Perhaps owing to these gonzo genetics, apples are remarkably susceptible to disease and rot. Their tender skin and light flesh are a haven for small creatures. Their trees embrace myriad molds, viruses, and fungi: apple scab, black pox, southern blight, union necrosis. For farmers and hobby gardeners, the business of apple-growing is not so much aiding the fruits in their growth as scrambling to ward off their demise. Blight spreads quickly, and it’s not always apparent on the fruit’s surface. Even without the influence of invader or infection, an apple abets its own spoilage: its skin, minutely porous, exhales ethylene, a gaseous compound that induces ripening, and the fruit has no interest in stopping at the point where it serves our needs.

source: DF