Diagnostics for Master Gardeners

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Diagnostics for Master Gardeners
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Diagnosing Plant Disorders

• A systematic approach to determining the cause of
  plant problems..and the most important step in
  controlling them!

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Tools of the Trade

• Hand lens
• Pocket microscope
• Pocket knife
• Hand trowel
• Pruners, hand saw
• Soil probe

• Clear plastic bags, containers
• Camera
• References see list in the Diagnostics chapter
  of the MG Supplement

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Guidelines for Taking Samples

• Lawns/Turf grass one square foot, with roots
  and soil, where healthy and affected area meet
• Woody and herbaceous plants 12 to 18 length of
  stem showing both healthy and affected areas
• Insects whole,with body parts intact
• Soil representative of the area for testing

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The Diagnostic Process

• Identify the plant
• Describe the abnormality - samples
• Site history and analysis - tools
• Refer to a list of common problems culprits
• Analyze the symptoms - use references
• Make recommendations based on your diagnosis

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What are the Possible Causes of Plant Problems?

• Cultural
• Environmental
• Insects Mites
• Diseases
• Weeds
• Nuisance wildlife

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Cultural Environmental Problems

• Construction
• Salt
• Desiccation
• Mechanical damage
• Compaction
• Pesticides
• Drought
• Flooding
• Poor cultural practices

• Improper planting
• Poor plant selection
• Avoid weak or short lived species, such as
• Poplar
• White birch
• Silver maple
• Willow
• Boxelder
• Siberian elm
• Ornamental prunus

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Cultural and Environmental Disorders

• Of
• Ornamentals

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Wind Breakage
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Ice Storm Damage
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Winter Burn, or Desiccation
Localized on the west side, and above the snow
line
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Winter Injury or Twig Blight on Juniper?
Salt damage
Phomopsis twig blight
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Winter Injury
Yews planted too late in the fall
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Frost Damage
On pine candles
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Flooded Planting Hole how well does the soil
drain?
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Spruce - Poor soil drainage
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Wet Feet Decline of Yew
Dieback and death due to too much soil moisture
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Poor Plant Selection Pachysandra in full sun
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Poor Plant Selection Care - Arborvitae, drought
kill
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Leaf Scorch - Restricted roots, drought, road
salt, reflected heat
Maple
Oak
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Iron Chlorosis
Pin oak
Rhododendron
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Manganese Chlorosis on Red Maple
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Girdling Roots Guy Wires
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Lawn Mower Blight
These wounds are points of entry for canker
diseases and borers
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What Caused this Yew to Brown?
How about this one?
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Another Example of Lawn Herbicide Damage
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Shade Tree Decline
Symptoms include bare branches, smaller and
fewer leaves, and early leaf drop. Many causes
possible, including anything that disrupts root
or trunks.
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Fall Needle Drop - a natural occurrence
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Cultural and Environmental Disorders

• Contribute to poor growing conditions, which lead
  to landscape plant injury.
• Weakened plants are more susceptible to pest
  attack, therefore..
• Pest problems are often a result of, rather than
  the cause of, poor quality landscapes!

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Insect and Mite Pests

• Of Ornamentals

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Aphids
Many different colors and sizes, depending on the
host plant
Many predators and parasites feed on aphids!
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Two Spotted Spider Mites Equal opportunity
pests
Prefer hot and dry weather
Sucking damage stipples the leaves
Close up view
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Spruce Spider Mite
Damages spruce, arborvitae, pine, yew, juniper
and other evergreen hosts
Damaged
Healthy
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Four-Lined Plant Bug
Damage can look like a disease, localized on the
tips.
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Scale Insects - Soft vs Hard
Many landscape plants are hosts to scale
Sooty Mold- a harmless black fungi
Cottony maple scale on silver maple a soft
scale
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Euonymus scale
Hard Scale Insects
Pine needle scale
Euonymus scale
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Gall Insects and Mites
Galls produced by wasps and midges on oak
Galls produced by eriophyid mites on maple
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Cooley Spruce Gall
Caused by an adelgid (aphid-like) insect
Galls form on the tips of the shoots
Gall on left is new
Gall on right has exit holes

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Eastern Spruce Gall
Caused by an adelgid (aphid-like insect)
Galls form at the base of shoots
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Gypsy Moth Caterpillar - an exotic
pest!
Damage is due to defoliation
Not found in webs
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Eastern Tent Caterpillar - a native!
Webs found in tree forks of apple,
crabapple and cherry. Damage by defoliation.
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Fall Webworm - a native!
Webs are formed near the tips - over 88 hosts!
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Slug Damage on Hosta
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Japanese Beetle Adults
Damage by skeletonizing the leaves
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Black Vine Weevil on Yew
Both larvae and adults are destructive!
Larvae eat roots crowns
Pupa
Adult Weevil damages by notching the leaves
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European Pine Sawfly
Adult is a fly, larvae are sawflies
Larvae feeding Damage is by defoliating old
needles
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Birch Leafminer
Larvae and damage
Adult is a sawfly
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Bronze Birch Borer
Adult borer exit hole
Larval damage under the bark
Crown dieback
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Emerald Ash Borer - a new exotic pest!
Adult beetle emergence hole
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Emerald Ash Borer
EAB larvae
EAB galleries
Bark split with galleries
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Emerald Ash Borer
Woodpecker activity
Prepupae chambers - folded larvae
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Zimmerman Pine Moth
Pitch glob on trunk
Larvae damage
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Diseases of Ornamentals
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Lichen on Bark
Harmless moss and algae growth
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Vascular Diseases
Verticillium Wilt
Fungus is found in the soil.
Vascular streaking
Tale of two maples - left is declining, right is
healthy.
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Dutch Elm Disease
Flagging
Vascular streaking
Bark beetle galleries
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Oak Wilt
Another vascular disease! Can also spread by root
grafts.
Occurs in pockets
Leaf symptoms
Sap beetle vector
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Canker Diseases - Infections of the branches and
trunk
Nectria or bull's-eye canker on birch
Symptoms include sunken, raised, and discolored
bark.
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Cytospora Canker of Spruce
White patches of resin ooze from cankered areas
on the stem - caused by a fungus
Progressive lower branch dieback
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Fire Blight
A bacterial canker disease
Shepherds crook
Host plants appear scorched
Bacterial ooze on branches
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Foliage Diseases
Anthracnose
Sycamore anthracnose foliage symptoms
Sycamore twig blight - witches broom
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Oak anthracnose
Ash anthracnose
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Apple Scab Disease
Defoliation
Spotted leaves
Also occurs on Mountain ash
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Septoria Leaf Spot Disease
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Black Spot on Rose
Symptoms include defoliation and infection of
canes.
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Powdery Mildew
Mildew on lilac
Host plants include lilac, rose, turfgrass,
phlox and monarda
Rose
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Diplodia Tip Blight
Fungal fruiting bodies on needles
Infected tree
New shoots killed
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Cedar Rust Diseases
A fungus which requires two hosts!
Galls on juniper produce spores to infect the
hawthorn
Infected hawthorn leaf produces spores to infect
junipers
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Galls Caused by Diseases
Crown gall on Euonymus bacterial
Black Knot gall on Cherry or Plum - fungal
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Cultural and Environmental Disorders

• Of Turfgrass

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Roadside Salt Injury
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Dog Urine
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Fertilizer Spill
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Moisture Stress
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Stress Blight
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Insect Pests of Turfgrass
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(No Transcript)
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Grub Damage
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Chinch Bug
Scouting
Damaged turf
Chinch bug
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Diseases of Turfgrass
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Necrotic Ring Spot on Bluegrass
Susceptible lawn
Resistant lawn
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Snow Mold
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Leaf Spot
Overall view of damage
Leaf symptoms
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Rust
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Nuisance Wildlife on Turfgrass
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Skunk Damage
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Vole Damage
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Mole Damage
Eastern mole
Star-nosed mole
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Share Your Knowledge

• Not all organisms are pests
• Natural control allows some pests
• Is the damage cosmetic or lethal?
• Prioritize the injury, using Treeage
• Category 1 plants will survive without help
• Category 2 plants will survive with intervention
• Category 3 plants will die, no matter what we do
• Monitor pest levels often
• Proper timing for pest management
• select least toxic options

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Photo Credits

• Greg Patchan, MSU Extension (retired)
• Mary Wilson, MSU Extension-Genesee
• University of Missouri Extension
• University of Maryland Cooperative Extension
• The Ohio State University