What is a researcher at the University of Georgia developing to alert farmers to when crops are under attack?

Answer: sensors that detect a plant's "cry for help"

When under stress or attack -- or even if they're just thirsty -- plants cry for help. Invisible and often odorless, green leaf volatiles emitted from vegetation act as a defense mechanism, communicating to other foliage that danger is near, according to engadget.com. And now, a researcher at the University of Georgia is developing a chemical sensor -- that works in a similar fashion to a sensor that detects glucose in the blood -- to alert farmers when crops are under attack from pests, allowing them to trigger defenses reactively, and in a localized area.