Höfchen estate field trial station: Ensuring crop protection products do not affect bees

Putting product safety to the test

Crops provide food, which is why farmers need to protect their harvests against destructive pests, weeds and diseases by using effective crop protection products. Equally, healthy pollinators such as honey bees and bumble bees are important for ensuring abundant harvests. Therefore, crop protection products must work alongside pollinators in a way that does not harm them. Bayer uses the Höfchen field trial station to perform semi-field tests as part of the pollinator safety test process.

Höfchen estate field trial station: Ensuring crop protection products do not affect bees


// The Höfchen estate is Bayer’s longest-standing crop field trial station.

// Researchers at the experimental station test new crop protection products for their safety to honey bees and their colonies.

// Semi-field trials under insect-proof netting tunnels apply a realistic worst-case scenario to investigate the effects of new products on honey bees.

// Researchers investigate acute toxicity and possible long-term effects.

It is spring and the sound of buzzing fills the giant white tents standing in the blossoming apple orchard. Thousands of honey bees are whizzing around in them on the search for pollen and nectar. The insects land on trees that have been treated with a new product to protect against fungal infection. Later, researchers observe and analyze whether the fungicide application has impacted the pollinators in any way.

Bee safety is one of the most important criteria crop protection products must fulfil if they are to be approved for the market.

Bayer uses the Höfchen estate field trial station near Burscheid, Germany, to conduct many of these tests on its herbicides, fungicides and insecticides. “We have over 60 years of experience in testing whether crop protection products are safe for beneficial insects such as honey bees,” says Dr Dirk Ebbinghaus, trial station manager at Bayer’s division Crop Science. His 17-strong team conducts semi-field studies to investigate if pesticides affect honey bees and their colonies. This involves applying the product to about 50 square metres of flowering plants, covering everything with a white tunnel tent and positioning a hive containing up to 3,000 honey bees inside. The tent prevents the insects from escaping to look for food outside the test area. This set-up allows the researchers to simulate a worst-case scenario. The bees spend up to twelve days collecting nectar and pollen from the treated plants only, which means they gather the largest amount of the substance that is realistically possible. “We measure the worker bees’ mortality to determine the acute toxicity,” explains Dr Ebbinghaus. “Worker honey bees usually live for up to six weeks. If the bees die after just a few days or hours, the product is not fit for further use in flowering crops that are visited by bees.” Another crucial factor for Dr Ebbinghaus’ team is whether the bee brood hatches unharmed after the experiment as these young bees will be needed to keep a strong colony going.

Bee tents in the field

In a field of flowering Phacelia, new products are tested. The honey bee colonies in the tents collect food from treated flowers.

In addition to the effects that are immediately visible, the experts also evaluate a potential long-term impact in other study types. “If fewer bees in the test hive survive the winter than in reference colonies, the substance may be weakening the bees,” says Dr Ebbinghaus. The team puts the substances through at least three randomized replicates in every trial. Afterwards, the results are passed on to the environmental experts at headquarters who analyze the data. These experts also developed the bee larval test (see also “Protecting bees for generations to come”, page 50). These intensive tests, though lengthy, are necessary to ensure there is no compromise on safety. It can take up to ten years for a product to pass from the first laboratory investigations through to the market launch. “It’s also not uncommon for us to re-test approved products to verify their pollinator safety profile when new questions on their environmental profile have been brought up by the environmental authorities,” says Dr Ebbinghaus. His team is also involved in the development of similar tests for bumble bees in close collaboration with colleagues from Bayer’s Ecotoxicology Department.

Bayer has been running its experimental station since 1940, and the first apiary was built in the following year. These days, the station is used for more than just testing the safety of crop protection products – it also puts new technologies for the safe application of the products through their paces. For instance, the experts have investigated Dropleg systems, which allow farmers to spray products onto oilseed rape plants from underneath, further minimizing the exposure of pollinators (see “Lower Application for Higher Protection”, BEENOW 2015). “Almost every farming-related product or new technology from Bayer gets thoroughly tested here,” says Dr Ebbinghaus. And that helps farmers and bees alike.


Bayer is continually striving to make crop protection products even safer for pollinators. Bees have long been of interest at the field station, from the time when honey bees were only used to help pollinate fruit crops, through to today when testing of crop protection products and new technologies for the safe application of those products are put through their paces.

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