Can Aphids Kill a Tree?

Aphids can cause a lot of damage to plants and crops that are grown in your garden. But can they damage and possibly even kill trees?

Can Aphids Damage Trees?

Aphids can damage trees, but the damage and fatality rates vary depending on what type of tree they have inhabited. Sturdier trees can often withstand the onslaught of an aphid colony. But some weaker trees, such as fruit trees, can often succumb to the damage of an aphid population quite quickly. 

What Trees Can Aphids Kill?

Aphids usually only kill trees that are not fully matured. If they are young or saplings, they still have a lot to grow, and the presence of aphids will often stunt the growth of trees and can cause severe damage quite easily and quickly. 

How Do Aphids Kill Trees?

Now that we know it is actually possible for aphids to kill trees let’s look at what they actually do to cause such damage: 

Prevent Photosynthesis

Aphids feed by extracting sap from the leaves, stalks and roots of plants. They also deposit some saliva in the area from which they drew the sap, which prevents their wounds from closing, which often causes wilting in leaves.

As well as this, aphids excrete honeydew after feeding. This sticky substance will stay attached to the leaves of the plant, and it will block out the sunlight and prevent the plant from photosynthesising. 

Aphids Carry Diseases

Aphids are transmitters of many plant diseases, and they can pass these diseases onto trees. This is usually the cause of fatality amongst trees that are larger, sturdier and even fully grown. 

What Aphids are Commonly Found on Trees?

There are many species of aphids, and not all of them are found on trees. The ones found on trees are usually more specific as many common species of aphids will not inhabit trees. Let’s have a look at some common examples of aphids that you may find on trees. 

Woolly Elm Aphids

These aphids are often found on large elm trees. They are found on elm trees’ leaves and usually are dark brown or black in colour with white bits of wool on their backs. They are most common in the spring and summer months.

Black Willow Aphids

These aphids are often very dark green or black in colour. They are found on a variety of willow trees but most commonly on black willows. They will usually inhabit trees that are about two years old and suck sap from the twigs of the tree.

Giant Conifer Aphid

These aphids are found on various coniferous trees, but they are often seen inhabiting pine trees. As you may expect from the name, these aphids are unusually large compared to other species of aphids. They are also usually very dark brown or black in colour and are most common in the spring and summer months. 

How to Prevent Aphids from Killing Trees

In the garden, aphids will usually be a bigger problem for smaller plants and flowers that you are growing. However, in certain areas you may experience problems with aphids on your trees, so it is a good idea to know how to deal with them.

Manually remove them

You can remove aphids by hand if you want. They are practically harmless. If you don’t want to handle insects, then blasting them with water from a hose will knock them prone and keep them away. However, these are not the most practical methods for taller trees, as you will never be able to remove them all. 

Employ Natural Predators

Using natural predators of aphids is probably the most effective way to control aphid numbers. Especially if they are in trees with tall leaves that you cannot reach, you can purchase natural predators of aphids from biological control suppliers, and they will eat large numbers of aphids every day.

The most common primary predators of aphids are ladybugs and lacewing larvae.

Final Summary

To summarise, here are a few key points from this article discussing whether aphids can kill a tree.

Aphids can kill trees either by stunting their growth and preventing photosynthesis or by transferring plant diseases to the trees. They are most likely to do severe damage to saplings and young trees.

Some common aphids you will find on trees are the woolly elm aphid and the black willow aphid. A good way to control aphids on your trees is to release natural predators like the ladybug to consume and control the aphid population.