Diagnosis and plant disorders

Diagnosis and Plant Disorders

Ann Koenig, Urban ForesterMissouri Department of Conservation

Ann.Koenig@mdc.mo.gov573-882-8388 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