Dandelions are troublesome weeds that are detested by most gardeners. Yet dandelions also have many insect enemies in nature. However, they are able to protect themselves with their latex, a milky, bitter-tasting sap. Scientists at the Max Planck Institute for Chemical Ecology in Jena, Germany, and the University of Bern, Switzerland, have now demonstrated that a single compound in the latex protects dandelion roots against voracious cockchafer larvae. Thus, latex plays a crucial role in dandelion defense against root feeders.

Dandelions (Taraxacum officinale agg.) are well-known plants of European and Asian origin that have spread around most of the temperate world. Children love their yellow flowers and even more the fluffy seed heads with their parachute-like seeds that can travel long distances by wind. Young plants grow with such force that they can penetrate even asphalt. Therefore dandelions have become a symbol for survival in modern cities.

In fields and meadows, the plant must fend off many herbivores, among them cockchafer larvae. The common cockchafer (Melolontha melolontha) spends the first three years of its life cycle underground as a grub feeding on the roots of different plants. One of its favorite foods is dandelion roots. Like many other plants, dandelions produce secondary metabolites to protect themselves against herbivores. Some of these defenses, such as terpenes and phenols, are of pharmaceutical interest and are considered promising anti-cancer agents. The most important dandelion metabolites are bitter substances which are especially found in a milky sap called latex, a substance found in almost ten percent of all flowering plants.