The vast majority of insect species that call your tree home are harmless. Many are even beneficial to the tree. However, there are also a number of insect species which, left unchecked, can do a great deal of damage to your tree, and even kill it. The trick is to get the populations of these threatening species under control without damaging the tree or harming the population of beneficial insects. Here are a few tips that will help you do just that:
Identify which species are harmful
Every tree has insects living in it, the majority of which will not cause any harm to your tree. But how do you figure out which insects are the ones that damage trees? In this case, it pays to do some research and to watch out for specific tell-tale signs. For example, regularly inspect the area around your tree for a fine, sawdust-like material. This is the excrement left behind by certain types of bugs known as borers – beetles which will burrow directly into the wood – and also by carpenter ants. Check the leaves of your tree as well. If the leaves are yellowing and curling up, this could be a symptom of any number of things. However, if you look at the leaves closely and discover that they are covered with clumps of very small green, black or white bugs, these are aphids. Aphids and other sucking insects can damage the leaves of a tree by injecting toxins directly into them as they feed on sap. Caterpillars are another common threat to trees, as they can defoliate trees and leave them vulnerable to disease. It helps to do some research on what the most common pest species are in your area and what signs they leave behind.
Encourage beneficial insects to visit
Sometimes, you won’t have to do much to keep harmful insect populations under control as there are helpful bugs that can do that for you. Ladybugs are a well-known example as they feed on aphids and other small pests. Besides these, lacewings, dragonflies and spiders also eat harmful bugs as part of their regular diet.
To encourage the helpful insects to visit your tree, there are a number of steps you can take. Try planting a variety of plants in your garden – local plants are the best choice of all – in order to encourage a variety of visitors, including pollinators such as bees and helpful beetles. A layer of mulch, spread around the base of your tree (though not touching it) serves as a hiding place for spiders and other predators which prey on pests. Importantly, try to avoid the use of pesticides to control harmful bugs as these can harm the helpful species as well. If you cannot avoid using pesticides entirely, try using only organic ones, and spray them directly onto the pests rather than all over the tree.
Keep your tree healthy
It sounds obvious, but the fact is that most pest invasions happen to trees that are already sick or injured. Carpenter ants, for example, will burrow into rotting and weakened wood. Therefore, keeping pests at bay is often as simple as making sure your tree is in tip-top shape year round. Regularly check the pH of the soil to ensure it suits the tree species. You’ll also want to make sure your tree is getting plenty of water and nutrients. You may need to make occasional use of an organic fertilizer to give your tree the tools it needs to strengthen and defend itself. Regularly prune weak or damaged branches and clean up dead, fallen wood and dropped fruit around the tree, which can attract harmful insects.
Apply oils to pest-infested areas
We’ve cautioned against using pesticides if you can avoid it as these tend to harm the good bugs just as much as the bad bugs. For a safer alternative, use a spray made from oil. The oil, while not directly toxic, will smother soft-bodied insects such as aphids by clogging their breathing pores. You will want to research the products that you are purchasing as some of them are stronger than others and should not be used when trees are blooming. Once you have selected the oil you wish to use, carefully apply it to the bark and leaves where you see signs of pest damage. You will need to get plenty of coverage, so saturate the branches until they are dripping a bit.
Don’t be afraid to call a professional
While educating yourself on the helpful and harmful bugs that populate your area is important, sometimes contacting a professional is your best bet when it comes to the health of your tree. The Portland area is full of a wide variety of pest species, and it may take a trained arborist to recommend the best course of action for restoring your tree to health. An arborist, or tree surgeon, is trained to recognize signs of damage to your tree and take the necessary steps to solve the problem. Have an arborist check your tree regularly to keep it in good health.