Core Concept: Probing the phytobiome to advance agriculture.

The Colorado potato beetle had Gary Felton stumped. Felton, an entomologist at Pennsylvania State University, has built his career on revealing how plants defend themselves against voracious insects. Plants often detect chemicals in an insect’s oral secretions and respond by producing proteins that wreak havoc on insect digestion and nutrient absorption. But the Colorado potato beetle was different. Felton found that oral secretions from its larvae actually prevented potato and tomato plants from launching a proper defense. He tested chemical factors in the secretions that might help the beetle foil the plant, but came up short. “Maybe there is something else here that we’ve totally overlooked,” he recalls thinking. That something else turned out to be bacteria. If he applied antibiotics, the plants could launch a defense and inhibit potato beetle larvae growth (1). Bacteria in the insect’s oral secretions were tricking the plants into defending against microbial invaders instead of insect ones. Kill the bacteria and the cover is blown. Myriad factors affect crop health, such as genetics, insects, microbes, weather, soil nutrients, weeds, fertilizer, tilling. Until recently, scientists typically studied one variable at a time, says plant pathologist Jan Leach of Colorado State University. “When a plant is sitting in the field, it’s not just exposed to one pathogen, one temperature, one insect. It’s exposed to everything at once,” says Leach. “If we want to understand how plants