If you have a plum tree in your garden, you know you have to be on the lookout for plum tree pests. The good news is that in general, plum trees are fairly hardy and don’t usually attract the attention of pests if they are otherwise well cared for.
However, it’s always a good idea to know what the most common types of pests look like and how they affect your tree so you can take quick action, if necessary.
Top Plum Tree Pests
Read on for a list of the most common plum tree pests. Not all of them are a threat in every region, but it is a good idea to learn about how they can affect your plum trees and what external signs they cause.
1. Plum Curculio
Plum curculio are a type of weevil that infests plum trees, destroying fruit and causing it to fall prematurely. Adult weevils look like a gray-brown beetle with a long snout and ridged back. As their larvae hatch, they burrow into the fruit and eat it from the inside.
How To Recognize a Plum Curculio Infestation
The most distinctive sign of a curculio infestation is a crescent-shaped mark on fruit. You will also notice fruit dropping off the tree and might see worms or beetles in the branches.
How To Treat Plum Trees For Circulio
To get rid of plum curculio, remove dropped fruit from the area daily. Spread a sheet or tarp on the ground and knock the tree vigorously with a rake to knock out remaining larva. Remove them from the area. Repeat daily for three weeks.
You can also treat a curculio infestation with a general fruit tree insecticide.
How To Prevent Plum Curculio
The best way to reduce the risk of a plum curculio infestation is to apply insecticide early in the growing season.
2. Leaf-Curl Plum Aphids
Aphids are tiny insects that attack the leaves of your tree, causing them to die. On their own, aphids aren’t capable of causing serious destruction. But they do leave behind secretions that increase the risk of your tree developing disease.
How To Recognize an Aphid Infestation
The main sign of an aphid infestation is your tree’s leaves curling in on themselves. When you pull the curled leaf flat, you will notice clusters of small green or white bugs. You might also notice a sticky residue on the leaves.
How To Treat Plum Trees For Aphids
To remove aphids, apply a commercial insecticide or citrus oils as soon as you notice the infestation. It can also be effective to spray your tree with your hose on a jet setting, which will knock most of the aphids off.
How To Prevent Aphids
To prevent aphids, spray your tree in the fall to kill any eggs that will shelter there through the winter. Check your tree regularly for signs of an infestation.
3. Apple Maggots
Apple maggots or railroad worms have earned their name because they often infest apple trees. But they’re attracted to many types of fruit trees, including plums. These fruit fly larvae can destroy your crop by eating it on the tree.
How To Recognize an Apple Maggot Infestation
The telltale sign of a maggot infestation is small blemishes on the outside of the fruit. When you cut the fruit open, you may notice a dry, brittle brown tunnel or streak and even see actual insects.
How To Treat Plum Trees For Apple Maggots
To treat trees for apple maggots, spray with a commercial insecticide and hang sticky traps in your tree. Clear infested fruit and change traps regularly. Some gardeners have luck in treating an infestation with kaolin clay.
How To Prevent Apple Maggots
To reduce the risk of attracting apple maggots, keep your garden clear of standing water and excessive leaf debris. Mow your lawn and consider bagging your plum trees to provide a physical barrier against pests.
There are several types of mites that can infest plum trees. But most of them cause similar problems and can be treated with the same products. The biggest concern of mites is that they leave secretions that can cause disease.
How To Recognize a Mite Infestation
Depending on the type of mite infesting your tree, the symptoms may vary. But some of the top signs of a mite infestation include mottling on leaves (may be red or white) and discoloration. Severe infestations might include webs on branches. When you turn the leaf over, you’ll notice small bugs about the size of a pinhead.
How To Treat Plum Trees For Mites
To get rid of mites before they cause the tree to be infected, apply a commercial bug spray or insecticidal soap.
How To Prevent Mites
To reduce the risk of a mite infestation, spray your tree in the autumn to kill any eggs. This will prevent them from wintering in your tree and hatching in the spring. You may also want to consider planting ground plants that attract mite predators like ladybugs.
Scale insects are some of the most common bugs to infest not only plums, but many types of fruit trees. Though they cause ugly deformities on branches, they can be controlled with the proper tools. The biggest concern of scale is that they feed on the sap of the tree and weaken it.
How To Recognize a Scale Infestation
It’s pretty easy to recognize a scale insect infestation thanks to how dramatically they affect the branches of fruit trees. If you see branches and leaves breaking out into large brown lumps or spots, you probably need to treat for scale insects.
How To Treat Plum Trees For Scale
Use an insecticide made for scale insects or aphids. Spray your tree in May or June when the insects begin to move. You can also remove them manually with your hands or a toothbrush, and spray the tree to knock remaining insects off.
How To Prevent Scale
To prevent scale, spray your plum tree in the autumn. This will keep scale insects from laying their eggs in the tree. These lay dormant through the winter and hatch in the spring.
6. Plum Moths
Plum moths are a particularly nasty infestation that ruin a fruit crop. These moths burrow into fruit, eating it and leaving excrement behind. For obvious reasons, you don’t want them in your plum tree!
How To Recognize a Plum Moth Infestation
Often, people don’t realize they have a plum moth infestation until they cut or bite into a plum. Then they will notice holes filled with brown insect waste and small pink caterpillars. Other signs include discolored fruit, premature dropping, and bits of gum surrounding holes in the fruit.
How To Treat Plum Trees For Moths
Once you have a plum moth infestation, you will need to throw away the earliest fruit affected. Luckily, you may be able to save later fruit. Place pheromone traps around the tree in the late spring and spray with insecticide if these aren’t effective.
How To Prevent Plum Moths
As with many pests that infest plum trees, the best way to prevent plum moths is to treat your tree in the period before insects are likely to lay their eggs. In this case, you’ll want to tree your plum tree in the early summer to reduce the risk of a moth infestation.
7. Plum Sawflies
Plum sawflies are frustrating pests, since they completely ruin a fruit crop — sometimes for an entire year. These unpleasant insects burrow into fruit almost undetectably before eating it from the inside.
How To Recognize a Plum Sawfly Infestation
It can be difficult to recognize a plum sawfly infestation unless you have sharp eyes. Usually, the only giveaway is a small brown spot or pinprick on the outside of the fruit. You might also notice gum exuding from the trunk, a stress response from the tree itself.
If you suspect you have a sawfly infestation but aren’t sure how extensive it is, hang pheromone traps to start. This will help you measure the activity of male sawflies to gauge how serious the problem is.
How To Treat Plum Trees For Sawflies
Treating plum trees for sawflies is a bit intensive, since it involves getting rid of all infected fruit and burning it. Unfortunately, it won’t solve a problem that has already begun, but it will stop next year’s crop from being infested as well.
Another good measure is to turn the soil surrounding the tree over with a spade. This will expose any remaining larvae to birds and other hungry predators.
How To Prevent Plum Sawflies
To prevent plum sawflies, spray your tree with insecticide when the flowers begin to emerge. This will deter mature flies from laying their eggs in or near the tree.
Thrips are small winged insects that are common in gardens and yards. They can infest many plants, including plum trees, where they eat leaves, branches, and fruit. They can ruin fruit crops because they puncture the skin and suck up the inside.
How To Recognize a Thrip Infestation
Damage from thrips include white or silver spots on foliage or holes in fruit. That’s because thrips suck nutrients out of the plant, robbing it of its color.
How To Treat Plum Trees For Thrips
If you notice signs of a thrip infestation on your plum tree, start by removing any damaged fruit and foliage. Move it away from the area to ensure that the insects don’t return. You can usually get rid of them by spraying a mild insecticidal soap on the branches.
How To Prevent Thrips
Pruning your tree regularly will help reduce the likelihood of attracting thrips. An annual application of mild insecticide should also do the trick.
When Should I Spray Plum Trees?
When and how to apply insecticide to your plum trees depends at least in part on what bugs are attacking it. As preventative care, however, it’s a good idea to apply a dormant oil insecticide containing either malathion or endosulfan.
Apply this in the autumn just before early freezes. This will protect the tree as it goes dormant for the winter. Many pests lay eggs in trees in the autumn, where they stay safe until hatching in the spring.
What Should I Use To Spray My Plum Tree?
Sprays containing sulfur or malathion are a great way to protect your plum tree against invading pests, while commercial fungicides protect against many diseases that can injure or kill the tree.
Final Thoughts On Plum Tree Pests
Luckily, most plum trees thrive with basic care. Just make sure you check them regularly for signs of infestation. This will ensure that you can act quickly if one occurs, saving your tree and fruit crop!
If you have a trick for protecting plum trees from pests, share it in the comments.
Wondering about diseases that could affect your plum harvest? Read our blog post about common plum tree diseases and how to treat and prevent them.