Several damaging pests can increase the chance of trees dripping an excessive amount of sap. The bark beetle lays its eggs beneath the surface of the tree bark. Once the larvae hatch, they continue to bore through the tree, creating tunnels. As a defense against the pest, the tree produces sap into the holes bored by the bark beetle to prevent the insect from laying eggs. This excessive sap can be seen seeping out of holes in the tree bark. The best defense against bark beetle is prevention; however, infected trees may be saved with the proper insecticides applied by a licensed pesticide applicator. Common garden pests such as scales, aphids and mealybugs feed on the sap of trees and excrete a sticky substance known as honeydew, which can be mistaken for sap. If not treated, the honeydew will increase the chance of sooty mildew growth. These sap-sucking insects can generally be treated with insecticidal soaps and horticultural oils. Many fungi and diseases that attack trees will cause sap to seep out of the bark. The bacterial infection known as wetwood is a common infection of elms and causes sap to seep out of the cracks and wounds of the tree bark.
Trees infected with wetwood may have yellow, wilting leaves and branch dieback.
Last summer, we ran into a predicament where sap was dripping off the leaves of a nearby tree. Unfortunately, this covered my car in a sticky substance, which led to the accumulation of dirt, as well as the arrival of flies, bees, wasps and other annoying insects. After searching around online, I quickly realised that I was wrong. Simply put: It wasn t sap at all. Sap doesn t drip from the leaves of a tree. Instead, it comes out of the bark. So what was it? Aphid Infestation. Aphids (aka plant lice) are small little insects that will suck the fluid out of a tree. As they are feeding, they will secrete a sticky substance called honeydew. As soon as the aphid infestation has reached a point where it has spiralled out of control, this sweet honeydew residue will begin to drip from the leaves of the tree in question, leading many people to think that it is plant sap.
Ants. Ants are the real troublemakers in this situation. They carry the aphids up the tree so that the aphids can suck the fluid out of the tree. This is so that the ants can feed off the sticky honeydew substance that the aphids are secreting. Basically, the ants are using the tree as a farm. They will herd the aphids up the tree and then protect them from other insects. What to do? To rid the tree of this aphid infestation, you will need to do the following: 1. Prevent the ants from climbing up the tree. Get some trickle or another sticky tape-like product that can be wrapped around the base of the tree. Make sure that it is wrapped tightly, as you do not want to have a situation where the ants can crawl up underneath it. The material that you use should be relatively weather-proof and it should be able to last for a couple of weeks. PThis should prevent the ants from being able to carry more aphids up into the tree. 2. Water down the tree. Now that you ve taken away the ants ability to restock their aphid farm, you should hose down the leaves of the tree.
The goal here is to git rid of the aphids that are currently feeding on the tree. Be sure to spend a few minutes at this, just to make sure that you ve reduced the vast majority of them. Leftover aphids will die off pretty quickly, especially seeing as their bodyguards can no longer climb up to protect them. It is also worth noting that an aphid only has a lifespan of about 20-40 days. 3. Ant Killer. As an additional measure against the aphid infestation, you can place ant killer at the base of the tree (in many cases, this is where the ant nest is located). If you re against the notion of killing ants, then you can use a natural repellent such as mint tea (grind the leaves up and sprinkle them at the base of the tree). That s it. If you follow the above steps, the infestation will be gone and that horrible sticky residue will no longer drip from the leaves of the tree. Typically This will solve the issue until the sticky tape around the tree dries out and the ants start to return.