How do borers affect trees?

100 3113 How do borers affect trees?The subject of insect infestation on trees is enormous and cannot be adequately covered in a few paragraphs.

It is my intent to highlight the main points and suggest ways to minimize their damage. Bores are the larvae life stage of either beetles or moths. The parent insect lays eggs on the host tree where they hatch and bore into the tree and live just under the bark. The tree acts as food and housing for the newly developing larvae. Almost all the life in a tree is just under the bark in the cambium layer. This is where the new growth takes place and where the tree adds growth in diameter. All the flow of water, nutrients and photo synthesis happens in the cambium as the roots and leaves exchange water and energy. As they eat this “cambium,” they disrupt the flow of nutrients and photo synthesis thus starving the tree. Some larvae like to travel up and down as they feed on the tree and only sever part of the flow of energy of their host. This tree is sickly and tries to recover. The most damaging bore larvae travel the circumference of the tree completely severing any flow up or down, thus quickly killing the tree.

There are many insecticides intended to control this problem but I want to focus on prevention. There are three things you can do to minimize their destruction.


1. As a bore eats it creates “feeding galleries”.  The tree will try to produce sap that will fill the holes as a defense mechanism and push the larvae out. A properly hydrated tree has a much better chance of accomplishing this than a water stressed tree. A thirsty tree cannot produce enough sap to do the job, it’s dehydrated so to speak. The salvation of a Pine or fruit tree is proper watering… water the soil under the whole canopy of the tree weekly. Deep watering does the most good.

100 3114 How do borers affect trees?

2. Borer eggs usually overwinter on, in or under the tree. Proper landscape maintenance is required to remove unwanted vegetation, needles, leaves etc… where they are protected from the extremes of weather. Do your best to keep your yard clean so as to remove any possible overwintering haven. This clean up does not take place in the forest so you’d expect the bores to destroy it in a few seasons but the forest experiences much colder temperatures for a longer duration and kills most of the eggs. Albuquerque is fairly warm for pine and fruit borers so temperature is not our friend.


3. To reduce the eggs that overwinter on the tree or bark it is very important to apply a product referred to as “dormant oil.” It is a highly refined oil that when diluted and applied to the tree suffocates the eggs preventing hatching. This is to be performed during the colder months of the year. When in the warmer months a modified dormant oil called horticultural oil can be applied to control crawling insects or larvae before they enter the tree. Timing of this application is critical and the Cooperative Extension Service can be of great help indicating “when” to spray.


This is a big and confusing subject and trees are a valuable part of your Albuquerque landscape. If you would like a consultation to look at your trees feel free to contact us, we’ll be glad to help.