Adult beetles have a long snout 1/3 the length of the body that projects downward and forward (Fig. 1). The body surface is very rough or warty. The basic color is brown with lighter patches. The larvae are legless, smooth, and slightly curved. They have a brown head and a yellowish-white or grayish-white body (Fig. 2).
A preference is to be shown for peaches, plums and other stone fruits. It also attacks apples and occasionally pears. The primary injury is caused by the female plum curculio during egg laying. She makes a crescent shaped cut in the skin of the fruit and then lays eggs under the flap of skin. This results in D-shaped scars on the fruit surface. Later in the season both males and females make round feeding punctures on the fruit. If the eggs hatch, the larvae tunnel into the fruit. Larval feeding also makes the fruit worthless.
Plum curculio adults overwinter in trash, brush piles, and other protected places near the orchard. At blossom time, when temperatures reach about 70°F, the adults leave the overwintering sites and move into the trees where they feed on developing fruit and leaves. Eggs are laid and the larvae enter the fruit. The infested fruit usually drops to the ground. After two or more weeks the larvae leave the fruit, burrow into the ground, and pupate. About a month later the first generation adults emerge, move into the trees, and begin laying eggs. This occurs in mid-June and throughout July. Again the larvae feed for a while, drop to the ground and pupate. The second generation adults emerge in the fall, move to the hibernation areas and overwinter.
Homeowners and small growers can achieve at least partial control by picking up and destroying fruit that drops early. All growers can benefit by practicing good sanitation. Brush piles and other potential overwintering sites should be removed or cleaned up. Chemical controls should be applied after the petals have fallen to control the first generation. Three sprays, the first in mid-June and the second the end of June and the third in early July will control the second generation adults. Homeowners can use carbaryl (Sevin) or malathion for control of plum curculio. These materials are often found in premixed home orchard spray packages or may be applied by themselves. Larger growers have other options available. Additional information can be obtained from your local County Extension Agent.
Prepared by Clyde S. Gorsuch, Extension Entomologist/ Professor, Department of Entomology, Soils, and Plant Sciences, Clemson University.
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