Overige insecten

Pestizide wirken auf Vögel und Säugetiere entweder direkt durch Vergiftung oder indirekt durch Reduktion der Nahrung und der Deckung. In diesem Bericht behandeln wir vor allem die indirekten Effekte und das dafür erforderliche Risikomanagement. Nach einer jahrzehntelangen Intensivierung der Landwirtschaft in Deutschland befinden sich viele Populationen von Vögeln und Säugetieren der Agrarlandschaft in einem schlechten Erhaltungszustand. Für 27 Vogel- und 22 Säugerarten der Agrarlandschaft stellen wir Daten zu Trend, Habitatwahl (Wahl der Feldfrucht), Bedrohungen und Risiko-Managementmaßnahmen zusammmen. Die indirekte Wirkung von Pestiziden auf Populationsniveau ist für vier europäische Agrarvogelarten und einige Säugerarten außerhalb Europas nachgewiesen.

This year’s National Insect Week is being hailed a huge success with thousands of people taking part in more than 300 events across the country. The Royal Entomological Society’s (RES) biennial initiative proved more popular than ever before, breaking previous event numbers and scoring a coup with HRH Prince Charles holding a bioblitz in his Clarence House garden. Children and adults took part in bug hunts, mini-beast safaris, moth-trapping and glow-worm hunting to learn more about the wonderful world of insects and their role in nature. A series of competitions and teaching resources have also opened up the insect world to the younger generation.

Laboratory toxicity test designs are far from reality and therefore extrapolations to field situations may be more difficult. In laboratory experiments with the amphipod Gammarus roeseli exposed to the insecticide imidacloprid it was investigated if test conditions closer to reality influences its sensitivity and if it is possible to extrapolate results from these laboratory tests to results from a stream mesocosm study. Experiments were run by varying medium, temperature, size, and seasonal origin of gammarids. Age and seasonal aspects had strongest effects with juveniles and animals taken from a spring population being most sensitive with an EC50 (96 h) of 14.2 mg/L imidacloprid. The test designs closest to the conditions in the stream mesocosms reflected best the results in mesocosms study on basis of LOEC values. However, the ECx extrapolation failed to predict the effects of short term imidacloprid pulses in the field.

Integrated pest management programs (IPM) promote the use of multiple cultural, biological, and chemical tactics to reduce the abundance of pest insects, while conserving pollinators and beneficial insects. Much research has focused on the impact of systemic neonicotinyl insecticides on the colony health and foraging behavior of bees, but few papers considered these impacts on pollen and nectar-feeding beneficial insects, such as parasitoids, lacewings, lady beetles, and butterflies. Contact insecticides only contaminate pollen and nectar of flowers that are open at the time of spraying. In contrast, soil-applied neonicotinyl insecticides are translocated to pollen and nectar of flowers for a longer duration, often months. Neonicotinyl seed-treated crops (imidacloprid, 0.11 mg/canola seed and 0.625 mg/corn seed) translocate less than 10 ppb to nectar and pollen. However, higher rates of soil-applied imidacloprid are used in urban landscapes and nurseries (270-300 mg/3gallon pot, 67g imidacloprid applied to soil surface for 24 diam. tree), which should result in residues higher than the 10 ppb in nectar and pollen compared to seed-treated crops. This study shows that the translocation of imidacloprid from soil (300 mg) to flowers of Asclepias curassavica resulted in imidacloprid residue in nectar of 6,000 ppb for 1X and 10,000 ppb for 2X treatments. A second imidacloprid soil application 7 months after the first resulted in residues of 21,000 ppb in 1X and 45,000 ppb in 2X treatments. Consequently, landscape use of imidacloprid applied to flowering plants can result in 697 to 1,162 times more imidacloprid in milkweed nectar compared to a seed treatment, where most research has focused. These higher residue levels caused significant mortality in both 1Xand 2X treatments at day 12 in three lady beetle species, Coleomegilla maculata, Harmonia axyridis, and Hippodamia convergens, but not a fourth species, Coccinella septempunctata. Survival and fecundity of two nymphalid butterfly species, monarch, Danaus plexippus and painted lady, Vanessa cardui, were not reduced when free-ranging butterflies foraged on 1X and 2X treated milkweed plants or when butterflies were force-fed lower amounts of imidacloprid (0 ppb, 15 ppb, or 30 ppb imidacloprid). However, larval survival was significantly reduced on plants treated with soil-applied imidacloprid at1X and 2X treatments. Consequently, the use of systemic, neonicotinyl insecticides, such as imidacloprid, increased the insecticide’s duration in pollen and nectar, and increased the insecticide’s exposure to beneficial insects, thereby increasing the risk of mortality.

Eriopis connexa is a native coccinelid predator in the Neotropical Region. In Argentina it is commonly found associated to sucking pests in several crops and among them aphids and whiteflies. These pests are usually controlled with newly developed systemic insecticides, such as the neonicotinoids. However, the compatibility between selective pesticides and natural enemies is required before incorporating them in integrated pest management (IPM) packages. Within this frame, the objective of this study was to evaluate the side effect of various concentrations/doses of one commonly used neonicotinoid in vegetal crops, acetamiprid, on immature stages of E. connexa by dipping or topical exposure for eggs and larvae, respectively. Acetamiprid reduced egg hatching from 34 to 100 %. Moreover, the embryogenesis was disrupted by insecticide at early embryo
stage at all tested concentrations. Second larval instar was more susceptible to acetamiprid than the fourth one and this susceptibility was positively related with the tested concentrations. On the other hand, the survival reduction at larval stage reached 100 % from 20 mg a.i./L (10 % of maximum field concentration). Besides, the reproduction of the females developed from topical bioassays on fourth instar larvae was strongly affected, with reduction in fecundity and fertility from 22 to 44 % and from 37 to 45 %, respectively. Overall the results showed a high toxicity of acetamiprid on immature stages of E. connexa, demonstrating that this broadly used insecticide could reduce biocontrol services provided by this predator and could also likely disturb IPM programs.

Nicotinic acetylcholine receptors (nAChRs) are ligand‑gated ion channels that mediate fast synaptic transmission in the insect nervous system and are targets of a major group of insecticides, the neonicotinoids. They consist of five subunits arranged around a central ion channel. Since the subunit composition determines the functional and pharmacological properties of the receptor the presence of nAChR families comprising several subunit‑encoding genes provides a molecular basis for broad functional diversity. Analyses of genome sequences have shown that nAChR gene families remain compact in diverse insect species, when compared to their nematode and vertebrate counterparts. Thus, the fruit fly (Drosophila melanogaster), malaria mosquito (Anopheles gambiae), honey bee (Apis mellifera), silk worm (Bombyx mori) and the red flour beetle (Tribolium castaneum) possess 10‑12 nAChR genes while human and the nematode Caenorhabditis elegans have 16 and 29 respectively. Although insect nAChR gene families are amongst the smallest known, receptor diversity can be considerably increased by the posttranscriptional processes alternative splicing and mRNA A‑to‑I editing which can potentially generate protein products which far outnumber the nAChR genes. These two processes can also generate species‑specific subunit isoforms. In addition, each insect possesses at least one highly divergent nAChR subunit which may perform species‑specific functions.

Aquatic ecosystems are characterized by fluctuating conditions that have direct effects on aquatic communities but also indirect influences such as changing the toxicity of chemicals. Because the effect of food quality on pesticide toxicity has rarely been studied, in the present study Daphnia magna juveniles supplied with 4 different food quality levels were exposed to a range of imidacloprid concentrations for 21 d. Food quality was expressed as carbon:phosphorus ratios of algae Pseudokirchneriella subcapitata (C:P 35, C:P 240, C:P 400, and C:P 1300). Survival, growth rates, and reproduction of D. magna were monitored, and the combined effects of imidacloprid exposure and the phosphorus content of algae were analyzed. A stronger effect on survival was observed at the P-deficient diet (C:P 1300), confirmed by lower 10% effect concentration (EC10) values at days 7, 9, 15, and 21 compared with diets with higher phosphorus contents. Similarly, the growth rate was reduced when D. magna were supplied with algae of low phosphorus content at imidacloprid exposure conditions. The highest reproductive output was observed for D. magna fed the optimal phosphorus diet (C:P 240), both at control and exposed conditions. Poor food quality increased the sensitivity of nontarget species to pesticide exposure, potentially leading to an underestimation of adverse effects on aquatic communities in the field.

Imidacloprid, the largest selling insecticide in the world, has received particular attention from scientists, policymakers and industries due to its potential toxicity to bees and aquatic organisms. The decline of aquatic macro-invertebrates due to imidacloprid concentrations in the Dutch surface waters was hypothesised in a recent paper by Van Dijk, Van Staalduinen and Van der Sluijs (PLOS ONE, May 2013). Although we do not disagree with imidacloprid's inherent toxicity to aquatic organisms, we have fundamental concerns regarding the way the data were analysed and interpreted. Here, we demonstrate that the underlying toxicity of imidacloprid in the field situation cannot be understood except in the context of other co-occurring pesticides. Although we agree with Van Dijk and co-workers that effects of imidacloprid can emerge between 13 and 67 ng/L we use a different line of evidence. We present an alternative approach to link imidacloprid concentrations and biological data. We analysed the national set of chemical monitoring data of the year 2009 to estimate the relative contribution of imidacloprid compared to other pesticides in relation to environmental quality target and chronic ecotoxicity threshold exceedances. Moreover, we assessed the relative impact of imidacloprid on the pesticide-induced potential affected fractions of the aquatic communities. We conclude that by choosing to test a starting hypothesis using insufficient data on chemistry and biology that are difficult to link, and by ignoring potential collinear effects of other pesticides present in Dutch surface waters Van Dijk and co-workers do not provide direct evidence that reduced taxon richness and abundance of macroinvertebrates can be attributed to the presence of imidacloprid only. Using a different line of evidence we expect ecological effects of imidacloprid at some of the exposure profiles measured in 2009 in the surface waters of the Netherlands.

Changes in food uptake by detritivorous macroinvertebrates could disrupt the ecosystem service of leaf litter breakdown, necessitating the study of shredding under anthropogenic influences. The impact of the neonicotinoid insecticide imidacloprid on the feeding rate of individual Gammarus pulex was measured at a daily resolution both during and after a 4-d exposure period. The authors found that imidacloprid inhibits feeding of G. pulex during exposure at concentrations ≥30 µg/L and that there was no recovery in feeding on transfer into clean media for 3 d. Exposure to imidacloprid at concentrations ≥0.81 µg/L and ≤9.0 µg/L resulted in increased feeding after exposure even though there was no significant effect on feeding during the exposure itself. Comparison with the literature shows that concentrations found to influence feeding lie within the range of estimated and measured environmental concentrations. Additionally, effects on feeding rate were observed at concentrations 2 orders of magnitude lower than those causing mortality. The lethal concentration for 50% of test organisms after 4 d of exposure (270 µg/L, literature data) and the effect concentration for a reduction in feeding by 50% (5.34 µg/L) were used for this comparison. The present study discusses the potential that effects on feeding may evoke effects at the population level or disturb leaf litter breakdown in the environment.