Plant Disease Symptoms and Signs

Symptoms (Symptom) is indicated by changes in vegetation due tothe presence of disease.
The sign is the identification of disease in addition to the reactionof host plant parasites mmisal tubh fruit, mycelium, slime, sporecolor.


SYMPTOMS
• Local symptoms are symptoms that are limited to certain areassuch as leaf spot, leaf rust, discoloration and others.
• Systemic symptoms are present in the whole body of plants such as wilting, stunted.
• Symptoms are subtle because of the influence of certaincircumstances of disease symptoms will disappear or not show upanymore.

The primary symptoms are symptoms that occur in the affected areas by pathogens
Secondary symptoms are symptoms that occur elsewhere on theplant as a result of damage caused by the primary symptom.
Type of symptoms according to changes in cell
1. Symptoms of damage or necrotic cell death
2. Hypoplastic symptom is due to obstructed or cessation of cell growth (under development)
3. Symptoms are due to hyperplastic growth of cells that are more than usual (over-development)


Signs
Signs or macroscopic appearance of pathogens or their organsmore important role than the symptoms
These signs are limited to fungi and bacteria:
1. mycelium
Certain fungi form a mycelium or house spider
2. rust
Layer of flour or brown spots on the surface of tumb, becauseuredospora
3. flour
Powdery white layer consisting of mycelium and spores / konidiumfungi. Eg powdery mildew (powdery mildew) and a layer of fluffywhite (Downy mildew)
4. black fungus
Often called soot diseases (sooty molds) that form a black layer
5. scorched
Usually fire attacked by fungi, eg sugar cane shoots attacked byUstilago scitaminea
6. white pox
White pox on kale or cabbage
7. ter spotting
Layers like drops of tar on the leaf surface
8. fruiting body
Basiodokarp fruiting body or, in fomes lignosus, Ganoderma,Rigidiporus
9. Sklerotium
10. slime bacteria

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Causes of Pain in Plants

How do pathogens cause the plants to be sick? 
1. Weaken the host with the way food is absorbed continuously from the cell to its needs. 
2. Stop or disrupt the metabolism of host cells with toxin, enzyme, or a secreted ZPT 
3. Inhibit the transport of food, mineral nutrients and water through the carrier network.
4. Consuming content of host cells after contact.


Disease progression? 
Plant diseases which existed since time immemorial since emerged plants on earth. There is fossil evidence of leaf spot. Some events cause plant diseases fatal to humans who: 
1. Year 1000 in Europe. Famous Holy Fire (Holy Fire) or the fire of St. Anthony 
2. In 1844 in the U.S.. Potato late blight by Phytopthora infestans 
3. Years 1845-1860 in Ireland. Because the potato famine devastated, SHG 1 / 8 pddk died. 
4. Years 1945-1948 in Bangladesh. Famine because of paddy destroyed by Helminthosporium oryzae. 
5. Year 1880 in Indonesia. Coffee leaf rust devastated by Hemelia vastatrik. 
6. 1950 in Tawangmangu. Oranges were destroyed because CVPD 


Why plant diseases are always evolving?
 This is because agricultural technology ever developed for example: 
1. Excessive use of artificial fertilizers 
2. Planting cultivars that produce high but vulnerable to disease
3. Planting a cultivar in a broad area 
4. Importation of new plants from other regions. 


Why plant disease causing harm? 
1. Losses Directly 
Ie losses due to disease reduces the quantity and quality, increase production costs, reducing the ability of farming. 
2. Indirectly loss 
That loss to society because consumers must pay high fees.

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