Oak trees use delaying tactics to thwart hungry caterpillars
Two oak trees in the spring, with varying degrees of leaf growth Sven Finnberg If caterpillars have munched through a lot of an oak tree’s leaves one year, then, the following spring, the tree’s buds open three days later. This delay means the caterpillars don’t have food available when they hatch, and so many die, halving how many leaves get eaten. In spring, longer, warmer days drive trees to start growing again, opening buds and unfurling young leaves. Many species time their life cycle to match this, so some caterpillars, for example, hatch when the leaves are new and soft, so they can start eating immediately. Now, Soumen Mallick at the University of Würzburg in Germany and his colleagues have discovered that oak trees have a way to fight back. They analysed the condition of tree canopies in images from Sentinel-1 radar satellites for a 2400-square-kilometre area in the northern Bavaria region of Germany between 2017 and 2021. The forests there are dominated by two species of oak: the pedunculate or English oak (Quercus robur) …
