Fruits Affected

Apple, Peach, Plum, Pear, Nectarine, Cherry, Apricot

Also See

The plum curculio (Conotrachelus nenuphar) is a "true weevil" or a "snout beetle" (look up a picture and you will see why), found primarily east of the Rockies in America and Canada. As the name suggests, this insect is fond of plums, but it is also a pest on other stone fruit, apple, and pear.

Symptoms

Scarred, malformed, rotted fruit; crescent-shaped punctures on fruit skin; larvae in fruit.

Organic Treatments

To help limit curculio, dropped fruit and infested wild trees should be removed. Organic growers may be interested in protecting their fruit with kaolin clay (Surround).  Petal fall is when curculio starts to emerge from the woods.

Conventional Treatments

There is a long list of chemicals for Curculio. Sevin and Avaunt are two that do not require a restricted license.

Insect Cycle

The plum curculio (Conotrachelus nenuphar) is a "true weevil" or a "snout beetle" (look up a picture and you will see why), found primarily east of the Rockies in America and Canada. As the name suggests, this insect is fond of plums, but it is also a pest on other stone fruit, apple, and pear. Curculio overwinter in debris and emerge in spring to feed on blooms, buds, and young fruit, and to lay their eggs. The female digs a small hole in the fruit and lays her egg in it. She then cuts a crescent-shaped slice, about 1/8 inch long, in the fruit under the egg, so that the egg will not be crushed as the fruit grows. She's a clever and careful mom! When, after about five days, the larva hatches, it burrows its way into the fruit and feeds for about two weeks. It is a grey-white grub with a brown head, about 1/3 inch when fully grown, and it will emerge from a clean hole, unlike codling moth that leave a little pile of "frass" (excrement) around their hole. The grub drops to the soil, from which it will emerge in five-six weeks as an adult.

Both the feeding and egg laying activities of the plum curculio damage the fruit. The burrowing larva can cause rot and premature fruit drop, and the wounds created on the surface of the fruit can result in scarring, decay, and knobbly, stunted growth. These wounds will be the easiest way to diagnose a plum curculio infestation; the insect itself is quite hard to spot, as its rough, brown body is designed to blend in with bark.

For more information, see A Grower's Guide to Organic Apples and the Cornell IPM Factsheet on Plum Curculio.