Anyone who has recently entered Chile via Santiago airport will have noticed a major crackdown by the Chilean agriculture and livestock service (SAG). If you don't declare animal or plant products you will get fined, even if it's just an apple you were given on the 'plane and forgot to throw away. On the spot fines average around us$200.
If you're not sure, declare it; otherwise you're going to get a pretty unpleasant welcome to the country. Chile isn't alone in trying to protect it's multi-billion dollar agricultural trade. Australia has similar draconian measures in place.
I'm all for it-although they seem over the top, the rules are clear and simple and easy to follow. They really do help protect Chile's agriculture- one mistake could cost this country millions of dollars.