NEW SCIENTIFIC ARTICLE: Multiple Routes of Pesticide Exposure for Honey Bees Living Near Agricultural Fields

Thursday 05 January 2012

Thiamethoxam soil seed coating Pollen neonicotinoids nectar honeybee Exposure Dust Clothianidin

Dust during seeding (dust-girolami.jpg)Scientists form the University of Purdue University, Indiana, USA, have just published a study in which the show the different ways bees can get in contact with pesticides in agricultural fields. Pesticides from the family of neonicotinoids, with systemic properties and highly toxic for bees, were targeted. This US study confirms the findings of European researchers on the way bees and other beneficial insects that provide us pollination services are exposed to pesticides.

Regardless the way of application (as spray, seed treatment, soil treatment, irrigation water, etc), systemic products go inside the plant to protect it from pests "from inside". Another characteristic of these compounds is that they are extremely toxic for bees (up to 7.000 times more than DDT).

Unfortunately, both pests and beneficial insects (like pollinators) can get in contact with these pesticides. Some routes described are pollen and nectar produced by these plants, plant exudates (water sources for bees), dust produced from seeding operations, spraying, etc. Furthermore, these compounds have the characteristic of remaining in the soil over long periods. Therefore, they can be available for pollinators for years.

The study mentioned have studied residues in honeybees, pollen stored in the hive and other several potential exposure routes associated with plantings of neonicotinoid treated maize. During spring, extremely high levels of clothianidin and thiamethoxam (two neonicotinoid compounds) were found in planter exhaust material (dust) produced during the planting of treated maize seed. These results are in line with what European researchers found. Neonicotinoids were also found in the soil of each field sampled (same as in France), including unplanted fields. Very interestingly, the study have shown that plants visited by foraging bees (dandelions) growing near these fields were found to contain neonicotinoids as well. This indicates deposition of neonicotinoids on the flowers, uptake by the root system, or both. Guttation Dandelion - Germany (guttation-dandelion.jpg)

As a result, the risk for bees is not just restricted to the field in which the application of pesticides is done.

Dead bees collected near hive entrances during the spring sampling period were found to contain clothianidin as well, although whether exposure was oral (consuming pollen) or by contact (soil/planter dust) is unclear.

Pollen collected by bees and stored in the hive also contained the insecticide clothianidin. Maize pollen from treated seed was found to contain clothianidin and other pesticides; and honey bees in the study readily collected maize pollen.

These results have implications for a wide range of large-scale annual cropping systems that utilize neonicotinoid seed treatments.

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