In protected spaces, bumblebees are used to enhance the pollination and fertilization of tomatoes.
Bumblebees (Bombus terrestris) are insects that belong to the bee family (Apoidea) and the subfamily of bumblebees (Bombinae). Bumblebees produce very small amounts of honey, too little for industrial production, but they have become one of the most important pollinators today.
Bumblebee production began in Belgium in 1987, and they have been used in the Netherlands since 1988. Initially, they were applied to 3% of tomato crops, but by 1991, their use had expanded to 95% of the area. Due to excellent pollination results, by 1992, they were used on 100% of tomato crop areas. Today, bumblebees are frequently used to pollinate a wide variety of fruit and vegetable species, and they have become an indispensable agronomic practice in protected cultivation. Bumblebees are highly efficient pollinators, typically searching flowers from bottom to top, thus never visiting the same flower again. Their sense of smell guides them in finding flowers, and in one minute, bumblebees visit 20 – 30 flowers. Pollinated flowers show brown spots, which helps monitor pollination, and the color change is visible a few hours after the bumblebee’s visit.
It has been proven that bumblebees enhance pollination, increasing yields by at least 3% compared to manual pollination. Bumblebees are active at temperatures from 10 to 30 °C, most active between 15 and 25 °C, and remain active even when the air temperature drops to 5 °C or when light levels are low, although the fertilization rate decreases under these conditions. Their broad range of activity is facilitated by their body structure and adaptability.
Bumblebees are among the few insects that can regulate their body temperature by vibrating their flight muscles to produce heat, aided by their furry coats, which serve as insulation. This adaptation allows them to thrive in cooler climates and at high altitudes.
Advantages of Bumblebees over Other Pollination Methods:
Bumblebees produce high-frequency vibrations with their bodies, known as the “buzz effect,” without moving their wings. For optimal fertilization, tomato flowers require vibrations around 400 Hz, which bumblebees can achieve with their bodies.
Bumblebees easily navigate protected spaces and, unlike honeybees, do not attack or sting workers under high-temperature conditions. Worker and queen bumblebees have stingers like bees but will only sting in self-defense, typically only when squeezed (e.g., in a human hand) and unable to fly away.
Before stinging, bumblebees usually try to escape by falling to the ground, flipping onto their backs, buzzing loudly, and displaying their black abdomen to scare off potential threats. If they feel threatened, they may also release a specific odor as a defense mechanism. If a female bumblebee (worker, queen) does sting someone, the sting will not signal other colony members to attack, as is the case with honeybees.
Bumblebees fly from flower to flower much faster than honeybees, even at low temperatures (< 12 °C), and continue to work in cloudy or rainy weather.
Bumblebees, with their large bodies covered in dense, long hairs, can carry large amounts of pollen from flower to flower.
Unlike honeybees, bumblebees do not habitually collect food only from attractive flowers; they gather food from flowers closer to their nest, and bumblebee workers stay out much longer during foraging compared to honeybees.
Honeybees only pollinate during certain times of the year, while bumblebee colonies, raised in controlled conditions, are available for pollination throughout the year. Bumblebee colonies are not threatened by pests, unlike honeybees (which suffer from diseases like acariasis and varroosis), and therefore do not require chemical treatments.
Using hormonal preparations for fertilization can harm human health and produce lower-quality fruits that are uneven, hollow, with few seeds, often underdeveloped, and lacking aroma.
Manual pollination (e.g., shaking plants) is costly, time-consuming, and results in poor flower fertilization, leading to lower yields and poorer quality, uneven fruits.
For 1 hectare of protected space, 5 – 7 bumblebee hives are needed, which remain active for 8 – 10 weeks. If the first flowering occurs during the summer, it is recommended to start with a larger number of hives per hectare, ideally 8 – 10 hives/ha.
In spring, when outdoor vegetation is in bloom, it is advisable to increase the number of hives in the facility, as workers may leave the protected space.
Bumblebee hives consist of a cardboard box with doors (through which bumblebees can enter and exit) and a nest, under which there is a container with additional food.
The hives are placed on a stand 0.5 to 1 m above the ground, in a horizontal position, sheltered from direct sunlight, with the entrance facing east. It is important to avoid placing them in dense foliage or to remove leaves that obstruct the bumblebees’ entry and exit from the hive.
To utilize all the liquid food from the hive, it is necessary to raise the rear of the hive by 5 mm after 3 to 4 weeks.
After being brought into the protected area, the hive should not be opened for at least half an hour, and it is best to open it at night. If the hives are opened at night, the workers will gradually leave at dawn, perform their first orientation flight, and begin pollinating the flowers. The optimal temperature for bumblebees in the greenhouse is between 18-30 °C.
Throughout the colony’s life, it is important to avoid any disturbance to the bumblebees, such as tapping on the hive, unnecessary opening of the hive lid, and similar actions. Additionally, it is not recommended to move the hive to another location, as this can result in the loss of some workers due to their separation from the brood and the rest of the colony, reducing the colony’s efficiency and lifespan.
The greatest threat to bumblebees is unthinking and unskilled human actions. Bumblebees are highly sensitive to chemicals used to control pests, as they have a similar metabolism. Pesticides harmful to bumblebees can also harm humans and other mammals, as they typically affect the nervous system.
Therefore, before using plant protection products, it is important to carefully read the instructions. If the hives are allowed to remain in the protected space, the hives should be closed early in the morning while the bumblebees are still inside. If the hives need to be removed from the protected space, they should be kept in indoor conditions at temperatures of 18 – 23 °C.
Hives should be placed in the greenhouse when the first flowers begin to bloom, and during the winter, it is advisable to start with at least three hives per hectare to cover the entire crop. Every two weeks, two new hives per hectare should be introduced to maintain colonies of different ages in the greenhouse.
The use of bumblebees for pollination offers many advantages over other pollination methods, resulting in larger, juicier, and higher-quality fruits.
