TUCSON, ARIZ. ? Wasting money on bad fruit could be a thing of the past.

A University of Arizona professor has invented a sticker that can tell consumers if a fruit or vegetable is ripe. That means no more waiting for avocados to ripen or throwing out fuzzy peaches.

The stickers will be available to growers next year and should make their way to supermarkets within two to three years, said Mark Riley, an assistant professor of agricultural and biosystems engineering at UA, in Tucson.

A marker on Riley’s RediRipe stickers detects a chemical called ethylene gas, which is released by fruit or vegetables as they ripen.

As that happens, the sticker turns from white to blue.

The more ethylene gas the fruit produces, the darker the blue, Riley said.

The color shift is not instantaneous once a sticker is attached. It takes about 24 to 48 hours, depending on how fast the fruit is ripening, Riley said.