Sweet success: chocolate research to boost harvest

JCU graduate student Samantha Forbes and Dr Tobin Northfield from the Centre for Terrestrial Environmental and Sustainability Science, worked with local commercial farmers, the Puglisi family, near Mossman in far north Queensland.

Ms Forbes added rotten cacao fruit husks left over from processing the cacao beans to some plots, and not others.

“I found the addition of cacao husks below trees, which normally would be discarded, dramatically increased pollination rates, and increased the abundance of predators that may help control pests. This simple change tripled the number of fruits, and quadrupled the yield harvested per tree,” she said.

The transformation from cacao flowers to fruit pods containing beans used for chocolate production relies on small midges that develop in decomposing organic matter.

The use of insecticides is also thought to harm these pollinators, so Ms Forbes and Dr Northfield also investigated how native insect predators, including green ants, spiders and skinks, helped to control pests on the farm.

Ms Forbes showed that green ants didn’t deter midge pollinators away from the cacao flowers, and by hand-pollinating some trees she demonstrated that the main benefit of adding cacao husks was through increased pollination.

Dr Northfield said it is a simple and effective technique.

“There are many other insects using the rotting cacao husks as habitat, that likely serve as prey for larger predators like spiders and skinks. So, adding cacao husks is a simple management technique that simultaneously improves pollination and pest control, while practicing species conservation,” he said.

The scientists said their research showed a simple habitat manipulation can enhance both species conservation and pollination in cacao plantations. But multiple-year studies would be useful to evaluate whether the ‘win-win’ combination could be sustained long term.

Images: http://bit.ly/2jGCOXa

Paper available on request.