Articles in category: Insects & Diseases
- Disease fact sheets (2012)
These links lead to the fact sheets on disease. Anthracnose of shade treesApple scabBlack knot of ornamental cherry and plumCanker diseasesCedar-apple and related rust diseasesDutch elm diseaseFire blightGround cover diseasesJuniper tip blight...
- Insect Fact Sheets (2012)
The links below will lead you to the insect fact...
- Symptoms of Emerald Ash Borer Infestation
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Emerald ash borer (EAB) infestations often go undetected until the trees begin to show symptoms. A tree may be infested for a year or more before symptoms first appear. The symptoms listed below may indicate the presence of emerald ash... - Emerald Ash Borer
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Emerald Ash Borer Information for the Homeowner and for Community Groups/Green Industry Community Groups/Green Industry The Community Trees program at The Morton Arboretum has prepared a new guide for use by municipal leaders as well as... - Magnolia Scale
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MAGNOLIA SCALE(Neolecanium cornuparvum) Magnolia scale is our largest soft scale insect, reaching ½ inch in length. This scale spends the winter on one-to-two-year-old twigs as tiny, dark-colored nymphs. In the spring, the scales begin to feed,... - Armillaria Root Rot and Native Oaks
Armillaria Root Rot and Native Oaks By Karel Jacobs, Ph.D.Plant PathologistThe Morton Arboretum Concern over declining oaks is impossible to soothe. Rare is the tree so long-lived and evocative in its gnarled architecture. Maybe only the squirrel,...
- Cottony Maple Scale (Pulvinaria Innumerabilis)
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COTTONY MAPLE SCALE (Pulvinaria innumerabilis) The primary host of cottony maple scale is the silver (or soft) maple and boxelder. It can also infest other maples, white ash, hackberry, dogwood, beech, apple, oak, linden, elm, black and honey... - Viburnum Crown Borers (Synanthedon viburni and Synanthedon fatifera)
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DESCRIPTION Viburnum borers are wood-boring insects that feed on the lower part of viburnum trunks, branches, and roots. There are two species of viburnum crown borers which have a similar look and biology. The adult viburnum clearwing borer... - Spruce Gall Adelgid
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Spruce Gall Adelgid Two species of small, soft-bodied insects infest spruce species during the course of rather complicated life cycles. These aphid-like insects called adelgids, produce galls that can disfigure and even kill their hosts. The two... - Elm Leaf Beetle (Xanthogaleruca luteola)
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The elm leaf beetle is often considered as much of an indoor nuisance as a garden pest since large numbers of adults migrate into homes seeking a protected place to overwinter. Outdoors, both adults and larvae feed on the emerging leaves of... - Carpenter Ants (Camponotus pennsylvanicus)
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While often associated with wood that is dead or rotting, the carpenter ant is not the source of the deterioration, as is generally thought. Wood that is soft and moist is the carpenter ant’s preferred nesting site, and it is the telltale sawdust... - Periodical Cicadas (Magicicada septendecim)
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Each year, somewhere in the United States east of the Rocky Mountains, a brood of the periodical cicadas emerges. Periodical cicadas have two distinct races based on required time to complete their life cycle: a 17-year northern race and a 13-year... - Slugs
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Anyone who has watched their hosta foliage turn “lacy” has experienced the work of slugs. Slugs, a common plant pest in wet weather, are snails without shells. They are mollusks, which means they are related to oysters, octopi, and... - Scale Insects
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DESCRIPTION There are many species of scale insects that feed on a wide range of host plants. Scale insects are a unique group, that look quite different from other insects. In their juvenile growth stage, they are referred to as "crawlers". As... - Gypsy Moths
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The gypsy moth, Lymantria dispar, was introduced into this country in 1869 and has since become a serious pest in the northeastern part of the United States. In some areas it has changed the ecology of native forests, defoliating more than 13... - Pine Sawflies
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DESCRIPTION There are more than 100 species of sawflies known in the United States, and the most common feed on conifer foliage. In reality, the sawfly is not a fly, but in the order Hymenoptera, which includes ants, wasps, and bees. It gets the... - Pine Moths
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Updated 10/2012 Although there are many species of small moths that infest conifers, two in particular are troublesome to pines in the Midwest: the European pine shoot moth and the Zimmerman pine moth. The larvae of both species inflict damage by... - Mites
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DESCRIPTION There are several different species of mites that can cause damage to a wide variety of ornamental plants, including deciduous trees and shrubs, evergreens, and garden plants. As the name implies, mites are so small that they often... - Minor Plant Pest Problems
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There are a number of conditions in gardens that may affect the appearance of a plant, but not pose a serious threat to its overall health. These conditions have a variety of causes, from environment and climate, to insects and bacteria or fungi.... - Japanese Beetles
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The Japanese beetle is native to Japan and was accidentally introduced into the United States in 1916. Since that time it has slowly spread from southern Maine to Georgia, and westward from Missouri to Minnesota. DESCRIPTION Japanese beetle adults... - Honeysuckle Aphid (Hyadaphis tataricae)
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In recent years, honeysuckle shrubs have become prone to infestations of the honeysuckle aphid, whose feeding habits cause a serious distortion of growing tips known as “witches’ brooms”. While attacks from the honeysuckle aphid do not usually... - Honey Locust Plant Bug (Diaphnocoris chlorionis)
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DESCRIPTION The honey locust plant bug is approximately 1/8 inch long and pale to light green when full grown. There are two stages: the nymph and adult. The nymph is a miniature replica of the adult. Both stages are quite active and will fly when... - Cankerworms
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SYMPTOMS Commonly known as the “inchworm”, there are actually two species of cankerworms that attack fruit and ornamental trees: the “fall” and “spring” cankerworms. Their names refer to the season during which their eggs are laid,... - Bronze Birch Borer (Agrilus anxius)
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This native insect is a serious pest of ornamental birch (Betula spp.), one of the more popular trees found in landscapes today. Grown as a specimen, white-barked birch is often sited in heavy clay soils or grown under other adverse conditions,... - Black Vine Weevil (Otiorhynchus sulcatus)
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One of the most destructive and widespread root weevils in the northern U.S. and Canada, the black vine weevil, can cause damage to susceptible plants at both the adult and larval stages of its life cycle. Feeding on a wide range of herbaceous and... - Boxelder Bugs (Leptocoris trivittatus)
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While the boxelder bug can cause minor damage to its preferred host plant, the boxelder tree (Acer negundo), it is primarily a nuisance for the homeowner who finds large colonies of adults seeking places to overwinter. The boxelder bug will seek... - Aphids (Aphis spp.)
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There are many species of aphids, varying in size, color and habitat. As individuals, they do little harm to a host plant, but large infestations can produce severe damage. While their behavior is determined largely by food preference and feeding... - Asian Longhorned Beetle (Anoplophora glabripennis)
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Updated 11/2012 Click here to listen to a podcast on Asian Longhorned beetle The Asian longhorned beetle is an insect that can do very serious damage and even kill trees while in its larval stage. It is believed that the beetle, while in the... - European Elm Flea Weevil (Orchestes alni)
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DESCRIPTION The European elm flea weevil has been a pest on elms in the upper Midwest only since 2003, though it was first discovered in the U.S. in 1982. It is especially common on Siberian elms. The insects are tiny weevils about 1/16th of an... - Borers
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Borers are a group of insect pests that spend part of their adult or larval life stage feeding inside roots and branches, or tunneling beneath the bark or into the heartwood of many trees and shrubs. Many species of boring insects are capable of... - Plant Galls
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Description Galls are abnormal growths that occur on leaves, twigs, roots, or flowers of many plants. Most galls are caused by irritation and/or stimulation of plant cells due to feeding or egg-laying by insects such as aphids, midges, wasps, or... - Wetwood
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Wetwood, also known as slime flux, is a very common bacterial disease that occurs in many kinds of trees. Nearly all elm and poplar species are affected, as are numerous other trees including crabapple, beech, birch, maple, dogwood, horsechestnut,... - Verticillium Wilt
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Verticillium wilt is a serious fungal disease that causes injury or death to many plants, including trees, shrubs, ground covers, vines, fruits and vegetables, and herbaceous ornamentals. It is a disease of the xylem, or water-conducting tissues, in... - Spruce Diseases
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CYTOSPORA CANKER Cytospora canker, caused by the fungus Cytospora kunzei (also known as Valsa kunzei var. piceae), is the most prevalent and destructive fungal disease of Norway and Colorado blue spruce. Occasionally, Cytospora canker is found on... - Diplodia Tip Blight
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Diplodia tip blight, previously known as Sphaeropsis tip blight, is a common fungal disease of stressed conifers, especially pines with needles in bunches of 2’s and 3’s. Austrian pine (Pinus nigra) is the most susceptible host, although the... - Powdery Mildews
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Powdery mildews are caused by over 1,000 species of fungi that affect most landscape plants. Most grow only on the upper leaf surface and stems of plants, and do not invade the leaf tissue of the host plant. In most cases, powdery mildew is not a... - Pine Diseases
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Besides Sphaeropsis tip blight (see leaflet #60), common pine diseases found in the Chicago area are pine wilt, Dothistroma needlecast, and Lophodermium needlecast. PINE WILT Pine wilt is a serious disease caused by the pinewood nematode,... - Oak Wilt
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Oak wilt, caused by the fungus Ceratocystis fagacearum, has become a serious disease threat to oaks in the eastern and central United States. While the spread of oak wilt has not been rapid, it can be found in all counties of Illinois and 18 other... - Ground Cover Diseases
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Ground covers often make our jobs as gardeners easier by preventing weeds, holding soil in place, and helping to moderate soil temperature extremes. Ground covers, however, are not maintenance free. Like all plants, they can be susceptible to... - Cedar-Apple and Related Rust Diseases
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There are several cedar-rust diseases that spend part of their life cycle on Eastern red cedar (Juniperus virginiana) and other junipers, and another part of their life cycle on apple, hawthorn, and other members of the rose family. Both hosts are... - Canker Diseases
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Canker diseases are common, widespread, and destructive to a wide range of trees and shrubs. A ‘canker’ is really a symptom of an injury often associated with an open wound that has become infected by a fungal or bacterial pathogen. Canker... - Black Knot of Ornamental Cherry and Plum
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Black knot is a serious disease of plum and cherry trees (Prunus species) throughout the United States. Black knot is a disease that gets progressively worse each year unless controlled, and it will eventually stunt or kill the tree. It is... - Apple Scab
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Apple scab is one of the more serious diseases of ornamental crabapples. It is caused by the fungus Venturia inaequalis. Apple scab mainly affects members of the rose family, including nearly all commercial cultivars of apple (Malus spp.), crabapple... - Tent or Web-Making Caterpillars
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Two of the most common pests of deciduous trees are the Eastern tent caterpillar and the fall webworm, whose conspicuous gauzy tents deface roadside trees, home landscape trees, and fruit tree orchards. Although people often confuse the two or... - Bagworms (Thyridopteryx ephemeraeformis)
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Description Bagworms are pests on many kinds of conifers and deciduous trees, though they’re most frequently found on arborvitae and junipers. The dark brown bagworm caterpillars are 1/8 to 1/4 inch long when they first hatch, eventually... - Ash Flower Galls
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Many homeowners become alarmed when they see green or brown clusters hanging from branches on their ash trees. The clusters are ash flower galls and do not harm the tree. Most ash trees are dioecious – that is, the tree has either all male flowers... - Juniper Tip Blight
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Juniper tip blight is a common disease of junipers found in most states east of the Mississippi River. There are many varieties of junipers susceptible to tip blights; however, the disease is most serious on young or newly transplanted plants. As... - Fire Blight
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Fire blight is caused by a bacterium, Erwinia amylovora, and it only affects members of the rose family. This includes more than 75 different kinds of trees and shrubs, including apple and crabapple (Malus), cotoneaster (Cotoneaster), hawthorn... - Dutch Elm Disease
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This disease is not of Dutch origin, but because early work on the disease was done by Dutch pathologists in the 1920s, the disease has been called Dutch elm disease (DED). In all probability the disease is of Asiatic origin. DED is caused by a... - Anthracnose of Shade Trees
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One of the most common and unsightly diseases of shade trees is anthracnose. Anthracnose is a foliar disease caused by several species of fungi whose spores, when released, infect newly emerging leaves. The disease, which becomes active in spring,... - Emerald Ash Borer Identification
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Emerald ash borer (EAB) adults are bright metallic green beetles that are approximately 1/2 inch long and 1/16 inch wide. They have flat backs and rounded abdomens. Larvae reach a length of approximately 1 inch and are creamy white, flattened, and...