Diagnosing Health Problems of Woody Plants at the Shade Tree Short Course 2020

Encyclopedia Article

Below are the common problems PIDC diagnosed in 2019 that where showcased in the hands-on workshop Diagnosing Health Problems of Woody Plants at the Shade Tree Short Course 2020.

To learn the term uses to describe symptoms and signs see our glossary

Tree(s) Symptoms observed Signs present (visible)? (Y/N) Notes
Oak Cottonwood Branches (terminlal) in the ground, not cut clean separation (not chew) N Nature of the problem: Abiotic
Diagnosis: Cladaptosis
Management: Promote healthy plants, reduce stress, avoid site impacts
Various, euonymus Dieback. trees & shrubs that were ok in fall 2018, had symptoms in the spring 2019 N Nature of the problem: Abiotic
Diagnosis: Winter damage/ cold injury
Management: Proper plant section for hardiness
Oak  Dead tufts of leaves, slower twig growth, busshier look Y, round scale insects on branch Nature of the problem: Insect
Diagnosis: Kermes Scale
Management: No management for large trees recommended, Dormant oils can be used on smaller trees
maple, lilac, many other woody plants Chlorotic or dead leaves, early fall color, poor growth Y, scale insects on branches and/or trunk Nature of the problem: Insect
Diagnosis: Oyster shellscale  
Management: Pruning out heavily infested branches.  Insecticides targeting crawler stage.
Various oaks Leaf spots, tree crown thining form the bottom up, defoliation (leaf drop) N, magnification in the lab need for confimation Nature of the problem: Disease
Diagnosis: Tubakia leaf spot
Management: Promote tree health, see more at https://hortnews.extension.iastate.edu/tubakia-leaf-spot-oaks
White pine Burn, discolored needles, needle drop? N Nature of the problem: Abiotic
Diagnosis: Ice Melt (salt) damage
Management: Avoid planng white pine near road that will be treated prunning afected branches is nor recommended
Many trees Leaf distortion,sticky honeydew, sooty  mold, ants on plant Y, aphids on leaves Nature of the problem: Insect
Diagnosis: Aphids
Management: Soap or oil based insecticides if warranted.  No treatment large trees.
Maple, apple, oat, others Leaf discoloraiton, distorted growth, dead areas on leaves. Y, small green leafhoppers that run fast Nature of the problem: Insect
Diagnosis: Leaf hopper burn  
Management: no long term damage expected in stablish, healthy trees
Arbovitae, oak, and  others Distorted leaf growth N Nature of the problem: Abiotic
Diagnosis: Suspected chemical injury, herbicide like damage
Management: read and follow pesticide label, proper herbicide use. Consider alternatives weed managment in the landscape
Liden and Maple Dieback, deline over a long period of time (years) N Nature of the problem: Abiotic
Diagnosis: Stem gridling roots
Management: Prevention, proper planting practices, select quality tree stock, root inspection, correct planing depth etc. correction may be effective only in young trees
Sycamore and others Vein disoloration, dieback, withces broom alike N, magnification in the lab need for confimation Nature of the problem: Disease
Diagnosis: Sycamore anthracnose
Management: Promote health!!, see more at https://hortnews.extension.iastate.edu/anthracnose-shade-trees-0
Lilacs, rhododendrum, oaks Leaf sport, scorth tip burn, blight N, lab testing need for confimation Nature of the problem (circle) Disease
Diagnosis: Ramorum blight/ sudden death oak
Management: monitor rododendrum purchased/installed in 2019 submit samples to PIDC if supected, remove positive plants inlcuding roots https://hortnews.extension.iastate.edu/2019/07/be-alert-diseased-rhodode...
Spruce, arbovitae, locust, many others Missing needles or leaves.  Brown needles. Y, bags hanging on the tree Nature of the problem (circle) Insect
Diagnosis: Bagworm
Management: Hand removal in winter.  Insecticides targeting smaller caterpillars.
Oak, elms, catalpa and others Scorched leaves, yellow boder in some hosts N, lab testing need for confimation Nature of the problem (circle) Disease
Diagnosis: Bacterial Leaf scorch
Management: monitor, test and remove positives plants https://hortnews.extension.iastate.edu/2015/09-11/scorch.htm
Oak  Leaf scorched, leaf loss, wilt Y, fungal mats under the back or dead red oaks in the spring (remove tree!!!) Nature of the problem (circle) Disease
Diagnosis: Oak wilt
Management: monitor trees, submit sample to PIDC for test (sample cold cain to avoid false negatives) https://hortnews.extension.iastate.edu/oak-wilt
Last Reviewed: 
February, 2020