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Plant Pathology


Plum Curculio

Plum curculio (PC) is found throughout Kentucky. It is an important pest of stone fruits as well as apple, pear, quince and related species. In apples, the larvae will COMPLETE development only in FRUIT DROPS.

The adult is a brown-gray, hard bodied snout beetle. The adult beetle will reach a length of about 1/4 in. The larva is a white legless worm with a brown head. Its length will be about 1/3 inch at full growth.

Plum Curculio

Winter is passed in the adult stage. Adults hibernate in protected places. Early in the spring, adults will become active, feeding on early foliage. These adults will feed for five or six weeks, during this time eggs will be placed in small fruits. The eggs are laid in crescent shaped cavities the female makes using her mouthparts. Hatching requires about five days and the larva feed for two to three weeks. When the larvae are fully developed, they will leave the fruit through clean-out holes. No frass or webbing will be evident. The larvae then enter the ground and pupate. A second generation of adults will emerge in about one month. These curculios will produce a second full generation, the resulting adults will overwinter in local, protected habitats.

Major curculio damage is a result of larva developing within the fruit, causing apples to be decreased in size. However, the feeding scars left by the female on the fruit skins results in lower quality fruit. If this damage was inflicted on young fruit "catfacing" may result. Fruit infested with plum curculio larva usually drop from the tree prematurely.

SCOUT: Because the adult curculio often is found on the tree only at night, predicting when damage will occur is difficult. Examine the 100 fruit for the adults and fruit scars.

RECORD: The number of fruit with feeding or oviposition scars per 100 fruit.

ACTION THRESHOLD: Damaging infestations of plum curculio cannot be predicted accurately. Use preventive sprays at the petal-fall and first-cover stages to reduce damage.

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Apple IPM web site created by Kerry Kirk - 2001 - Send questions or comments to Patty Lucas