Cocoa Gets a Big Boost

Yuran Zhang, plant biology graduate student, sprays a glycerol treatment on the leaves of a Theobroma cacao tree as Siela Maximova, professor of horticulture and Mark Guiltinan look on. Photo by Steve Williams.

Chocolate is getting more and more expensive, no thanks to pests and disease, which will cause cocoa farmers to lose an estimated 30 to 40 percent of their crops this year alone.
But worse than the money we must dish out for the delicacy are the environmental and human health risks posed by the toxic agrichemicals—organochloride insecticides and heavy-metal-based fungicides—that are used to fight pests and disease.

Scientists in the college have found—in a safe, biodegradable compound—a potential alternative to the hazardous antifungal agents currently being used to combat one of the most damaging cacao diseases, Phytophthora pod rot (also known as black pod), responsible for an estimated 20 to 30 percent loss in yield annually.

They have discovered that spraying the leaves of the Theobroma cacao tree with a low-concentration glycerol solution triggers the plant’s defense response and enhances its natural disease resistance.

“Right now, cocoa farmers are using fungicides and other chemicals that are very effective, but they are also highly toxic compounds, very persistent in the soil, and relatively expensive,” said Mark Guiltinan, professor of plant molecular biology. “Glycerol, on the other hand, is extremely nontoxic, super safe, super cheap, biodegradable, and triggers the plant’s defenses very efficiently—it only takes small amounts to trigger the whole plant’s defense system.”

As the researchers prepare to take their discovery to the field for trials, Guiltinan is hopeful that cocoa farmers will begin to adopt the use of glycerol in their operations.

—Seth Palmer