Popular Tree Insects and Harmful Tree Diseases

There are hundreds of different abnormalities and diseases that plague the trees, forests and landscapes across the United States. From insect infestations, to wide spread disease, arborists across the country must learn what to watch for in the trees, forests and environment that they tend to. Taking enough time to learn what to keep an eye out for could help you to efficiently maintain the health and well-being of your trees. This link is to an expert arborist, http://www.72tree.com and below is a list of the most common tree insects and diseases.

tree insects and pests

Tree Insects:

  1. Hemlock wooly adelgid – This furry little insect has been munching its way across the Eastern portion of the United States since the 1950’s. When it was originally discovered, arborists used pesticides to keep it under control. But once it spread to the natural stands of hemlock, the entire hemlock population of the United States is in jeopardy because this cottony insect lives exclusively on this coniferous plant.
  1. Gypsy moth – This lone moth species is the most notorious of the hardwood pests in the United States. The Moth itself isn’t the real problem, the larvae is the real threat. Each year, on average, they will consume nearly one million forested acres across the Eastern United States. In a particularly bad year, such as in 1981, they can deforest up to twelve million acres of forested land.
  1. Scale insects – Scale insects are often overlooked as insects because they don’t resemble what the typical insect looks like. The general appearance of scale insects is that they look like brown or white scales on the stems and branches of trees and plants. The females and the nymphs of the species usually do not have wings and will live off of a plant by inserting its mouth suckers into the plant and sucking out the nutrients. When trees or plants are infested with these insects, they will start to wither and die back. At first small branches may fall off, then eventually larger branches begin to die. They are spread by brushing up against other plants, the wind blowing them to other plants, or birds and humans accidentally transfer them.
  1. Japanese beetles – Though beautifully colored, the Japanese beetle is a real concern for shade trees, shrubbery, vines, and other garden plants. They are particularly destructive when they eat as they consume the tender tissue that is found between the veins of a leaf and the stem and often leave what can be described as lacelike leaf skeletons in their wake. Though there are no chemical methods of controlling these little pests, they are big enough that you can remove them by hand. If the thought of catching beetles is not quite your thing, you can also fill a bucket with hot soapy water and knock them off the trees into the bucket of water.
  1. Emerald ash borers – These borers are native to China, Korea, Russia, and Japan. It is believed that they were introduced to the United States and Canada through shipping pallets. These insects’ larvae burrow into and feed on the outer sapwood of ash trees. They are currently infesting Michigan, Ohio, Pennsylvania, Indiana, Illinois, Maryland, West Virginia, and Windsor, Canada. Once a tree is infested, the larvae makes short work of it. The tree will usually die within one to three years after being infested.

Tree Diseases:

  1. Bacterial leaf scorch – Named so because it causes the leaves of the plants that become infected with it to look scorched. This bacteria is a relatively newly recognized ailment of trees. The bacteria, Xylella fastidiosa, causes damage to trees and plants by restricting the flow of water from the roots of a plant to the upper portion. This disease was first noticed in grapes, but can affect any plant. Trees may not show symptoms until July or August when you might notice the first signs of scorched leaves. While there are some experimental treatments being administered, if they are not followed up regularly the plant will eventually die.
  1. Phytophthora root rot – This particularly nasty fungus type organism grows in the root structure of woody plants and destroys the root system. This prevents water from flowing to the rest of the plant and causes it to die. This fungus is common in soil that has poor drainage or gets irrigated. A troublesome symptom of this type of root rot is that the fungus can live in dry soil for a long time until conditions are right for it to germinate. If your plants develop it, you can treat it with an approved Phytophthora treatment product.
  1. Cankers – Phytophthora fungi which belongs to the water molds type of fungus, they tend to do well in moist warm environments. This fungi is frequently found in ornamental trees, fruit and nut trees and their fruit. They will attack any type of tree from California to the Northeast and up through Canada. Treatment can include soil treatments for fungus and bark treatment for fungus.
  1. Fireblight – This disease causes severe damage to trees and shrubs in the rose family. Depending on how the plants are treated, the disease can cause symptoms ranging from the death of a few limbs to death of the entire plant. The easiest symptom to spot is the wilting and withering of blossoms and stems on the plant. Though these wilted parts are still attached to the main stem, they will appear as though they have been scorched by fire. The disease is transferred from plant to plant by wind, rain splash and insects. The best way to treat fireblight is to prevent it.
  1. Wood decay – Originally thought to be caused by injuries or damage to trees, it is now believed that such wounds in trees provide a way for the bacteria that causes decay to get into the trees flesh. Though there has not been any identification of a bacteria to support this theory, it is believed that wood decay is worsened when additional punctures are made to treat the tree.

Though these are only the top five insects and the top five diseases, there are many other pests and infections to be aware of if you are going to successfully care for your trees and landscape. Through a little research and proactive maintenance, you will be able to enjoy years of beautiful forestry and landscape to come.


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