By identifying a natural predator of the troublesome coffee berry borer, a group of international researchers, which includes entomologists from the University of Kentucky College of Agriculture, made an important discovery that could potentially give an economic boost to coffee growers worldwide.

Coffee is one of the biggest cash crops in many parts of the world, and the coffee berry borer is the most important and widespread pest of the coffee berry. A female borer drills a hole about 1 millimeter in size into the berries where she lays her eggs. The larvae hatch and complete their development by feeding on the coffee bean. The tiny pest causes economic losses estimated at $500 million each year, which affects the income of the more than 20 million families in coffee producing countries.

Juliana Jaramillo, a researcher with the International Centre of Insect Physiology and Ecology in Nairobi, Kenya, noticed the thrips species, Karnyothrips flavipes, feeding on the pests in coffee berries collected from Western Kenya. The tiny thrips entered through the same hole the pest bored and fed on its eggs and larvae inside the berry.

Since the majority of insect predators use enzymes to liquefy their prey before consuming them, it is virtually impossible to validate predator/prey relationships without using molecular techniques. To validate this relationship, Jaramillo sent the thrips for gut content analysis to Eric Chapman, a post doctoral scholar in UK entomologist James Harwood's laboratory. During gut content analysis, researchers obtain and analyze DNA of prey from a predator's digestive tract.  Harwood's laboratory at UK is one of only a handful in the world that performs this type of analysis. Chapman confirmed that thrips are predators of the coffee berry borer.

"Eric designed species-specific markers to identify the coffee berry borers inside the guts of these tiny predators," said Harwood, an assistant professor. "Identifying predators and prey in a food web could lead producers to more sustainable methods of pest control and ultimately allow us to disseminate management recommendations, based on these results, to coffee farmers worldwide."

Chapman's research found that the highest percentage of thrips preying on borer larvae and eggs occurred early in the growing season when borer populations were at their peak. The thrips did not prey on adult borers.

Data from gut content analysis allows researchers to not only identify predators and prey, but it can determine predators' foraging preferences, the rate the predators are consuming the prey and how an abundance or limited number of prey changes the structure of the food web.

While this research is a significant beginning, Chapman and Harwood said more research is needed to determine how effective the predator is in biologically controlling the pest, especially in other parts of the world.

"This research opens up large avenues for future investigation to see if the thrips are preying on the coffee berry borer in other coffee producing countries and how we can conserve predator populations in coffee plantations, so the predators attack the prey with greater voracity and earlier in the season," Chapman said.

The research was published in Naturwissenschaften-The Nature of Science. In addition to Jaramillo, Chapman and Harwood, Fernando Vega from the U.S. Department of Agriculture was a co-investigator.