Insecticides

Third and fourth instar Harmonia axyridis Pallas larvae feed directly on corn seedlings; therefore they may be at risk if the seedlings are chemically treated. Neonicotinoids are broad-spectrum systemic insecticides that are frequently applied to corn seeds prior to planting to protect seedlings from early-season root and leaf-feeding. In this study, H. axyridis larvae were exposed for 360 min to corn seedlings that had been grown from seeds treated with either thiamethoxam or clothianidin. Neurotoxic symptoms (trembling, paralysis, and loss of coordination) were observed in 72% of the H. axyridis larvae; recovery following neurotoxic symptoms rarely occurred (7%). Starvation of larvae for 48 h prior to seedling exposure may increase tissue consumption; however, there was no difference in the number of starved or satiated larvae that displayed neurotoxic symptoms and died. Neurotoxic symptoms and larval mortality were significantly more likely to occur if larvae were exposed to seedlings grown from seeds treated with neonicotinoids compared to the control. In addition, clothianidin resulted in significantly greater larval mortality (80%) compared to thiamethoxam (53%). Symptoms and mortality were rarely observed if seedlings were not treated with a neonicotinoid seed treatment (3% and 3%, respectively). Coccinellids are abundant in agroecosystems in which neonicotinoid seed treatments are likely to be applied. Therefore, the use of neonicotinoids may have negative effects on these non-target species if early-season leaf-feeding occurs in the field.

We studied, under laboratory conditions, the possible effects of sublethal doses of two soil applied insecticides (carbofuran and imidacloprid) on development, survival and fecundity of the predator Hippodamia undecimnotata. For studies, predator fed upon Aphis fabae that was reared on Vicia faba plants treated with the systemic carbofuran and imidacloprid. Survival of immature stages in insecticides treatments (67.6% and 52.2%, for carbofuran and imidacloprid, respectively) was lower than control (77.4%). Both insecticides did not affect significantly total immature developmental time, while carbofuran caused a significant reduction of adult weight. Adult average longevity was significantly higher for the control than the insecticides treatments. Moreover, females oviposited fewer eggs in both insecticide treatments than the control (33% and 55% reduction in average fecundity for imidacloprid and carbofuran, respectively). Population increase parameters were also adversely affected by insecticides application. The importance of the adverse effect of sublethal doses of systemic insecticides on designing and management of insects’ pests are discussed.

Ecotoxicological risk assessment of contaminants often is based on toxicity tests with continuous-exposure profiles. However, input of many contaminants (e.g., insecticides) to surface waters typically occurs in pulses rather than continuously. Neonicotinoids are a new group of insecticides, and little is known about their toxicity to nontarget freshwater organisms and potential effects on freshwater ecosystems. The aim of the present research was to assess effects of short-term (24-h) exposure to the neonicotinoid insecticide thiacloprid, including a postexposure observation period. A comparison of several freshwater insect and crustacean species showed an increase of sensitivity by three orders of magnitude in the following order: Daphnia magna < Asellus aquaticus = Gammarus pulex < Simpetrum striolatum < Culex pipiens = Notidobia ciliaris = Simulium latigonium, with median lethal concentrations (LC50s) of 4,400, 153, 190, 31.2, 6.78, 5.47, and 5.76 μg/L, respectively (postexposure observation 11–30 d). Thiacloprid caused delayed lethal and sublethal effects, which were observed after 4 to 12 d following exposure. Reduction in LC50s found when postexposure observation was extended from 1 d to a longer period (11–30 d) was up to >50-fold. Hence, delayed effects occurring after short-term exposure should be considered in risk assessment. The 5% hazardous concentration (HC5) of thiacloprid obtained in the present study (0.72 μg/L) is more than one order of magnitude below the currently predicted worst-case environmental concentrations in surface water. Concerning the selection of test organisms, we observed that the widely employed test organism D. magna is least sensitive among the arthropods tested and that, for neonicotinoid insecticides, an insect like the mosquito C. pipiens would be more suitable for predicting effects on sensitive species.

Zwei Jahre nach dem großen Bienensterben in Süddeutschland, bei dem etwa 20000 Bienenvölker durch das Insektizid Clothianidin getötet oder schwer geschädigt wurden, werden in der Landwirtschaft beim Raps-, Mais-, Gemüse- und Getreideanbau weiter bienengefährdende Pestizide eingesetzt.

Présentation et traduction Christian Pacteau.
Steve ELLIS est un des apiculteurs choisi par ses pairs, fin observateur et fin politique. Son propos, non dépourvu d'humour, peut se résumer en ceci.

The UK Government and retailers are under pressure to impose a ban on sale of pesticides linked to bee population decline following new research which groups call a 'growing body of evidence'. Environmental groups including the Soil Association and Buglife are making a renewed call for an end to the use of neonicotinoid pesticides, which are among the most commonly used pesticides worldwide, after a new study linked them to a decline in bee populations.