For hungry insects, walking along a tomato stalk in search of a green meal can be like navigating a minefield.

Jared Popowski at the University of Amsterdam in the Netherlands was trying to measure the mechanical properties of tomato plants in the lab. Then a tiny hair on one of the stalks started oozing liquid – and it happened so quickly that his camera barely caught it. He had inadvertently triggered one of the plant’s pest-protection mechanisms.