In the heart of Colombia, researchers from the Universidad Nacional de Colombia are combing through bean fields. They hope this study, funded by Bayer, will help identify which bee species pollinate bean crops and which are simply visiting the flowers.
// There are still some knowledge gaps concerning which insect species are attracted to different crops.
// A study in Colombia is therefore investigating the insect community foraging on blossoms in bean fields.
Legumes have already made history in the realm of research. In the early 20th century, for example, the Danish botanist Wilhelm Johannsen used bean plants to find out to what extent genes affect specific plant characteristics, such as the weight of a seed or the height of a shrub. In 1865, Gregor Mendel also conducted experiments on pea plants and established some of the fundamental genetic laws of inheritance.
The bean is the king of legumes, which are vegetables contained within a pod. It is one of the staple foods in many South and Central American countries and a plant which is also valued by farmers. In Latin America, they cultivate beans alongside corn and coffee because the legume enriches the soil with nitrogen, thanks to the special bacteria found in its roots, thereby fertilizing the other crops. In addition to this, the broad bean is usually self-pollinating, meaning it doesn’t need to rely on insects. Nonetheless, honey and bumble bees can help: It is currently thought that, in general, only two percent of plants at most are totally dependent on insects for pollination but scientists suspect that a higher percentage of plants could benefit through increased yields.
In order to investigate this possibility, researchers first need to gather some basic information, such as finding out if bean plants and their flowers are in any way an attractant to honey bees and other insects. For this reason, scientists at the Universidad Nacional de Colombia have developed a study with funding from Bayer. Dr Roberto Ramírez Caro, responsible for public and governmental affairs and stewardship in northern Latin America, and his colleague Beatriz Arrieta locally managed and coordinated the research project on the Bayer side. “If we’re talking about pollinating cultivated plants, the honey bee Apis mellifera is normally dominant in Colombia. It can be found in most crops,” explains Dr Ramírez Caro. “However, until now, it was not clear whether the honey bee is also prevalent in the bean fields.”
Dr Roberto Ramírez Caro coordinated the study in Colombia from Bayer’s side.
At the beginning of the study, the university’s researchers selected five commercial bean farms near Bogotá, the country’s capital in the heart of Colombia. Many varieties of the common bean are grown there, including the cargamanto bean, also known as the cranberry bean, which was first bred in the country. The researchers, supported by Bayer experts, studied two to five hectares of land on each of the farms to discover how many and what kind of pollinators were found in the bean fields. The scientists observed the insects’ activity at different times of day and also collected samples. Back in the laboratoy they then identified which insect species they had found.
Honey bees struggle with the structure of bean flowers.
“The latest results show that honey bees do not find the common bean particularly attractive,” says Professor Dr Augusto Ramírez Godoy, who was in charge of the study at University together with Professor Rodulfo Ospina, who adds: “That’s due to the structure of the flower. It is almost closed and this makes it difficult for the honey bees to reach the nectar and pollen.” The researchers did find, however, that other types of bee were able to open the flower to reach the sweet food source inside. Stingless bees, for example, particularly members of the Trigona genus, can open the flowers with their mandibles and access the nectar.
Stingless bees such as Trigona (left) force their way into the almost closed structure of bean flowers (right). Other insects can benefit from the opening that is made.
By forcing their way in, these bees often pierce the base of the bean flower but that does not prevent it from developing into a bean. As such, the Trigona bees’ forced entry does not have a negative effect on crop yield. In fact, other insects even benefit from it: Honey bees, which tend to struggle with the shape of the flower, can take advantage of the opening made by others and access the food with ease. “The frequency of this phenomenon – Trigona bees making flowers accessible to honey bees – varies a great deal,” says Professor Ospina. In the initial evaluation, this only happened on seven percent of the bean flowers in one test area. The figure was five times higher in another field. “We suspect that this level of variation is linked to the fact that food resources for insects vary from place to place,” explains Professor Ramírez Godoy. Trigona bees live socially and in colonies, much like honey bees. So, depending on the farming methods used on the bean field and the kind of landscape that surrounds it, the bees have more or less of an opportunity to nest near the field.
As well as honey bees and Trigona bees, bumble bees and spider wasps also foraged in the bean fields. Bean flowers are presumably an important source of food for them all. Since these insects are comparatively large in size, strong, and have long tongues, they can reach the nectar more easily than the smaller species, such as the honey bee.
Professor Dr Rodulfo Ospina (2nd from right) and his team studied the pollinators that were found in the bean fields.
In addition to observing the bees’ activities in the test fields, the researchers also examined the insect populations in the surrounding areas. The land around the bean fields was covered in either grass or other cultivated plants, such as vegetables, potatoes or corn. The predominant species found was honey bees but various wild bee species, including members of Halictidae and Megachilidae families were also present. The researchers still need to work out exactly how many bee species come into contact with the bean plants and nearby crops but they are already planning other projects. “We want to conduct similar studies in other regions of Colombia,” explains Professor Ramírez Godoy. The professors also want to study the pollen collected by the insects, as well as the pollen taken straight from the bean flowers and nearby crops. “By analyzing the pollen, we can see which bees actually collect it – compared to those just flying through the field. We also want to know which and how many other plants in the area the insects are attracted to.” The study will therefore fill a gap in our knowledge of insect pollinators – especially when it comes to bees that forage on bean blossoms.
In some cases, it is not known which bee pollinators are found in particular agricultural fields. The study conducted in Colombia fills the knowledge gap for bean crops. As pollinator populations can vary from country to country, depending on climate and geography, Bayer is providing funding for other, similar projects to better understand pollinator-crop interactions in Colombia and other South American countries.