Red sticky traps are used either for early warning of arrival of a pest insect or in some cases actual control of a pest insect if you set out 4 or 5 traps. They are used for Cherry Fruit flies, Apple Maggot flies, Traps work est when theuy are positioned in branches where flies can alight as they approach the traps. Place traps in trees one or two weeks before buds break in early spring, and usually it is best to take the traps down after about 4 weeks to avoid attracting beneficial insects. Some yardeners however leave them out until harvest time. You need to keep an eye on these traps during the summer and fall in case they start to attract beneficial insects; then you may want to take them down.