The Miracle Process of Cacao Pollination
I am seriously starting to believe that the cacao tree was never meant to be bothered, manipulated by humans, altered in any way, and especially turned into something edible. Super sensitive to diseases, less productive than its potential, needing constant care and attention, who even thought about making a profitable food out of this fussy plant?
Jokes aside (we all adore you cacao tree, just the way you are), it’s hard to comprehend how chocolate can be so readily and widely available when it is so hard for this plant to grow and bear healthy fruits. The struggle doesn’t even start with the fruits, but begins all the way back at the flower level.
Cacao flowers
“The number of flowers that are pollinated is way lower than the maximum number of fruits a cacao tree can produce.”
If we step aside from chocolate products and mentally travel to the tropical fields where cacao grows, we understand that cacao pollination is truly a miracle process. The cacao tree produces 250,000 flowers every year, but only 10% get pollinated. This means that 90% don’t receive any or enough pollen, and is therefore aborted by the tree. The main factors that make cacao pollination difficult are:
The tiny size and the intricate reproductive structure of the cacao flower.
The self-incompatibility of the cacao tree.
The specific kind of pollinators needed to get the job done.
Whenever you hear about cacao being on the brink of extinction, this is one of the contributing factors (together with the old age of cacao trees, the lack of young cacao farmers, ridiculously low prices, deforestation, etc.). But let’s try to understand this problem starting from the basics. How is a cacao flower even pollinated?
How Cacao Pollination Works
The cacao flower is hermaphrodite: it has both a female part (where the ovules are) and a male part (the pollen-making structure). The goal with pollination is to make the pollen reach the ovule. Since they are both located on the same flower, the path should be pretty straightforward, right? Nope! Remember that it’s the cacao tree we are talking about. Nothing is ever that easy.
Male and Female parts of the cacao flower. PHOTO CREDIT: CacaoPollination.com
The cacao tree is an auto-incompatible tree. What does this mean? The cacao flowers on the same tree can’t pollinate/get pollinated by each other, but only by flowers from a different tree. Cross-pollination is the only successful way (cacao flowers that receive pollen from same-tree flowers won’t produce fruits). But since cacao trees are stuck on the ground, they clearly need some sort of “vehicle” to take the pollen from tree A and deposit it in the female parts of tree B, or vice versa. Unfortunately wind won’t do, because the pollen is too sticky, viscous and heavy to be transported simply by air. So the cacao flowers rely on flying insects to get the job done. And what’s the big deal, you may ask?
Cacao pollination performed by flying insects would be totally doable and easy (it happens every day with the most common flowers) if it wasn’t for a crucial inconvenient: the cacao flower is very, incredibly, absurdly tiny, measuring anywhere from 1 to 2 inches (or from 2,5 to 5 centimeters). Not only this, but its reproductive structure is intricate, hidden and hard to reach. This means that the cacao flower can only welcome equally petite and barely visible insects. Therefore, only specific kinds of insects are suitable for cacao pollination.
The Best Insects for Cacao Pollination
Forget the bees.
They are way too big to enter a cacao flower and, if they manage to get any pollen, they are just stealing it for themselves. You can see bees hanging around cacao flowers, but this doesn’t mean they are helping with pollination. Actually, many insects visit the beautiful cacao flower (hard to resist even for the human eye), but they aren’t necessarily interacting with the flower’s reproductive system.
To access the flower’s reproductive structure and carry an acceptable amount of pollen, the insects must be:
of the right size (smaller than 2-3 mm),
hairy (so that the sticky pollen can get attached to their bodies),
suitable for the environment where cacao grows (very humid).
So who are the best cacao pollinators?
Biting midge inside the cacao flower. PHOTO CREDIT: Mark Moffett, photographer for National Geographic
Biting midges from the Ceratopogonidae family and (to a lesser extent) gall midges from the Cecidomyiidae family are among the most important known cacao pollinators worldwide. Fun fact: female midges visit cacao flowers more frequently than male midges, therefore being the main contributors to pollination. But even when the most perfect pollinators are around, there are still some difficulties.
“The crop’s sustainability currently appears to depend on several species of tiny fly pollinators, who are frankly struggling to get the job done.”
For example:
These midges are surrounded by an attractive variety of flowers that can provide them with pollen, not only cacao flowers. Therefore cacao flowers, that already can only be pollinated by a tiny portion of all the insects available, are also “competing” with other flowers to get attention and successful action from these midges.
Midges are awesome to enter the cacao flower and reach its reproductive system, but they are also limited in the amount of pollen that they can carry. For a tiny flower to develop into a football-size fruit, 100 to 250 grains of pollen are required, while a single midge can only carry around 30 grains of pollen at a time.
Since the cacao tree is self-incompatible, midges need to fly from tree to tree and travel longer distances compared to just going from flower to flower on the same plant, or on the ground.
Do you start to see the struggle here and how miraculous cacao pollination is? However, there is hope and room for improvement!
Two main strategies can be used to increase pollination rates in cacao flowers:
Create the best environment for the midges to thrive and multiplicate.
Perform pollination by hand.
How Agroforestry Helps Improve Cacao Pollination Rates
If we give these midges the best house to live in, they will want to stay, get active and reproduce. By creating the most welcoming environment for them, they will pollinate many more cacao flowers in return.
It just so happens that the most favorable environment for these midges coincides with the most favorable environment for the cacao trees to flourish: damp, shady, humid, in semi-aquatic or moist soil conditions, surrounded by other plants and animals, with lots of decomposing organic matter to feed from (leaf litter, cocoa pod husks, rotting fruits from shade trees). This is where midges love to lay their eggs and let their larvae develop. It’s only in these agroforestry conditions that the cacao trees and the midges can thrive in a beautiful exchange of value for one another. Biodiversity at its finest! Unfortunately, the same doesn’t happen in monocultures: where there is no shade, little organic matter, drier soil and a heavy use of pesticides, pollinators find a hostile environment for reproduction, therefore decreasing the amount of cacao flowers they can pollinate.
A technique used to improve cacao pollination even further is hand pollination.
Hand Pollination OF CACAO FLOWERS
Definitely a meticulous and laborious approach, hand pollination means to artificially transfer the pollen from the male part of the flower to the female part. This process has to be done by hand, both for the tiny size of the cacao flower and also because the female part is very hidden inside the flower. Pollinators need to use a precise tool like forceps or tweezers to get the job done.
Cacao flower pollinated by hand with tweezers. PHOTO CREDIT: Jochen Weber
Learning how to pollinate cacao flowers by hand requires great eyesight, a fair deal of training and a lot of practice to reach a satisfying number of pollinated flowers in a specific amount of time (watch this video to see how it is done).
“Fertilizers or pesticides is not a guarantee for increasing yields, but hand pollination can really boost cocoa production — and, therefore, profits. ”
This practice is highly rewarding: the number of pollinated flowers increases exponentially, resulting in more fruits and expected yields by a significant percentage. This is why many believe that hand pollination should become an integral part of cocoa farming, equally important as grafting, weeding, pruning and organic fertilizing.
Solutions to Improve Pollination Rates
Cacao pollination is truly a miraculous process based on all the difficulties it has to encounter for its success. But there are actions that cacao farmers can take to increase pollination rates (which translates in higher tree’s productivity and higher profits):
Add organic material on farm.
Reduce/avoid use of pesticides.
Adopt agroforestry methods/improve biodiversity.
Practice hand pollination.
As for consumers, this info shows how hard it is to bring chocolate to life. Therefore, it’s time to appreciate every single bite even more!
