Droplegs – a solution for bees in agricultural landscape?

Droplegs – a solution for bees in agricultural landscape?

Last week I was at a demonstration of a technology that might help to calm down the conflict between beekeepers and farmers. Droplegs reduce the exposure of bees to pesticides by simply lowering the nozzles under the level of the flowers. This is especially interesting for oilseed rape (OSR): for many beekeepers it is an important (if not most important) honey crop. According to Dr. Klaus Wallner from the State Institute of Apiculture in Hohenheim, OSR is the main source for residues in pollen collected by bees.

The demonstration was organized by a working group including different stakeholders. Beekeepers, farmers, environmentalists are working together to solve the problems for (honey) bees in agricultural landscape. Which is great, there are plenty of such local or regional initiatives, working really well. There was much interest: 95 persons came to the event, though it took place with awful weather. Just before the demonstration started, it began to rain heavily. No weather for a real application, but it was ok for seeing how this new technique works.

What are droplegs?

Droplegs resulted from a joint effort of beekeeping and agricultural institutes. They searched for a solution to the a very specific problem: farmers treat OSR during the flowering period. Beekeepers locate their bees on the fields for getting honey and to help the colonies during spring development. By this, they get exposed to the substances used against fungal diseases and insect pests. Usually, farmers spray over the flowers, which wets them with the compounds. During flowering, only substances tested not to harm bees are allowed. However, foraging workers bring in residues to the colonies, which may alter the hive products. In addition, sublethal effects have attention only since a decade and new testing methods are required.

In this situation, the solution was to reduce the exposure of bees to any pesticides. So what if instead of spraying from above, the nozzles were below the flowers? Would this reduce the bees’ contact with plant protection products? Would the efficacy against the plant pests and diseases still be sufficient? Could this harm the crop? That was when the dropleg technology was developed.

The nozzles are mounted on long, flexible rods. By this, they get under the level of the main flowers, “combing” throug the crop. The spray is directed downwards and to the sides. Thus, no product reaches the flowers and bees can collect uncontaminated pollen. The results until now show that residues in the bee collected pollen decrease substantially using this technique. As you can see above, the nozzles disappear completely as soon they are in the crop. Fortunately, OSR plants are flexible and robust enough to weather such a “combing” practice.

Why treat at all?

Heavy rain and thunderstorms made us get into a machine hall for the discussion round that made clear the positions of the different stakeholders. For the professional beekeepers, droplegs are the only possible alternative for treatments in flowering crops. Yet, they would prefer that OSR and other crops visited by honey bees were not sprayed at all.

oilseed rape, OSR, agriculture and bees, pesticides

A button from the professional beekeepers in Germany demanding the only use of droplegs in flowering crops.

For the farmers however, treatments are necessary to maintain the profitability of OSR. This is a very “labour intensive” crop, susceptible for diseases, especially Sclerotinia, a fungal disease. Without spraying, the yield would dicrease to an extent that farmers couldn’t afford growing it anymore. In fact, a representative of the local authorities remarked that hardly any organic farmers grow OSR. In a quick research I found only data from 2013 discussing some Sclerotinia resistant varieties. I did not find any data on the percentage of organic farms with this crop, though. If you know any resources, please tell me!

Open questions

A technology like droplegs could therefore be a compromise that satisfies all parties. However, there are certain caveats. First of all, this method is quite expensive. A single nozzle costs 150 €, on a regular 30 m spraying device (with 60 nozzles) this would mean 9,000 € – a lot of money for single farmers that may only have small areas with OSR. A solution for this could be to first equip service providers that do the treatments for different farmers. Also public funding and obliging the agrochemical industry to support the technology were discussed.

Most importantly though, the farmers must be convinced that it is worthwhile to use droplegs. The main argument for them is the efficacy of the treatment compared with the conventional spraying. Tests all over Germany showed good results for treating Sclerotinia with this method. For the insecticides, data are still missing for clear recommendations. The problem was a low infestation pressure during the test years.

Not enough flowers in agricultural landscape

OSR is very important for beekeepers, but for farmers in some regions this crop is losing attractivity. For a certain period, it was subsidised as energy crop, but now maize has become the more profitable crop. In certain regions, the areas cropped with OSR decline continously, leaving both honey bees and beekeepers without an important crop. Therefore, more effort should be done to maintain crop diversity in agricultural landscape.

OSR is nearly the only remaining flowering arable crop, with only little semi-natural areas in many regions. This aspect of the problem was noted both from the beekeepers as well as from the environmental associations. This problem, however, will not be solved by droplegs or other technical solutions. This must be addressed by other measures, like agro-environmental schemes, that will be the subject of a separate post.


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