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Why diagnose plant disease?
Accurate diagnosis is needed for effective disease control
Diagnosis of plant problems/diseases
1. I'd the plant effected
- scientific name and variety
2. Examine the entire area for disease signs and symptoms
- look for patterns and how the disease developed
3. Determine the primary symptoms of disease
4. Look for signs of the pathogen
5. Isolate and Id the pathogen
6. Consulate literature for checklists and diagnostic aids
What are differences between a symptom and signs of a plant disease?
Symptom- is a response of the host to the pathogen
Sign- a part of the pathogen
List symptoms of plant disease
Death of plant tissue
Abnormal growth increase or decrease
Defoliation fruit drop
Replacement of plant tissue
Type disease concept (type of disease)
- a group of diseases that have similar symptoms and affect the same plant part
- similar pathogens (but not always)
-similar environmental conditions
-similar disease cycles
- similar control measures
Types of plant disease
Root and foot rots
What is step one of diagnosing plant problems?
Identifying the affected plant
What is step two of diagnosing plant problems?
Examine the area where the sick plant was growing
- is there a pattern to the occurrence of the disease or is it an isolated plant
- is there more than one plant species affected
- look at the weather history
- where herbicides applied recently
What is step three of diagnosing plant problems?
Determine the symptom syndrome
-compare diseased plant with health plant for comparison
-describe the symptoms of the diseased plant
What is step four of diagnosing plant problems?
Look for signs of a pathogen
- signs of a pathogen are more valuables tan symptoms because they are part of the disease.
- example of a pathogen sign are mushrooms or sclerotia produced in heads of plants with ergot or slimy ooze from vegetables with soft rot
What is chlorosis?
The yellowing of normally green plant tissue
What is albinism?
A normally green tissue that loses chlorophyll and becomes white
What is anthocyanescence?
Plant tissues become purple or red due to the build up of anthocyanins
Plant tissues have Silver or bronze metallic luster due to the separation of the upper epidermis
Leaf veins remain green while the tissue around them becomes chlorotic
The veins of the leaf become clear or white while the rest of the leaf remains green
What is a mosaic symptom?
A variegated pattern consisting of light and dark green and yellow colored plant tissue. Are some times associate with viruses
What is mottle?
Similar to a mosaic but the color change is less distinct.
What is virescence?
Development of chlorophyll is tissues that don't normally have it
What is necrosis?
Tissue becomes brown black grey or tan in color. Necrotic tissue can be dry and brittle or wet and mushy.
What is rot?
Disintegration and decomposition of plant tissue due to the activity of extra cellular enzymes.
What is a canker?
A localized sunken dead area on the stem trunk or twigs of woody plants.
What is blasting?
Flowers on an infected plant are sterile as a result of the disease.
What is mummification?
Normally fleshy fruit is transformed into dry hard shriveled structures that are resistant to decay.
What is damping off?
Death of a plant before or after emergence of the seedling.
WHat are galls?
Localized swellings or overgrowth on a plant
What is fasciculation?
Excessive branching or advantageous development of twigs roots flowers or fruits around a common point. Also known as witches broom.
What is phyllody?
The development of leaves at sites from which ovules normally develope.
What is fasciation?
A flattening and widening of stems flowers or fruits
What is stunting?
A general reduction in the size of an infected plant
What is rosette?
A short bunchy growth around a common point due to failure of internodes to elongate ( think dandelion)
What is wilting?
The loss of turgidity such that a plant becomes flaccid
What is ergot?
Diseases caused by a specific group of fungi that only infects the flowering parts of grasses and place the ovary with a dark colored compact survival structure called a sclerotium.
What is leaf curl?
Diseases characterized by distortions of the leaves and flowers ranging from small barley visible blister like areas to grossly distorted leaves.
What is powdery mildew?
Diseases characterize by the presence of white to gray colored growth on the surface of infected plants
What is root and foot rot?
Diseases characterized by necrosis of the roots crown or lower stem region of the plant immediately above the soil surface. Other symptoms may include nutrient deficiency wilting and stunting
What are rust diseases?
Characterized by yellow-orange to rusty rd color of infected plants and are often covered in small pustules containing pollen like granules
What is a smut disease
They are characterized by the presence of black dusty masses of spores on the host on any above ground structure
What are vascular diseases!
Are characterized by wilting mild to severe chlorosis followed by necrosis and plant death. Discoloration of the vascular system is the most diagnostic symptom of theses diseases but not the most common
What are yellows?
Diseases characteristics by General yellowing and stunting