what’s wrong with your plants and why? tony glover regional extension agent
TRANSCRIPT
Abiotic vs. Biotic Problems
• Abiotic – non-living agent (non-infectious).
Extreme temperatures Excess or deficient
water, light or nutrients Soil compaction, soil
grade changes Damage from cultural
practices: herbicides, fertilizers, pruning, mulching
Abiotic vs. Biotic Problems
• Biotic – living agent (infectious).
Pathogens - parasitic microorganisms that cause disease (fungi, bacteria, viruses, phytoplasma)
Pests – insects, mites, nematodes or mammals feeding on or damaging plants.
Abiotic vs. Biotic Problems
Symptom Progression• Biotic disease –
symptoms progress and nearby plants become infected.
• Abiotic disease – generally a lack of symptom progression. Does not spread.
Exception – nutritional deficiency symptoms progress slowly.
Abiotic disease – Herbicide Injury
Steps in Problem Diagnosis
Know the Plant Inspect the Site and Look for Patterns Look for Symptoms or Signs Examine cultural practices and
weather conditions Identify Potential Causes Consult Resources and Reach
Diagnosis
Steps in Problem Diagnosis
Know the Plant• Identify the species and cultivar affected• Know what problems commonly affect
the species. For example: Red Maple – Phyllosticta Leaf Spot, gloomy
scale Flowering Dogwood – Powdery Mildew, spot
anthracnose
Steps in Problem Diagnosis
Know the Plant• What’s normal for specific plant?
Fall Needle Drop on White Pine
Steps in Problem Diagnosis
Know the Plant• Look at the Whole Plant (foliage, stems,
branches, leaves, and roots)• Note the color, size, and thickness of the
foliage• Check the trunk and branches• Examine the Roots
Check the Trunk and Branches
Look for wounds, cankers, exit holes and other clues
Pitch Tubes on Bark, Southern Pine Beetle
Check the Trunk and Branches
Sapsucker damage to sugar maple
Don’t mistake sapsucker damage for borer exit holes
Too Much Mulch Over The Root Ball
Problems caused by too much mulch• Keeps trunk tissue wet• Can increase rodent
damage• Mulch can intercept
rain and irrigation• Can keep poorly
drained soils too wet• Can encourage surface
roots• Can encourage
development of stem girdling roots
Steps in Problem DiagnosisInspect the Site and Look For Patterns
• Determine prevalence of problem. Large area, all plants – generally abiotic. Scattered, localized – generally biotic.
• Check for distribution of symptoms. Uniform – generally abiotic. Random – generally biotic.
• Are the symptoms/patterns related to geography? (soil, low spot, etc)
• Is the damage limited to one type of plant? Multiple plant species - often abiotic One species – often biotic
Observation of Field PatternsAbiotic Problem
Symptoms distributed in a large area. Damage pattern is uniform.
Gas leak from building
Observation of Field PatternsRandom vs. Uniform
Boxwood Phytophthora Root Rot Oak Nutrient Deficiency
Uniform StripesRandom Patches
Observation of Field PatternsRandom vs. Uniform
Bermuda spring dead spot Fertilizer application problems
Steps in Problem Diagnosis
Know the Plant Inspect the Site and Look for Patterns Look for Symptoms and/or Signs Examine Cultural Practices and
Weather Conditions Identify Potential Causes Consult Resources and Reach
Diagnosis
Look for Symptoms and/or Signs
Symptoms - plant reactions or alterations of a plant’s appearance due to a disease or disorder.
Signs - actual presence of the pathogen, it’s parts or by-products seen on a diseased host plant.
Steps in Problem Diagnosis
Know the Plant Inspect the Site and Look for Patterns Look for Symptoms and/or Signs Examine Cultural Practices and
Weather Conditions Identify Potential Causes Consult Resources and Reach
Diagnosis
Steps in Problem Diagnosis
Examine Cultural Practices and Weather Conditions• Ask questions - Collect as much background
information as possible• When was the problem noticed?• Was the damage sudden or gradual?• Has the problem spread?• How old are affected plants?• What cultural practices have been performed
recently? Herbicide Sprays?
Steps in Problem Diagnosis
Identify Potential Causes Consult Resources and Reach
Diagnosis Get Laboratory Assistance
• Take samples (plant, soil)• Don’t forget pictures
Most Common Diseases of 2009Ornamentals
• Phytophthora Root and Crown Rot • Boxwood, Juniper, Hydangea, Leyland Cypress, Pansy, Petunia,
• Fungal Leaf Spots (Oak Leaf Blister, Anthracnose, and other leaf spots)
• Armillaria Root Rot• Oakleaf Hydrangea, Cotoneaster
• Pythium Root Rot • Pansy and other flowers
• Powdery Mildew • Dogwood, Crape Myrtle, Rose
• Botryosphaeria Canker /Dieback • Leyland Cypress, Japanese Maple, Cleyera
• Bacterial Leaf Spots• Basil, Begonia, Oakleaf Hydrangea, English Ivy
• Azalea Leaf Gall• Sooty Mold
• Various Trees and Shrubs (Hackberry Woolly Aphid)
Diseases Caused by Phytophthora
Some of the most economically important and damaging diseases on woody plants in the Southeast, USA, and worldwide
The name Phytophthora derives from Greek and literally means “plant destroyer.”
Cause problems annually Notorious Phytophthora diseases include
rhododendron root rot, sudden oak death, and potato late blight.
Particularly serious in or following “wet” years Diseases often are associated with wet or
saturated soils
Phytophthora 101
Phytophthora species resemble fungi but are not.
They are most closely related to aquatic organisms, such as brown algae and diatoms.
Phytophthora organisms are often referred to as ‘water molds’ because they do need water to complete their life cycle.
This group of organisms produces swimming spores .
Some Trees and Shrubs Attacked
Abies – fir Acer – maple Arbutus – madrone Betula – birch Buxus – boxwood Camellia – C. japonica Castanea – chestnut Cedrus – cedar Cercis – redbud Chamaecyparis - false
cypress Citrus - orange, lemon, etc. Cornus – dogwood
Cryptomeria -Japanese cedar
Cupressus - cypress Elaeagnus Eucalyptus Fagus – beech Ficus - fig Forsythia Ilex - holly Juglans—walnut Juniperus –juniper Kalmia – laurel Malus - apple
More Trees & Shrubs Attacked...
Pieris – andromeda Pinus – pine Platanus – sycamore Prunus - cherry, plum, etc. Pseudotsuga - Douglas fir Pyrus - pear Quercus – oak Rhododendron -
rhododendron, azalea Robinia – locust Rosa - rose
Rubus - raspberry Syringa - lilac Taxus - yew Thuja - arborvitae Tsuga - hemlock Vaccinium - blueberry Viburnum -arrowwood Ulmus – elm
Phytophthora as Pathogens of Woody Plants
They can attack all parts of the plant Blight & dieback on shoots & foliage
—uncommon Cankers on stems & trunk —e.g.,
“bleeding” cankers – occasionally Root & crown rots — most common
Symptoms—Above Ground Appear after roots are diseased Chlorosis & yellowing of the foliage
• very slight at first, then becoming obvious Stunted growth Overall wilting & decline Cankers - orange/red/brown discoloration
• on stems and trunk• distinct margin between healthy & diseased
tissues Plant death
Trunk and Stem Cankers “bleeding” cankers - Oak
outer bark inner bark
Photo: Bruce Moltzen, Missouri Department of Conservation
Symptoms—Below Ground
Must expose roots for examination• this usually requires digging! • need to know what healthy roots look like!
Reduced root volume/lack of feeder roots Roots discolored - red, brown, dark brown
• healthy roots are white or off-white Cortex sloughing/root rot Cankers on root crown
• may move up stem above ground
Field Diagnosis
Above-ground symptoms alone usually are not diagnostic—merely indicate vascular dysfunction
Therefore, look below ground at roots & crown
Together, these may be diagnostic Other pathogens also can cause root rot
• Armillaria, Fusarium, Sclerotium, Thielaviopsis, etc.
• and sometimes Pythium spp., especially on boxwood
Fungal Leaf Spot Diseases
Typically have tan to gray centers surrounded by a darker border
Fungal fruiting structures (pycnidia, spores, etc.) can be seen within the leaf spot
Defoliation is common Fungi survive on fallen leaves Prolonged leaf wetness, high humidity and poor
air circulation increase disease development Spores are spread by wind and water-splashing,
but can also be spread by insects, on clothes, tools, and hands
Defoliation due to Entomosporium leaf spot disease - Indian Hawthorn
Less water stays on this protected area
Oak Leaf Blister
Common fungal disease on oaks, especially red oaks (s. red and water oak)
Disease favored by cool, wet springs
Symptoms appear in late spring as yellow, blister like, circular, raised areas
Oak Leaf Blister
Spots become dull brown with age
As leaves mature, become resistant to infection
Affects appearance not tree health
Fungicides not needed, but one application of chlorothalonil or mancozeb before budbreak will control disease
Armillaria Root Rot - Rose
White fungal growth under bark
Drainage? Irrigation? Death
by watering hose? No fungicides for
control Resistant plants
best replacement option
Bacterial Leaf Spots
Plant wetness, high humidity and warmer temperatures favor disease development
Bacterial cells spread by water splashing, tools, hands, or insects
No Fruiting structures in spots
Many controlled with copper fungicides (Kocide)
Angular leaf spots running along veins
Oak Leaf Hydrangea
Sooty Mold Common name for group
of black-colored fungi that grow on honeydew on plants and other surfaces
Fungal growth gives appearance of being covered with a layer of soot
Honeydew produced by aphids, mealybugs, soft scales, whiteflies
Control sooty molds by controlling the honeydew producing insect. Drenches with Merit or Safari for hackberry aphids (early spring)
Sooty mold on crape myrtle
Azalea Leaf Gall
Occurs in cool, moist springs
Spores for next year’s infection are released when leaf galls turn white
Prune infected leaves
Camellia Leaf Gall
Camellia leaf gall early symptoms and lastyear’s infected leaves
Spores for next year’s infection are released when backside of leaves turnwhite
Leaf Gall Control Remove galls and destroy before they turn white
with spores Disease most severe when foliage becomes wet
during leaf expansion in spring. • Avoid planting in heavy shade • Avoid wetting foliage in spring
If the disease was severe in previous years and galls were too numerous to pick, apply a fungicide before new leaves and flowers emerge.
Applications can stop when leaves become full size Bayleton. Apply first spray as new leaves and
flowers appear. Repeat 2-3 times at 10-day intervals.
Powdery Mildew Common disease on dogwood
and other plants Looks like baby powder Use Resistant Cultivars:
• Cherokee Brave, Karen’s Appl. Blush, Kay’s Appl. Mist, Jean’s Appl. Snow
Start sprays at first sign of disease (early May)
Fungicides:• Heritage • Spectricide Immunox• Fertilome Systemic Fungicide• Fertilome Halt Systemic
Fungicide
Spot Anthracnose
Small reddish spots on bracts and leaves, trees in sun
Rake leaves in fall Heritage, Daconil,
Mancozeb, Halt, Immunox
Spray before budbreak, after bract fall, and one month later, and September after new flower buds form
Dogwood Anthracnose Different disease than
spot anthracnose Spots with reddish or
purple borders Spots enlarge over
time Leaf, twig blights,
cankers, can kill tree Blighted leaves
remain attached through winter
Resistant Cultivar ‘Appalachian Spring’
Hydrangea – Leaf Spot Several fungi cause leaf spots
on hydrangea – Cercospora, Corynespora, Colletotrichum
Often in combination with powdery mildew
Adequate plant spacing for good air circulation
Avoid watering late in the day Remove fallen leaves Apply fungicide at first sign of
disease:• Heritage, Daconil*, Immunox
Mancozeb*, Fertilome Systemic Fungicide
• * Poor control of powdery mildew, but good leaf spot control
• Ultra-fine Spray Oil
Control of Canker Diseases Difficult to control once infection has occurred Prevent canker diseases by proper
establishment and care:• Plant in well drained soils• adequate plant spacing• Irrigate plants to prevent drought stress, mulch
plants• Remove branches with cankers. Trace the dead
wood back to the base of the canker and prune at bud or branch fork. Prune 4-6 inches below canker.
• Sterilize pruning tools frequently• Avoid canker susceptible plants
Fungicides are of little value