The Russian invasion of Ukraine threatens millions of tiny spring-time sprouts that should emerge from stalks of dormant winter wheat in the coming weeks. If the farmers can't feed those crops soon, far fewer of the so-called tillers will spout, jeopardising a national wheat harvest on which millions in the developing world depend.

The wheat was planted last autumn, which, after a brief growing period, fell dormant for the winter. Before the grain returns to life, however, farmers typically spread fertiliser that encourages the tillers to grow off the main stalks. Each stalk can have three or four tillers, increasing the yield per wheat stalk exponentially.