Diagnosing Tree Disorders in the Landscape

What is a plant disease? Anything that damages plant health Plant pathology deals with infectious organisms that reduce plant health, multiply, and spread: biotic diseases

Plant Diseases Biotic Factors –Viruses –Bacteria –Fungi –Nematodes Abiotic Factors –Environmental Problems –Herbicides –Nutritional Deficiencies –Pollutants

Damage from herbivores Animals and Rodents InsectsMitesNematodes

Insect Damage Identification Know Common Pest Arthropod Groups! Numerous lepidopteran caterpillars (ex. armyworms, cutworms) Beetles (Order Coleoptera): numerous leaf- feeding and wood-boring pests Sawflies (Order Hymenoptera) Various flies (Order Diptera) Various insects with piercing-sucking mouthparts including scales, mealybugs, whiteflies, aphids, psyllids, hoppers, various other members of the Order Hemiptera. Spider Mites

Symptoms vs. signs Symptoms are changes in growth or appearance of a plant in response to a damaging factor Signs are evidence of the damaging factor

Symptom or sign?

Diagnosis Compare plants with disorder to healthy plants –Roots, stems, leaves, fruits Ask questions! –History, conditions, variety, soil, etc. Hypothesis of cause

Diagnosis - Continued Look for signs of pathogen –Microscopic examination –Culturing on artificial media –Immunological methods (ELISA, etc) –Nucleic acid methods (PCR, etc) –Electron microscope Look for signs of insect or animal –Organism itself, eggs –Frass –Honeydew –Webbing

What questions do you ask? History: herbicide application, fungicide application, insect activity Pattern: isolated plant, entire field, near edges, etc? Any spread? Any variety differences? Certified planting stock?

What are viruses and viroids? Very small particles of nucleic acid and protein (viruses) or naked nucleic acid (viroids) icosahedral rods flexuous rods geminivirus tospovirus viroid inclusion body

Symptoms of Viruses

Plum Pox Virus

Bacterial diseases Bacteria are single-celled, prokaryotic organism (lack a membrane around the nucleus of the cell) Most plant pathogenic bacteria are gram negative, which means they do not retain the stain crystal violet when you do a gram stain –LPS (lipopolysaccharide) layer around cell wall

What do bacteria look like? Can’t see with the naked eye unless there are a LOT of them Culture on artificial media (some are not culturable on media)

Bacterial disease symptoms

Fire blight Erwinia amylovora Apple, pear, mountain ash, raspberry, hawthorne, contoneaster

What are fungal diseases? Cause the majority of economically significant plant diseases Caused by fungi – organisms with threadlike hyphae and reproductive structures (spores)

Fungal Plant Diseases Root Diseases - Soilborne and Residue borne –Cankers –Rots –Wilts Foliar Diseases – Residue borne, wind- blown and rain-splashed spores –Leaf spots and leaf molds

Fungal symptoms & signs

Dutch Elm Disease in Montana Beetle Galleries Lesser European Elm Bark Beetle Staining in twig

Cytospora canker - Spruce

Verticillium Wilt

Root Rots and Diseases Wind-thrown Trees Armillaria Phytopthora

Sudden Oak Death Phytopthora ramorum

Rhizosphaera needle cast Rhizosphaera kalhkoffii Rainsplash dispersed Symptoms: –Reduced needle retention –Dead (brown) older needles –Healthy, new needles do not show signs of infection

Powdery mildew Obligate Parasite Spores airborne over long distances –

Nematodes: a very small, worm- like animal

Pine Wilt Nematode

Piercing Sucking Insects Insects with piercing-sucking mouthparts cause stippling and/or chlorosis on the host. Example groups: aphids, true bugs, hoppers, scale insects, whiteflies Example groups: aphids, true bugs, hoppers, scale insects, whiteflies Plant Bugs Aphids

Sooty Mold

Leaf miners Insects that produce characteristic “mines” in leaves by feeding. Formed by various insects including flies, wasps, moths, and beetles. birch leafminer

Leaf Defoliaters Damage caused to a plant by insect feeding. “Skeletonizing” results when the veins or the “skeleton” of the leaf is left behind. Grasshoppers Japanese Beetles

Spider Mite Damage Leaf damage includes flecking, bronzing, and/or scorching of leaves.Leaf damage includes flecking, bronzing, and/or scorching of leaves. Several natural enemies. Most problematic in heavy insecticide use areas.Several natural enemies. Most problematic in heavy insecticide use areas. twospotted spider mite

Damage by Boring Insects Insects that bore into a stem, or seedhead Damage often results in weakening or killing the host

Emerald Ash Borer What does the damage look like? 1.Canopy starts to thin and water sprouts may start 2.Serpentine feeding just below bark 3.Small, D-shaped exit hole 4.Woodpecker damage another clue to infestation

Emerald Ash Borer What does it look like? 1.Adult is metallic green, about ½ inch 2.Larvae are flat bodied, about 1 inch 3.Larvae pupate in the tree and adults emerge from D shaped exit holes

Cottony Ash Psyllid

Woodpeckers and Sapsuckers

Porcupines

Deer and Elk Rubs

Drought Damage Trees will shed leaves and needles to prevent water loss

Herbicide? History Soil analysis or bioassay Tissue analysis

Symptoms of herbicide injury

Winter Injury Desiccation Frost Damage

Seasonal Needle Cast

Planting too deep

Iron Deficiency - Chlorosis Common in high pH Soils Apply sulfur to lower soil pH Apply chelated iron fertilizer foliar or soil applications

How to be a diagnostician Know the plant involved –What a healthy plant looks like! Look for symptoms and signs Look for patterns Question the environment Make a diagnosis, and check the facts!

Montana State University Schutter Diagnostic Lab Physical address 121 Plant BioScience Bldg. (PBB) Mailing Address 119 Plant BioScience Bldg. P.O. Box Bozeman, MT (406)