California’s most troublesome tourist, a tiny, mud-coloured moth from Australia with a taste for Napa valley’s finest grapes – not to mention all other crops and the state’s fir trees – is generating panic. Theories as to how the moth reached the Golden State abound; the most likely is that the first entered the country on a plant imported from Australia. By the time a retired entomologist from Berkeley found one in a trap behind his house, it was too late. The invasion was under way – resulting in a $100 million (£50 million) crisis for California’s farmers and a political battle in Washington over how future invasions of exotic pests might be prevented. As California’s farmers have found out, the Australian light brown apple moth is a very hungry creature. It might have a passion for grapes but it will happily eat anything else grown by California’s farmers. Its caterpillars will eat everything from corn and tomatoes to cherries, peaches and plums. It is able to procreate at an astonishing pace even if its life-span is shorter than the average summer holiday.