Pesticide Effects on Bumble-Bees

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In the current standard risk assessment of pesticides, the risk of adverse effects on honeybees is assessed by short-term (48 hours) tests, in which only the effect on adult survival is measured. However, regulations based on these risk assessments may not protect these beneficial insects sufficiently. In order to investigate sub-lethal effects of pesticides, studies using lower dosages and measuring effects over a long-er period are required.
Furthermore, in laboratory tests, conditions are generally optimal for the test animals, while in nature pesticides are seldom the only stressor of bees. In most landscapes in Northern Europe, periods of food scarcity occur, and bees are exposed to a range of different pathogens and parasites. Thus, an interesting aspect to investigate is whether bees exposed to other stressors, including nutritional stress or pathogens are more sensitive to pesticides than non-stressed bees.
Honeybees are not the only pollinating insects affected by pesticides. However, it is unknown whether the sensitivity of wild pollinators including bumble-bees, solitary bees, hover flies and butterflies differs from honeybees, which have a very different life history. Therefore, this project focusses on another common pollinator, the buff-tailed bumble-bee, Bombus terrestris. We have investigated the impact of three in-secticides (Biscaya, Fastac and Karate), all of which are used in flowering crops that attract flower-visiting insects. Hence, foraging bumble-bees are expected to be ex-posed to pesticides by direct contact when handling sprayed flowers or by ingesting them with pollen and nectar.
Four types of tests were included in the study:
1. Short-term laboratory tests, in which bumble-bees are tested as in the hon-eybee acute tests. Results from these tests show mortality after 48 hours.
2. Long-term (14 d) laboratory studies that, in addition to mortality, assess ef-fects on reproduction, such as numbers of eggs and larvae. In these stud-ies, we used queen-less micro-colonies, which are easy to manage.
3. Semi-field tests, in which the bees in the micro-colonies did not only live in the small box, but had access to a larger cage in which they could move around and forage on artificial flowers. Effects were measured in the same manner as in the long-term laboratory tests.
4. Field studies, in which hives with queen-right colonies of bumble-bees were exposed by feeding them sugar solution containing pesticide and thereafter released into landscapes with a low pesticide load. The development of the bee families was measured by weighing the nests on a weekly basis for eight weeks.
In the laboratory and semi field tests, in addition to studying the effect of pesticides alone, we tested whether the sensitivity of bumble-bees to effects of pesticides in-creased when the bees were infected by an insect-pathogenic fungus or were starved prior to the experiments.
Original languageEnglish
PublisherMiljøstyrelsen
Volume181
Number of pages140
ISBN (Electronic)978-87-7038-062-1
Publication statusPublished - 11 Jun 2018
SeriesPesticide Research

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