Insecticides

Farmland birds are important indicators of the ecological health of our countryside and the recently published figures show how bad the situation is. BirdWatch Ireland and BirdLife Europe have revealed that farmland bird populations in Ireland and across Europe are at their lowest levels since records began. Grey partridge Perdix perdix numbers are down a massive 82pc, the skylark Alauda arvensis 46pc, the linnet Carduelis cannabina 62pc and the corn bunting Miliaria calandra 66pc. I wrote recently about how the curlew Numenius arquata is facing extinction and yellowhammer Emberiza citrinella numbers are at their lowest ever levels, while many other previously common farmland birds have shown significant, long-term declines. Intensive farming creates difficulties for almost all wildlife. Monocultures of grain and grasses provide little food for seed eaters unless generous margins are left at the headlands. Early mowing for silage removes vital springtime habitat. Drainage destroys wetlands and the damage done by removing hedgerows is well known. Pesticides can kill far more than the target 'pests' by also harming beneficial insects and the birds that feed on them, and continuous tillage depletes the organic matter in the soil. Slug pellets harm the creatures that eat slugs and rat poison can end up in the digestive systems of birds like barn owls. Careless spreading of slurry and silage effluent often causes serious pollution, as do incorrectly installed septic tanks, yet howls of protest are heard whenever someone points this out.

Currently there are more than 17,000 pesticide products on the market in the U.S., and scientists say there is much that remains unknown about their impact on the environment, including the effect of combinations of compounds. While many credit the EPA with doing a good job at making sure pesticides are safer and safer for humans, they have a lot to answer for when it comes to honey bees.

Sources within the EPA tell us that agency scientists have been voicing concern over the neonicotinoids since they first came up for registration over 15 years ago with special concern raised over impact to honey bees. Our sources also told us, however, that scientists can't even suggest a connection between pesticides and colony losses for fear of being ostracized and excluded from meetings. With decisions being made by administrators, who are not necessarily scientists, sources say they don't even know themselves what goes into these ultimate decisions of what to approve for sale. And sources report that EPA scientists feel demoralized, when they work so hard to get risk assessments out that decision makers ultimately ignore.

Two systemic neonicotinoids, imidacloprid and thiamethoxam, are widely used for residual control of several insect pests in cotton (Gossypium spp.), vegetables, and citrus (Citrus spp.). We evaluated their impact on six species of beneficial arthropods, including four parasitoid species—Aphytis melinus Debach, Gonatocerus ashmeadi Girault, Eretmocerus eremicus Rose & Zolnerowich, and Encarsia formosa Gahan—and two generalist predators—Geocoris punctipes (Say) and Orius insidiosus (Say)—in the laboratory by using a systemic uptake bioassay.

Wastewater treatment plants receive organic contaminants, such as pesticides, which reach the sewage system from domestic, industrial or agricultural activities. In wastewater, which is a complex mixture of organic and inorganic compounds, biotic or abiotic degradation of contaminants can be affected by the presence of co-solutes. The photodecomposition in natural sunlight of two neonicotinoid insecticides, thiamethoxam and thiacloprid, was investigated in wastewater, aqueous extracts of sewage sludge and in aqueous surfactant solutions, which are abundant in wastewater. Dissipation in the dark was also studied in wastewater, due to reduction of transmitted sunlight in wastewater ponds.

Several compelling lines of evidence suggest that environmental agents, including commonly used pesticides, can act as triggers for the development of Parkinson's Disease (PD). In fact, a progressively greater odds ratio for developing PD was associated with pesticide exposure, and several other epidemiological studies have implicated specific pesticides, including rotenone (an organic insecticide) and paraquat (a chemical herbicide still widely used throughout the world), in the development of parkinsonism.

The purpose of this study was to evaluate the impact of malathion on the immune system of wild birds, using Japanese quail (Coturnix coturnix japonica) as a model. Quail were exposed to malathion in drinking water at environmentally realistic concentrations (0 ppm, 1 ppm, and 10 ppm). In the fifth week, several arms of the immune response were tested using the T-cell based phytohemagglutinin (PHA) skin test, the B-cell mediated antibody response, and the chemiluminescence assay measuring innate immunity. After the sixth week of malathion exposure, quail were challenged with E. coli O2. The bursa of Fabricius and the spleen were assessed for histopathology.

Because of health concerns, persistence, and long-term environmental effects, the impact of pesticides on agriculture and public health has been the subject of considerable research. People exposed to pesticides had over a fourfold increased risk to Non-Hodgkin’s lymphoma (NHL), neuroblastoma, child brain development defects, Parkinson’s disease, prostate cancer, leukemia in children, male infertility and miscarriage.

A subacute toxicity study of acetamiprid was undertaken in 72 female wistar rats in four groups (18 each). Three different concentrations of acetamiprid (25, 100 and 200 mg/kg of body weight) were administered orally to rats. Untreated rat served as control. The antibody titre of sheep red blood cells (SRBC) in all the treated groups and decrease in cell mediated immune response (CMI) were evaluated by delayed type hypersensitivity reaction to dinitroflurobenzene (DNFB). Our results revealed that in 200 mg/kg body treated rats, there were significant (Pd≤0.01) decrease in mean values of total leukocyte count and relative lymphocyte count in rats. Globulin was also decreased significantly (Pd≤0.01) in acetamiprid treated rats compared to control. There was a significant decrease (Pd≤0.01) in spleen weight in rats treated with 200 mg/kg dose as compared to control. Histopathological examination of spleen revealed depletion of lymphocytes from Malpighian corpuscles in all treated groups in a dose dependent manner. The results indicated that acetamiprid suppressed both CMI and antibody forming ability of lymphocytes.

Ingestion is probably the most common way that birds are exposed to pesticides. Birds can swallow the pesticide directly, such as when a bird mistakes a pesticide granule for a seed, or indirectly, by consuming contaminated prey. They may also ingest pesticide residues off feathers while preening, or they may drink or bathe in tainted water. Pesticides can also be absorbed through the skin, or inhaled when pesticides are applied aerially.

Pesticides can also affect birds indirectly by either reducing the amount of available food or altering habitat.