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Definition Definition of Plant Diseases Plant Diseases
The condition in which the cells & tissues of plants are not functioning normally, which caused due to continuous interference by the pathogenic agent or environmental factors (abiotic) and cause symptoms.
The term diagnosis is widely used both in human medicine, veterinary, and plant diseases in the world. Diagnosis is the process of identifying the disease, thus found the name of the disease. Identification can be done about the symptoms and the causes of disease. Diagnosis is a process, which means it takes time. Diseases that have been reported in the literature, relatively easy and quick diagnosis. Diseases that have not been reported in the literature is relatively difficult and the diagnosis process requires a long time. This is because to do Koch's postulates.
Importance of Diagnosis
Diagnosis is an important process. The result of the diagnosis will determine the success of a plant disease management. Failure of a diagnosis will lead to failure in the control phase. As stated by Fry's classic contah (1982) in sugar beet cropping dipinggiran city of New York there are problems stunt plants. Alleged beginning stunt is caused by nutrient deficiency. But it does not solve the problem of fertilizer application. Consultation with plant disease experts concluded that the plants attacked by the nematode Heterodera schachtii. Thus, a good diagnosis should be highly effective. Besides, the diagnosis should also be fast. Delay in diagnosis results for a variety of things can cause the disease has been growing rapidly, so that results can not be saved. In addition to effectively and quickly, the diagnosis should also be cheap. The cost of an expensive diagnosis will not be affordable by small farmers, so they are reluctant to go to the clinic to check their plants.
Koch's postulates
In Koch's postulates explained that the disease-causing microorganisms is said as if it fulfills the following criteria
(1) microorganisms that cause disease are always associated with symptoms of the disease in question,
(2) must disease-causing microorganisms can be isolated on artificial media ririskiky pure,
(3) of the isolated microorganisms that cause disease have can cause symptoms similar to symptoms of the disease, when inoculated, and
(4) must disease-causing microorganisms can direisolasi of symptoms lnokulasi results.
Koch's postulates are by Smith (1906) modified, to obligate parasites, it is not necessary on artificial media, but must be pure bred though the host.
Scientific Method
One of the weaknesses of Koch's postulates are often require a very long time, so this way more widely used for diseases that have never been reported in the literature. Diseases that have been reported in the literature would be more practical when using other methods. Fry (1982) using the scientific method in making a diagnosis.
Observation
Unlike the human disease, one by one people come to doctors for diagnosis, but the owner must be active farmers. In countries with less advanced agriculture and even government officials who must be active. In plant disease that must be considered not as individuals, but in the population. In general, farmers / officers checked the plants that showed typical symptoms. However, it should be familiarized examination based on the results obtained, whether the loss results. Thus needs to be done in-depth observation, not only against the symptoms on the plants, but also on weather, soil and nutrient media, water and chemicals are dipaka, and how culture (form 1). From the observation will be known what the question, what is the question. Why are many of the dwarf plants, why plants wilt much? Can also be a question why this commodity production is low? In a good crop disease management is a key issue in low productivity should be known. In many ways the low production is not only a particular disease, but several diseases. For example, the observation was found tomato plants experiencing problems kelayuan. The question that arises is why the tomato plants have withered?
Hypothesis
Of the question why the tomato plants have kelayuan course regardless of the fact that there will be many answers as there are so-called hypothesis. But by using the fact that there is any hypothesis can be tested directly the truth. Hypothesis tomato plants withered because of lack of water may be rejected directly due to the fact that there are shows of the rainy season. Thus eventually there would be only one answer while specific. Answers while the truth is what needs to be tested by an analysis. From the hypothetical example can be drawn to wilt tomato plants attacked by the fungus F. oxysporum f.sp. lycopersici.
Hypothesis Testing / Analysis
The analysis conducted is based on literature. In the literature there are two important things that need to be verified are the symptoms and signs. In certain respects to the typical symptoms only owned by a particular disease, the presence of pathogens is not required.But in many cases, some diseases have similar symptoms, so the presence of pathogens is required. On the hypothesis of tomato wilt fungus attacked by F. oxysporum f.sp. lycopersici, of course that need to be present adala wilt symptoms and the fungus.
Hypothesis Accepted or Revised
Hypothesis was accepted if there is, both symptoms of wilt or F.oxysporum f.sp. lycopersici. If it was not fungus found then the hypothesis must be rejected and the subsequent need to be revised based on new facts emerge. The new hypothesis is then tested again to obtain an acceptable hypothesis. Hypothesis subsequently received a diagnosis.
PLANT DISEASE SYMPTOMS:
Is the response of plants to infection (which can be measured), for example, increased respiration, decreased photosynthesis, etc. of certain diseases can be differentiated from other diseases based on symptoms. Symptoms can also vary depending on the environment, varieties of host and pathogen races. Symptoms are always changing with the progression of the disease because the disease is a dynamic process. Syndrome is a sequence or series of symptoms of the disease.
Typical Symptoms
Typical symptoms are found in certain pathogens. The fungus Colletotrichum spp. pda generally cause symptoms antraknosa and Alternaria spp. cause symptoms of target spot.
OBSERVATIONS DISEASE SYMPTOMS CAN divided into
1. Primary Symptoms: Symptoms that arise immediately and directly visible. In general, the cause of disease is very close to the damaged plant tissue.
2. Secondary symptoms: Symptoms that occur far from the plant tissue attacked. Gerjala secondary emerged as a result of the primary symptoms of the attack.
For example, root rot and stem rot of peanut caused by the soil caused by Sclerotium rolfsii: Root rots and stem is the primary symptom is the primary symptoms of leaf wilt is a secondary symptom. Here Fungi Sclerotium rolfsii attack plant roots and stems neck so that the plant is attacked (Roots and neck rod) become damaged it is the primary symptom. As a result of damage to the roots and stems neck crop plants wither. This withered state of the so-called secondary symptoms.
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