitated barn owl (Tyto alba) pellets to analyze diet composition of owls on livestock farms in western Germany. 256 of them were fresh pellets that were collected during brodifacoum baiting. Fresh pellets and 742 liver samples of small mammals that were trapped during baiting in the same area were analyzed for residues of ARs. We calculated exposure risk of barn owls to ARs by comparing seasonal diet composition of owls with AR residue patterns in prey species. Risk was highest in autumn, when barn owls increasingly preyed on Apodemus that regularly showed AR residues, sometimes at high concentrations. The major prey species (Microtus spp.) that was consumed most frequently in summer had less potential to contribute to secondary poisoning of owls. There was no effect of AR application on prey composition. We rarely detected ARs in pellets (2 of 256 samples) but 13% of 38 prey individuals in barn owl nests were AR positive and substantiated the expected pathway. AR residues were present in 55% of 11 barn owl carcasses. Fluctuation in non-target small mammal abundance and differences in AR residue exposure patterns in prey species drives exposure risk for barn owls and probably other predators of small mammals. Exposure risk could be minimized through spatial and temporal adaption of AR applications (avoiding long baiting and non-target hot spots at farms) and through selective bait access for target animals.

Elevated root retention of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in coniferous trees

For decades, the explosive RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) has been used for military and industrial applications. Residues of RDX pollute soils in large areas globally and the persistence and high soil mobility of these residues can lead to leaching into groundwater. Dendroremediation, i.e. the long-term use of trees to clean up polluted soils, is gaining acceptance as a green and sustainable strategy. Although the coniferous tree species Norway spruce and Scots pine cover large areas of military land in Central Europe, the potential of any coniferous tree for dendroremediation of RDX is still unknown. In this study, uptake experiments with a 14C-labelled RDX solution (30xa0mgxa0L−1) revealed that RDX was predominantly retained in the roots of 6-year-old coniferous trees. Only 23xa0% (pine) to 34xa0% (spruce) of RDX equivalents (RDXeq) taken up by the roots were translocated to aboveground tree compartments. This finding contrasts with the high aerial accumulation of RDXeq (up to 95xa0%) in the mass balances of all other plant species. Belowground retention of RDXeq is relatively stable in fine root fractions, since water leaching from tissue homogenates was less than 5xa0%. However, remobilisation from milled coarse roots and tree stubs reached up to 53xa0%. Leaching from homogenised aerial tree material was found to reach 64xa0% for needles, 58xa0% for stems and twigs and 40xa0% for spring sprouts. Leaching of RDX by precipitation increases the risk for undesired re-entry into the soil. However, it also opens the opportunity for microbial mineralisation in the litter layer or in the rhizosphere of coniferous forests and offers a chance for repeated uptake of RDX by the tree roots.

Binding of RDX to Cell Wall Components of Pinus sylvestris and Picea glauca and Three-Year Mineralisation Study of Tissue-Associated RDX Residues

Contamination of soils with the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX, Research Department Explosive) as a result of military applications is a large-area problem globally. Since coniferous trees dominate the vegetation of large areas of military land in Central Europe, particularly in Germany, the long-term fate of 14C-RDX in the conifers Scots pine and Dwarf Alberta spruce was studied. Acetic acid was the most effective solvent for the removal of extractable RDX residues from homogenates of RDX-laden tree material (85%, 80–90% and 64–80% for roots, wood and needles, respectively). On average, only a fifth of RDX-derived 14C was bound in non-extractable residues (NER). Within the main cell wall compartments, lignin was the dominant binding site for NER (needles: 32–62%; roots: 38–42%). Hemicellulose (needles: 11–18%; roots: 6–11%) and cellulose (needles: 12–24%; roots: 1–2%) were less involved in binding and a considerable proportion of NER (needles: 15–24%; roots: 59–51%) was indigestible. After three-year incubation in rot chambers, mineralisation of tree-associated 14C-RDX to 14CO2 clearly dominated the mass balance in both tree species with 48–83%. 13–33% of 14C-RDX-derived radioactivity remained in an unleachable form and the remobilisation by water leaching was negligible (< 2%).

Two-year field data on neonicotinoid concentrations in guttation drops of seed treated maize (Zea mays)

We present neonicotinoid concentrations in guttation drops of commonly used maize (Zea mays) cultivars, germinated from seeds coated with active substances (a.s.): i) imidacloprid (IMD), ii) clothianidin (CTN) and iii) thiamethoxam (THM) over two growing seasons. In one variant clothianidin was applied as seed granule. The trial took place at the experimental fields of the Julius Kühn-Institut in Berlin in 2010 and 2011. Data from 2010 are related to a presentation of “Pesticides in guttation droplets following seed treatment – field studies” (Schenke et al., 2011) [1] presented at the SETAC North America conference and only some figures were used in the “Scientific opinion on the science behind the development of a risk assessement of plant protection products on bees (Apis mellifera, Bombus spp. and solitary bees)” (EFSA, 2012) [2]. Only parts of the data from 2011 was presented in relation to the “Exposure of Coccinellidae to guttation droplets on maize seedlings with seed or granule treatment of neonicotinoids” (Schenke and Heimbach, 2014) [3]. The article describes the study sites, the variants of treated maize seeds, sample collection and the analytical methods used to quantify the neonicotinoids and relevant metabolites of IMD (5-OH-IMD and IMD-olefine) and of THM (CTN) in guttation drop samples. The complete field data set is publicly available at the OpenAgrar repository under https://doi.org/10.5073/20180907-142020 (Schenke et al., 2018) [4].

Neue Daten zur Exposition von für Bienen gefährlichen Wirkstoffendurch Aussaat von behandeltem Saatgut in Nachbarflächen und Auswirkungen auf Bienen

In fur Honigbienen attraktiven Anbaukulturen wie Raps und Obst ist es vielfach ublich, und auch zulassig, wahrend der Blute mehrere Pflanzenschutzmittel aus verschiedenen Wirkstoffklassenals Tankmischung auszubringen (z.B. Fungizide, Herbizide, Wachstumsregler, Insektizide oder Mikronahrstoffe). In der Regel werden die Bienen dabei nicht gefahrdet, wenn alle Vorschriften eingehalten werden, die fur die beteiligten Mischungskomponenten gelten. Fur manche Wirkstoffgruppen sind jedoch auch synergistische Wirkungssteigerungen bekannt, wie fur die bereits hinreichend untersuchte nsynergistische Wirkung von Insektiziden aus der Wirkstoffgruppe der Pyrethroide in Kombination mit bestimmten Fungiziden aus der Klasse der Ergosterol-Biosynthese-Hemmer. Hier kann bei einer gemeinsamen Ausbringung in einer Tankmischung eine Verscharfung der Anwendungsbestimmungen und Auflagen erfolgen, aus zwei bienenungefahrlichen Produkten (B4) wird somit eine bienengefahrliche Mischung (B1/B2). Da in der landwirtschaftlichen Praxis jedoch immer wieder neue Wirkstoffe entwickelt werden und Mischungskombinationen hinzukommen, arbeitet das Julius Kuhn-Institut praventiv an der Erstellung eines einfachen Screening-Verfahren auf Laborebene zur schnellen Detektion potentiell risikobehafteter Wirkstoff- und Mittelkombinationen. In einem ersten Schritt wurden hierfur Pflanzenschutzmittelmischungen in Laborversuchen (Spritzkammer) getestet, welche haufig im Raps- bzw. Obstanbau eingesetzt werden. nIn einem zweiten Schritt werden dann potentiell kritische oder haufig eingesetzte Wirkstoffkombinationen in Halbfreiland- bzw. Freilandversuchen gepruft. Dabei wird untersucht, ob und inwiefern ein erhohtes Risiko fur Bienen besteht und ob, und wenn ja welche zusatzliche Auflagen erforderlich sind. nFur die Versuche in der Spritzkammer werden junge Honigbienen einen Tag vor der Applikation aus dem Honigraum gesunder Wirtschaftsvolker entnommen, in Gruppen von 10 Bienen in Versuchskafige uberfuhrt und uber Nacht in einen Klimaschrank (25 °C) gestellt. Am folgenden Tag werden die Bienen auf ihre Vitalitat hin uberpruft und zwei Stunden vor der Applikation in eine Kuhlkammer (4 ° C) uberfuhrt. Die Bienen befinden sich njetzt in einer Kaltestarre und werden in einer Kuhlbox, zum Applikationsstand gebracht. Vor der Applikation werden die Bienen einer Variante jeweils aus den Beobachtungskafigen in offene Petrischalen gelegt und in der Spritzkammer direkt uberspruht. Zusatzlich wird eine weitere Petrischale mit Filterpapier und 10 toten Bienen fur ruckstandsanalytische Untersuchung aufgestellt. Nach der Applikation werden die immer noch in der Kaltestarre befindlichen Bienen anschliesend in die Kafige zuruckgesetzt und anschliesend wieder zuruck in den Klimaschrank (25 °C) gebracht. Bonituren auf Verhalten, Vitalitat und Mortalitat der Bienen werden 2, 4, 24 und 48 Stunden nach der Applikation durchgefuhrt. nNach der letzten Bonitur werden alle toten und lebenden Bienen der verschiedenen Varianten bei -20 °C fur eine die spatere Ruckstandsanalytik eingefroren um aus den Analysen der Ruckstande in toten und lebendigen Bienen Ruckschlusse uber die Metabolisierung der Wirkstoffe und auch weitere Erkenntnisse fur eine bessere Interpretierbarkeit der Ruckstandsanalysen in Schadfallen mit Verdacht auf Bienenvergiftungen zu gewinnen.Die Daten der Vergleichsbetriebe stellen den Status quo im Pflanzenschutz in Deutschland dar. Der nBehandlungsindex in Mohre und Frischkohl betrug im Durchschnitt der Jahre (2007-2014) bei 6,2 nbzw. 9,2. Mohren wurden vorrangig mit Herbiziden und Frischkohl mit Insektiziden behandelt. Unter ndem Aspekt des Pflanzenschutzes und zur Reduktion der Behandlungsintensitat mit Insektiziden kann nAbbildung 1: Behandlungsindex der Herbizide n(Herbizid-BI) in Abhangigkeit der Vorfrucht nin den Vergleichsbetrieben fur Mohre, n2007-2014, in Deutschland, ungleiche nBuchstaben symbolisieren signifikante Unterschiede n(p<0,05), nBlattfrucht=58, nGemuse=28, nnHalmfruchte=115 n208 72. ALVA-Tagung, Seminarhotel Wesenufer, 2017 nder Fruhkohlanbau empfohlen werden. Im Kohl- und Mohrenanbau konnen Halmvorfruchte Schadlingsbefall nvorbeugen. Die Mittelaufwandmengen wurden vorrangig bei Herbizidanwendungen reduziert nIn beiden Kulturen wurden Abweichungen vom notwendigen Mas verzeichnet. Die Pflanzenschutzberatung nsowie die regelmasige Durchfuhrung von Bonituren konnen Pflanzenschutzmittelanwendungen ndem notwendigen Mas naher bringen und die Umsetzung des IPS in der Praxis verbessern. nFur die Ausschopfung nichtchemischer Masnahmen sind Praxisdemonstrationen und der intensive nAustausch zwischen Wissenschaft und Praxis notig, genauso wie Forschungsforderung zur Entwicklung nneuer und Optimierung bestehender integrierter Verfahren und neuer Wirkstoffe. Vorbildhaft nwird der IPS von den Demonstrationsbetrieben u. a. in den Kulturen Mohre und Weiskohl, seit n2014 umgesetzt. Die Betriebe werden individuell und intensiv betraten, um Pflanzenschutzmittelanwendungen nauf das notwendige Mas zu beschranken. Hierfur werden Bonituren unter Nutzung von nSchadschwellen, Warndiensthinweisen und Monitoringverfahren durchgefuhrt.

Distance a useful risk mitigation measure for honeybees exposed to frequently guttating seed-treated fields?

Findings of high concentrations of bee-toxic compounds in guttation drops from crop plants treated with a neonicotinoid seed dressing gave rise to concerns about a potential risk to honeybee colonies. As bee colonies seem to prefer water sources in the near surroundings, several field trials were set up, aimed to investigate if setting minimal distances of bee colonies to a frequently guttating seed-treated field could be a method to minimize the potential risk of water collecting bees ingesting contaminated guttation drops. The experiments were conducted in 2011 and 2012 on conventional managed maize, wheat and oilseed rape fields near Braunschweig (Lower Saxony, Germany). Every experimental field consisted of two plots; one planted with a neonicotinoid treated seed batch and one adjacent plot with an untreated seed batch. The bee hives were placed in the untreated plot before or immediately after emergence with a 0 m to maximal 85 m distance to the adjacent treated plot. The entrance of every hive pointed toward the treated plot. At each distance a minimum of three bee colonies containing approximately 11.000 20.000 bees were set up. During the whole experiment climatic conditions, growth stage of the crop plants and presence of guttation, rain and dew drops were recorded. If guttation occurred, droplets were sampled. Furthermore, colony development (Liebefelder method) and mortality (Gary-dead bee traps) were assessed. After completion of the field experiment residue analyses of guttation drops and dead bees were conducted. Guttation occurred frequently during the experimental phase. Residues in guttation droplets were detected during the entire experiment from BBCH 10 up to a maximum of BBCH 59, depending on the investigated crop. However in most cases the number of dead bees per colony was at a normal level, regardless of the tested crop and the distance between the bee colony and the treated field. The only exception was a slightly increased number of dead bees in tests with oilseed rape which was occasionally observed at 0 m distance to the treated crop. Furthermore, in some dead bees residues of the seed treatment were detected but without link between mortality and residues. However, no long term effects on bee brood and honey bee colony strength and development were observed independently from the distance and tested crop. Taking into account the results of all experiments there were no indications of an unacceptable risk for bee colonies from contaminated guttation drops in our trials. However, results of individual samples from the dead traps suggest that individual honeybees occasionally use guttation droplets as water source. Therefore, to maintain a certain distance between beehives and insecticide-treated fields of 60 m could be a potentially useful measure to further reduce the potential risk although the applicability and practicability of such a mitigation measure may be questioned. In many cases, it is neither for beekeepers nor growers possible to move the apiary or the field. It is possible that such a mitigation measure could further complicate the discussions between beekeepers and farmers in real life.Dust drift during sowing of maize seeds treated with neonicotinoids has led to several severe honey bee poisoning incidents in the past. Studies have been conducted to assess the abrasion potential of treated seeds, the influence of different sowing machines, and effects on honey bees in semi-field and field conditions. In the JKI a number of field and semi-field trials with sowing of treated seeds assessing effects on honey bees and also with manual application of small amounts of dusts were conducted. Several trials were conducted with sowing of winter oil seed rape (4 trials) and maize (3 trials) and an adjacent flowering crop, either winter oil seed rape or mustard both downwind and upwind of the sown area. Sowing was conducted when wind direction was at the achievable optimum. Residue samples from petri dishes for 2-D and gauze collectors for 3– D drift of dust drift were taken as well as samples from the adjacent flowering crop. Honey bee colonies were placed both upwind and downwind of the sowing area and served as treated variant and respective control. As sowing was conducted during bee flight activity, hive entrances of colonies in the semi-field experiments were closed from early morning until end of sowing. Thus a worst case scenario was obtained for exposure of bees to dusts deposited on flowers, nectar and pollen. The high number of the trials conducted between 2009 and 2014 allows a detailed insight of the correlation between Heubach a.i. values, 2-D and 3-D exposure and effects on honey bees after sowing of different crops.152 Julius-Kühn-Archiv, 450, 2015 2.16 Semi-field and field testing on the honey bee working group Frank Bakker, Heino Christl, Mike Coulson, Axel Dinter, Hervé Giffard, Nicole Hanewald, Gavin Lewis, Mark Miles, Jens Pistorius, Job van Praagh, Marit Randall, Christine Vergnet, Connie Hart, Christoph Sandrock, Thomas Steeger 1Eurofins, 2Tier 3, 3Syngenta, 4DuPont, 5Testapi, 6BASF, 7JSC, 8BCS, 9JKI, 10ICPPR, 11Norwegian FSA, 12ANSES, 13Health Canada, 14IES, 15US EPA

Dust drift- from exposure to risk for honey bees

Findings of high concentrations of bee-toxic compounds in guttation drops from crop plants treated with a neonicotinoid seed dressing gave rise to concerns about a potential risk to honeybee colonies. As bee colonies seem to prefer water sources in the near surroundings, several field trials were set up, aimed to investigate if setting minimal distances of bee colonies to a frequently guttating seed-treated field could be a method to minimize the potential risk of water collecting bees ingesting contaminated guttation drops. The experiments were conducted in 2011 and 2012 on conventional managed maize, wheat and oilseed rape fields near Braunschweig (Lower Saxony, Germany). Every experimental field consisted of two plots; one planted with a neonicotinoid treated seed batch and one adjacent plot with an untreated seed batch. The bee hives were placed in the untreated plot before or immediately after emergence with a 0 m to maximal 85 m distance to the adjacent treated plot. The entrance of every hive pointed toward the treated plot. At each distance a minimum of three bee colonies containing approximately 11.000 20.000 bees were set up. During the whole experiment climatic conditions, growth stage of the crop plants and presence of guttation, rain and dew drops were recorded. If guttation occurred, droplets were sampled. Furthermore, colony development (Liebefelder method) and mortality (Gary-dead bee traps) were assessed. After completion of the field experiment residue analyses of guttation drops and dead bees were conducted. Guttation occurred frequently during the experimental phase. Residues in guttation droplets were detected during the entire experiment from BBCH 10 up to a maximum of BBCH 59, depending on the investigated crop. However in most cases the number of dead bees per colony was at a normal level, regardless of the tested crop and the distance between the bee colony and the treated field. The only exception was a slightly increased number of dead bees in tests with oilseed rape which was occasionally observed at 0 m distance to the treated crop. Furthermore, in some dead bees residues of the seed treatment were detected but without link between mortality and residues. However, no long term effects on bee brood and honey bee colony strength and development were observed independently from the distance and tested crop. Taking into account the results of all experiments there were no indications of an unacceptable risk for bee colonies from contaminated guttation drops in our trials. However, results of individual samples from the dead traps suggest that individual honeybees occasionally use guttation droplets as water source. Therefore, to maintain a certain distance between beehives and insecticide-treated fields of 60 m could be a potentially useful measure to further reduce the potential risk although the applicability and practicability of such a mitigation measure may be questioned. In many cases, it is neither for beekeepers nor growers possible to move the apiary or the field. It is possible that such a mitigation measure could further complicate the discussions between beekeepers and farmers in real life.Dust drift during sowing of maize seeds treated with neonicotinoids has led to several severe honey bee poisoning incidents in the past. Studies have been conducted to assess the abrasion potential of treated seeds, the influence of different sowing machines, and effects on honey bees in semi-field and field conditions. In the JKI a number of field and semi-field trials with sowing of treated seeds assessing effects on honey bees and also with manual application of small amounts of dusts were conducted. Several trials were conducted with sowing of winter oil seed rape (4 trials) and maize (3 trials) and an adjacent flowering crop, either winter oil seed rape or mustard both downwind and upwind of the sown area. Sowing was conducted when wind direction was at the achievable optimum. Residue samples from petri dishes for 2-D and gauze collectors for 3– D drift of dust drift were taken as well as samples from the adjacent flowering crop. Honey bee colonies were placed both upwind and downwind of the sowing area and served as treated variant and respective control. As sowing was conducted during bee flight activity, hive entrances of colonies in the semi-field experiments were closed from early morning until end of sowing. Thus a worst case scenario was obtained for exposure of bees to dusts deposited on flowers, nectar and pollen. The high number of the trials conducted between 2009 and 2014 allows a detailed insight of the correlation between Heubach a.i. values, 2-D and 3-D exposure and effects on honey bees after sowing of different crops.152 Julius-Kühn-Archiv, 450, 2015 2.16 Semi-field and field testing on the honey bee working group Frank Bakker, Heino Christl, Mike Coulson, Axel Dinter, Hervé Giffard, Nicole Hanewald, Gavin Lewis, Mark Miles, Jens Pistorius, Job van Praagh, Marit Randall, Christine Vergnet, Connie Hart, Christoph Sandrock, Thomas Steeger 1Eurofins, 2Tier 3, 3Syngenta, 4DuPont, 5Testapi, 6BASF, 7JSC, 8BCS, 9JKI, 10ICPPR, 11Norwegian FSA, 12ANSES, 13Health Canada, 14IES, 15US EPA

Exposure of Coccinellidae to guttation droplets on maize seedlings with seed or granule treatment of neonicotinoids

The exposure of non-target organisms to pesticides is expected to be reduced, if the pesticide application is performed via seed treatment instead of a spray application. But the phenomenon of guttation was not taken into account as a potential exposure pathway of systemic pesticides like neonicotinoids, though guttation in maize occurred frequently under climate conditions of Central Europe. During guttation events ladybird beetles were observed on the upper side of leaves of maize seedlings (BBCH 13 - 14) between large guttation droplets on day 3, 5, and 11 after crop emergence. Neither aphids nor leaf tissue feeding were observed. The neonicotinoids and corresponding metabolites were analyzed in guttation water and in Coccinellidae with LC-ESI/MS/MS. Because the same a. i. and their corresponding metabolites were detected in guttation water and ladybirds from the same variant, this indicates that the excretion of guttation droplets is an exposure pathway for leaf-visiting adult Coccinellidae.