Introducing one of my research areas: #cocoa #pollination
Cocoa (Theobroma #cacao) is a fascinating crop. It originates from...somewhere in the Amazon* and likes wet tropical places with year-round warm temperatures and moderate to high rainfall.
*Not my debate, various countries like to claim the origin of cocoa!
As a crop, cocoa is propagated mostly clonally. But fruit production requires, or benefits from, insect (or manual) #pollination. (Depends on the variety.)
The flowers are beautiful and complex, fragile structures that come out of "cushions" on the trunk and branches. They're only viable for a day or two before they senesce and drop off.
If they're pollinated, they develop into tiny pods...and eventually in full sized cocoa pods if the tree has sufficient resources.
What does the pollination?
About a century ago...nobody knew. But research from scientists like Macfie, Posnette, and others between 1940 and 1980 or so found it was not wind, and seemed to be mostly flying (not crawling) insects...
Cocoa is especially #pollinated by #Ceratopogonidae midges, particularly the genus #Forcipomyia. However...lots of other insects of similar size may play a role. This could include thrips, gall midges, fruit flies, etc. Gall midges are particularly common on cocoa plantations.
But Forcipomyia respond to the odour of #cocoa flowers, and have hairy bodies that cocoa pollen clings to, so they can carry more grains than many other flower visitors. So it's likely that they're most efficient.
OK, so #CocoaPollination is sorted, then, and takes care of itself?
Not quite. We know a little bit about cocoa midge #ecology, but not nearly enough. We know they breed in rotting plant material, like discarded cocoa pods, rotting banana pseudostem (the "trunk" bit), moss and leaf litter. But we don't know nearly enough about which materials suit which species...
We also don't know which #Ceratopogonidae species are the best #pollinators for #cocoa, how they're distributed within and between farms, or how they respond to modern pest, weed and disease control strategies.
And how they interact with each other, and other plants on the farm remains a huge unknown.
Here's a male Ceratopogonidae from a cocoa plantation in Ghana...
Another new innovation entering the #cocoa world is commercial-scale #ManualPollination. This involves training technical staff, or the farmer themselves, to use forceps to move pollen between flowers.
This is really taking off in some parts of Ghana, like Mampong and Bechem. And it seems to produce some dramatic results. But we are still learning what this means for the tree - how can you make sure you don't exhaust the tree doing it year on year?
At the centre of it all is the farmers. #Cocoa farmers are often older, busy people (cocoa farming alone is rarely enough to pay the bills), and have to make careful decisions about yield versus labour and other inputs. We're discussing the priorities, and what areas farmers feel warrant research and training focus.
Ultimately, what we are hoping is to identify a route to #environmentally and economically #sustainable cocoa #pollination.
Sarah Arnold
Drew McDaniel