Plant path lab

Accurate diagnosis is needed for effective disease control

• 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

• Symptom- is a response of the host to the pathogen
• Sign- a part of the pathogen

• Color changes
• Death of plant tissue
• Abnormal growth increase or decrease
• Wilting
• Defoliation fruit drop
• Replacement of plant tissue

• - 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

• Downy mildew
• Ergot
• Galls/rumors
• Leaf curls
• Mosaics/mottles
• Powdery mildew
• Root and foot rots
• Rusts
• Seedling diseases
• Smuts
• Vascular wilts
• Yellows

Identifying the affected plant

• 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

• Determine the symptom syndrome
• -compare diseased plant with health plant for comparison
• -describe the symptoms of the diseased plant

• 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

The yellowing of normally green plant tissue

A normally green tissue that loses chlorophyll and becomes white

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

A variegated pattern consisting of light and dark green and yellow colored plant tissue. Are some times associate with viruses

Similar to a mosaic but the color change is less distinct.

Development of chlorophyll is tissues that don't normally have it

Tissue becomes brown black grey or tan in color. Necrotic tissue can be dry and brittle or wet and mushy.

Disintegration and decomposition of plant tissue due to the activity of extra cellular enzymes.

A localized sunken dead area on the stem trunk or twigs of woody plants.

Flowers on an infected plant are sterile as a result of the disease.

Normally fleshy fruit is transformed into dry hard shriveled structures that are resistant to decay.

Death of a plant before or after emergence of the seedling.

Localized swellings or overgrowth on a plant

Excessive branching or advantageous development of twigs roots flowers or fruits around a common point. Also known as witches broom.

The development of leaves at sites from which ovules normally develope.

A flattening and widening of stems flowers or fruits

A general reduction in the size of an infected plant

A short bunchy growth around a common point due to failure of internodes to elongate ( think dandelion)

The loss of turgidity such that a plant becomes flaccid

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.

Diseases characterized by distortions of the leaves and flowers ranging from small barley visible blister like areas to grossly distorted leaves.

Diseases characterize by the presence of white to gray colored growth on the surface of infected plants

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

Characterized by yellow-orange to rusty rd color of infected plants and are often covered in small pustules containing pollen like granules

They are characterized by the presence of black dusty masses of spores on the host on any above ground structure

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

Diseases characteristics by General yellowing and stunting