The Dayton area is plagued by a number of destructive pests that attack trees. Learning to identify them is the first step in preventing an outbreak that could seriously injure, or even kill, your trees.
In this article we share the five insect pests most commonly found around Dayton, describe what to look out for, and the trees they typically attack.
Emerald Ash Borer
Emerald ash borer (EAB) is a highly destructive insect that was introduced into the USA from China. It arrived in Ohio in 2003 and has now spread to all 88 counties in the state.
Ash trees infested with EAB generally die within 3 to 5 years if not treated early – without treatment there’s a 99% mortality rate.
The adult emerald ash borer is a small beetle (only 3/8 to ½ inch long) that’s a bright, metallic green color. The larvae (immature EAB) are white, slightly flattened, grub-like creatures that grow up to 1.5 inches long. They feed and grow under the tree’s bark, creating S-shaped galleries that can only be seen if you peel back the bark. It’s this feeding that eventually kills the tree. When the larvae mature into adult beetles they chew their way through the bark, leaving D-shaped exit holes as they leave the tree.
Targets: The EAB only targets ash trees. All five of Ohio’s native ash species are susceptible to EAB.
Bagworms are leaf-eating caterpillars commonly found in the eastern USA. They’re named for the bags they create from silk and pieces of foliage to protect them while they’re feeding and maturing.
The caterpillars feed on the outer layer of leaf tissues, eventually killing the leaves. When there is a large population of bagworms it’s not usual to see a tree completely defoliated. Healthy deciduous trees can usually recover but evergreens may not.
The adult male bagworm is a small moth with clear wings that can be seen flying around during September and October. The adult female doesn’t leave her bag so is rarely seen. Immature bagworms (larvae) generally feed on leaves from May to August but are very small and difficult to see. Damage to the tree is usually already done before bagworms are identified.
Targets: Bagworms can be found on a wide variety of trees, including evergreens such as arborvitae, fir, hemlock, juniper, pine and spruce, as well as deciduous trees such as bald cypress, black locust, honey locust, sweetgum, sycamore, boxelder, cotoneaster, maple, elm, buckeye, willow, crabapple, linden, poplar, and many more.
Spider mites are tiny arachnids (similar to spiders and ticks) that are less than 1/20-inch long. It’s difficult to see them clearly but if you tap a leaf from an infested plant over a sheet of white paper, some mites should fall off onto the paper where you can see them with a magnifying glass.
Spider mites can multiply quickly, particularly in hot, dry environments, and prefer plants with higher levels of nitrogen, phosphorous and carbohydrates in their leaves (think lush, green foliage).
The first signs of spider mite damage typically involve leaves with tiny yellow spots and fine webs throughout the plant. Spider mites feed on plant tissues and sap, literally sucking the juice out of the leaves, causing dead spots. Over time, a large population can kill most of the leaves on a plant.
Targets: Spider mites can infest a range of common trees and shrubs, including juniper, boxwood, cryptomeria, arborvitae, and Leyland cypress.
If you notice white or brownish raised “dots” on the trunk and/or branches of trees that don’t look healthy, it’s probably scale. Scale insects are typically small (only about 1/8 to ½ inch) and have either a hard shell that’s not attached to the body (armored scale) or a soft shell that can’t be separated from the body (soft scales).
There are many species of scale insects, with different species preferring to feed on different plants. Here in Ohio we typically find oystershell scale, an armored scale that feeds on the trunk and branches of shade trees and shrubs, and lecanium scale, a soft scale that produces large amounts of a clear, sticky substance called honeydew as it feeds. Other common types of scale in Ohio include euonymus scale, pine needle scale, European elm scale, Fletcher scale, cottony maple scale and magnolia scale.
Long-term and/or heavy infestations of scale can be extremely damaging to the plants on which they feed, leading to leaf/needle discoloration, defoliation, stunted growth, limb dieback, vulnerability to other pests and diseases, and even plant death.
Be on the lookout for unusual bumps on tree trunks and branches, dying, discolored and drooping leaves, and a sticky substance on the tree. Honeydew attracts wasps and bees so look for an increase in their activity around your trees. Black sooty mold often develops on the honeydew, covering twigs and branches with a chalky grey/black substance.
Targets: Many Ohio trees and woody plants are susceptible to scale. Oystershell scale is often found on ash, cotoneaster, willow and lilac, while lecanium scale typically appears on maple, oak, linden, and birch trees.
For more information about specific scale insects and treatment, visit our Scale Insects in Southwest Ohio page.
Eastern Tent Caterpillar
Similar to bagworms, Eastern tent caterpillars are leaf-eating caterpillars that can easily defoliate an entire tree.
The caterpillars are hairy, with a distinct white stripe down their back. The biggest distinguishing feature is the web-like silk nests they build in the forks of tree and shrub branches. These nests continue to grow throughout the spring as the caterpillars feed during the day, returning to nest at night for protection. In May or June, they leave the nest to find a place to pupate, eventually becoming furry brown moths with two white lines across the wings.
Targets: You can find Eastern tent caterpillars on many different trees. Common targets in Ohio include ash, birch, maple, oak, cherry, and crabapple trees.
If your trees have, or you suspect they have, any of these insects, please give us a call. We’ll inspect your trees, confirm/make the diagnosis, and recommend an effective treatment. All of these pests are manageable if they’re identified soon enough. Or, in the case of emerald ash borer, if treatment is started before your ash tree is infested.