Keep berries off the ground, and practice frequent, complete picking. Remove overripe and damaged berries, and bury culled berries. Because picnic beetles are attracted to overripe fruit, infestations usually build up after harvests are underway, and the use of insecticides is precluded by a combination of frequent picking and required preharvest intervals. Ripe berries are destroyed by Japanese beetles and green June beetles. Flower buds are destroyed by rose chafers.
Japanese beetle is most troublesome in the first two to three years after a planting is established.
Rose chafer is most common in areas with light sandy soil. Green June beetles are most numerous in plantings near sites where manure or compost has been spread. The green June beetle is 1 inch long, metallic green on top and brown on the sides. Larvae of all are soft white grubs with six legs and a brown head, usually found in a curled position. There is one generation per year of all three of these beetle species.