Plum trees are popular fruit trees that are grown throughout the world. Two main types of plum trees exist: the European and the Japanese. European plums are sweeter in taste and the Japanese plums are larger in size. Plum trees are less susceptible to pests than most other fruit trees, but some pests will cause extensive destruction to the tree if they are not controlled.
Plum trees are susceptible to the Leaf Curl Plum Aphids. They feed by sucking sap from the leaves, which causes the leaf to curl. Leaf Curl Plum aphids will not kill a tree, but can weaken it and affect the growth as well as the sugar content of the plums. They produce a sticky waste material called honeydew that will cover leaves and branches of the plum tree.
Rid plum trees of aphids and their honeydew by spraying a solution of 25 percent dish soap and 75 percent water over the leaves and tree branches. Aphids breathe through their skin, and the soap residue builds up on the aphids and causes them to suffocate. Ladybugs are known to eat aphids, but they will not damage your tree. Purchase ladybugs at your local garden store and let them keep your plum trees aphid free.
A metallic green beetle that is small but mighty, the Japanese beetle will munch its way through the leaves, flowers and fruit of your plum tree from mid June until late August. Some pesticides will rid your trees of this pest but if you don't want to use chemicals on your fruit trees, there are other ways to remove beetles. Shake trees in the early morning hours when beetles are still sluggish from the cold. Catch beetles in a bucket of soapy water and allow them to drown.
Should you prefer not to spend your mornings shaking trees, you can concoct your own insecticidal soap by mixing a tablespoon or two of castor soap in with one quart of water and spray the beetles with the mix. Beetle traps sometimes work, but some theories indicate that the pheromones that attract the beetle to the traps will attract more beetles to your tree.
Capable of causing great damage, the Plum Curculio is difficult to control. This 1/2-inch-long beetle is found almost everywhere east of California. They are particularly fond of stone fruits such as apricots and plums. The male adult beetle attacks the fruit as soon as it forms, eating holes into the skin and feeding on the pulp and pit of the plum. The female will lay her eggs in the fruit. Low-toxicity insecticide sprays work well when trying to control these pests. Contact county Extension Service offices for a recommended spray schedule for trees.
When infestation is minor, manual removal of the plum curculio is possible. Spread plastic sheets around the tree, shake the tree and carry the fallen insects away and destroy. Repeat this daily when bugs are most active in the spring. Keeping the area around the plum tree clean will help control plum curculio beetles. Collect and burn wormy fruits. Remove leaves and mulch from under trees in the late fall; curculios are known to hibernate in leaf litter during the winter.