The Manila Bulletin has a feature: “Declining Agri Yield Worrisome” in February 20th 2012 about mango yields …
MANILA, Philippines — The yield and export of the world’s famous Manila mango has been dwindling over the years in tandem with other Philippines agricultural products and lagging behind other ASEAN countries, a situation that has alarmed leaders in the industry.
In 2009, Philippine mango output stood at only 771,000 tons from a high of over one million tons in 2007. The Philippines yield of mango is amongst the lowest in the Asia, at only 4.55 tons per hectare in 2010. This is only about 40% of the yield of Cambodia and 35% that of Indonesia. The mango crop supports about 2.5 million farmers in the Philippines, who so often are trying to boost yields relatively unsuccessfully with extra fertilisers, and appear to have overlooked the critical pollination needs.
For a mango fruit to develop the mango flower has first to be pollinated. Many studies have been done on mango pollination and the relative success of this for setting the fruit depends on many factors including the mango variety, the weather, the height and age of the trees, spraying of chemicals and the availability of pollinators.
The West Australian Department of Agriculture in their Bee pollination benefits for mango (4) bulletin includes 10 Abstracts of scientific papers on mango pollination, and there is clear and repeated evidence of the importance of bee pollinators to obtaining satisfactory and good pollination. The studies involve a variety of approaches to assessing mango pollination from a number of different countries.
Honeybee on mango flowers (5)
Mango flower (right) and new fruit after pollination (left).
It has been observed that the flowers are visited by a wide variety of insects including flies, honeybees and stingless bees. Mango flowers produce relatively few pollen grains – often not more than 200 or 300 to an anther. The pollen grains tend to cling together, especially in damp weather; even in dry sunny weather it is difficult to dislodge them with a strong draft of air. The stigma is small and not provided with projections of any sort to assist in catching pollen. Bees are adapted to pick up and carry pollen more effectively than flies or other insects, and hence even though flies may often be seen on mango flowers, it is considered by many agriculturalists that bees are more effective pollinators – especially if there are good numbers of bees in the pollinator environment.
The relative importance of bees to mango production can be summarized by The South African Mango Growers Association (1) which has considered the various factors and states: ‘Placement of beehives in mango orchards is of utmost importance to ensure sufficient pollination.’
It is remarkable that the Philippine Department of Agriculture and the ‘High Value Crops Development Program’ websites do not mention the need for pollinators (with the single exception of the squash crop). The HVCDP attributes declining production of mangos (and coffee) to several causes, but does not mention pollination issues.
Mangos are highly dependent on bees (1) (2) (3) (4) for pollination and the setting of fruits – with no bees the crop would be very poor indeed. In a healthy bee environment with all the native bees present, when the mango flowering season occurs in a plantation there would be sufficient pollinators available to share the large task of visiting all the flowers carefully enough to produce heavy crops. Uncontrolled ongoing destructive honey hunting and other factors have reduced native honeybee populations, leaving the pollination of many mango crops to the available reservoir of stingless bees and other insects. It is noted that there will also be other factors involved in the dwindling mango production, but not considering the critical issue of pollination is a mistake – mango yields per hectare in many regions have fallen by around 50% in the last ten or more years.
Unless farmers make arrangements to bring in honeybee colonies in beehives from a beekeeper, the crops will continue to lag behind other countries with more developed beekeeping industries and a greater honeybee population. Another method being tried now in the Philippines is to bring in hived Trigona biroi stingless bee colonies. Bringing in hived bees (if they were available) would usually be an added cost to the mango farmer, unless they are lucky enough to be close to one of the few beekeepers.
In the Philippines there is such a small beekeeping industry that it does not affect significantly the national pollination environment for crops like mango. In addition ongoing uncontrolled destructive honey hunting is removing the key Putyokan and Ligwan pollinators, and mango yields are also suffering.
Since it will take time to build a significant beekeeping sector, it will be important to consider the status of the native pollinators. Thinking now and acting as soon as possible to improve awareness of the issues and to bring about ‘honey gathering’ rather than ‘honey hunting’ in rural communities could then have widespread benefits for the 2,500,000 mango farmers (as well as millions of other farmers dependant on the many other crops associated with bee pollination).
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1) South African Mango Growers Association
2) List of crop plants pollinated by bees
3) Pollination Requirements of Some Tropical Crops
4) Bee pollination benefits for mango
Dept of Food and Agriculture, Western Australia
5) Save the Bees Blog