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Plum curculio

Conotrachelus nenuphar (Herbst)
Coleoptera: Curculionidae

The adult is mottled grayish black and brown (A). Its head is prolonged into a large but short snout that bears antennae. Each elytron has a series of humps with the 2nd and 3rd pairs separated by a clear transverse band. The white elliptical eggs are deposited under the skin of the fruit in a crescent-shaped slit. The whitish larva, with no functional legs, has a C-shaped body, an elliptical head and a brown thoracic shield (B).

Distribution

Widespread and a major pest in most fruit-growing states and provinces in eastern North America.

Damage

Attacks all deciduous tree fruits. A crescent-shaped scar (C) is left by egg laying activities of the adult on the young apple and pear fruit beginning shortly after petal fall. The larvae bore into and create galleries in stone fruits. In August, the adults that will overwinter (north) or those that will produce a second generation (south) feed on fruits (D) before seeking overwintering sites in leaf litter near the orchard. Some oviposition of this brood also results in larval fruit infestations in late summer.

Similar Species

The apple curculio (Anthonomus quadrigibbus Say) is smaller (4.5 mm) with a longer and slender snout (E) and rarely causes damage to apples in commercial plantings, as larvae feed mainly on June drops or mummified apples on the tree.

Management

Monitor regularly for fresh damage on fruit. Apply protective sprays during the egg laying period, starting at petal fall; a degree-day model can be used to predict the portion of the oviposition period during which insecticide protection would be required.

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