Oak Tree in Cherry Tree Wood

Dear Readers, there is an on-going arms race between plants and the creatures that eat them, that can involve everything from camouflage to chemical weaponry. However, scientists in at the University of Würzberg in Germany have discovered that oak trees that are badly infested with caterpillars in one year will delay opening their leaves by three days during the following year.

Caterpillar eggs are usually laid so that their hatching coincides with the newest, greenest leaves appearing – these are the most nutritious, and the easiest for those little jaws to munch. The scientists did an aerial survey of oak forests in 2019, during which time there was a dramatic infestation of gypsy moths, which caused extensive damage to many of the trees. It was found that the trees who had suffered the most drastically were the ones who delayed producing their leaves by three days in the following year, meaning that any caterpillars that hatched on them starved. This reduced leaf damage by some 55 percent.

While scientists agree that there’s a correlation between leaf opening time and caterpillar predation, it still hasn’t been proved that one causes the other – it could be that the delay is the result of the tree being weakened, rather than a precaution against future leaf loss. But  it’s certainly intriguing, and I look forward to future studies revealing more.

You can read the New Scientist article here.

The journal article is here.