ASK THE HORT AGENT
Question What is causing sap to ooze from my plums?
Answer It’s probably an insect called a plum curculio. This pest is actually one of many native weevils. Over 60,000 species of weevils exist around the world. There are rice weevils, wheat weevils, pine weevils, flea weevils, acorn weevils, biscuit weevils and even the infamous boll weevil. Eventually, you get tired of saying weevil. The abundance of weevil names may have caused this insect to be called plum curculio. It sounds more distinguished than plum weevil.
Most weevils sport a name which describes their specific host. For example, wheat, acorn, boll, biscuit, etc… On the other hand, plum curculios are not specific to plum trees. They will attack apples, peaches, pears, cherries and other wild and cultivated fruit. They’re not even limited to fruit. Plum curculios also feed on buds, blossoms and leaves. I guess they got their name from being plum hungry.
Adult curculios emerge from the ground in early spring and feed over a 5 to 6 week period. When fruit begin to develop, females hollow out small cavities and deposit an egg in each cavity. The eggs hatch and the babies (larva) eat on the inside of the fruit.
Adult feeding may scar or misshape the fruit. Larval feeding usually causes the immature fruit to drop off the tree. Plum and peach fruit damaged from feeding will often ooze sap and become gummy. Apples and pears will typically scar without bleeding as much. It is important to know that these insects do most of their damage at night.
Homeowners with few trees can control this pest by placing a white sheet under the tree and lightly shaking or jarring the limbs. The clumsy curculios will fall onto the sheet where you can pick them up. It is also very important to pick up the immature fruit which drop from the trees. These fruit contain the baby curculios (the next generation).
Of course insecticides are an option. General orchard spray programs contain a fungicide and an insecticide. Begin spraying when the flower petals begin to fall off. Follow the label for frequency (typically every 9 to 14 days).
For more plum curculio info, visit http://ohioline.osu.edu/hyg-fact/2000/2043.html If you do not have internet access, then call me at 910-893-7533 or email me at firstname.lastname@example.org
Zyzzyva, a genus of tropical American weevils, is the last word in many dictionaries including the Official Scrabble Players Dictionary. Ironically, there is only one Z per Scrabble game. Not counting double or triple letter scores, weevil is worth 12 points and curculio is worth 24 points – more distinguished.
Gary L. Pierce
Horticulture Extension AgentHarnett County