Plum Curculio (PC)
Spotted the first Plum Curculio (PC) in the orchard today. We have still not set a biofix on codling moth (CM) and it is very unusual that we would spot PC before a CM biofix. Nevertheless, when I spot just one PC, I know they are in the orchard and we have to spray for them. This is one of the most difficult pests to avoid in any orchard. Our temperatures have not been high enough for them to start feeding yet, but just as soon as we hit the 60's, they will start feeding and laying eggs, so we have to spray right away!
Damage: Both adults and larvae cause damage. Adults damage fruit when their feeding and egg-laying causes scarred and malformed fruit. Adult damage also provides entry sites for fungal rots. Larvae tunnel and feed inside developing fruit. Most fruit infested early in the season drop prematurely. Fruit infested later in the season are of no market value due to the presence of the grubs.
Life Cycle: Adults overwinter in ground litter or other protected places. They become active shortly before peaches bloom. Adults fly to trees, mate, and lay eggs. Females deposit each egg in a hole under a crescent-shaped cut eaten in the fruit. Eggs hatch in about five days. Grubs feed in the fruit for eight to 22 days.
Mature larvae tunnel out of the fruit, enter the soil, construct small earthen cells and pupate after about two weeks. The complete life cycle, from egg to emerged adult, may require five to eight weeks. There are usually two generations and possibly a partial third generation each year.
Control: Controls should be aimed at overwintering adults to prevent the laying of first generation eggs. Adults can be monitored by traps or limb jarring over a ground sheet. Sprays for curculio should be initiated at petal fall with the initial application followed by two or three sprays at 10-day intervals. Additional applications may be necessary for the second generation (ca. June). Destruction of nearby wild plums, abandoned fruit trees and other alternate host plants can help to reduce infestations.
For further information on this pest visit Fruit IPM Resources at Michigan State University.