My tree has bugs

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My tree has bugs, now what do I do? Trees have insects for many different reasons; some are even beneficial. There are three major categories of problem bugs: chewing insects (defoliators), boring insects (tunnel into wood leaving galleries), and sucking insects (feed on sap). Identify the category of insect and then identify the species of tree. While some insects are generalist s(like ants) that can feed any many species, others only feed on a particular genus or species of trees. Identifying the species of the tree and the tell-tale signs of the insects is the first step to taking action to care for your tree. Defoliators typically feed on the leaves of a tree which shows up as bite marks and missing portions of leaves. Some chewing insects eat the fruit of the tree. Defoliators are mostly beetles and caterpillars, which often leave “webs” or “tents” from their silk cocoons. Chewing insects don’t usually kill trees unless it’s a large epidemic outbreak. Most outbreaks are simply endemic and only last one season. Webs can be removed manually to get rid of eggs and larvae and improve the look of the tree. Boring insects are the most harmful to trees and can cause mortality to an individual tree or entire stand of trees. Borers typically focus on one genus of trees, so knowing your tree is important. Boring insects tunnel below the bark of the tree, leaving “galleries” on the inside of the bark or outermost layer of wood. Galleries are formed when an adult insect bores into the tree and lays eggs. The larvae hatch and eat their way through the tree leaving the gallery and an exit hole upon maturity (photo, right). Two major signs of infestation is sawdust, or “frass” at the base of the tree and the other is the exit hole itself (certain size and shape exit holes can help identify particular insect species). Depending on the insect, the tree might already be fatally wounded. Identifying insect infestations can help neighboring healthy trees by providing treatment options early, therefor lowering the likelihood of mortality. Sucking insects feed on the sap (sugars) in twigs, leaves, and branches. Examples include scale insects (photo, left), spider mites, aphids, thrips, and leafhoppers. Scale insects attach to leaves or branches in the thousands and feed on the tree. Scales form hard shells and are immobile as they continue to feed. Sometimes sucking insects excrete a sticky substance known as honeydew, which can lead to molds forming further harming the tree. Removal of a small portion (leaf or branch) can be done, but it’s not typically necessary. How do I treat my tree for insects? The best medicine is preventative; try to maintain a strong healthy tree though proper watering and healthy, noncompacted soil. Add a shallow layer of mulch around the tree, and prune any dead or damaged branches. Pay close attention to any wounds on your tree as they can attract insects and begin an infestation. Common wounds are caused by broken branches (people, vehicles), mechanical damage (lawn mowers and grass whips), and animal damage (squirrels). If you see a fresh wound, you can make a proper pruning cut and lower the chance for infection. Insects often work in concert with diseases to quickly overwhelm a tree. Bacterial Wetwood, for example, attracts insects like flies and beetles which can further damage your tree. Some problem insects may be treated with insecticides or biological controls. Contact an ISA Certified Arborist for recommendations.