Risk posed to honeybees (Apis mellifera L, Hymenoptera) by an imidacloprid seed dressing of sunflowers

Abstract

In a greenhouse metabolism study, sunflowers were seed-treated with radiolabelled imidacloprid in a 700 g kg-1 WS formulation (Gaucho WS 70) at 0.7 mg AI per seed, and the nature of the resulting residues in nectar and pollen was determined. Only the parent compound and no metabolites were detected in nectar and pollen of these seed-treated sunflower plants (limit of detection < 0.001 mg kg-1). In standard LD50 laboratory tests, imidacloprid showed high oral toxicity to honeybees (Apis mellifera), with LD50 values between 3.7 and 40.9 ng per bee, corresponding to a lethal food concentration between 0.14 and 1.57 mg kg-1. The residue level of imidacloprid in nectar and pollen of seed-treated sunflower plants in the field was negligible. Under field-growing conditions no residues were detected (limit of detection: 0.0015 mg kg-1) in either nectar or pollen. There were also no detectable residues in nectar and pollen of sunflowers planted as a succeeding crop in soils which previously had been cropped with imidacloprid seed-treated plants. Chronic feeding experiments with sunflower honey fortified with 0.002, 0.005, 0.010 and 0.020 mg kg-1 imidacloprid were conducted to assess potential long-term adverse effects on honeybee colonies. Testing end-points in this 39-day feeding study were mortality, feeding activity, wax/comb production, breeding performance and colony vitality. Even at the highest test concentration, imidacloprid showed no adverse effects on the development of the exposed bee colonies. This no-adverse-effect concentration of 0.020 mg kg-1 compares with a field residue level of less than 0.0015 mg kg-1 (= limit of detection in the field residue studies) which clearly shows that a sunflower seed dressing with imidacloprid poses no risk to honeybees. This conclusion is confirmed by observations made in more than 10 field studies and several tunnel tests.

Modes of honeybees exposure to systemic insecticides: estimated amounts of contaminated pollen and nectar consumed by different categories of bees

“…In Gaucho  seed-dressed sunflower and maize plants it is about 3.4 µg of imidacloprid per kilo of pollens (Bonmatin et al, 2001;Schmuck et al, 2001). -Pollen pellets in traps: pollen traps are installed at the hive entrance to catch some of the pollen pellets brought back by pollen foragers.…”

Espécies, número e frequência de visitantes florais em culturas agrícolas submetidas à aplicação de produtos fitossanitários

“…Blacquière et al (2012) demonstraram a susceptibilidade de algumas abelhas a moléculas inseticidas do grupo dos neonicotinoides e de outros compostos, como permetrina, diazinon e metomil. Schmuck et al (2001) imidacloprido afetou o ciclo de postura de ovos de rainhas e a quantidade de larvas e pupas de Apis mellifera (Linnaeus, 1758) (Hymenoptera: Apidae). Isso demonstra que produtos fitossanitários, além de influenciar o comportamento de visitação floral, também podem afetar diversos aspectos do desenvolvimento de insetos benéficos (Decourtye et al, 2005;Devillers, 2010).…”

“…Vários estudos têm demonstrado que muitos inseticidas, como, por exemplo, os do grupo dos neonicotinoides, podem estar presentes em diferentes partes da planta em que são aplicados, como pólen e néctar, os quais são fontes de alimento para polinizadores e visitantes florais (Schmuck et al, 2001). Uma vez que esses recursos são consumidos, abelhas polinizadoras podem estar expostas aos efeitos desses inseticidas, sendo que metabólitos desses compostos químicos podem ser encontrados em grãos de pólen coletados, no pró-prio mel ou na cera produzidos por esses insetos (Blacquière et al, 2012).…”

Pesticide exposure of honeybees (Apis mellifera) pollinating melon crops

“…The neonicotinoid insecticides imidacloprid, acetamiprid, and thiamethoxam were found in the honey of bees that pollinate melon crops. Application of neonicotinoid insecticides to plants is known to result in residual pesticide concentrations in the nectar and pollen of flowers, even when it is used to treat only the seeds (Schmuck et al 2001;Bonmatin et al 2003;Rortais et al 2005). Furthermore, the guttation drops of muskmelon treated with imidacloprid may contain high concentrations Pesticide exposure of honeybees Table V.…”

“…The LD50 of acute oral exposure to imidacloprid in honeybees was estimated to be 3.7 to 40.9 ng per bee, or 0.14 to 1.57 mg kg −1 in food (Schmuck et al 2001), and the LD50 of acute oral exposure to thiamethoxam in honeybees was estimated to be 5.0 ng per bee (Godfray et al 2014). However, bees are much more sensitive to chronic exposure to imidacloprid: reduced survival rates were observed in honeybees that ingested a cumulative dose of 0.01 ng per bee for 8 days (Suchail et al 2001).…”