Why did my bees die?

by Normand Mrd February 1, 2024

Bees have an essential role in our ecosystem, they are responsible for the reproduction of more than 80% of plant species, they play a role in the production of more than three quarters of the world's crops (the majority of fruit, vegetable, oilseed and protein crops, nuts, spices and stimulants), they represent 10% of the turnover of world agriculture and bring in 153 billion euros per year.

For around ten years, the bee population has been in sharp decline, with a total disappearance in certain areas. The phenomenon of “bee colony collapse disorder” or CCD (“colony collapse disorder”) suddenly causes bees to disappear in hives without any corpses being found nearby.

This syndrome is of great concern due to the ecological importance of the bee as a pollinator. In France, nearly 30% of bee colonies disappear each year. In ten years, 15,000 beekeepers have ceased their activity.
These figures are all the more worrying when we see that in one region of China bees have completely disappeared due to the intensive use of pesticides.

Indeed, bees are the first victims of pesticides and more particularly neonicotinoid insecticides. While article 125 of Law No. 2016-1087 of August 8, 2016 for the reconquest of biodiversity, nature and landscapes prohibited the use of neonicotinoids for seed treatment from September 1, 2018, with possible adjustments until July 1, 2020, beekeepers are very worried about the decision of the national agency for food, environmental and occupational health safety (ANSES) to authorize, on September 27 2017, two new insecticides, which have the active ingredient sulfolaxaflor. These products have a real impact on the nervous system of insects, increasing their dysfunction and mortality, thus devastating bee colonies.
Honey production over the last twenty years has fallen and been halved, the mortality rate of bees can even go up to 80% in some hives.

Bees killed by varroa

Bees killed by varroa are often found in clusters at the bottom of the hive. They can also be found in the brood, where varroa mites feed on the larvae.

Bees that die from varroa often show signs of malnutrition, such as atrophied wings or swollen abdomens. They may also show signs of diseases, such as nosemosis or American foulbrood.

It is important to carefully monitor bee colonies for signs of varroa infestation. Beekeepers can use methods such as checking the brood or counting dead varroa mites at the bottom of the hive to assess the extent of the infestation.

Varroa infestation rate in Europe

The rate of varroa infestation in Europe has been steadily increasing since the parasite was introduced to Europe in the 1970s. By 2024, it is estimated that more than 90% of colonies will of European bees are infested with varroa.

The infestation rate varies from one country to another, but it is generally higher in southern European countries, where climatic conditions are more favorable to the development of the parasite.

In France, for example, the average infestation rate is estimated at 3.5%, but it can reach 10% in the south of the country.

Factors that contribute to the increased rate of varroa infestation include:

Climate change, which favors the development of the parasite
The decrease in the diversity of honey plants, which offers fewer resources to bees
Using varroa control methods that are not effective in the long term

The number of bees killed by varroa varies depending on several factors, including:

The severity of the infestation
Resistance of bees to infection
Environmental conditions

In general, it is estimated that a bee colony infested with varroa can lose up to 30% of its population each year. In the most severe cases, the infestation can lead to the death of the entire colony.

How to prevent a Varroa infestation?

There are several ways to prevent a Varroa infestation. Best practices include:

Monitoring

Beekeepers should inspect their bee colonies regularly, at least once a month. They may use a method called "brood checking" to detect varroa mites. This method involves examining the brood, the part of the hive where bees lay their eggs, to look for adult varroa mites and varroa eggs.

Colony health

Healthy bee colonies are more resistant to infections and infestations. Beekeepers can boost the health of their colonies by providing healthy habitat, planting honey flowers near hives, and providing bees with a supply of water and food.

Preventive control methods

There are several methods of preventive control against varroa. The use of treatment Stop Varroa is the most effective. Beekeepers can also use biological treatments, such as varroa nematodes, to control varroa populations.