Honey bee survival is affected by interactions between field-relevant rates of fungicides and insecticides used in apple and blueberry production

Abstract

Certain compounds of low toxicity can increase the susceptibility of an organism to toxic substances; this is known as potentiation. Demethylation inhibiting (DMI) fungicides can potentiate insecticides by impairing the production of detoxification enzymes. As both DMI fungicides and insecticides can be used near or during crop bloom, the combination may be hazardous if exposed to pollinators. Using pesticides used in blueberry or apple production, we conducted laboratory bioassays to test how combinations of field-relevant concentrations of DMI fungicides and insecticides affected honey bee (Apis mellifera) survival. We found propiconazole, a DMI fungicide, potentiated the toxicity of the neonicotinoid insecticide acetamiprid. We found no evidence of propiconazole potentiating field-relevant concentrations of the spinosyn insecticide spinetoram. We also found that the DMI fungicide flusilazole potentiated spinetoram but not acetamiprid. A fungicidal formulation combining pyraclostrobin and boscalid did not potentiate either insecticide. Given that bees can be simultaneously exposed to multiple pesticides, understanding the potential of pesticide potentiation and synergism may help mitigate risks associated with pollinator exposure to pesticides.

Interaction of Insecticides and Fungicides in Bees

“…A combination of thiacloprid and triflumizole even led to a 1,141-fold increase in toxicity ( 44 )! Similar results were demonstrated for a combined application of acetamiprid and the SBI fungicide propiconazole ( 131 ). Chronic exposure to these two substances caused synergistic negative effects on the mortality and weight of Asian honeybees ( Apis cerana ) ( 17 ).…”

“…Wernecke et al (140) showed that tank mixtures containing the non-SBI fungicides boscalid and dimoxystrobin and the neonicotinoid thiacloprid had no effect on bee toxicity both in laboratory, semifield and field standard assays. Likewise Manning et al (131) showed that the non-SBI fungicides pyraclostrobin and boscalid did not enhance toxicity of the neonicotinoid acetamiprid in honeybees. However, a study of Tsvetkov et al (147) showed that the acute toxicity of the neonicotinoids clothianidin and thiamethoxam was increased when they were co-applied orally in combination with field realistic concentrations of the non-SBI fungicide boscalid.…”

Antioxidant Enzymes of Honeybee Larvae Exposed to Oxamyl

“…As a sensitive biosensor of environmental changes, the bee colony reacts even to small deviations caused by pollutants. Sublethal effects of plant protection products can be manifested by the changed behaviour of bees when: searching for food, memory disorders, ability to learn, rejection of food, loss of orientation and similar situations [16,24]. The flying worker bees directly affected by insecticide may not have enough energy to return to the bee hive [21].…”