Plum Curculio

Conotrachelus nenuphar

Injury:

The plum curculio (PC) is a serious pest of plums, prunes, cherries and apple in New York. It also attacks apricot, nectarine, pear and quince as well as wild plum, hawthorn and native crabapples. This insect is most abundant in orchards adjoining hedgerows and woodlands that offer shelter or overwintering adults. Both feeding and egg laying scars result in russeted areas on the surface of the fruits. The crescent-shaped scar from oviposition is useful in diagnosing damage from this pest. Severely injured fruits become misshapen. Infested fruits often drop early and with smaller fruits, such as cherry, the entire fruit may be ingested by the larva.

Description:

The adult PC is a small 1/5 in.(3cm) snout beetle, mottled with black, gray and brown. The beak or snout is 1/4 the body length and sharp biting jaws are located at the tip of the snout. The larva is a grayish-white, legless, slightly curved grub, about 1/3 inch (8 mm) long. Larvae are found inside fruits.

Life History:

The adults pass the winter hidden under leaves, along fence rows, in brush piles, rock walls and in other protected places. In spring when the weather warms up (mean temperature 60 degrees F or maximum temperature above 75 degrees F, about the same time apples are blooming, the adults become active. Emerging from overwintering quarters they feed on buds, blossoms and newly set fruit. The beetles attack the fruits as soon as they appear, usually at the shuck split in stone fruit. Some feeding injury occurs consisting of small round openings in the skin extending about 1/8 inch into the pulp. The oviposition damage occurs as the female cuts through the skin and deposits a tiny white egg in the opening which she pushes to the bottom of the cavity with her snout. In front of the egg cavity she cuts a crescent shaped slit that extends obliquely under the egg to leave it in a flap of flesh. Each female is capable of depositing from 100 to 500 eggs. The larvae develop in the fruits where they feed for several weeks before reaching maturity. Infested fruits may drop from the tree early. Mature larvae leave the fruit and crawl into the soil to a depth of several inches where they construct earthen pupal cells. During July and August, the new brood of adults begins to emerge. They feed on developing fruits until low fall temperatures force them into hibernation. There is one generation of this insect in New York each year.

Management:

The first step should consist of removing hibernating shelters. This includes cleaning up overgrown fence rows, hedges, and removing brush piles and leaf litter under which the beetles might hibernate.

Pick up and destroy dropped fruit in June and early July.

Jarring, a mechanical method of control, is sometimes helpful; results may vary. If a tree is suddenly jarred with a padded mallet, plum curculio beetles loosen their hold, contract their legs and fall to the ground. Jarring should be done in the early morning. Place sheets on the ground to collect beetles and then destroy them. Note: Young trees can be severely damaged if hit too hard.

• For stone fruits (peaches, nectarines, apricots, and cherries): apply multipurpose spray mixture (captan, malathion and carbaryl) or Surround at shuck split stage and 10 days later.
• For plums and prunes: apply multipurpose spray mixture (captan, malathion and carbaryl) or Surround when shucks start to split, and at the first and second cover sprays.
• For apples: apply multipurpose spray mixture (captan, malathion and cabaryl) or Surround at petal fall plus 10 to 14 days after petal fall (and two weeks later in eastern New York).

Prepared by: Carolyn Klass, Senior Extension Associate, Entomology, Cornell University, 1/77.
4/91 Revised

Pesticide recommendations obtained from: Part I Pest Management around the Home, Cultural Methods, 139S74I, and Part II -- Pest Management Around the Home, 2005-2006 Pesticide Guidelines, Miscellaneous Bulletin 139S74II, 4/03, A Cornell Cooperative Extension Publication.

This publication contains pesticide recommendations. Changes in pesticide regulations occur constantly, and human errors are still possible. Some materials mentioned may no longer be available, and some uses may no longer be legal.

Read the label before applying any pesticide.

TK: 6/2006 #165