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Diseases & Conditions
Diseases and conditions commonly found in trees and shrubs in the Chicagoland & Northwest Indiana region
Anthracnose—and canker are general terms for a large number of different plant diseases, characterized by broadly similar symptoms including the appearance of small areas of dead tissue, which grow slowly, often over a period of years.
Apple Scab Disease is caused by the fungus, Venturia inaequalis and it affects almost all fruit trees, including crabapples, purple plums, sand cherries and mountain ash trees. Disease development is favored by wet, cool weather that generally occurs in spring and early summer.
Cedar-Quince Rust is caused by a fungal pathogen called Gymnosporangium clavipes. This fungus occurs on a wide range of rose family plants, including mountain ash, hawthorn, quince, flowering quince, serviceberry, crabapple, and apple (though apples are somewhat resistant).
Dieback is a disease of vascular plants characterized by a dying backward from the tip of twigs and branches and caused by parasites, insufficient moisture, etc.
Diplodia (Tip Blight) dead, brown needles at the tips of pine branches may signal the presence of Diplodia tip blight. Surveys indicate that no species of pine (Pinus) is immune to this disease, although some species are more severely affected than others. Austrian pine (Pinus nigra) is one of the most severely damaged species.
Hawthorn Rust most often infects leaves and may lead to premature leaf drop. The bright yellow spots can make an entire plant appear yellow. Hawthorn rust may also form spindle-shaped galls on shoots.
Leaf Scorch is a physiological problem that can occur on any kind of plant. It can be caused by transplanting, soil compaction, nearby excavation, a nutrient deficiency, chemical injury, unfavorable weather conditions (such as drought), poor soil, or limited room for root growth.
Needle Cast is a fungus that affects conifer trees causing infected needles to become discolored and die and eventually be cast from the tree. Begin scouting for this disease in early April before bud break.
Powdery Mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of fungi in the order Erysiphales. It is one of the easier diseases to spot, as its symptoms are quite distinctive.
Insects commonly found in trees and shrubs in the Chicagoland & Northwest Indiana region
Aphids are small, soft-bodied insects with long, slender mouth parts with which they pierce stems, leaves, and other tender plant parts to suck out plant fluids. Almost every plant has one or more aphid species, which occasionally feed on it.
Bagworms disfigure evergreen trees and shrubs by feeding on leaves and needles and girdling twigs. As worm-like larvae they spin silken bags around themselves, to which they attach pieces of the leaves they are eating. They carry this bag with them as they feed.
Emerald Ash Borers are exotic beetles that have been wreaking havoc in the Midwest region since 2002, primarily in Michigan but have now found their way to Illinois. The adult beetles nibble on ash foliage but cause little damage. The larvae feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients.
Fall Webworms Create white hair-covered egg masses contain several hundred light yellow eggs. Young larvae are pale yellow with 2 rows of black marks along their bodies. When fully grown, they are covered with whitish hairs that originate from black and orange warts.
Japanese Beetles as an adult are a colorful beetle 1/3 – 1/2 inch long with a shiny metallic green color and coppery brown wing covers. There is a row of five tufts of white hair along each side of the abdomen and two additional tufts on the top of the abdomen tip.
Lace Bugs (Plant Bugs) use their sucking mouth parts to feed on plant sap. Damage ranges from many small white spots on the leaves to distortion or destruction of plant tissue, depending on the pest and host plant.
Leaf Hoppers consist of any of the small, slender, often beautifully colored and marked sap-sucking insects of the large family Cicadellidae (Jassidae) of the order Homoptera. They are found on almost all types of plants; however, individual species are host specific.
Scale Insects are parasites of plants, feeding on sap drawn directly from the plant’s vascular system. A few species feed on fungal mats and fungi, e.g., some species in the genus Newsteadia in the family Ortheziidae.
Spider Mites are common plant pests. Symptoms of injury include flecking, discoloration (bronzing) and scorching of leaves. Injury can lead to leaf loss and even plant death.
Tent Caterpillars attack several kinds of broadleaf trees and shrubs and produce unsightly webs, or tents, which detract from the home landscape. Trees with substantial defoliation will have reduced growth and vigor.
Zimmerman Pine Moths in recent years, the Zimmerman pine moth, Dioryctria zimmermani, has become very established among the region. Austrian pines have been most commonly infested.