Transcript Managing Diseases in Perennial Beds

Module 3: Diagnosis
Requirements to do diagnostics
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Organized, logical approach
Able to ask the “right” questions
Access to reference materials
Knowledge of local soil and weather
characteristics
• Common sense and a “detective” enthusiasm
Steps in diagnosing plant diseases
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Identify the plant
Define the problem
Develop list of potential disease candidates
Refine diagnosis
Confirm the Diagnosis: Get additional help
Step 1: Identifying the plant
• ALWAYS identify the plant to most appropriate level
possible (Species, Variety, etc.)
• KNOW what it is suppose to look like at the current time
of year.
• Learn about difference characteristics among cultivars.
Normal plant development is NOT a disease problem
Is there a problem?
• Normal development or plant problem?
Step 2: Define the problem
• Tissue affected: Leaves, Stems, Roots, etc.
• Symptom Description: Leaf Spots, Canker, Blight, etc.
• Part of the Plant affected: Top, Bottom, New Growth, Old
Growth, etc.
• Timing and duration of problem: Spring, Summer, 3 wks ago, etc.
• Site of problem: Front or back yard, shade or sun, low or high
ground, etc.
• Stressful Conditions: Excessive water, etc.
Step 2: Define the problem
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Collect as much information as possible during the initial
contact, follow up with more questions as necessary
Ask questions that are applicable to the situation
Step 3: List of suspects
• BIOTIC
– Symptoms is usually
scattered
– Symptoms develops
gradually over time (on
individual and whole
plantings)
– Sign of pathogen is
observable
• ABIOTIC
– Symptoms are uniformed
– Generally appear all at one
time
– Does not appear to spread
– Affects more than 1 type
of plant in immediate area
List of Suspects
• Biotic
– Bacterial
– Fungal
– Nematode
– Virus
– Arthropod (Insect,
Mites, etc.)
• Abiotic
• Cultural:
– Improper management
– Chemical Toxicity
• Environmental /
Physiological
– Soil, Water, Light,
Temperature
– Nutrient Imbalances
Gathering information and use keys to find
potential suspects
• Review:
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Master Gardener Handbook
Extension Publications
Extension, University, or Government Websites
Text books
Plant Disease Compendium (available from apsnet.org)
• Use a key or diagnostic tool
– Plant Problem Diagnostic Key (J. Johnk – see handout)
– Tomato or Cucurbit Problem Solver (aggie-horticulture.tamu.edu)
– Web search: ‘name of the plant’ diseases extension
Step 4: Refining diagnosis
• Gather known information and Compare with
gathered information
– Did what I see and find out about the problem
MATCH what I read about this suspect?
Step 5: Confirm Diagnosis:
Get additional help
– Other Master Gardener
– County Agent
– Plant Pathologist
– The Texas Plant Disease Diagnostic Lab
– Use Additional literature (books/reliable websites)
The Diagnosis
• Did you find a perfect match?
• Many times we have to use the available information to
select the most likely causal agent
• Diagnosis are not always definitive
• Take the opportunity to educate the client about proper
plant care and horticultural practices
• Teach them ways to avoid disease
• Promote the Earth Kind Environmental Stewardship
Program to avoid future problems
Scenario
Time: Late May, 2002
My oak tree is dying. It is
covered in yellow brown spots
and the leaves are somewhat
curled.
OAK LEAF BLISTER
Scenario
Time: Early September
Conditions: Wet spring, hot
summer. Soil are alkaline and
heavy.
My pittosporum just turn brown
and died within 1 week. What
happened? Are my other plants
going to die?
Cotton Root Rot
Scenario
Time: Spring
I just notice that the rose I planted
last year had some funny stuff
growing at the soil line. It feels
hard and stony. What is it? It is
going to kill my plant?
Crown Gall
Scenario
Time: August
The leaves of my cucumber vine looks spotty. Soon
after they have reddish-brown (dead) spots on
them. On the back is fuzzy.
Downy Mildew
Scenario
Time: Late October
I was clearing out my garden when
I pulled out my tomato plants
and notice that their roots were
galled. I also remember that my
tomatoes did not do too well this
year.
Root Knot Nematode
Scenario
Time: Late August
My maple tree is showing
scorching symptoms at the
margin of the leaf. It is all over
the tree especially at the tips.
I read on the internet that it
may be a bacterial disease.
Physiological/Environmental
Scenario
Time: Mid September
I had a pretty nice stand of
tomatoes. It was ripening just
nicely, but then it started to
have big white blotches then
it just rotted. It occurs on
many of the fruits but not all
of them. My eggplant also
started to look bad about the
same time. What is going on?
Sun Scald
Scenario
• Time: Summer
My Zinnias are having
this spots that begins
at the lower leaves
and seems to be
traveling upwards. Is
it a bacteria?
Xanthomonas campestris pv. zinniae
Define the problem
(Information gathering)
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When did the symptoms first appear?
Have the same or similar symptoms occurred before?
Is there any pattern to symptom occurrence: in the landscape
(perhaps in low areas only), or on the plant (both old and new
foliage affected equally)?
Is more than one kind of plant (species or cultivar ) affected?
What is the appearance of the roots?...
Are cankers, holes, or wounds evident on the stems?
- Do the holes or wounds follow a pattern or are they random?
Define the problem
(Information gathering)
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What percentage of leaves are affected on the plant?
Where are the leaves affected? Top, Bottom, Inner, Outer
What is the appearance of the leaves? Color?
Are the flowers or fruit normal in appearance? Are any spots or
deformed areas apparent?
11. Where is the plant located?
12. How many hours of sun does the plant receive?
13. Has there been any significant disturbance or compaction that
has occurred recently?
Define the problem
(Information gathering)
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Has the soil or plant been exposed to:
pool water, soil sterilant, fence stain, heat from appliances, etc.
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What is the condition of the soil?
dry (how long), wet (how long), compacted, etc.
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What is the soil texture: sand, silt or clay?
What is the soil pH? Organic Matter content? Mulch?
Is the soil well drained?
How often and how much fertilizer do you use?
Was there any application of pesticides in the vicinity: herbicides,
insecticides, fungicides, etc.
Did you follow the labeled instructions?
Define the problem
(Information gathering)
22. How many inches of rainfall did you receive during the past
________?
23. Have you provide supplemental irrigation? How much and how
often?
24. Do you have a sprinkler system? Do you know what it is
programmed for?
25. Do you have overhead sprinklers watering you landscape plants? Or
just the turf grass?
26. Do you have city water or well water? What is the quality of the
water? Is there high levels of total soluble salts?
What is wrong here?
Module 4: Solutions to disease problems
Disease Control Principles
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Resistance
Exclusion
Protection
Eradication
Avoidance
Therapy
Resistance
Using inherent traits of the plants
against diseases
– Resistant traits
– Adapted traits
• Fast growing
– Quality traits
• High yields
Exclusion
Keeping the pathogen out
– Using only healthy plants
– Buying certified plant material
– Aware of what materials are brought into your
garden
– Filtered greenhouse
– Maintaining clean equipment
– Quarantine & Inspection
Protection
Using a barrier to protect plants from diseases
– Chemical barrier
– Biological barrier
– Physical barrier
– Modified environments
Eradication
Killing or getting rid of the pathogen
– Removing and/or destroying diseased plant debris
(Sanitation or roguing)
– Fumigating area of planting
– Do not plant a host for some time (rotation)
– Solarization
Avoidance
Avoiding the pathogen or situation
that cause disease
– Different planting sites
– Different planting times
– Using adapted varieties
– Carefully watering
Therapy
Helping the plant to heal
– Pruning out diseased material
– Systemic chemicals
Cultural controls
– Proper Horticulture Practices !!!!
– Improve soil quality
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“Healthy Soil, Healthy Plants”
Cover crops, compost, mulch
Ensure proper drainage
Fertilization
Reduces splashing of soil borne diseases
Helps regulate soil moisture
Helps encourage beneficial microbes
– Irrigation
• Proper watering methods to minimize plant stress
• Reduce leaf wetness
Cultural controls
• Sanitation
– Removing disease plant material from growing area.
• Pruning out disease branches
• Raking and destroying leaves with fungal spots
• Weed control
• Crop Rotation
What is Landscape IPM?
• Integrated Pest Management is a strategy of
managing pests that is designed to meet individual
goals in the most economically and environmentally
sound manner possible using a combination of
control tactics.
http://earthkind.tamu.edu/
http://txipmnet.tamu.edu/
IPM Tactics
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Cultural control
Biological control
Mechanical control
Chemical control
IPM Decision-Making
6 step process:
1. Identify the problem or pest
2. Determine the severity of the problem and determine if the action
threshold has been reached.
3. Assess the management options (do nothing, cultural, biological,
chemical control)
4. Select and apply one or more options
5. Measure the success of options employed
6. Record the results
Pesticides Terminology
Protectant:
to be applied and is most effective prior to infection
Curative:
can be applied post infection and is capable to curing plant
Broad spectrum:
affects many different pathogens
Narrow spectrum:
affects only one or few specific pathogens
Contact fungicide:
is only effective when in contact with fungi
Systemic fungicide:
is able to be taken up and moved through out a plant
When prescribing chemical treatments
• Maximize pesticide performance
– Use the least amount in the most efficient way
“More is NOT always better!”
– Consider environmental condition when spraying
– Use proper spraying techniques
– Follow the label, It’s the Law!
Extension publication of interest
• E-159 Chemical for Plant Disease Control at Home.
• L-2016 Non-Chemical Control of Plant Diseases in the Home Garden
• Additional Extension Publications can be found at:
Agrilifebookstore.org
Click Advanced Search
Internet Resources
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Plantclinic.tamu.edu
Plantpathology.tamu.edu
Aggiehorticulture.tamu.edu
Apsnet.org
Web Search: Plant Disease Extension
Web Search: “Plant Name” Disease Extension
Plant Pathology Images
Anemone sp. Little
Cold Injury from drops of cold Myrothecium leaf spot
(Myrothecium
Happy Master Gardening!