Earth-friendly pesticides

摘要

The fungus spreads slowly, hibernating through winter in the dried and diseased branches of citrus trees. Come spring, it disperses its spores in raindrops that fall on budding leaves and branches. The pathogen then creeps to the fruit stems, where it waits until fall's harvest to spread a shadow of rot over the fruit. In the early 1970s, Yutaka Arimoto, then a young researcher at RIKEN, wondered why the invasion of the citrus tree fungus Diaporthe citri followed the seasons. Perhaps that cycle could be used to defeat it, he thought. Having grown up on a farm, Arimoto had seen firsthand the damage pests and diseases cause to crops, but he also knew that many pesticides used to prevent them were later taken out of use. "Unexpected things can happen, and there is never a guarantee that current testing methods are infallible," he says. "No chemical is 100 per cent safe, but by selecting compounds that people have been consuming for a long time without adverse effects, we assume that there is a very small chance of unexpected problems arising."