Neonicotinoid insecticides translocated in guttated droplets of seed-treated maize and wheat: a threat to honeybees?

The immune system of bees is influenced by a diversity of factors, some of which have changed in the last 10 years such as the application of pesticides. In addition to pollen, nectar and dust, guttated water of seed-dressed plants might be a new source of contamination to bees. Our experiments demonstrated that guttated water of plants germinated from seeds dressed with neonicotinoids contains neonicotinoids. Maize seeds treated with clothianidin (PonchoA (R) 0.5 mg/seed and PonchoA (R) Pro 1.25 mg/seed) resulted in neonicotinoid concentrations up to 8,000 ng mL(-1) in the guttated fluid. This concentration decreases rapidly, but remained detectable over several weeks. Seeds treated with PonchoA (R) Pro did not result in higher concentrations in guttated droplets in the first stages of plant development, but the concentration decreased more slowly. Triticale seed treated with imidacloprid contained small quantities of this active agent (up to 13 ng mL(-1)) in the guttated fluid the following spring after overwintering. During the sampling of guttation fluid, no bees were observed collecting these droplets from triticale or maize. To evaluate the attractiveness of guttation fluid exuded from seed-treated plants under field conditions, more studies are required.