This past winter, the mortality rate among honeybees was again significant. During the initial inspections of beehives, beekeepers found that many colonies had died or were severely weakened. There are various causes for this, and further research is certainly needed. However, it is already clear that the high bee mortality rate this time is not caused by neonics. But neonics are not the only enemies bees face. Several other factors can weaken a bee colony. Let’s explore some of these causes.

But first... let’s talk about the honeybee

The honeybee (Apis mellifera) forms large colonies led by a single queen, supported by worker bees (female) and drones (male). Honeybees are kept in hives and can grow to a population of over 50.000 during the summer. They are crucial pollinators of flowering plants and indispensable for the ecosystem and agriculture. In our region, beekeepers primarily keep two breeds: Carnica bees and Buckfast bees. Both are gentle during hive inspections. The beekeeper’s job is to care for the bees and prevent swarming. In a good honey flow year, the beekeeper is rewarded with delicious honey. There are approximately 360 species of wild bees in the Netherlands and Belgium, which mainly live solitary lives. They too are important for the pollination of flowering plants. However, this pollination is at risk due to the severe bee mortality we are experiencing, caused by various factors.

CAUSE 1: the impact of the harmful Varroa mite

The Varroa mite is one of the most severe challenges for modern beekeeping. The ectoparasite, scientifically known as Varroa destructor, causes the Varroa mite disease (varroatosis) in bees. This exotic parasite poses a significant threat to the European honeybee. The Varroa mite originated in Asia and was first discovered in the Netherlands in 1983.

Varroa mites weaken bees and can transmit viral diseases, leading to high winter mortality. Beekeepers combat this harmful mite using oxalic acid, formic acid, or variants of those products. Additionally, there are on-going trials with brood restriction methods to remove the mites along with the infested brood.

CAUSE 2: limited food supply

Bees need good host plants for both nectar and pollen. Various databases indicate the value per plant species. Not every flowering plant is valuable to bees. While there is plenty in bloom during spring and summer, early spring and autumn offer very few good forage plants. Native species alone are not sufficient. In gardens, we can use the best bee-friendly plants available from our growers’ wide assortment. Bees perceive the colour purple better than other colours. So it makes sense that the best bee plants often have purple flowers, such as lavender (Lavandula), ornamental onions (Allium), butterfly bush (Buddleja), and catnip (Nepeta faassenii).

CAUSE 3: weather conditions

Weather also greatly influences bee flight behaviour. A wet, cold spring and/or a wet summer have significant consequences. Bees can barely fly in bad weather, and many trees and shrubs bloom irregularly or too briefly. This severely limits forage availability and directly impacts the bee population. Additionally, it can lead to bees entering winter significantly weaker, reducing their chances of survival.

CAUSE 4: pollution

In our modern society, we frequently deal with pollution. We use many chemicals that affect our health, as well as the health of our flora and fauna. Some of these substances remain unnoticed by the general media, such as dioxins, PCBs, PFOS, lead, cadmium, arsenic, and mercury. However, these substances can be found in high concentrations in certain areas and are known to be harmful. The media and various environmental organisations often portray crop protection as the main culprit. While it is clear that crop protection should be used judiciously and its impact should not be downplayed, our growers do possess sufficient expertise. They all must undergo annual training to maintain their spraying or phytosanitary licenses. A few years ago, one of the potential causes of bee mortality was attributed to so-called neonics (neonicotinoids). Since 2013, restrictions have been in place in Europe, and since 2018, there has been a total ban on their use. It’s now been six years, and winter bee mortality remains alarmingly high, indicating that the influence of neonics might not have been as significant as once thought.

CAUSE 5: invasive Asian hornet

This relatively new invasive species is a voracious predator that can devastate entire bee colonies. In recent years, the Asian hornet has been spreading rapidly and must be controlled. This predator could become the biggest threat to our honeybees in the future. The Asian hornet is now included on the EU list of invasive alien species, meaning that within the European Union, measures are agreed upon to prevent the spread of such species as much as possible.

Bee mortality remains alarmingly high

The increasing bee mortality rate remains a serious concern. Although winter mortality of honeybees occurs annually, it can be problematic in some years due to various causes, often involving a combination of factors. Proper care and disease management are crucial to mitigate the effects as much as possible. Ensuring sufficient forage plants throughout the entire flight period is also essential. It’s recommended to use as many plants as possible that attract bees and provide ample pollen and nectar. For good advice and a wide selection of suitable plants, you can, of course, turn to the growers at the GrootGroenPlus trade fair. And if you encounter the Asian hornet, please alarm beekeepers, waarneming.nl or vespawatch.be.

We asked several GrootGroenPlus participants for their insights:

Didier Hermans of Herplant BV and BetterBuxus®, both participants at trade fair GrootGroenPlus, has been keeping bees at his tree nursery for years, which do produce great honey. Didier says: “Boxwood (Buxus) is an excellent bee plant, as is Prunus. Contrary to claims made in the media, that boxwood doesn’t contribute to biodiversity and is just an ordinary garden plant, boxwood is actually a great bee plant! Naturally grown and minimally pruned boxwood blooms annually and is visited by both honeybees and various wild bees and insects.” He continues: “Judicious use of crop protection does not lead to increased bee mortality. Ornamental growers play a crucial role in providing forage plants for bees due to their knowledge of plant varieties.” Laura Bruni from Tuscany Growers, a participant at the GrootGroenPlus trade fair, shared her views. Tuscany Growers cultivates ornamental outdoor plants. The nurseries are located in Pistoia, within the beautiful region of Tuscany in Italy. VIVAI PIANTE BIAGINI and VIVAI PIANTE MASETTI SABINO have contributed to Pistoia’s reputation as the capital of European greenery. Laura tells KwekersBode: “Bees are essential for life: without bees, plants cannot survive and reproduce. We must do everything we can to protect our world and the bees, so BE BEEFRIENDLY!!!” She adds: “Good bee plants include Lagerstroemia indica and Osmanthus aquifolium.” Ad van Heesbeen from ASRA Plant B.V., known for its brand Sense of Nature and a participant at the trade fair, discussed bee mortality. “As tree growers, we are at the forefront of solving the bees’ food problem. Tree nurseries grow plants that can be a great source of food for bees, for use by consumers, in commercial landscaping, and in government and municipal plantings,” says Ad. He continues: “Everyone can contribute to feeding the bees, even if you only have a balcony! Public green spaces can also be improved significantly. Consider the grassy verges and off-ramps of major roads; these areas could be filled with woodland and hedge plants, perennials, etc. There is plenty of choice.” ASRA Plant grows plants that are highly favoured by bees and bumblebees, such as the Stokesia with its blue-purple flower. These are available at garden centres across Europe and, by planting them in private gardens, they help provide food for the bees. 

Long story short: the honeybee

Honeybees are commonly found in large numbers and are valued for their role as pollinators of many plant species, including fruit trees. Additionally, the honeybee is a key provider of various natural products such as honey, beeswax, royal jelly, and propolis.

Solitary or wild bees, along with bumblebees and honeybees, form the superfamily Apoidea s.l. In the Netherlands, about 350 species exist, including the following genera: silk bees, sweat bees, sand bees, mason bees, and leafcutter bees. While honeybees and a few bumblebee species have a social lifestyle, solitary bees do everything alone: making a nest, foraging for food, and laying eggs. Sometimes, nests that are close together can form a colony, but this is not always the case. It is also possible for bees to use the same entrance for their nests (communal nesting), but this depends on the species. Solitary bees typically only live a few weeks, with their offspring overwintering as larvae, pupae, or adult insects (imago) after metamorphosis.

Honey is a natural, sweet, liquid substance created when honeybees and/or honey ants collect nectar from flowers and convert it. The nectar is transformed into honey through the addition of enzymes and thickening by evaporation. Local honey is often recommended because it contains pollen from nearby plants. This local exposure could help the body get used to the pollen you are allergic to. Preferably choose local honey from Dutch sources if you live in the Netherlands and suffer from pollen allergies. 

On behalf of Trade Fair GrootGroenPlus: Frans van Wanrooij, secretary

“As Laura concludes to powerfully: ‘Bee Beefriendly’. GrootGroenPlus participants have a lot of knowledge in this area, including unexpected solutions. Our growers are very willing to share this information with you.”