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Estonian scientists are working to replace herbicides with biowarriors

Probably everyone loves big, beautiful, tasty strawberries. But how do we avoid excessive use of herbicides and instead use pollinating insects as a pest barrier? Life in Estonia talked to Marika Mänd, Professor of the Estonian University of Life Sciences and participant in the international research group. She let us have a closer look into the nature of biowarriors.

What is the entomovector technology?

This new technology first emerged in 1990. Scientists, who studied different bee species and pollinators found that, in addition to pollen, they also carry a wide variety of fungi or micro-organisms. They had an idea: if insects carry fungi with them, then, on the one hand, they are the distributors of the diseases, but on the other hand, they could also distribute the compounds that are useful to us. They figured out how to use bees to transfer pathogen-destroying bacteria from one plant to another.

The development of the area has been difficult and, in the beginning, it was more researched in Canada. The results showed that in greenhouses it works perfectly. Unfortunately, outside we can’t force bees to fly to the place we want. Beekeepers have struggled to find ways to pollinate and guide bees. For example, they put a scent in the hive so that bees could find food, but no method has produced good results so far. That’s why the entomovector technology has not developed so far, because people were sure that it wouldn’t work on the fields, and there was no point in trying. Now, however, that interest is rising again.

Most of the fields are in wilderness, whereas greenhouses use very accurate technology to keep the humidity and temperature at the optimum. We can use bees to fight grey mould, but it doesn’t make sense to use them in greenhouses. There was an interest in how to solve this problem all over the world, but instead, we must focus on local conditions. In Estonia, we have researched the grey mould found on strawberry, raspberry, tomato and other crops, but if we’re going to test it on the field, we need to know the different aspects.

First of all: which microorganism is going to work? We are a northern country. Any available and effective microorganism may not work. Secondly, which pollinator type to use? We think all pollinators are on blossoms, but different species prefer one or another plant, and this culture has to offer something to the bee. If it doesn’t provide suitable food, the bees won’t come. Most importantly, if we spread any micro-organism in the environment, then it must be safe for everyone – to the environment, bees and humans. Its development in each specific region is very specific and cannot be done simply by taking over.

Where is this research going on?

Professor Heikki Hokkanen from Finland is the head of this joint European research project and we have people from Turkey, Italy, France, Germany and Belgium. Every country conducted their own tests and in Estonia we tried with bumblebees and honey bees. Previous studies by professor Hokkanen showed that honey bees are perfectly capable of pollination and dispersion.

The thing is that the honey bee comes from tropical regions. That bee flies to find a great source of food for her large family and when she finds it, she informs the hive. She’s recruiting the whole family on a couple of blossoming trees that are nearby, and here the bee behaves the same way. If a honey bee finds a great food resource, she won’t go anywhere else. We have rape crops blossoming at this time, which are the great love of honey bees, because that pollen has three amino acids that are extremely necessary for the development of bee larvae.

We were experimenting here with strawberries that were not of particular interest. Although there was a huge 12-hectar field of flowering strawberries by their side, our bees from twelve hives went to rape. Only 2% of pollen was collected from the strawberries, which showed that they did not generally go there. The bumblebees, on the other hand, were not so enthusiastic about the rape, but were picking up the strawberry pollen about as much as the rape.

The results showed that we could use the bumblebee and the European honey bee for entomovector here. From the perspective of production, a honey bee hive can always be bought because the production of bumblebees has begun. It has had a very good impact on pollination and the whole area of entomovector technology.

What happens in nature at the time we’re going to pollinate the strawberry?

We get the same species we have ourselves: buff-tailed bumblebee. We can also buy this species from Belgium and the Netherlands, but in the wild, we have only female bees, who are just beginning to nest; we have no base for pollinators yet. So, it’s possible to buy bumblebees, put them on a field and see what’s going to happen. As the bumblebee began to work, it surprised us a little, but at the same time it was also very good, precisely because it was not yet the season for bumblebees. Even though the strawberry is not their greatest love, the bumblebees still visited the strawberries.

It turned out that pollen in some parts even had 40% from strawberry pollen and in some parts less, but on average it was around 22-25%. Then we checked if the bees carried the compound to the flowers. The most striking result was that the fungi were evenly distributed over the blossoms and that surprised us very much. We counted the bugs on the flowers and saw that there was a secondary distribution of the product taking place. The large number of insects led to pollination and also to the dispersion of the product. So entomovector technology has two effects: on the one hand, it promotes disease control and on the other, pollination.

Pollinated strawberries are bigger, more beautiful and more money can be asked for them. When one starts to use the same technology on a raspberry, one can use a honey bees who love raspberries. My doctoral student took the bees to a friend’s raspberry plantation: he was very surprised how much harvest he got. We have forgotten a very important thing in agriculture: in certain cultures, we need to grow pollinators for more crops because we have large areas of monocultures that need extra pollination.

When could this new technology replace existing herbicides?

A lot of growers are already using it, but it’s not a panacea and very much depends on the weather. The damager of the plants is a fungus whose development starts when plants bloom. At this stage, we could distribute the compound with a machine, but bees are better, because during the blooming period we can’t spray the fields every day. The bees visit these blossoms and immediately carry the compound. It’s “precision biocontrol”, which means that the substance goes exactly where it’s needed. The use of bumblebees is, however, better in our conditions, as there can be very cold weather during strawberry blooming season.

The real disease control scheme used in Europe is that the harvesters pick the strawberries and then spray the fungicide to try to suppress the rest of the grey mould. In a few days, the ripened berries will be collected and the field will be poisoned again, but no one will want berries that are sprayed too much. If it rains, high efficiency may not be achieved with this technology, as rain will wash the product off the blossoms.

For our compound, we use a fungus that is separated from the soil of the Nordic countries and is developed by a Finnish company. The initial idea was to use this product to eradicate soil pathogens, but then it was also tried as an entomovector and it turned out that the pathogens were equally affected.

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