Plum Curculio: Appearance, Territory, Damage and Life Cycle

Latin Name: Conotrachelus Nenuphar

Appearance: Plum curculio (Conotrachelus nenuphar), sometimes known as American plum weevil, is a North American insect pest of the Curculionidae family that causes significant damage to a variety of fruit plants. Plum curculio larvae are normally 6 to 9 mm long when fully developed, but only 5 to 7 mm when they reach the pupal stage; all adult traits are apparent in this stage prior to metamorphosis. Adult plum curculios are 4 to 6 mm length with a tiny, rough nose speckled with black, gray, and brown spots. The wings are covered with four pairs of ridges, however due to the center humps, they appear to have only two ridges.

Hosts Plants: Plum curculio, a beetle endemic to the midwestern United States, is one of Wisconsin’s most prevalent and damaging apple pests, causing severe damage to tree fruit. It also infects pear, quince, and stone fruits such as plum, cherry, peach, and apricot, in addition to apple.

Territory: Midwestern United States

Damage Insect Cause: Plum curculio insects may wreak havoc on a fruit harvest. Large scars and bumps caused by eating can be seen in highly damaged fruit. The majority of internally injured fruit (due to digging inside the fruit) drops early.

Life History and Habits: The mature beetle measures 4 to 6 millimeters in length and has a rough coating of mottle black, gray, brown, and orange. The jaws are positioned at the tip of a lengthy snout. These insects spend the winter under yard detritus. Plum curculio harm starts when the adults appear in the spring, just after peaches bloom. Adults eat on buds, flowers, and freshly set fruit, and they mate and deposit eggs in newly appearing fruit. The initial plum curculio harm occurs when the female eats a crescent-shaped slit to lay her eggs; it seems as though a fingernail penetrated the skin.

The grayish white grub of the little plum curculio worm eats its way to the center of the fruit, where it will feed for the next two weeks after the eggs hatch in five days. Because the little plum curculio worm can be crushed by the firm, developing fruit of apples and pears, soft skinned fruits are preferred. At this time of year, immature fruit drop is common. At the right stage of growth, the plum curculio worm crawls out of the fruit and falls to the ground. Adults emerge from the dirt five to six weeks later to feed. The plum curculio targets the harder fruits here. Smooth skin is a favorite food of these young people.