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THE MYSTERY OF PERU’S COCOA TREE POLLINATION

When it comes to talking about Cocoa, a lot of focus goes into the processes behind chocolate production – from growing and fermentation to roasting and processing. Still, one key element rarely makes it into the discussion: pollination of the Cocoa trees.

With Cocoa being such an important global commodity, it may seem surprising that little is known about the pollination of the Cocoa tree from a biological standpoint. As it turns out, observing Cocoa pollination is challenging since each tree hosts thousands of tiny Cocoa flowers and attracts a diversity of equally small insects.

A new study conducted in Peru by an international research team at Julius-Maximilians-Universität in Germany has brought attention to some of the complexities of Cocoa flower pollination.

Glue was applied to Cocoa flowers in 20 different agroforestry systems across northern and southern Peru to help researchers identify the animals visiting the flowers. The study also took into account the amount of shading and proximity to surrounding forests and how these factors influenced the flower’s visitors.

The Results

In the north of Peru, where conditions are dry, aphids (38%), ants (13%) and thrips (10%) made up the majority of the flower’s visitors. In the south, where weather conditions are more humid, thrips made up 65% of visitors, with midges accounting for 14% and parasitic wasps making up 10%.

The plantation’s level of shade also seemed to have an effect on its visitors. Insects in the north prefer the shade, whereas in the south, more insects were found in the less shaded plantations. The study took place during the rainy season, so the results can only be interpreted based on visitor activity under these conditions. It was also noted that the distance to the nearest forest had no relation to the number of visitors received in either region.

The team of researchers also observed that the transfer of pollen and the resulting fruit from pollinated flowers was very poor; only 2% of the pollinated Cocoa flowers bore fruit. This number tripled to 7% if the pollen was transferred by hand; however, it still represents a low number. It is not clear why the fruit set in these regions is so low, though researchers speculate that it could be due to a lack of efficient Cocoa pollinators in Peru. Biologist Justine Vansynghel, a researcher on the project, said. In Indonesia, you can achieve a fruit set of around 50 percent with hand pollination. This is probably because the plantations there do not use the native South American Cocoa clones but ones with higher yields.

Genetic incompatibility, as well as a low pollen grain count, could be the reasons we are seeing such a low fruit set in Peruvian Cocoa trees. An average of 30 pollen grains were counted on the Cocoa flowers observed in the study, which is only a quarter of what is needed for successful pollination.

While Cocoa plantations in Africa and Asia see greater success in terms of yield, the researchers explained that high-yielding non-native Cocoa clones only produce five to ten years of a good harvest. After this period, the plantations are abandoned, and more forests are cut down to make way for new plantations. With deforestation posing a major problem for the industry, this process is unsustainable and far from ideal. It seems then that a balance needs to be struck between longer-lasting plantations and those with high yields.

Photo by Marlon del Aguila Guerrero/CIFOR

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