Brazilian researchers develop technique for mass breeding of stingless bees

Method will be tested in strawberry fields – one of the 30 crops that benefit from pollination by these insects.

By Elton Alisson

Agência FAPESP – Stingless bees, such as the jataí (Tetragonisca angustula) and the uruçu (Melipona scutellaris), are well known as important pollinators for several crops such as eggplant, strawberries, tomato and coffee.

One of the main limitations on their use for this purpose, however, is the difficulty of producing colonies in sufficient quantities to meet the demands of farmers, as the majority of these species have small numbers of queens.

However, a new technique that could help overcome this limitation was developed by a group of researchers who reared the queens of one of these species in vitro: Scaptotrigona depilis, commonly known in Brazil as mandaguari.

The study was conducted by scientists at the Brazilian Agricultural Research Corporation (Embrapa) in partnership with colleagues from the Universidade de São Paulo’s School of Philosophy, Sciences, and Letters in Ribeirão Preto (USP – FFCLRP) and the Universidade Federal Rural do Semiárido (Ufersa), Mossoró campus (RN).

The result of a doctoral study conducted with a FAPESP fellowship, the technique was described in the September issue of Apidologie magazine and will be tested in the field in coming years through a project conducted with support from the FAPESP Innovative Research Program in Small Companies (PIPE).

“We managed to develop a methodology for artificial production of queens of the species Scaptotrigona depilis. The technique has proven to be a fantastic application for the large-scale breeding of this type of bee to meet the demands of rural farmers,” said Cristiano Menezes, researcher at Embrapa Eastern Amazon in Belem (PA) and author of the study.

According to the researcher, who completed his doctorate at FFCLRP under the supervision of Vera Lucia Imperatriz-Fonseca, the mandaguari is most common in the Southeast region of Brazil. It belongs to a genus of bees – Scaptotrigona – whose taxonomic classification is currently being reviewed. The genus includes eight other Brazilian species with atrophied stingers.

The colonies of these species of bees are composed, on average, of 10,000 worker bees, each approximately 5 millimeters in length, and are ruled by a mother queen that is approximately 1.5 centimeters long and can lay eggs.

To increase the numbers of colonies of this species of bee – which produce honey, pollen and propolis in addition to their activities as pollinators – Brazilian bee breeders have used a technique whereby a colony is split in half to start another with a new queen.

However, it is only possible to utilize this method to multiply the colonies of the majority of stingless bee species once a year, affirmed Menezes. “With this technique, one would need 50,000 queen bees to produce 50,000 colonies of jataí and pollinate approximately 3,500 hectares of strawberries,” he estimates.

“Strawberries are one of several crops that depend on pollination, but strawberries have the smallest growing area in Brazil of any of these crops. Just imagine how many queen bees would be necessary to pollinate tomato crops, whose planting area is much larger,” he explained.

New technique

To increase the production of mandaguari queens and colonies, Menezes developed a technique to culture newborn bee larvae during his doctoral studies from 2006 to 2010. With this method, newborns are given six times the volume of food that they normally ingest. As a result, all supernourished females become queen bees.

According to Menezes, 97.9% of the queen bees produced by this method survived and were capable of laying eggs and forming colonies in vitro. The size of the in vitro queens can be equal to that of natural queens if they receive the right food, he said.

“We optimized this in vitro production technique for queen bees. We have a very well-defined protocol, and we can produce any quantity of insects needed,” he affirmed.

Currently, he and the other participants in the research project have improved the artificial feeding system, which uses a diet based on soybean rather than their natural food to increase the number of colonies produced.

The bees are raised in climate-controlled greenhouses, where they are protected from natural predators. “With the advance of these new techniques of in vitro production of queen stingless bees, we are testing the possibility of producing ten colonies of daughters from one mother per year. With this, we will have created a viable method to produce colonies,” said Menezes.

Through the FAPESP PIPE Program, researchers intend to apply this technique to a single production system of colonies and test the approach in the field. In a second phase, they will evaluate the effect on bees of the main agrotoxins utilized today in strawberry crops.

With this aim, they have joined forces with a company that produces biological agents, Promip, located in São Paulo municipality Engenheiro Coelho, where five climate-controlled greenhouses have been built for strawberries.

The bees will be introduced to these greenhouses and exposed to the ten most common agrotoxins used to fight plagues that attack strawberry crops to evaluate the separate effect of each product on the survival of bees and the existence of colonies.

Based on the results, the researchers intend to elaborate a list of recommendations for farmers. This advice will specify the care to be taken in utilizing a given agrotoxin so that it does not kill the bees. The advice to farmers will also identify natural predators that can be used in the place of agrotoxins to eliminate plagues, such as Tetranychus urticae Koch, that impact strawberry crops.

“At the end of the project, we want to have a list of recommendations based on studies to speak confidently with farmers and inform them that if they use bees for pollination, they cannot use certain agrotoxins,” said Menezes.

Efficacy tests

The researchers are also evaluating the increase in productivity resulting from the introduction of stingless bees for pollination in several agricultural crops.

In the case of strawberries, for example, the measure increased agricultural productivity by 20% to 40% – depending on the variety – and reduced the formation of poor-quality fruit by 80%, affirmed Menezes.

Strawberry flowers occur on structures termed inflorescences that are visited by several groups of bees, including bees with stingers and solitary species. If several bees fly to and land on an inflorescence, they pollinate the microflowers. The fruit that results is well formed, round and appealing.

If few bees visit a strawberry inflorescence, the resulting pollination is incomplete, producing a deformed fruit, according to Menezes.

“In the past, this type of malformation was associated with thrips, an insect plague that attacks the fruit. For this reason, the farmers applied more pesticide, hoping to combat the plague, but ended up killing more bees and harming the productivity of agricultural crops,” he explained.

In principle, tests in the field will be conducted with mandaguari because this species has proven more resistant to multiplication. Initially, colonies of mandaguari will be introduced in strawberry crops because it is the crop for which the benefits of stingless bee use as pollinators are most widely known.

The idea, however, is to expand application to other crops where pollination is known to generate larger fruit, with more seeds and more accentuated color and flavor. “There are approximately 30 crops that benefit from pollination by stingless bees,” estimated Menezes.

“We are already conducting preliminary tests with some of them, such as tomatoes in São Paulo and açaí, in Belém do Pará, utilizing a stingless bee of the same mandaguari genus but of another very similar species,” he explained.

To introduce the bees into fields with selected crops, the artificial colonies are maintained in confinement for three to six months until the population consists of at least 3,000 bees.

When this number is attained, the colony is taken to the crop at night during moderate weather conditions and placed on a stand so that the insects are free to fly over the plantation and pollinate.

One of the advantages of utilizing this type of pollination, according to Menezes, is that the stingless bees have a lower flight radius – 900 meters, compared with the 2.5-kilometer flight radius of bees with stingers.

For this reason, there is a greater chance of reaching the target crop for pollination. “As the flight radius of bees with stingers is greater, if they find another plant flowering on their trajectory they will stop and land on it instead of the target crop,” he explained.

“It is harder for stingless bees to get distracted during the trajectory,” he notes.

The article An advance in the in vitro rearing of stingless bee queens (doi: 10.1007/s13592-013-0197-6), by Menezes and others, can be read by subscribers to Apidologie at www.apidologie.org or at http://link.springer.com/article/10.1007%2Fs13592-013-0197-6.