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Diagnosis and Plant Disorders
Ann Koenig, Urban ForesterMissouri Department of Conservation
[email protected] x 227
Objectives
Distinguish between plant problems caused by living and nonliving disorders.
Understand the principles of a systematic approach to the plant diagnostic process.
Learn to recognize the signs and symptoms of tree disorders.
Become familiar with various types of insect and disease problems and their impact on trees.
Key Terms
The Key Terms as listed in the Arborist’s Certification Study Guide will be defined and highlighted throughout the presentation.
Challenges to diagnosis
Trees don’t talk! Asking all the
necessary questions
History is hard (or impossible) to come by and answers may not be accurate.
Most of the time – it’s too late
Symptoms and Signs of tree disorders Symptom: how a tree
responds to a disorder Often times not
specific to the disorder
Several at same time Examples
Wilting Chlorosis (yellowing) Scorch Dieback Witch’s broom Stunted growth
Symptoms and Signs of tree disorders Sign: direct indication of the cause of the
problem, in other words something actually left behind to whatever is causing the tree harm. Insect holes Fungal fruiting bodies
Systematic Steps to Diagnosis
1. Accurately identify the plant.2. Look for a pattern of abnormality.
Multiple kinds of trees-abiotic3. Carefully examine the site.
Drainage, construction, herbicide use,4. Note the color, size and thickness of
the foliage.5. Check the trunk and branches.6. Examine the roots and root color.
1. Accurately identify the plant.
2. Look for patterns of abnormality
3. Examine the site
4. Note size, color and thickness of leaves
5-6, Check the trunk and branches, roots and root collar
Rule out possibilities
Time of year can help: Fall webworm Wilting oaks in summer
Certain species are vulnerable to specific problems Oaks: oak wilt Maples: girdling roots Redbuds: herbicide sensitivity
80 % of tree problems come from adverse conditions such as: Soil compaction Mechanical injury Poor species selection
Tree stress
Can be cumulative and lead to “spiral of decline”
Necessary basic factors: sufficient water, air movement, drainage, optimal temperature and light, and proper balance of nutrients
Acute stress
Short term Causes immediate
damage More likely to
recover? Acute – disorder or
disease that occurs suddenly or over a short period of time
Examples Lightning, herbicide,
late frost
Chronic stress Disorder or disease
occurring over a long period of time
Examples: Poor drainage Soil compaction Poor species
selection
How stress exhibits itself Reduced
growth Abnormal
foliage color or size
Vigorous watersprouts
Premature leaf drop
Common causes of stress Not Right tree,
right place! H2O extreme cold or
heat soil compaction soil pH mechanical
damage
Two Major Groups of Plant Health Problems
Biotic – pertaining to a living organism; pathogens (microscopic disease organisms) e.g. fungi, bacteria, viruses and nematodes [microscopic roundworm] as well as insect pests, mites, and other animals; a.k.a. infectious as they can spread from one plant to the next.
Abiotic – non living; a.k.a. non-infectious and include environmental problems such temperature and moisture extremes, mechanical and chemical injuries, mineral deficiencies and many others
Abiotic Disorders
Often the primary stress factor(s) that cause the spiral of decline
Can be difficult to recognize – often mimic biotic disorders and are part of a complex
Tree and site history often give the best clues
Types of abiotic disorders
Soil and site problems Right tree/right place helps
tons! Physical injuries
Prevention more helpful than treatment
Weather: Frost , ice, hail wind damage Lightning Frost cracks Sun scald on south side of
trunk. Thin barked, young trees with no shade
Heat stress De-icing salts
Types of abiotic disorders continued
Competition shade turf allelopathy▪ Black walnut▪ Sugar maple▪ Black locust
Pollution damage Difficult to
diagnose, often seen in foliage and mimics nutrient deficiency
Types of abiotic disorders continued Chemical injury
2, 4 D From drift, movement through soil, root grafting Leaves cup and curl, shoots twist Chlorotic, browning Most of the time, plants recover
Types of abiotic disorders continued Water availability Girdling roots
Often not detected until symptoms in above ground portion.
Prevention is best. Plant at correct depth. Can be possible to remove girding root
Biotic Disorders
Insects and Other Pests Disease
Fungus bacteria
What is an insect?
NOT an insect!
Insects…
may or may not be host specific Japanese beetle vs.
emerald ash borer May prey on harmful
insects have complex life cycles
that may have both harmful and innocuous stages
Either feeding or egg laying damage
Chewing Insects
May feed on entire leaf May feed on leaf margins May skeletonize [leaves that have had the
tissue removed from between the veins by inects] Japanese beetle
Leaf mining inside leaf May bore through wood
EAB in inner bark Asian Longhorn Beetle in wood itself
Piercing-sucking Insects Some pierce plant
cells and feed on the contents Aphids Scales, can go
undetected Usually don’t kill
trees outright, but cause stress
Honeydew=Liquid poo! Substrate for sooty mold
Scales
Gall – swelling of plant tissues; frequently caused by insects nematodes, fungi, or bacteria
Galls are a plant response – not a cocoon
Insects…
Can also be vectors, organism that transmits a pathogen [causal agent of a disease]
Mites and Nematodes Mite: very small,
spider like, can cause galls
Nematodes: Microscopic roundworms most of which are not parasites of plants
Scotch’s pine is an example
May enter tree through roots, wounds
Other animals Sapsuckers Deer, bud feeding Squirrel, bark
stripping Rabbits in winter
Diseases
Four requirements are necessary for a pathogen to infect
Most pathogens are host specific
Some need alternate host
The afflicted plant part will give an indication of the severity of disease Foliage, not so bad but
noticeable Vascular tissue, not so good
Necrosis – localized death of tissue in a living organism
Vascular discoloration darkening of the vascular tissues of woody plants in response to disease
Fungi
Most plant diseases are caused by fungi.
Not all are bad! Mycorrhizae= beneficial relationship between roots and fungus.
Look for fruiting bodies
Symptom or Sign?
Powdery Mildew
white or grayish fungal growth on the surface
of stems or foliage
Anthracnose-leaf fungus
Bacteria
Bacterial leaf scorch
Fire blight on pears, kills young tissue
Infected plant tissues may appear water soaked and have a foul odor
Bacterial wetwood
Where do I go from here? Extension MDC Missouri Community Forestry Council Sample:
fresh, cool, interface between diseased and healthy
tissue, early in week, good written description of problem and site