The cause may be a weevil named plum curculio. Plum curculio (Conotrachelus nenuphar), a native of North America, is widely distributed east of the Rocky Mountains. The name is somewhat misleading because this insect attacks not only plums, but also apples, peaches, pears, cherries, quince, and other wild and cultivated fruits. It can be very destructive if no control measures are applied. The fruit is injured in four stages: the spring feeding of adult beetles, then punctures by the female when laying eggs in the fruit, followed by larvae feeding within the fruit, and finally early fall feeding of adult beetles.

One method of nontoxic mechanical control is shaking and beating the sluggish beetles from trees in the morning and capturing them on sheets or tarps spread under the tree. While an old control method, it can still be practical today on a small scale. Insects that fall on the sheet should be removed and crushed.

Another nontoxic control tool is kaolin clay.. The clay forms a thin clay barrier around the fruit that repels adults and prevents them from depositing eggs in the fruit. A suspension of kaolin clay in water is sprayed on the trees when the flower petals fall and applications continue until one week before harvest. .

Heavy raking of the soil beneath trees during pupation in late spring/ early summer can help destroy larvae that have fallen on the ground.

Natural control of the plum curculio results from winter mortality, attacks by birds and other predators and from parasites. You can also pick up fallen fruit two to three times a week, put it in a plastic bag, tie it tightly, and place it in the trash can. This will help keep larvae in fallen fruit from developing in the soil and, if done regularly, should lessen the damage done by this insect.

If the adult beetle population is severe and chemical treatment is needed, contact your county's cooperative extension office for information on products that are licensed and effective for treatment in your area.

For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service