Oak trees do have sap. Sap is essential because it transports nutrients throughout the tree. However, it’s a sign of insect infestation or disease if your oak tree is dripping sap. Sap dripping from an oak is not a normal part of a healthy lifecycle. Most often, the falling sap is actually “honeydew,” which is sap that has been eaten and excreted by insects. To drive off insects and save your tree, contact an arborist for assistance or use an imidacloprid insecticide.
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What is the Sticky Stuff Falling from Oak Trees?
If a sticky substance is falling from your oak tree in spring and early summer, it is most likely “honeydew,” which is the nickname for the excrement of insects that have bored into your oak tree to eat its sap. If your oak is dripping something sticky in late summer or fall, it may actually be sap, but this is caused by insects infesting the oak tree’s acorns.
- Most often, a sticky substance falling from your oak is the excrement of invasive insects feeding on oak sap.
- Oak may drip sap in summer and fall if insects infest the growing acorns.
- Dripping sap may be caused by bacterial wetwood infection or Sudden Oak Death in some cases.
The less common causes of oaks dripping tree sap are bacterial wetwood diseases and Sudden Oak Death, which cannot easily be treated. Long story short, if there’s something sticky falling from the branches of your oak, an infestation of insects is the likely cause.
Signs of Oak Infested by Insects
Sticky “honeydew” and tree sap falling from your oak can be caused by a variety of insect species, including aphids, lace bugs, scale, filbert weevils, and filbert worms. To determine if your oak is dripping because of insects feeding on your tree, look for the following signs:
- Sticky substance on leaves, plants, and other items beneath the tree. This substance may have turned black and “sooty” from bacteria.
- Aphids (small, usually green-horned insects) on the undersides of leaves.
- Scale insects on leaves, branches, and bark.
- Holes bored in acorns.
While these signs may not be life-threatening, invasive insect species can do damage to oaks. More importantly, insects are more likely to attack trees that are already weak or struggling. If your oak is dripping, it may be in danger.
The Danger of Oak Dripping Sap
The smell of oak sap or honeydew from sap-eating insects can attract other dangerous pests to your tree. Nitidulid Beetles are drawn to the smell of oak sap. These beetles not only feed on your oak, but they also carry the fungus that causes Oak Wilt, a disease that is deadly to oak trees. If your oak is dripping sap or honeydew, the infestation should be taken care of immediately to prevent an invasion of worse pests.
- Your tree may be damaged by the insects feeding on sap.
- The smell of oak sap attracts Nitidulid Beetles, which can infect your tree with deadly Oak Wilt.
- Ants, wasps, hornets, and other insects are drawn to the smell of sap and honeydew because they feed on the pest insects.
It’s also important to note that predatory insects are drawn to the sweet smell of a dripping oak. Hornets and wasps may arrive quickly to feed on the aphids, lace bugs, or scale. If the problem isn’t dealt with quickly, you’ll be working to both save your oak and drive stinging insects off your property.
How to Treat Oak Insect Infestation
If you have spotted aphids, lace bugs, scale, or other signs of insect activity, you can treat this problem yourself with a pesticide containing imidacloprid. Alternatively, it may be a good idea to contact an arborist for a professional opinion.
- Contact an arborist for oak tree treatment.
- Use this imidacloprid-based pesticide to kill insects.
- Systemic pesticides like imidacloprid are much more effective for use on large trees than neem oil and similar treatments.
Imidacloprid works by applying the pesticide at the base of your oak tree. Your tree will then absorb the pesticide through the roots and distribute it through the tree to help it drive off and resist bugs. Neem oil and other essential oils only attack aphids and other bugs if they are directly applied to the insects. When dealing with a 50-foot oak tree, it simply isn’t possible to spray every leaf. Imidacloprid is the best choice.
Why is Sap Coming Out of My Oak Tree?
If your oak tree is leaking or dripping sap, it is most likely because insects have invaded. The dripping sap is either the excrement of insects feeding on your tree or it’s produced when bugs drill into oak acorns. In rare cases, it can be caused by bacterial infection.
Inspect your oak tree. If aphids have clustered on the underside of leaves, bumpy “scale” insects have moved in, or filbert weevils have chewed holes in the acorns, it’s time to treat the problem. You can treat the infestation using an imidacloprid pesticide, but it’s a good idea to call an arborist. Often, oak trees attacked by insects are already weak or ailing. A professional will be able to consult you on the health of the tree and offer solutions to save your oak.