Abstract: A protective bag is applied to fruit growing on a plant for protecting the fruit from disease, insects, birds and so forth. The bag is colored with a coloring agent which has a property to gradually lower its sunlight shielding characteristic in response to irradiation by sunlight. The coloring agent initially provides substantially complete sunlight shielding characteristic and the sunlight shielding characteristic is lowered at a given rate to its minimum sunlight shielding characteristics.