Despite our best efforts to take care of our trees, sometimes even healthy trees are attacked by pests and diseases. Here in the Mid-Atlantic region, there are a number of common tree pests and diseases we see every day. It is not an all-inclusive list, but it covers the majority of the culprits that plague the trees in the area.
Hemlock Woolly Adelgid
Hemlock woolly adelgid originally came to the United States from Asia almost a hundred years ago and spread to the East Coast in the 1950s. Adelgid are tiny insects that suck sap, causing needle drop and dieback of branches, which often leads to the death of the tree. The telltale sign is a white, woolly substance on the needles and branches. The good news is that hemlock woolly adelgid infestations can be controlled.
Anthracnose is a twig and leaf fungus found on a number of tree and plant species, especially sycamore, ash, oak, dogwood, and maple. Symptoms can include irregularly shaped markings of different colors that appear on leaves, twigs, flowers, and fruits, sometimes forming cankers on the twigs and branches. Anthracnose may just be unattractive in mild cases, or it may result in the death of the host tree in more severe cases.
Discula anthracnose is a fungal disease of flowering dogwood trees. It has spread down the Appalachian mountain range from the northeastern states into many of the southern states along the East Coast. The fungi thrive in cool, wet spring weather. It has led to the decline and death of many flowering dogwoods, especially those growing in shady environments.
Borers are wood chewers and come in a variety of types. They generally do their damage by tunneling around under trees’ bark. In most cases, borers attack trees that are already under stress. The larvae and adults chew through the vascular system, disrupting the flow of water and nutrients to the canopy of the tree.
Spider mites, although tiny, can suck the life out of leaves and the soft tissue of your trees. Most spider mites do the majority of their damage in the hot, dry months. But spruce spider mites are cool-season mites. Populations can increase very quickly, so infestations must be controlled aggressively.
Scale are small insects that suck the sap out of trees, killing off branches and stems. They overwinter under the bark. There are two main types of scale that attack trees—soft and armored—but there are many species. Scale damage is treatable, if the timing is right.
Eastern Tent Caterpillars
Eastern tent caterpillars build unsightly nests and, in large numbers, can defoliate a tree. They tend to infest fruit trees, including apple, cherry, crabapple, hawthorn, maple, plum, pear, and peach trees. Eastern tent caterpillars overwinter as eggs within an egg mass that can contain between 150 and 400 eggs. They hatch around the same time buds open in the spring and start feeding on leaves.
Dutch Elm Disease
Dutch elm disease came to the United States from the Netherlands in the 1920s and has had a devastating effect on elm populations. Elm bark beetles spread Dutch elm disease from tree to tree. There are treatments that can control it with a high degree of effectiveness, if applied correctly.
Lace bugs are tiny insects that feed on the underside of leaves by piercing the leaf to suck out the sap. They attack a wide variety of trees and shrubs and usually overlooked until they have caused significant damage to the host plant.
Bagworm caterpillars make long, narrow bags that are sometimes mistaken for pinecones. Heavy infestations can defoliate a tree. Several seasons of this may lead to the death of the host tree. Small infestations can be removed by hand. Larger infestations can be controlled, but only if the treatment is done with the right timing.
Japanese beetles attack a wide variety of plants in the eastern United States. They generally start feeding at the top of trees and plants and work their way down in clusters, eating leaves, flowers, and fruit. Most of the damage takes place over a period of about four to six weeks during the warm months, starting in the later part of June.
Timely Tree Treatments
Often by the time we notice visible signs of a tree pest or disease, the window of time to treat has come and gone. That’s why we need to monitor the health of our trees for the first signs of a problem. Some treatments work well, especially with certain types of fungi. But most treatments, whether preventive in nature or not, have specific windows of opportunity in which they are effective. The timing is usually contingent upon treating within a particular stage in the development of the pest or disease.
If you have noticed any signs of trouble with your trees, contact a certified arborist at Growing Earth Tree Care.