Insecticides

The guild of ‘aerial insectivores’ – birds that specialize on feeding on flying insects – includes Whip-poor-wills, nighthawks, swifts, swallows, martins, and flycatchers. Early results from the second Ontario Breeding Bird Atlas indicated some startling declines and even range contractions for this guild. Now that the 2001-2005 Ontario Atlas is complete, the plight of aerial insectivores is gaining increasing attention. The patterns of decline are mirrored very closely by the Breeding Bird Survey, not only in Ontario, but also across much of North America. Early results from the second Maritimes Breeding Bird Atlas and data from the recently completed second New York State Atlas also point to similar patterns. The magnitude of the declines, especially within the past 20 years or so, is alarming. The proverbial clock may well be ticking down on many common species of aerial insectivores in Canada. In the last two decades alone, populations have fallen by over 70% in the case of Bank Swallow, Common Nighthawk, Chimney Swift, and Barn Swallow, and by over 50% for Cliff Swallow, Olive-sided Flycatcher, Eastern Wood-Pewee, Northern Rough-winged Swallow, Eastern Kingbird, and Purple Martin. Declines have been so severe that Chimney Swift, Common Nighthawk, and Olive-sided Flycatcher were recently designated as nationally Threatened species. Barn Swallow, Bank Swallow, and Eastern Wood-Pewee may not be far behind.

En 1962, la biologiste américaine Rachel Carson alertait l’opinion, dans Printemps silencieux – livre demeuré célèbre pour avoir lancé le mouvement environnementaliste moderne –, sur les risques présentés par le DDT (dichlorodiphényltrichloroéthane). Quatre rapports d’expertise scientifique et une décennie plus tard, le célèbre insecticide était banni des pratiques agricoles aux Etats-Unis, avant d’être peu à peu interdit, partout dans le monde, dans ses usages de protection des cultures. Près d’un demi-siècle s’est écoulé depuis, et le DDT n’a pas fini de faire parler de lui. Une étude publiée mercredi 17 juin dans le Journal of Clinical Endocrinology & Metabolism (JCEM) suggère que les femmes qui atteignent la cinquantaine paient aujourd’hui le prix de son utilisation. Selon les résultats présentés par Barbara Cohn, directrice du Child Health and Development Studies (Public Health Institute à Berkeley, Californie), et ses coauteurs, les cinquantenaires américaines ayant été le plus exposées au DDT in utero, par le biais de leur mère, ont en effet un risque quadruplé de développer un cancer du sein, par rapport à celles qui ont été le moins exposées à ce perturbateur endocrinien. Pour parvenir à cette conclusion, les auteurs ont utilisé les données d’une grande cohorte de femmes californiennes dont le suivi remonte à plus d’un demi-siècle. Ces femmes ont donné naissance, entre 1959 et 1967, à plus de 20 000 enfants, et plusieurs paramètres biologiques de chaque grossesse ont été enregistrés.

One of nature’s best scavengers is under serious threat in Africa, largely from poison. According to the first analysis of African vultures, populations of seven species have fallen by 80% or more over three generations. Most of these species may qualify as critically endangered. “The rates of decline stand out as being pretty rapid,” says conservation biologist Rhys Green of the University of Cambridge in the United Kingdom, who was not involved in the new analysis. The situation for African vultures, he says, “is not yet irrecoverable, but it is serious.”

The stingless bee Scaptotrigona postica is an important pollinator of native and cultivated plants in Brazil. Among the factors affecting the survival of these insects is the indiscriminate use of insecticides, including the neonicotinoid imidacloprid. This work determined the toxicity of imidacloprid as the topical median lethal dose (LD50) and the oral median lethal concentration (LC50) as tools for assessing the effects of this insecticide. The 24 and 48 h LD50 values were 25.2 and 24.5 ng of active ingredient (a.i.)/bee, respectively.

Integrated Pest Management (IPM) is a decision making process used to manage pests that relies on many tactics, including cultural and biological control, which are practices that conserve beneficial insects and mites, and when needed, the use of conventional insecticides. However, systemic, soil-applied neonicotinoid insecticides are translocated to pollen and nectar of flowers, often for months, and may reduce survival of flower-feeding beneficial insects. Imidacloprid seed-treated crops (0.05 mg AI (active ingredient) /canola seed and 1.2 mg AI/corn seed) translocate less than 10 ppb to pollen and nectar. However, higher rates of soil-applied imidacloprid are used in nurseries and urban landscapes, such as 300 mg AI/10 L (3 gallon) pot and 69 g AI applied to the soil under a 61 (24 in) cm diam. tree. Translocation of imidacloprid from soil (300 mg AI) to flowers of Asclepias curassavica resulted in 6,030 ppb in 1X and 10,400 ppb in 2X treatments, which are similar to imidacloprid residues found in another plant species we studied. A second imidacloprid soil application 7 months later resulted in 21,000 ppb in 1X and 45,000 ppb in 2X treatments. Consequently, greenhouse/nursery use of imidacloprid applied to flowering plants can result in 793 to 1,368 times higher concentration compared to an imidacloprid seed treatment (7.6 ppb pollen in seed- treated canola), where most research has focused. These higher imidacloprid levels caused significant mortality in both 1X and 2X treatments in 3 lady beetle species, Coleomegilla maculata, Harmonia axyridis, and Hippodamia convergens, but not a fourth species, Coccinella septempunctata. Adult survival were not reduced for monarch, Danaus plexippus and painted lady, Vanessa cardui, butterflies, but larval survival was significantly reduced. The use of the neonicotinoid imidacloprid at greenhouse/nursery rates reduced survival of beneficial insects feeding on pollen and nectar and is incompatible with the principles of IPM.

Neonicotinoid insecticides have come under scrutiny for their potential unintended effects on non-target organisms, particularly pollinators in agro-ecosystems. As part of a larger study of neonicotinoid residues associated with maize (corn) production, 76 water samples within or around the perimeter of 18 commercial maize fields and neighbouring apiaries were collected in 5 maize-producing counties of southwestern Ontario. Residues of clothianidin (mean = 2.28, max. = 43.60 ng/mL) and thiamethoxam (mean = 1.12, max. = 16.50 ng/mL) were detected in 100 and 98.7%of the water samples tested, respectively. The concentration of total neonicotinoid residues in water within maize fields increased six-fold during the first five weeks after planting, and returned to pre-plant levels seven weeks after planting. However, concentrations in water sampled from outside the fields were similar throughout the sampling period. Soil samples from the top 5 cm of the soil profile were also collected in these fields before and immediately following planting. The mean total neonicotinoid residue was 4.02 (range 0.07 to 20.30) ng/g, for samples taken before planting, and 9.94 (range 0.53 to 38.98) ng/g, for those taken immediately after planting. Two soil samples collected from within an conservation area contained detectable (0.03 and 0.11 ng/g) concentrations of clothianidin. Of three drifted snow samples taken, the drift stratum containing the most wind-scoured soil had 0.16 and 0.20 ng/mL mainly clothianidin in the melted snow. The concentration was at the limit of detection (0.02 ng/mL) taken across the entire vertical profile. Our results suggest that neonicotinoids may move off-target by wind erosion of contaminated soil. These results are informative to risk assessment models for other non-target species in maize agro-ecosytems

Earthworms (Eisenia fetida) are one of the most abundant terrestrial species, and play an important role in maintaining the ecological function of soil. Neonicotinoids are some of the most widely used insecticides applied to crops. Studies on the effect of neonicotinoids on E. fetida are limited. In the present work, we evaluated the effects of five neonicotinoid insecticides on reproduction, cellulase activity and the tissues of E. fetida. The results showed that, the LC50 of imidacloprid, acetamiprid, nitenpyram, clothianidin and thiacloprid was 3.05, 2.69, 4.34, 0.93 and 2.68 mg kg−1, respectively. They also could seriously affect the reproduction of E. fetida, reducing the fecundity by 84.0%, 39.5%, 54.3%, 45.7% and 39.5% at the sub-lethal concentrations of 2.0, 1.5, 0.80, 2.0 and 1.5 mg kg−1, respectively. The cellulase activity of E. fetida was most sensitive to clothianidin. Significant disruption of the epidermal and midgut tissue was observed after 14 d exposure. In summary, we demonstrate that imidacloprid, acetamiprid, nitenpyram, clothianidin and thiacloprid have high toxicity to earthworm, and can significantly inhibit fecundity and cellulase activity of E. fetida, and they also damage the epidermal and midgut cells of earthworm.