Oak Trees Delay Spring Buds to Fend Off Caterpillar Outbreaks, Study Finds

German researchers found oak trees delay leaf-out by about three days after heavy caterpillar outbreaks, tracked with Sentinel-1 radar data over five years across 60 forests (137,500 observations). The delay reduces caterpillar survival and tree damage by about 55%, is more energy-efficient than producing extra tannins, and is reversible—showing trees actively adapt to biotic threats in a warming world.