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Assessing the impact of mixtures of pyrethroids and fungicides on honeybees - PN0945

There has been considerable concern over the last few years, including consideration by the Environmental Panel, over the potential for synergism between pyrethroids and fungicides applied to oilseed rape. In response to the concerns of the Environmental Panel there is work within WIIS to identify residues of fungicides in submitted honeybee samples and thus whether synergism is responsible for incidents. However, incidents reported through the Wildlife Incident Scheme have, according to field data, included mixtures of pyrethroids with fungicides which are not synergistic under laboratory conditions, i.e. Compass and Fastac. Interpretation and regulation may be difficult if it is unclear whether synergism or change in repellency is responsible for the incidents. The repellent nature of pyrethroids are important in limiting the exposure of honeybees to this highly toxic group of insecticides. Therefore it is important that this is investigated to ensure increased exposure of honeybees to pyrethroids is not occurring by reducing the repellent nature of the insecticide, i.e. the risk assessment based on repellency is valid. The pyrethroid varroacide fluvalinate is regularly detected in the incidents reported to WIIS due to its use as a varroacide in honeybee colonies. A concern is that synergy may occur between the varroacide in the hive and fungicides applied as pesticides to flowering crops. The exposure of bees to high levels of fungicides may affect their susceptibility to the toxic effects of the pyrethroid which are normally considered safe. This study offers the opportunity to compare the synergy of fungicides with pyrethroids applied as pesticides and those applied as varroacides within the project and therefore consider all sources of exposure to pyrethroids.
1. To determine if the mixing of fungicides with pyrethroids alters the repellent properties of the pyrethroid and thus increases the risk to honeybees when applied to flowering crops.
2. To compare synergy between pyrethroids applied as varroacides, pyrethroids applied as pesticides and fungicides applied as pesticides.
Project Documents
• Final Report : Assessing the impact of mixtures of pyrethroids and fungicides on honeybees   (1190k)
Time-Scale and Cost
From: 2001

To: 2004

Cost: £55,718
Contractor / Funded Organisations
Central Science Laboratory
Environmental Protection              
Nature conservation              
Wildlife conservation              
Fields of Study
Pesticide Safety