English

Earthworms play key roles in soils and sublethal effects of environmental toxicants on these organisms should be taken seriously, since they might have detrimental effects on higher ecological levels. Earthworms make important contributions to the breakdown of organic matter, soil fertility, and to the formation of soils. In laboratory experiments we have assessed sub-lethal effects of imidacloprid on two earthworm species commonly found in different agricultural soils (Lumbricus terrestris and Aporrectodea caliginosa). After 7 days of exposure in contaminated soil, a significant loss of body mass was found in both species exposed to imidacloprid concentrations as low as 0.66 mg kg-1 dry soil. These losses ranged from 18.3 to 39% for A. caliginosa and from 7.4 to 32.4% for L. terrestris, respectively. The detected sub-lethal effects were found close to the predicted environmental concentration (PEC) of imidacloprid, which is in the range of 0.33–0.66 mg kg-1 dry soil.

Neonicotinoids, agonists at the nicotinic acetylcholine receptors (nAChRs), induce neuromuscular paralysis. The high selectivity for nAChRs (particularly the a4b2 subtype) in insects compared with mammals results in their favorable toxicological profile. We describe fatal toxicity with one such insecticide, imidacloprid, considered relatively safe. This patient manifested neurological dysfunction and rhabdomyolysis. The initial neurological dysfunction, probably due to central nicotinic stimulation, was compounded by ischemic and metabolic encephalopathy. This report of imidacloprid toxicity sensitizes clinicians to an emerging cause of poisoning and highlights the need for a careful review of its toxicity profile.

A community of insect herbivores has established on eucalyptus species in California following their introduction from Australia. A number of the species are under complete or partial biological control. A response to introduction of additional pest species into the complex has been the application of systemic insecticides to infested trees. Natural enemies that have been introduced to control the various pest species feed on the nectar of treated trees, and thus may be affected by these pesticides. In this study, Eucalyptus rudis trees were treated at label rates with the neonicotinoid systemic insecticide imidacloprid and nectar sampled at 5 months post-treatment during the spring bloom. The insecticide appears to be concentrating in the nectar at higher levels than reported from other plant species and at concentrations exceeding the LC50 for two important parasitoids. If tree treatments become widespread as a result of continual introductions of new eucalypt herbivores, established biological control programs could be at significant risk.

With almost one million described species, insects eclipse all other forms of animal life on Earth, not only in sheer numbers, diversity, and biomass, but also in their importance to functioning ecosystems. However, human-induced changes to the natural environment threaten vast numbers of these organisms and the vital services they provide to ecosystems. Leading causes of insect endangerment are habitat destruction or alteration of habitat by chemical pollutants (such as pesticides). Pesticides are implicated in the decline of many native bees and some aquatic insects.

Western culture views insects and arachnids as pests and vermin that need to be controlled. They usually are not considered as something to be preserved. Accordingly, arthropods and other small organisms have not been taken seriously for conservation by policy makers and the conservation community at large. Arthropods, however, are major components of diverse ecosystems and are the major players in functioning of ecosystem processes. Arthropods are relentlessly vanishing before our eyes. They must be preserved because of their inherent values but also because we need them for human survival.

Since data documentation on neonicotinic toxicity to nontarget organisms should be enhanced, the effects of thiacloprid, a novel neonicotinoid insecticide, on the sediment-dwelling nontarget insect Chironomus riparius were investigated. C. riparius was impacted starting at concentrations of 0.5 μg/L, a concentration that can be considered environmentally relevant. Larval mortality, behavior, emergence, and Hsp70 protein level were sensitive indicators for the toxic effect of thiacloprid, whereas gender ratio and mouthpart morphology were not affected.

Turfgrass applications of imidacloprid were previously shown to suppress the abundance of certain soil arthropods. To ascertain whether those impacts harbor functional consequences, the effect of neonicotinoids on Japanese beetle (Popillia japonica Newman) predation was examined in three experiments that measured removal of eggs implanted into non-irrigated field plots. A first experiment confirmed that a single imidacloprid application reduced the abundance of nontarget fauna and the rate of egg removal. A second experiment compared the impacts of imidacloprid with those of three other neonicotinoids, while a third measured the impact of imidacloprid when applied in July, August or September. Egg removal declined 28.3–76.1% in imidacloprid-treated plots across all studies. Effects were detected as early as one week after treatment (WAT) and persisted as long as four WAT. The extent of suppression did not vary across month of application. Clothianidin, dinotefuran and thiamethoxam also suppressed egg removal, and the effects were similar among them and with imidacloprid. There was no discernible association between variation in rainfall and treatment effects, but this was not explicitly tested. Results support the hypotheses that a single neonicotinoid application can suppress predation on pest populations and that the effect does not vary with respect to active ingredient or season of application. Neonicotinoid application at the time of beetle oviposition puts intended effects (mortality of neonates) in conflict with unintended effects (disruption of egg predation).