Formerly exotic and rare outside of countries where they are grown, mangoes are now a regular sight in grocery stores around the world. These unique-tasting fruits are imported from tropical regions, where they are staple in numerous flavorful dishes. Thai cuisine is no exception. In fact, Thailand is the third largest producer of mangoes worldwide. Most of the 3.4 million tonnes produced yearly1 are consumed locally, but Thai exports in 2017 accounted for ten percent of all international trade in mango products.2
As mango is an economically important crop, Thailand has a vested interest in boosting this fruits’ production in a sustainable manner. That’s easier said than done. Cultivable land is sparse and knowledge about the requirements for these trees to set fruit is limited among medium and small-scale farmers.
A lady at Bangkok’s Kasetsart University has, nevertheless, taken on the challenge, partnering with Bayer Bee Care in her endeavors. Assistant Professor Chama Phankaew is an expert on pollinating insects, particularly stingless bees, and envisions a future where they abound in Thai mango orchards, visiting blooms and improving yields through pollen dispersion. In her own words: “Stingless bees are the key pollinator of mango flowers; more so than other insects.”
A long-lived, flowering tree capable of growing over 30 meters high, the mango tree was domesticated in India in 2000 BC. Mango has since become one of the most widely cultivated fruits in the tropics. Orchard trees are kept short (three to four meters) for easy harvesting and have been bred over the centuries to derive hundreds of mango varieties — or cultivars — that differ in fruit color and taste, from sweet and tangy to spicy and even a cultivar that tastes like coconut pie.
Different mango cultivars can be grafted onto a rootstock — the stem and roots of a native mango tree that is resistant to cold and disease. A grower can, thus, choose which cultivars to graft onto trees in his or her orchard based on demand for and the market price of different mango varieties.
A flowering Nam Dok Mai cultivar. This mango variety fruits multiple times per year, producing a yellow, smooth-fleshed and strongly aromatic crop.
Mango cultivars each have their own characteristic leaf, flower, inflorescence, fruit and tree canopy, as well as flowering season. Nam Dok Mai mango trees produce male and hermaphrodite flowers. Both flowers produce pollen but only the hermaphrodite ones also have a female, ovule-producing part (a pistil with an ovary) that develops into a fruit upon fertilization. A self-fertilized hermaphrodite flower usually falls to develop completely into a ripe fruit.
Of the 76 provinces in Thailand, 69 harbor mango plantations, which cover an area of over 98,000 square kilometers.
Mango production in Thailand has risen steadily over the last decade but could be limited at a certain point by low productivity, compounded by availability of land. Improving pollination of mango flowers with the help of managed stingless bees may be a way to boost mango production on the available land. * Data represent mango, mangosteens and guavas, as reported by the FAO.
Worldwide, the most commonly imported mango cultivar is Tommy Atkins because of its long shelf-life and robustness during transportation. In Thailand, the sweeter Nam Dok Mai is the most popular mango variety.
A favorite dessert in Thailand – ripe mango and sticky rice in coconut milk.
Insect pollinators in the tropics are very different from those in temperate zones around the world. Among them, stingless bees stand out as a diverse group of about 500 species, some of which are being managed in various tropical countries to pollinate crops like durian, macadamia nuts, avocados, lychees, longan and melon. Similarly, in Thailand, stingless bee pollination has also been studied on similar crops, including dragon fruit and rambutan.
Working with the mango variety Nam Dok Mai, Chama has demonstrated that the hermaphrodite flowers of a tree (see the surprising mango tree) fail to grow harvestable fruit when they self-pollinate. Furthermore, the male flowers produce low amounts of pollen grains which germinate only 50 percent of the time, if they even reach a hermaphrodite flower. Thus, the only effective way to increase fruit set of a tree is to move more pollen from male to hermaphrodite flowers. And this is exactly what stingless bees do. Attracted by the sweet smell of the flower, stingless bees can easily cross-pollinate hundreds of blooms in a day.
Chama first became intrigued by the potential benefits of native stingless bees for crop pollination as an undergraduate student at Maejo University. Since then, she has researched their distribution in Thailand, rearing behavior, pollination services and even pharmaceutical uses of the propolis they produce. “It can be hard to get funding to study beneficial insects,” she explains. “By exploring many aspects of their biology, I can tap into more funding sources, and what we learn paints a more compelling story when talking about stingless bees.”
Assistant Professor Chama Phankaew (left) and her two Master’s students, Patcharin Juiklin (middle) and Onnarin Srisuksai (right) in a mango orchard.
Telling a compelling story is crucial to Chama’s work. Her plan to boost mango production by introducing stingless bees into orchards depends on recruiting orchard owners to work with her. While many allow Chama and her two Master’s students to research mango blooms and assess insect populations in their trees, owners will need to manage stingless bee nests themselves for long-term crop improvements. Some owners are hesitant about the perceived additional work. Others are simply misinformed. “Orchard owners might believe that bees cause flowers to fall from their trees, preventing fruit growth,” she explains. “Other growers spray hormones on their trees, believing that this increases fruit set. But the hormones only cause the trees to produce more male flowers which do not yield fruit. We have to explain this and talk about the benefits of stingless bees, like that they also make small amounts of honey that can be harvested for sale,” says Chama. “Sharing what we learn about mango flowering and stingless bees can empower growers to improve their livelihood. Education is very important in our project.”
Among others, Chama and her team have described the life cycle stages of the stingless bee, Tetragonula iridipennis, and established techniques for mass rearing this small bee in hives.
Chama and her team are working out the details of raising and managing five stingless bee species in hives. She is confident that growers will adopt the managed colonies because she anticipates the nests to be “inexpensive to establish, easy to manage, and the bees will increase fruit set also in the off-season when mangoes achieve a higher price.” Musing about her work, she hopes for a community of researchers to double up efforts, someday. “We need help to carry out all the research we would like to do during the short flowering time,” she says half-jokingly. Establishing a network of bee researchers in South East Asia is a core goal of her collaboration project with the Bee Care Program. Disseminating through this network the expertise that she and her team are building could bring improvements to other parts of Asia and to other crops, potentially driving agricultural boom and economic expansion in the region. “We create useful knowledge for farmers to earn a good living,” Chama adds proudly. And the stingless bees benefit as well from the abundance of nectar-rich crop flowers.
Photographer: Banthoon Phankaew
1 Data from the Food and Agriculture Organization (FAO) of the United Nations, www.fao.org/faostat/en/#data/QC.
2 Data from the International Trade Centre.